One of the amputating surgeries in the field of medicine is a knee replacement. It involves removing the knee joint and replacing it with a modified prosthesis. However, several modifications of this surgery have been introduced into the high-powered world of surgery, including several alternatives for knee replacement. In this article, we are going to review the several modifications and knee replacement alternatives therein.
What is Knee Replacement?
Knee replacement, also known as knee arthroplasty, is a surgical procedure that involves the amputation or cutting out of a knee joint, the bones reams by a doctor, especially due to accidents or joint ailments such as arthritis. When the bone is removed, it is then replaced with a prosthetic device. Knee replacement can be partial, where selected or affected parts of the joints can be removed, such as the medial, lateral, and anterior compartments can also be removed and replaced with a modified prosthetic.
Why Should You Be looking for a Knee Replacement Alternatives?
Due to the dynamics of the human body, what works for the goose may not necessarily work for the gander. Certain post-symptoms of a knee replacement can be unbearable for most patients.
Pain After Knee Replacement.
Due to pain in the knee joint, a lot of patients embark on this old-time surgery to help reduce the pain they feel around their knee. But it is worthy of knowing that a substantial number of these patients still continue to feel pain after this audacious surgery. In a survey done by the government, 40% of patients that underwent knee replacement experienced miniature pain for over 3-4 years, while another 44% still felt some 3-5/10 degree of pain in 3-4 years. So, it is not worthy of looking in the direction of knee replacement alternatives in order to solve knee pain.
Knee Replacement Risks.
There is a risk in everything that we do, business, taking a walk, climbing a hill. Same way, certain risks exist in knee replacement which are:
Patients become more susceptible to heart attack and stroke immediately after knee replacement surgery.
Increased levels of metals in the blood.
Allergic reactions to the prosthetic material.
Possibility of infection.
Reduced activity of the patient as they thrive to become accustomed to the new prosthesis.
Even though social media and digital marketers paint a vivid picture of beautiful seniors riding a bike, continuing in their daily activities and hobbies, but this may not be true for everyone; in a study conducted by the government, there was seldom activity by patients after knee replacement surgery. Another study showed that patients who weren’t running before a knee replacement surgery couldn’t run after the surgery. But there are always two ways to everything; some other patients also showed an increase in physical activity after their surgery.
What are Knee Replacement Alternatives?
Steroids are made up of corticosteroids and cortisone. These corticosteroids carry out an anti-inflammatory function to prevent swelling around the knee regions as well as help reduce pain. But they do have a side effect; they destroy cartilage and may not be efficient as they are thought to be. If you are considering this knee replacement alternative, you probably should bear in mind that they do not offer long term remedies. Steroid injections are viable for knee replacement needs caused by arthritis but may proffer short-termed solutions.
Viscosupplementation is also another knee replacement alternative. They are in the form of gels for the knee, also knowns as hyaluronic acid varying across different brands in the market, likes of SynVisc, OrthoVisc, Supartz, and Euflexxa. They are administered to the patient, but a quick question one would ask is if really the shots help. The variations of results all over the web show support both sides of the notion. But one peculiarity of these results is that none says that they are hurtful or damaging as the steroid injections rather that they give a better solution to knee joint arthritis patients. In my own experience, these injections are efficient only when administered a few times, after which they begin to diminish in effects. The first dose may offer relief for some time, but a dose a far-reaching as the sixth dose may not offer any remedial effect at all.
Knee Nerve Ablation
Knee Nerve ablation is another breakthrough in the surgical world. Knee Nerve Ablation involves the use of technology to carry out a process where the specialist probes the nerves around the joint and passes electrical energy that is used to ablate (destroy) them. The work of these nerves is to relay signals from that region of the knee to the brain. So this technique deadens these nerves, and as such, you don’t feel any pain till those nerves grow back. The research on this type of knee replacement alternative is only a handful. Hence, they cannot conclude on the long term results since most of the studies on this new breakthrough are in their early stages.
Orthobiologics incorporation around the knee regions helps to enhance the healing of the knew joint or reduce the consequent degradation of orthopedic tissues. Orthobiologics are also knee replacement alternatives and can be gotten from the patient as autologous or a donor as allogeneic. The two primary derivations of orthobiologics are the PRP and the BMC short for Bone Marrow Concentrate. Another derivation that is commonly used is derived from natal tissues as in amniotic or umbilical cord. Just as the nerve ablation, the research on this type of knee replacement is at its early stages.
Platelet Rich Plasma (PRP)
We mentioned PRP earlier while discussing orthobiologics. PRP’s stand for Platelet-rich plasma that can be gotten from the patient. They contain healing factors that allow them to foster cartilage repair as well as reduce inflammation and balance the chemical dynamics of the knee. A lot of studies support the efficiency of PRP as knee replacement alternatives but may not offer much help when the arthritis is severe.
PKA (Percutaneous Knee Arthroplasty)
PKA (Percutaneous Knee Arthroplasty) comes in handy for severe cases of arthritic pain. This procedure involves the injection of rich bone marrow concentrates gotten from the patient or from a donor into the lax ligaments or other affected areas such as damaged meniscus tissues and tendons. This procedure is intricate and uses an ultrasound and fluoroscopy guides as compared to other quick knee shot techniques. Research proves that this method works pretty well, even in extreme cases of knee arthritis. This procedure also produces a lasting effect for about 2-7 years before the need for repetition.
Here you go!! Knee replacement alternatives. You sure would want to consider some of the alternatives; likes of PKA, PRP, and Bone Marrow concentrates that proffers a long-lasting solution.
1American Advanced Medical Corp. (Private Practice), Beverly Hills, CA,
2Western University of Health Sciences, Pomona, CA, USA
The prevalence of androgenic alopecia (AGA) increases with age and it affects both men and women. Patients diagnosed with AGA may experience decreased quality of life, depression, and feel self-conscious. There are a variety of therapeutic options ranging from prescription drugs to non-prescription medications. Currently, AGA involves an annual global market revenue of US$4 billion and a growth rate of 1.8%, indicating a growing consumer market. Although natural and synthetic ingredients can promote hair growth and, therefore, be useful to treat AGA, some of them have important adverse effects and unknown mechanisms of action that limit their use and benefits. Biologic factors that include signaling from stem cells, dermal papilla cells, and platelet-rich plasma are some of the current therapeutic agents being studied for hair restoration with milder side effects. However, most of the mechanisms exerted by these factors in hair restoration are still being researched. In this review, we analyze the therapeutic agents that have been used for AGA and emphasize the potential of new therapies based on advances in stem cell technologies and regenerative medicine.
The prevalence of androgenic alopecia (AGA) increases with age, and is estimated to affect about 80% of Caucasian men.1 Female AGA, also known as female pattern hair loss, affects 32% of women in the ninth decade of life.2 The consumer market for products that promote hair growth has been increasing dramatically.3 These products promote hair regeneration based on the knowledge about the hair follicle (HF) cycle.4,5 However, in most cases, the mechanisms of action of these products are not well characterized and the results are variable or with undesirable side effects.6 At present, only two treatments for AGA have been approved by the US Food and Drug Administration (FDA): Minoxidil and Finasteride.7–10Although these medications have proved to be effective in some cases, their use is limited by their side effects.11,12 With the emergence of stem cells (SCs), many mechanisms that lead to tissue regeneration have been discovered.13 Hair regeneration has become one of the targets for SC technologies to restore the hair in AGA.14 Several SC factors such as peptides exert essential signals to promote hair regrowth.15,16 Some of these signals stimulate differentiation of SCs to keratinocytes which are important for HF growth.17 Other signals can stimulate dermal papilla cells (DPCs) that promote SC proliferation in the HF.18,19 In this review, we describe HF characteristics and discuss different therapies used currently for AGA and possible novel agents for hair regeneration. These therapies include FDA-approved medications, non-prescription physical or chemical agents, natural ingredients, small molecules, biologic factors, and signals derived from SCs.
HF and SC niche
The HF undergoes biologic changes from an actively growing stage (anagen) to a quiescent stage (telogen) with an intermediate remodeling stage (catagen).4 HFSCs are located in the bulge region of the follicle and they interact with mesenchymal SCs (MSCs) located in the dermal papilla (DP).18 These signal exchanges promote activation of some cellular pathways that are essential for DPC growth, function, and survival, such as the activation of Wnt signaling pathway.19–21 Other signals, such as those from endothelial cells (ECs) located at the DP, are also essential for HF maintenance.22 EC dysfunction that impairs adequate blood supply may limits or inhibits hair growth.22 For instance, Minoxidil, a synthetic agent, is able to promote hair growth by increasing blood flow and the production of prostaglandin E2 (PGE2).7 It has been shown that proteins that belong to the transforming growth factor (TGF) superfamily, such as bone morphogenetic proteins (BMPs), also exert signals to maintain the capacity of DPCs to induce HF growing in vivo and in vitro.23 These BMPs may be released by several cells that compose the follicle, including ECs.24–26 ECs may provide signals for BMP receptor activation in DPCs similar to those signals that promote survival of MSCs in human embryoid bodies composed of multipotent cells.24,25 DPCs have been derived from pluripotent SCs in an attempt to study their potential for hair regeneration in vitro and in vivo.27 Together, dermal blood vessels and DPCs orchestrate a suitable microenvironment for the growth and survival of HFSCs.28,29 Interestingly, the expression of Forkhead box C1 regulates the quiescence of HFSCs located in the bulge region (Figure 1).30 HFSCs are quiescent during mid-anagen and maintain this stage until the next hair cycle.29,30 However, during early anagen stage, these cells undergo a short proliferative phase in which they self-renew and produce new hair.30 Therefore, the bulge region constitutes a SC niche that makes multiple signals toward quiescence or proliferation stages.30–34 It is known that fibroblasts and adipocyte signals are able to inhibit the proliferation of HFSCs.34 Additionally, BMP6 and fibroblast growth factor 18 (FGF18) from bulge cells exert inhibitory effects on HFSC proliferation.34 Dihydrotestosterone (DHT) also inhibits HF growth.35 Agents that reduce DHT, such as Finasteride, promote hair regrowth by inhibiting Type II 5a-reductase.8,14,36 In contrast to these inhibitory effects, DPCs located at the base of the HF provide activation signals (Figure 1).18,34 The crosstalk between DPCs and HFSCs leads to inhibition of inhibitory effects with the resultant cell proliferation toward hair regeneration (anagen).30,31,37 With the self-renewal of HFSCs, the outer root sheath (ORS) forms, and signals from DPCs to the bulge cells diminish in a way that the bulge cells start again with their quiescent stage.4,34As mentioned earlier, Forkhead box C1 transcription factor has an important role in maintaining the threshold for HFSC activation.30 The knockdown of these factors in bulge cells reduces the cells’ threshold for proliferation, and the anagen cycle starts more frequently due to promotion of HFSC proliferation in shorter periods of time.30
Figure 1 Diagram of the HF and factors involved in hair regeneration.
Notes: The HF is composed of different cell types including HFSCs, DPCs, and ECs, among others. HFSCs migrate from the bulge area after activation by growth factors released by DPCs. However, BMP6 and FGF18 from the bulge cells exert autocrine inhibitory effects in HFSC proliferation. Once the HFSCs are closer to DPCs and ECs, they differentiate and proliferate during anagen phase, forming new hair. Activation of Wnt signaling is essential for DPCs to release the factors that promote differentiation and proliferation of HFSCs. DHT interferes with this Wnt signaling and, in this way, inhibits hair growth and promotes hair miniaturization. Effective cell–cell interactions between HFSCs, DPCs, and ECs are essential for hair growth.
Prescribed and non-prescription products that promote hair growth and possible mechanisms of action
FDA-approved chemical agents
At present, the only therapeutic agents for AGA approved by the FDA in the USA are Finasteride and Minoxidil.9,10 Minoxidil promotes hair growth by increasing the blood flow and by PGE2 production.7Although Minoxidil is now a non-prescription medication, Finasteride and other drugs require a medical prescription for AGA treatment (Table 1). Dutasteride and Finasteride inhibit 5a-reductase, blocking the conversion of testosterone to DHT.36,38 While Finasteride is a selective inhibitor of type II 5a-reductase, Dutasteride inhibits type I and type II 5a-reductases. These medications have also been used to treat benign prostatic hyperplasia.39
Synthetic prostaglandin analog of PGF2a (originally used to decrease ocular pressure in glaucoma)
Activates prostaglandin receptor
Abbreviation: AGA, androgenic alopecia; PGF2a, prostaglandin F2a.
In addition to prescribed medications, some natural ingredients have been used to promote hair growth (Table 2). For example, procyanidin B-2 (found in apples and in several plants) is able to inhibit the translocation of protein kinase C (PKC) in hair epithelial cells.40 PKC isozymes, such as PKC-ßI and -ßII, play an important role in hair cycle progression and inhibiting their translocation can promote hair growth.40 Procyanidin B-3 can promote hair growth by inhibiting TGF-ß1.41 Another group of natural ingredients, such as saw palmetto, alfatradiol, and green tea (Epigallocatechin gallate), have the capacity to inhibit 5a-reductase and block DHT production.42–44 The natural ingredients and their proposed mechanisms of action are summarized in Table 2 (the commercial web page is included, since there are no formal studies about their mechanisms of action).
Non-prescription products used for AGA and their proposed mechanisms of action
Natural (flavonoid found in several non-citrus fruits, vegetables, leaves, and grains)
Abbreviations: AGA, androgenic alopecia; DHT, dihydrotestosterone; ECM, extracellular matrix; FDA, US Food and Drug Administration; PGD2, prostaglandin D2; PKC, protein kinase C; TGF-ß1, transforming growth factor ß1.
Light amplification by stimulated emission of radiation (LASER) generates electromagnetic radiation which is uniform in polarization, phase, and wavelength.45 Low-level laser therapy (LLLT), also called “cold laser” therapy, since it utilizes lower power densities than those needed to produce heating of tissue. Transdermal LLLT has been used for therapeutic purposes via photobiomodulation.46,47 Several clinical conditions, such as rheumatoid arthritis, mucositis, pain, and other inflammatory diseases, have been treated with these laser devices.48–50 LLLT promotes cell proliferation by stimulating cellular production of adenosine triphosphate and creating a shift in overall cell redox potential toward greater intracellular oxidation.51 The redox state of the cell regulates activation of signaling pathways that ultimately promotes high transcription factor activity and gene expression of factors associated with the cell cycle.52 Physical agents such as lasers have been also used to prevent hair loss in a wavelength range in the red and near infrared (600–1,070 nm).5,47,51,53 Laser therapy emits light that penetrates the scalp and promotes hair growth by increasing the blood flow.54 This increase gives rise to EC proliferation and migration due to upregulation of vascular endothelial growth factor (VEGF) and endothelial nitric oxide synthase.55,56 In addition, the laser energy itself stimulates metabolism in catagen or telogen follicles, resulting in the production of anagen hair.53,54A specific effect of LLLT has been demonstrated to promote proliferation of HFSCs, forcing the hair to start the anagen phase.57
Biologic agents that promote hair growth and their mechanisms of action
Recently, it has been found that SCs release factors that can promote hair growth.16 These factors and their mechanisms of action have been summarized in Table 3. These factors, known as “secretomes”, are able to promote skin regeneration, wound healing, and immunologic modulation, among other effects.58,59 Some of these factors, such as epidermal growth factor (EGF), basic fibroblast growth factor, hepatocyte growth factor (HGF) and HGF activator, VEGF, insulin-like growth factor (IGF), TGF-ß, and platelet-derived growth factor (PDGF), are able to provide signals that promote hair growth.15,60–64 As mentioned before, DPCs provide signals to HFSCs located in the bulge that proliferate and migrate either to the DP or to the epidermis to repopulate the basal layer (Figure 1).32,65 Enhancement in growth factor expression (except for EGF) has been reported when the adipose SCs are cultured in hypoxic conditions.15 Also, SCs increase their self-renewal capacity under these conditions.66–68 Low oxygen concentrations (1%–5%) increase the level of expression of SC factors that include VEGF, basic fibroblast growth factor, IGF binding protein 1 (IGFBP-1), IGF binding protein 2 (IGFBP-2), macrophage colony-stimulating factor (M-CSF), M-CSF receptor (M-CSFR), and PDGF receptor ß (PDGFR-ß).15,69,70 While these groups of factors promote HF growth in intact skin, another group of factors, such as M-CSF, M-CSFR, and interleukin-6, are involved in wound-induced hair neogenesis.71 HGF and HGF activator stimulate DPCs to promote proliferation of epithelial follicular cells.61 Epidermal growth factor promotes cellular migration via the activation of Wnt/ß-catenin signaling.60 VEGF promotes hair growth and increases the follicle size mainly by perifollicular angiogenesis.72 Blocking VEGF activity by neutralizing antibodies reduced the size and growth of the HF.72 PDGF and its receptor (PDGFR-a) are essential for follicular development by promoting upregulation of genes involved in HF differentiation and regulating the anagen phase in HFs.64,73 They are also expressed in neonatal skin cells that surround the HF.73 Monoclonal antibodies to PDGFR-a (APA5) produced failure in hair germ induction, supporting that PDGFR-a and its ligand have an essential role in hair differentiation and development.73 IGF-1 promotes proliferation, survival, and migration of HF cells.69,74 In addition, IGF binding proteins (IGFBPs) also promote hair growth and hair cell survival by regulating IGF-1 effects and its interaction with extracellular matrix proteins in the HF.70 Higher levels of IGF-1 and IGFBPs in beard DPCs suggest that IGF-1 levels are associated with androgens.74 Furthermore, DPCs from non-balding scalps showed significantly higher levels of IGF-1 and IGFBP-6, in contrast to DPCs from balding scalps.74
Stem cell factors and small molecules that promote hair growth and their mechanisms of action
Small molecules with low molecular weight (<900 Da) and the size of 10-9 m are organic compounds that are able to regulate some biologic processes.75 Some small molecules have been tested for their role in hair growth.76 Synthetic, non-peptidyl small molecules that act as agonists of the hedgehog pathway have the ability to promote follicular cycling in adult mouse skin.76 PGE2 and prostaglandin D2 (PGD2) have also been associated with the hair cycle (Table 3).77 PGD2 is elevated in the scalp of balding men and inhibits hair lengthening via GPR44 receptor.78 Also, it is known that PGE2 and PGF2a promote hair growth, while PGD2inhibits this process.77,79 Prostaglandin analogs of PGF2a have been used originally to decrease ocular pressure in glaucoma with parallel effects in the growth of eyelashes, which suggests a specific effect in HF activation.80 PGD2 receptors are located in the upper and lower ORS region and in the DP, suggesting that these prostaglandins play an important role in hair cycle.81 Molecules such as quercetin are able to inhibit PGD2 and, in this way, promote hair growth.82–84 Antagonists of PGD2 receptor (formally named chemoattractant receptor-homologous expressed in Th2 cells) such as setipiprant have been used to treat allergic diseases such as asthma, but they also have beneficial effects in AGA.85–87 Another small molecule l-ascorbic acid 2-phosphate promotes proliferation of ORS keratinocytes through the secretion of IGF-1 from DPCs via phosphatidylinositol 3-kinase.88 Recently, it has been described that small-molecule inhibitors of Janus kinase–signal transducer and activator of transcription (JAK-STAT) pathway promote hair regrowth in humans.89 Janus kinase inhibitors are currently approved by the FDA for the treatment of some specific diseases such as psoriasis and other autoimmune-mediated diseases.90–94 Also, another group of small molecules such as iron and the amino acid l-Lysine are essential for hair growth (Table 3).95
The multipotent SCs in the bulge region of the HF receive signals from DPCs in order to proliferate and survive.27,28,65,84,96 It has been shown that Wnt/ß-catenin signaling is essential for the growth and maintenance of DPCs.19,97 These cells can be isolated and cultured in vitro with media supplemented with 10% fetal bovine serum and FGF-2.37,98 However, they lose versican expression that correlates with decrease in follicle-inducing activity in culture.98 Versican is the most abundant component of HF extracellular matrix.99 Inhibition of glycogen synthase kinase-3 by (2’Z,3’E)-6-bromoindirubin-3′-oxime (BIO) promotes hair growth in mouse vibrissa follicles in culture by activation of Wnt signaling.98 Therefore, the increase of Wnt signaling in DPCs apparently is one of the main factors that promote hair growth.19 DPCs have been also generated from human embryonic SCs that induced HF formation after murine transplantation.27
Platelets are anucleate cells generated by fragmentation of megakaryocytes in the bone marrow.100 These cells are actively involved in the hemostatic process after releasing biologically active molecules (cytokines).100–102 Because of the platelets’ higher capacity to produce and release these factors, autologous platelet-rich plasma (PRP) has been used to treat chronic wounds.103 Therefore, PRP can be used as autologous therapy for regenerative purposes, for example, chondrogenic differentiation, wound healing, fat grafting, AGA, alopecia areata, facial scars, and dermal volume augmentation.101,104–108 PRP contains human platelets in a small volume that is five to seven times higher than in normal blood and it has been proven to be beneficial to treat AGA.10,105,109–111 The factors released by these platelets after their activation, such as PDGFs (PDGFaa, PDGFbb, PDGFab), TGF-ß1, TGF-ß2, EGF, VEGF, and FGF, promote proliferation of DPCs and, therefore, may be beneficial for AGA treatment.109,112–114 Clinical experiments indicate that patients with AGA treated with autologous PRP show improved hair count and thickness.109
In search of novel therapies
In this paper, we reviewed and discussed the use of therapeutic agents for hair regeneration and the knowledge to promote the development of new therapies for AGA based on the advances in regenerative medicine. The HF is a complex structure that grows when adequate signaling is provided to the HFSCs. These cells are located in the follicle bulge and receive signals from MSCs located in the dermis that are called DPCs. The secretory phenotype of DPCs is determined by local and circulatory signals or hormones. Recent discoveries have demonstrated that SCs in culture are able to activate DPCs and HFSCs and, in this way, promote hair growth. The study of these cellular signals can provide the necessary knowledge for developing more effective therapeutic agents for the treatment of AGA with minimal side effects. Therefore, advancements in the field of regenerative medicine may generate novel therapeutic alternatives. However, further research and clinical studies are needed to evaluate their efficacy.
The authors report no conflicts of interest in this work.
Blumeyer A, Tosti A, Messenger A, et al; European Dermatology Forum (EDF). Evidence-based (S3) guideline for the treatment of androgenetic alopecia in women and in men. J Dtsch Dermatol Ges. 2011;9(Suppl 6):S1–S57.
Motofei IG, Rowland DL, Georgescu SR, Mircea T, Baleanu BC, Paunica S. Are hand preference and sexual orientation possible predicting factors for finasteride adverse effects in male androgenic alopecia? Exp Dermatol. 2016;25(7):557–558.
Park BS, Kim WS, Choi JS, et al. Hair growth stimulated by conditioned medium of adipose-derived stem cells is enhanced by hypoxia : evidence of increased growth factor secretion. Biomed Res. 2010;31(1):27–34.
Talavera-Adame D, Wu G, He Y, et al. Endothelial Cells in Co-culture Enhance Embryonic Stem Cell Differentiation to Pancreatic Progenitors and Insulin-Producing Cells through BMP Signaling. Stem Cell Rev. 2011;7(3):532–543.
Lay K, Kume T, Fuchs E. FOXC1 maintains the hair follicle stem cell niche and governs stem cell quiescence to preserve long-term tissue-regenerating potential. Proc Natl Acad Sci U S A. 2016;113(1): E1506–E1515.
Leirós GJ, Attorresi AI, Balañá ME. Hair follicle stem cell differentiation is inhibited through cross-talk between Wnt/ß-catenin and androgen signalling in dermal papilla cells from patients with androgenetic alopecia. Br J Dermatol. 2012;166(5):1035–1042.
Yamana K, Labrie F, Luu-The V. Human type 3 5a-reductase is expressed in peripheral tissues at higher levels than types 1 and 2 and its activity is potently inhibited by finasteride and dutasteride. Horm Mol Biol Clin Investig. 2010;2(3):293–299.
Kamimura A, Takahashi T. Procyanidin B-3, isolated from barley and identified as a hair-growth stimulant, has the potential to counteract inhibitory regulation by TGF-beta1. Exp Dermatol. 2002;11(6):532–541.
Blume-Peytavi U, Kunte C, Krisp A, Garcia Bartels N, Ellwanger U, Hoffmann R. [Comparison of the efficacy and safety of topical minoxidil and topical alfatradiol in the treatment of androgenetic alopecia in women.] J Dtsch Dermatol Ges. 2007;5(5):391–395. German.
Bjordal JM, Couppé C, Chow RT, Tunér J, Ljunggren EA. A systematic review of low level laser therapy with location-specific doses for pain from chronic joint disorders. The Aust J Physiother. 2003;49(2):107–116.
Jimenez JJ, Wikramanayake TC, Bergfeld W, et al. Efficacy and safety of a low-level laser device in the treatment of male and female pattern hair loss: a multicenter, randomized, sham device-controlled, double-blind study. Am J Clin Dermat. 2014;15(2):115–127.
Rodrigues C, de Assis AM, Moura DJ, et al. New therapy of skin repair combining adipose-derived mesenchymal stem cells with sodium carboxymethylcellulose scaffold in a pre-clinical rat model. PloS One. 2014;9(5):e96241.
Lee YR, Yamazaki M, Mitsui S, Tsuboi R, Ogawa H. Hepatocyte growth factor (HGF) activator expressed in hair follicles is involved in in vitro HGF-dependent hair follicle elongation. J Dermatol Sci. 2001;25(2):156–163.
Fong P, Tong HH, Ng KH, Lao CK, Chong CI, Chao CM. In silicoprediction of prostaglandin D2 synthase inhibitors from herbal constituents for the treatment of hair loss. J Ethnopharmacol. 2015;175:470–480.
Weng Z, Zhang B, Asadi S, et al. Quercetin is more effective than cromolyn in blocking human mast cell cytokine release and inhibits contact dermatitis and photosensitivity in humans. PloS One. 2012;7(3):e33805.
Kwack MH, Shin SH, Kim SR, et al. I-Ascorbic acid 2-phosphate promotes elongation of hair shafts via the secretion of insulin-like growth factor-1 from dermal papilla cells through phosphatidylinositol 3-kinase. Br J Dermatol. 2009;160(6):1157–1162.
Quintás-cardama A, Vaddi K, Liu P, et al. INCB018424 : therapeutic implications for the treatment of myeloproliferative neoplasms Preclinical characterization of the selective JAK1 / 2 inhibitor INCB018424 : therapeutic implications for the treatment of myeloproliferative neoplasms. Blood. 2014;115(15):3109–3117.
Yamauchi K, Kurosaka A. Inhibition of glycogen synthase kinase-3 enhances the expression of alkaline phosphatase and insulin-like growth factor-1 in human primary dermal papilla cell culture and maintains mouse hair bulbs in organ culture. Arch Dermatol Res. 2009;301(5):357–365.
Gentile P, Garcovich S, Bielli A, Scioli MG, Orlandi A, Cervelli V. The Effect of platelet-rich plasma in hair regrowth: a randomized placebo-controlled trial. Stem Cells Transl Med. 2015;4(11):1317–1323.
Trink A, Sorbellini E, Bezzola P, et al. A randomized, double-blind, placebo- and active-controlled, half-head study to evaluate the effects of platelet-rich plasma on alopecia areata. Br J Dermatol. 2013;169(3):690–694.
Alves R, Grimalt R. Randomized placebo-controlled, double-blind, half-head study to assess the efficacy of platelet-rich plasma on the treatment of androgenetic alopecia. Dermatol Surg. 2016;42(4):491–497.
Cho JW, Kim SA, Lee KS. Platelet-rich plasma induces increased expression of G1 cell cycle regulators, type I collagen, and matrix metalloproteinase-1 in human skin fibroblasts. Int J Mol Med. 2012;29(1):32–36.
Exosomes are extracellular vesicles first described as such 30 years ago and since implicated in cell–cell communication and the transmission of disease states, and explored as a means of drug discovery. Yet fundamental questions about their biology remain unanswered. Here I explore what exosomes are, highlight the difficulties in studying them and explain the current definition and some of the outstanding issues in exosome biology.
What is the current definition of an exosome?
That is a very good question. Since the original description of exosomes over 30 years ago, the term has been loosely used for various forms of extracellular vesicle, muddying the field and contributing to the scepticism with which the research has sometimes been met. Exosomes are best defined as extracellular vesicles that are released from cells upon fusion of an intermediate endocytic compartment, the multivesicular body (MVB), with the plasma membrane. This liberates intraluminal vesicles (ILVs) into the extracellular milieu and the vesicles thereby released are what we know as exosomes (Fig. 1).
Exosomes correspond to intraluminal vesicles of multivesicular bodies. A transmission electron micrograph of an Epstein–Barr virus-transformed B cell displaying newly expelled exosomes at the plasma membrane. Multivesicular bodies (MVB) can be seen which can deliver content to lysosomes for degradation or can fuse with the cell surface to release intraluminal vesicles as exosomes, indicated by the arrows at the top of the picture
There are other types of microvesicle, including apoptotic bodies and ectosomes, which are derived from cells undergoing apoptosis and plasma membrane shedding, respectively. Although apoptotic bodies, ectosomes and exosomes are all roughly the same size (typically 40–100 nm) and all also contain ‘gulps’ of cytosol, they are different species of vesicles and understanding differences between them is of paramount importance but has too often been overlooked.
How were exosomes first recognized as distinct entities?
The presence of membranous vesicles outside cells was first recognized 50 years ago, although these were originally assumed to be waste products released via shedding of the plasma membrane. The recognition of what we now call exosomes didn’t come until 1983, from studies on the loss of transferrin during the maturation of reticulocytes into erythrocytes . These studies showed, by following transferrin-gold conjugates through the endocytic system, that ILVs generated in MVBs can be released to the extracellular space through fusion with the plasma membrane , although it was not until 1987 that the term ‘exosome’ was coined for them .
Even then, however, these extracellular vesicles were largely ignored, forgotten or, again, dismissed as a means of cellular waste disposal. It is only in the past decade that interest in exosomes has exploded, with a nearly tenfold increase in publications in as many years (115 in 2006, 1010 in 2015).
Why this explosion of interest?
For at least three reasons. First, they are thought to provide a means of intercellular communication and of transmission of macromolecules between cells. Second, in the past decade, exosomes have been attributed roles in the spread of proteins, lipids, mRNA, miRNA and DNA and as contributing factors in the development of several diseases. And third, they have been proposed to be useful vectors for drugs because they are composed of cell membranes, rather than synthetic polymers, and as such are better tolerated by the host. In fact, some of the earliest exosome research indicated that they can carry the MHC–peptide complexes that are recognized by T lymphocytes  and that secretion of such exosomes could promote antitumour immune responses in mice in vivo . Exosome therapies are now being explored in anti-cancer clinical trials and recent reports claim taxol-filled exosomes can be used to treat cancers in mice at 50-fold lower doses than conventional treatments, with the additional benefit that exosomes do not invoke an immune response .
Yet despite 20 years of research, the very basics of exosome biology are in their infancy and we know little of the part they play in normal cellular physiology.
So do we know how they are generated?
Yes and no. We do know that they are made as ILVs; but first of all, not all ILVs finish up as exosomes, and second, the mechanism of their generation in endosomes is not fully understood. Most conventional membrane budding processes deform membrane from an organelle into the cytoplasm but in ILV formation the membrane buds away from the cytoplasm and into the endosome. This unconventional budding process is not limited to ILV generation but also takes place during enveloped virus budding from the cytosol and during cytokinesis , and it requires specialised machinery.
ILVs (and thus exosomes) can be generated at the endosomal limiting membrane by at least two mechanisms, one of which depends on the ESCRT machinery (ESCRT stands for endosomal sorting complexes required for transport) whereas the other is ESCRT-independent (Fig. 2).
ILVs are generated by invagination of the endosomal membrane and have three possible fates. Inset: intraluminal vesicles (ILV) are formed by invagination of the endosomal membrane by either ESCRT-dependent or ESCRT-independent mechanisms. Matured endosomes accumulate ILVs within their lumen and have three distinct fates. They may deliver content that contributes to the biogenesis of specialized lysosome-related organelles (for example, melanosomes, Weibel-Palade bodies, azurophilic granules), they may fuse with lysosomes or they may fuse with the plasma membrane where released ILVs are now termed ‘exosomes’
The ESCRT machinery consists of a set of cytosolic protein complexes that are recruited to endosomes by membrane proteins that have been tagged, usually with ubiquitin on their cytosolic domains. The ubiquitin tag is recognized by the first of the ESCRT complexes, ESCRT-0, which is thus recruited to the endosomal membrane and passes ubiquitinated cargos to ESCRT-I, one of whose components, Tsg101, also recognizes ubiquitin. The recruitment of the ESCRT machinery acts to both cluster the ubiquitinated cargo proteins on the endosome and induce curvature of the endosomal membrane to form ILVs.
But ILVs are still able to form in the absence of ESCRTs , so other means of generating ILVs must exist, although the mechanisms for their generation are less clear. Generation of these ESCRT-independent ILVs requires the tetraspanin CD63—a protein abundant on ILVs but with unclear function —and may be facilitated by cone-shaped bending properties of lipids such as ceramide .
If not all ILVs become exosomes, what determines the fate of an ILV?
The destiny of ILVs is directed by the fate of the MVB they reside in. Confusingly, in addition to different types of ILVs, there are also different types of MVBs  and what regulates the fate of these endosomes is another interesting question. MVBs have several potential fates (Fig. 2) and can either fuse with lysosomes (where contents are degraded and recycled), fuse with the plasma membrane (where ILVs are released as exosomes), as I have already mentioned, or contribute to the generation of specialised organelles, such as melanosomes (in melanocytes), Weibel-Palade bodies (endothelial cells), azurophilic granules (in neutrophils) and secretory granules (in mast cells). The levels of cholesterol on MVBs appear to play a part in regulating their fate, cholesterol-rich MVBs being directed to the plasma membrane for exosome release, while cholesterol-poor MVBs are targeted to the lysosome .
But what regulates the balance between exosome release and alternative fates of ILVs remains engimatic.
What about differences between cells: do all cells release exosomes?
Well, not all cells have an endomembrane system, so no. But most mammalian cells contain endomembranes and generate ILVs within MVBs, though remarkably little is known about exosome release in most cell types.
Some cells—for example, the B cells, dendritic cells and mast cells of the immune system—appear to release exosomes constitutively; in fact, most of the data we have on exosomes comes from immune cells. As well as releasing exosomes constitutively, these cells may also be stimulated to secrete exosomes by cellular interactions. For example, murine dendritic cells, which are specialized to activate T lymphocytes, secrete higher levels of exosomes upon interaction with antigen-specific CD4+ T lymphocytes . In fact, lymphocyte interactions generally can be accompanied by exosome release; human T cells (including primary T cells from blood, T cell clones and Jurkat cell lines) release exosomes upon activation of their antigen receptors  and B cells release more exosomes upon engagement with antigen-specific CD4+ T cells .
Other cell types can be pushed to secrete exosomes by means of calcium ionophores or other stimuli[16, 17], but the extent of physiological exosome secretion in non-immune cells is largely unknown.
What happens when exosomes reach an acceptor cell?
We don’t know exactly. Exosomes that transfer membrane proteins or luminal content to the acceptor cell may be engulfed whole or the exosome membrane may fuse directly with the host plasma membrane (Fig. 3). Alternatively, exosomes may not need to be taken up by cells to elicit a physiological response: follicular dendritic cells, for example, carry on their cell surface exosomes that bear MHC–peptide complexes and other proteins that they do not express and are thereby enabled to activate immune cells with which they interact .
Exosome uptake by recipient cells. Fusion of MVBs with the cell surface releases ILVs as exosomes. In order for exosomes to elicit a response from recipient cells they might either fuse with plasma membrane (a) or be taken up whole via endocytosis (b), following which the exosome must be delivered to the cytosol, for example, via a back-fusion event (c). Alternatively, exosomes may attach to the surface of recipient cells to elicit a signalling response (d)
For intercellular transmission, various mechanisms of phagocytosis and endocytosis of extracellular vesicles have been described and which mechanism operates may depend upon vesicle size, which may in turn depend upon the cargo carried by the vesicle. In order for material to be released to an acceptor cell, exosomes must fuse with the host cell and this takes place via either direct fusion with the plasma membrane or a ‘back-fusion’ step from within a host endocytic organelle after the exosome has been engulfed. The process of back-fusion is not entirely clear, although it appears to require the unconventional lipid LBPA and protein Alix  (and is exploited by anthrax toxin lethal factor to escape from endosomes to the cytosol ).
Whether exosomes fuse with target cells or act via interactions with cell-surface proteins, or both, is another fundamental cell biology question that will need to be addressed if we are to understand the functions of exosomes.
So what are the consequences of all this information transfer? What biological functions have been established for exosomes?
There are many proposed functions for exosomes, the best-established being in immune responses. Exosomes isolated from B lymphocytes and bearing MHC class II molecules were shown in early experiments  to activate T lymphocytes in vitro, suggesting that they were communicating with the T lymphocytes in just the way that the parent B cells did. I have already mentioned later work by the same group, who showed that exosomes derived from dendritic cells, which are specialized to activate T cells in the initiation of immune responses, could promote antitumour immune responses in mice , exciting interest in the possibility of practical applications.
Or, as with follicular dendritic cells, exosome-associated MHC II can be found on the surface of cell types that neither express MHC II nor secrete exosomes, indicating that exosomes are delivered from one cell type to another .
However, exosomes may have roles other than in immune responses as several non-immune cells secrete exosomes. The only physiological role so far reported for non-immune cells is in keratinocyte-derived exosomes, which have been shown to modulate melanin synthesis by increasing the expression and activity of proteins within the melanosomes that modulate skin pigmentation .
How exactly would exosomes from one cell influence the expression and activity of proteins in an acceptor cell?
Exosomes transfer not only protein and lipids but mRNA and microRNA into acceptor cells and these RNAs have been shown in experiments in vitro to have functional effects in recipient cells. For example, exosomes from mice can be transferred to human cells and mRNA can be translated into mouse protein . Similarly, microRNAs—double-stranded RNA fragments that can regulate specific sets of mRNA (and so protein levels)—can act functionally in acceptor cells. The mode of action of exosomes has been a focus of special interest in cancer biology. Exosomes from breast cancer cell lines, for example, have been shown to be enriched for miRNAs relative to nontumorigenic breast cell lines and exposure of normal cells to exosomes derived from breast cancer cell lines increased both cell survival and proliferation, accompanied by loss of expression of some tumour-suppressor proteins . Exosome levels are elevated in the serum of some cancer patients versus controls. However, whether these vesicles are exosomes or other forms of extracellular vesicle, or a mix, is unclear—I have already mentioned this persistent problem in exosome research.
So exosomes can also contribute to disease?
Yes indeed. As exosomes provide a means of intercellular communication, they may also act as vehicles for ‘bad’ communication or spread. As well as miRNAs in the case of cancer, exosomes have been shown to contain numerous disease-associated cargos—for example, neurodegenerative-associated peptides, such as Aß  (in Alzheimer’s disease), tau  (in numerous neurodegenerative diseases), prions  (in transmissible spongiform encephalopathies), alpha-synuclein  (in synucleinopathies, including Parkinson’s disease) and superoxide dismutase 1  (in amyotrophic lateral sclerosis). Exosomes have thus been suggested to be propagators of neurodegenerative protein spread, although some cargos are easier to envisage than others.
Of the neurodegenerative-associated proteins, only some are integral membrane proteins, that is, proteins inserted into lipid bilayers, rather than cytosolic. Sorting of proteins into ILVs (and thus exosomes) is easier to envisage for membrane proteins, where tags such as ubiquitin regulate where they end up. So far, the presence of both Aß  and PrPc  has in fact been shown in ILVs, though this has not been demonstrated for other membrane proteins, such as alpha-synuclein and tau.
The mechanism whereby cytosolic proteins may be sorted to ILVs/exosomes, however, is not clear. In order for cytosolic proteins to become concentrated in ILVs, they would require positive incorporation and sorting, possibly by membrane-associated components on endosomes. All we can say is that there is evidence that this does in fact happen; cytosolic factors such as miRNAs are enriched in exosomes relative to cytosol, indicating that sorting must occur whereby certain miRNAs are concentrated and others are not .
The means by which disease-associated factors spread between cells remains poorly understood and exosomes would provide a means for such transmission. The presence of exosomal proteins, such as Alix, in association with Alzheimer’s senile plaques strengthens the circumstantial case for exosomes as a mediator in such spread. The hope is that having a means to regulate exosome release and spread may be useful in combatting some of these diseases but much more basic biology needs to be established before then.
Now I’m confused—what determines what exosomes contain?
Exosomes will contain whatever is sorted into them during their formation (as ILVs). For membrane proteins, this usually occurs through ubiquitination, which acts as a substrate for recruitment of the ESCRT machinery and subsequent generation of ESCRT-dependent ILVs.
The mechanisms that concentrate cytosolic factors are currently unknown. Although it seems clear that miRNAs, for example, are enriched relative to the amount in their parent cells, and are not randomly incorporated into exosomes, it is not clear how some are enriched more than others. There are currently a few hypotheses for miRNA sorting, including sorting via sumoylated heterogeneous nuclear ribonucleoproteins  or by a miRNA-induced silencing complex (miRISC) .
Because of the difficulties in separating exosomes from other extracellular vesicles, it is likely that some cargos reported to be enriched in ‘exosomes’ may in fact be contained in contaminant vesicles that are not exosomes. While many researchers are very stringent about applying the labels ‘exosomes’ and ‘extracellular vesicles’ correctly, others unfortunately are not. In addition, as I have said before, cytosolic proteins are likely to be found in exosome preparations because the exosome lumen is made of cytosol.
So how exactly can you be sure that a given extracellular vesicle is an exosome and not something else?
This is an interesting question that has a complex answer. Ideally, an intracellular compartment is identified by a specific biological marker, as, for example, in the case of the Golgi, nucleus or mitochondria, all of which carry proteins not found, or found at much lower levels, elsewhere.
One problem is that ILVs, and thus exosomes, represent an intermediate compartment of an intermediate. MVBs are not static organelles but rather undergo continuous maturation, in the course of which they gain and lose proteins. There will never be an exclusive marker for exosomes because any cargo on the ILV/exosome membrane must first be on the limiting membrane of the endosome and anything found inside must first come from the cytosol. A cargo may be concentrated on ILVs/exosomes but it will also be elsewhere. CD63 could be thought of as a pseudo-marker for exosomes. ILVs and exosomes are enriched in several such tetraspanins and my colleagues and I have show that CD63 is required for ESCRT-independent ILV formation . Alix also appears to be concentrated in ILVs/exosomes , as does Tsg101, a component of ESCRT-I, which has been used as a marker of exosomes in numerous studies [33,34], although the presence of Tsg101 in ILVs or exosomes does not fit with conventional models of ILV formation. Although Tsg101 is involved in ESCRT-dependent ILV formation, as mentioned earlier, it, along with other ESCRT components, should disassociate from the endosomal membrane prior to an ILV pinching off the endosomal membrane to allow it to participate in further events . Exactly when ESCRT-I components ‘fall off’ the membrane is unknown but it is conventionally thought to be prior to ILV formation, so Tsg101 should remain cytosolic and available for subsequent rounds of ILV formation. It is possible that some Tsg101 may be ‘swallowed’ into the forming ILV lumen, but levels should be negligible.
So are you saying there is no reliable marker for endosomes?
There may not be—not a single reliable one. Ultimately, perhaps the best method of defining exosomes biochemically may be through a combination of markers, including tetraspanins, Alix and others, with a concomitant exclusion of resident plasma membrane proteins. Although ILVs/exosomes will by their nature contain some plasma membrane proteins and the plasma membrane will contain some ILV/exosomal proteins, it should be possible to define relative levels and/or enrichment of proteins of exosomes that distinguish them from other microvesicles. Cargos such as MHC II from B cells and other cell type-specific antigens may also help to distinguish exosomes from other forms of extracellular vesicle. Common exosomal cargos include tetraspanins (CD63, CD81, CD9), antigen presentation molecules (MHC I and MHC II) and others (Alix, flotillin-1). An online database exists  where proteins, lipids and RNA are catalogued from published and unpublished exosomal studies.
If they are so hard to characterize reliably, how are exosomes isolated and studied?
Exosomes are rarely imaged by conventional methods as they are too small to be resolved by fluorescence microscopy and their release may be a rare event. A few studies have imaged exosome release occurring in cell cultures by various electron microscopic techniques but, more commonly, exosomes are pooled from cellular supernatant or animal fluids. Traditionally, they have been isolated by differential centrifugation from culture medium whereby larger contaminants are first excluded by pelleting out through increasing speeds of centrifugation before exosomes, small extracellular vesicles and even protein aggregates are pelleted at very high speeds (~100,000?×?g) . These preparations therefore represent an enrichment rather than a purification. Enriched preparations are commonly analysed by biochemistry, mass spectrometry or electron microscopy. Electron microscopy of isolated fractions as ‘whole mounts’ make it possible to immuno-label vesicles, with the limitation that isolated preparations do not provide the same internal controls as labelling sections of cells. Remarkably little attention has been paid to the characterization of exosomes, although efforts are being made to repair this omission with guidelines and criteria for defining groups of extracellular vesicles .
What would you say are the most important issues in exosome research?
Without doubt the single most important issue is actually understanding the biological significance of these structures. With so little known about their basic physiological functions, it may seem hard to understand how exosomes have been implicated in the pathogenesis of so many disparate disease states. Fundamental questions remain about exosome generation, fate and normal function but, ultimately, in order to understand exosomes, one must first understand ILVs, a fact that is too often overlooked. Meanwhile, it is important that publications on exosomes give a careful and explicit account of the criteria used for distinguishing them from other extracellular vesicles to avoid confusing the field and encouraging scepticism.
Harding C, Heuser J, Stahl P. Receptor-mediated endocytosis of transferrin and recycling of the transferrin receptor in rat reticulocytes. J Cell Biol. 1983;97(2):329–39.
Pan BT, Teng K, Wu C, Adam M, Johnstone RM. Electron microscopic evidence for externalization of the transferrin receptor in vesicular form in sheep reticulocytes. J Cell Biol. 1985;101(3):942–8.
Johnstone RM, Adam M, Hammond JR, Orr L, Turbide C. Vesicle formation during reticulocyte maturation. Association of plasma membrane activities with released vesicles (exosomes). J Biol Chem. 1987;262(19):9412–20.
Zitvogel L, Regnault A, Lozier A, Wolfers J, Flament C, Tenza D, et al. Eradication of established murine tumors using a novel cell-free vaccine: dendritic cell-derived exosomes. Nat Med. 1998;4(5):594–600.
Kim MS, Haney MJ, Zhao Y, Mahajan V, Deygen I, Klyachko NL, et al. Development of exosome-encapsulated paclitaxel to overcome MDR in cancer cells. Nanomedicine. 2015;12(3):655–64.
McDonald B, Martin-Serrano J. No strings attached: the ESCRT machinery in viral budding and cytokinesis. J Cell Sci. 2009;122(Pt 13):2167–77.
Stuffers S, Sem Wegner C, Stenmark H, Brech A. Multivesicular endosome biogenesis in the absence of ESCRTs. Traffic. 2009;10(7):925–37.
Edgar JR, Eden ER, Futter CE. Hrs- and CD63-dependent competing mechanisms make different sized endosomal intraluminal vesicles. Traffic. 2014;15(2):197–211.
Trajkovic K, Hsu C, Chiantia S, Rajendran L, Wenzel D, Wieland F, et al. Ceramide triggers budding of exosome vesicles into multivesicular endosomes. Science. 2008;319(5867):1244–7.
White IJ, Bailey LM, Aghakhani MR, Moss SE, Futter CE. EGF stimulates annexin 1-dependent inward vesiculation in a multivesicular endosome subpopulation. EMBO J. 2006;25(1):1–12.
Mobius W, Ohno-Iwashita Y, van Donselaar EG, Oorschot VM, Shimada Y, Fujimoto T, et al. Immunoelectron microscopic localization of cholesterol using biotinylated and non-cytolytic perfringolysin O. J Histochem Cytochem. 2002;50(1):43–55.
Buschow SI, Nolte-’t Hoen EN, van Niel G, Pols MS, ten Broeke T, Lauwen M, et al. MHC II in dendritic cells is targeted to lysosomes or T cell-induced exosomes via distinct multivesicular body pathways. Traffic. 2009;10(10):1528–42.
Blanchard N, Lankar D, Faure F, Regnault A, Dumont C, Raposo G, et al. TCR activation of human T cells induces the production of exosomes bearing the TCR/CD3/zeta complex. J Immunol. 2002;168(7):3235–41.
Muntasell A, Berger AC, Roche PA. T cell-induced secretion of MHC class II-peptide complexes on B cell exosomes. EMBO J. 2007;26(19):4263–72.
Savina A, Furlan M, Vidal M, Colombo MI. Exosome release is regulated by a calcium-dependent mechanism in K562 cells. J Biol Chem. 2003;278(22):20083–90.
Guo BB, Bellingham SA, Hill AF. Stimulating the release of exosomes increases the intercellular transfer of prions. J Biol Chem. 2016;291(10):5128–37.
Denzer K, van Eijk M, Kleijmeer MJ, Jakobson E, de Groot C, Geuze HJ. Follicular dendritic cells carry MHC class II-expressing microvesicles at their surface. J Immunol. 2000;165(3):1259–65.
Bissig C, Gruenberg J. ALIX and the multivesicular endosome: ALIX in Wonderland. Trends Cell Biol. 2014;24(1):19–25.
Abrami L, Lindsay M, Parton RG, Leppla SH, van der Goot FG. Membrane insertion of anthrax protective antigen and cytoplasmic delivery of lethal factor occur at different stages of the endocytic pathway. J Cell Biol. 2004;166(5):645–51.
Lo Cicero A, Delevoye C, Gilles-Marsens F, Loew D, Dingli F, Guere C, et al. Exosomes released by keratinocytes modulate melanocyte pigmentation. Nat Commun. 2015;6:7506.
Valadi H, Ekstrom K, Bossios A, Sjostrand M, Lee JJ, Lotvall JO. Exosome-mediated transfer of mRNAs and microRNAs is a novel mechanism of genetic exchange between cells. Nat Cell Biol. 2007;9(6):654–9.
Melo SA, Sugimoto H, O’Connell JT, Kato N, Villanueva A, Vidal A, et al. Cancer exosomes perform cell-independent microRNA biogenesis and promote tumorigenesis. Cancer Cell. 2014;26(5):707–21.
Rajendran L, Honsho M, Zahn TR, Keller P, Geiger KD, Verkade P, et al. Alzheimer’s disease beta-amyloid peptides are released in association with exosomes. Proc Natl Acad Sci U S A. 2006;103(30):11172–7.
Saman S, Kim W, Raya M, Visnick Y, Miro S, Saman S, et al. Exosome-associated tau is secreted in tauopathy models and is selectively phosphorylated in cerebrospinal fluid in early Alzheimer disease. J Biol Chem. 2012;287(6):3842–9.
Fevrier B, Vilette D, Archer F, Loew D, Faigle W, Vidal M, et al. Cells release prions in association with exosomes. Proc Natl Acad Sci U S A. 2004;101(26):9683–8.
Emmanouilidou E, Melachroinou K, Roumeliotis T, Garbis SD, Ntzouni M, Margaritis LH, et al. Cell-produced alpha-synuclein is secreted in a calcium-dependent manner by exosomes and impacts neuronal survival. J Neurosci. 2010;30(20):6838–51.
Gomes C, Keller S, Altevogt P, Costa J. Evidence for secretion of Cu, Zn superoxide dismutase via exosomes from a cell model of amyotrophic lateral sclerosis. Neurosci Lett. 2007;428(1):43–6.
Guduric-Fuchs J, O’Connor A, Camp B, O’Neill CL, Medina RJ, Simpson DA. Selective extracellular vesicle-mediated export of an overlapping set of microRNAs from multiple cell types. BMC Genomics. 2012;13:357.
Edgar JR, Willen K, Gouras GK, Futter CE. ESCRTs regulate amyloid precursor protein sorting in multivesicular bodies and intracellular amyloid-beta accumulation. J Cell Sci. 2015;128(14):2520–8.
Villarroya-Beltri C, Gutierrez-Vazquez C, Sanchez-Cabo F, Perez-Hernandez D, Vazquez J, Martin-Cofreces N, et al. Sumoylated hnRNPA2B1 controls the sorting of miRNAs into exosomes through binding to specific motifs. Nat Commun. 2013;4:2980.
Fabian MR, Sonenberg N. The mechanics of miRNA-mediated gene silencing: a look under the hood of miRISC. Nat Struct Mol Biol. 2012;19(6):586–93.
Bobrie A, Colombo M, Krumeich S, Raposo G, Thery C. Diverse subpopulations of vesicles secreted by different intracellular mechanisms are present in exosome preparations obtained by differential ultracentrifugation. J Extracell Vesicles. 2012;1:18397.
Thery C, Boussac M, Veron P, Ricciardi-Castagnoli P, Raposo G, Garin J, et al. Proteomic analysis of dendritic cell-derived exosomes: a secreted subcellular compartment distinct from apoptotic vesicles. J Immunol. 2001;166(12):7309–18.
Thery C, Amigorena S, Raposo G, Clayton A. Isolation and characterization of exosomes from cell culture supernatants and biological fluids. Curr Protocols Cell Biol. 2006;Chapter 3:Unit 3 22.
Lotvall J, Hill AF, Hochberg F, Buzas EI, Di Vizio D, Gardiner C, et al. Minimal experimental requirements for definition of extracellular vesicles and their functions: a position statement from the International Society for Extracellular Vesicles. J Extracell Vesicles. 2014;3:26913.
The author wishes to thank Scottie Robinson, Paul Luzio and Paul Manna for critical reading of this article.
The author declares that he has no competing interests.
Cambridge Institute for Medical Research, University of Cambridge, Hills Road, Cambridge, CB2 0XY, UK
When it comes to side effects, ease of preparation, fast treatment times, and cost, PRP is above them all in orthobiologics. However, aside from PRP, there is one other alternative that is showing promise: Amniotic Fluid.
Due to it being a really good source of regenerative material that is not only highly proliferative, but also that produces almost no immune response, Amniotic Fluid has been a popular substance to theorize about since the late 1930’s. That is not all though, as this fluid is also high in collagen, growth factors, and hyaluronic acids. These are found in high quantities, making them a good choice for promoting regeneration.
This fluid is also high in stem cells that contain B7H4, a substance that promotes wound healing and even shows promise as a way of growing functional blood vessels. This was demonstrated to be true by scientists at Rice University and Texas Children’s Hospital.
However, we are not going to talk about that kind of Amniotic fluid. The one that we are going to talk about has been frozen, thereby killing the stem cells. This is actually a good thing, as the FDA has banned the presence of stems cells in amniotic fluids.
How Allografts Of Amniotic Fluids are Created
Allografts (Grafts taken from someone besides the person receiving it) of Amniotic Fluids are like Platelet-Rich Plasma that is already ready to be injected. This way, you and your patients receive all of the benefits associated with PRP therapy, without having to extract it yourself.
This amniotic fluid is taken with consent from mothers who decided to donate this fluid during a c-section. Not only were the women themselves pre-screened, but the fluid is tested again afterwards, and then prepared to be instantly used for a wide watch of medical ailments.
The fact that Amniotic Fluid has very little effect on one’s immune system makes it a wonderful allograft. This means that the body is far less likely to attack the donor material, making it far less likely to be rejected. Also, much like PRP, they are also known to fight inflammation, and keep microbes at bay. They are also multipotent cells, meaning they can turn into any cell they need to, making them a gold standard for regenerative medicine.
Since Amniotic Fluid is not taken from the person it it being used on like PRP, it misses out on a lot of those benefits. However, the large amount of elastin, fibronectin, and collagen makes it a great substance to use in wound healing and cell regeneration. It also contains a ton of growth factors, including PDGF, EGF, VEGF, and FDF to name a few.
Amniotic Fluid Allograft
It is often used to improve chronic pain conditions, as well as sports injuries, arthritis, and potentially even the symptoms of aging. It can be used by doctors along with PRP therapy to increase the effectiveness of the therapy. It can also be combined with bone marrow aspirates or hyaluronic acid.
The Potentials Of This
Many doctors may not want to spend the time and money investing in PRP therapies, so we think that Amniotic Fluid in general, could be a wonderful alternative to PRP therapy. Also, this can also be used as a stepping stone to help providers that are new to regenerative medicine to potentially get to PRP or stem cells over time.
We are convinced that once you get started with regenerative medicine, whether it be Amniotic Fluids, PRP therapies, or stem cell therapy, you will prefer it over other invasive procedures for sports injuries, arthritis, and other wounds. This will help save at least a few patients from having to do any unnecessary surgical procedures.
Although they can perform surgeries, osteopathic physicians try to avoid doing so whenever possible. Because of this, PRP seems to be an excellent fit for their practice. Since Osteopathy was built on the idea of self-healing, PRP seems to be a perfect fit.
A little while ago, PRP research was reviewed by The Journal Of The American Osteopathic Association, and concluded that more studies and evidence would be needed to make a solid statement on it. A little while later, a case study was filed, showcasing an 18 year old high school football player who suffered from a sports injury. The case study showed that the muscle injury healed rapidly under the effect of PRP therapy. So although PRP is not constantly held up on a pedestal by the mainstream yet, does not mean that Osteopathic Physicians can’t learn a lot or benefit from the use of PRP in their practice.
How Osteopathic Physicians can Benefit From PRP
Due to the fact that Osteopathic Physicians prefer to treat the patient, as opposed to just treating a disease or the symptoms, PRP is a great fit. It works by using the body’s own resources and mechanics and helps the body to heal itself over time. It works because, instead of simply dealing with symptoms, like many practices and conventional medicine does, it works to deal with the problem head on.
For instance, there are many examples of PRP therapy taking the place of surgery and medicine. Such as the cases where female patients were able to revive their sex drive, although they were initially treated for incontinence. So although PRP therapy was created and pushed by allopathic doctors at first, PRP works wonders in the field of Osteopathic medicine, and can become one of the best methods of treatment for Osteopathic physicians.
In some practices, musculoskeletal pain can be something that Osteopathic Physicians deal with often. However, it is good to note that PRP is quickly becoming one of the main treatments for these kinds of issues. For instance, many researchers believe that PRP should be the main choice for people who suffer from knee meniscus.
In 2016, University of Missouri Doctor Patrick Smith published a FDA-sanctioned double-blind randomized placebo controlled clinical trial on PRP. These kinds of trials are considered the gold standard in research. The results of the study was that PRP provided safe and notable benefits for people who suffer from knee Osteoarthritis.
PRP has a great deal of potential
The third and most important reason why all physicians, including Osteopathic Physicians, should start using PRP therapy is due to how wide its scope is. Due to the fact that PRP is simple and common, it is safe to say that if PRP can work on knee joints and tendons, that it most likely works on other tendons, joints, bones, and muscles as well. PRP will soon be a commonplace treatment when it comes to pretty much all musculoskeletal diseases.
This means that PRP has a near limitless potential. This is especially important for Osteopathic Physicians, as if there is a problem with the patients wrist, it could be that the main issue appears further down the arm. This is why multiple PRP injections on various areas of the arm can work to not just heal the issue, but also enhance the other traditional methods that are used. This will help restore the balance t the body, and give full functionality back to the patient.
American Academy of Regenerative Medicine Doctor Peter Lewis has administered over 100,000 PRP injections to over 12,000 patients. He claims that more than 80% of his patients who have gotten PRP therapy has had fantastic results. Even people who have claimed to need surgery could be benefited by the use of PRP.
Are They FDA Approved?
As of this year, PRP treatments are not yet subject to FDA approval. This is because all of the treatments are performed on the same day as the extraction, and uses only materials that are already inside the patients own body. Because of this, the PRP therapy is within the scope of the FDA Code of Federal Regulation title 21, part 1270, 1271.1. As a result, it is exempt from needing approval.
How does the U.S. FDA regulate cell therapies? (351 vs 361 Products)
In the United States, cellular therapies are regulated by the FDA’s Office of Cellular, Tissue, and Gene Therapies (OCTGT) within the FDA Center for Biologics Evaluation and Research (CBER).
According to the FDA, the Center for Biologics Evaluation and Research (CBER) regulates:
Cellular therapy products
Human gene therapy products
Certain devices related to cell and gene therapy
CBER uses both the Public Health Service Act and the Federal Food Drug and Cosmetic Act as enabling statutes for oversight.
In the U.S., human tissues intended for transplantation are regulated by the FDA as “Human cells, tissues and cellular and tissue-based products” or “HCT/Ps.” Under U.S. law, any company that engages in the collection, processing, storage, screening/testing, packaging, or distribution of HCT/Ps must register with the FDA.
351 vs. 361 Products
Currently, the FDA’s Center for Biologics Evaluation and Research (CBER) is responsible for regulating HCT/Ps and it has two different paths for cell therapies that it constructed to reflect what it considers to be “relative risk”. These pathways are commonly called “361” and “351” products.
Cell therapies can potentially be regulated under either pathway, as described below:
361 products that meet all the criteria outlined in 21 CFR 1271.10(a) are regulated as HCT/Ps and are not required to be licensed or approved by the FDA. These products are called “361 products,” because they are regulated under Section 361 of the Public Health Service (PHS) Act.
In contrast, if a cell therapy product does not meet all the criteria outlined in 21 CFR 1271.10(a)), then it is regulated as a “drug, device, or biological product” under the Federal Food, Drug, and Cosmetic Act (FDCA) and Section 351 of the PHS Act. These 351 products require clinical trials to demonstrate safety and efficacy in a process that is nearly identical to that what is required for pharmaceutical products to enter the marketplace.
Here at Adimarket, we sell equipment to practices that are willing and able to add PRP and stem cell therapies to their lineup. The equipment we offer is among the best, and we have helped hundreds of doctors and practices to offer PRP and stem cell therapies. However, we also provide marketing services above that as well.
Although it might see odd that we offer both marketing services, as well as equipment, but it is not so odd once you understand why. Simply offering services and having the equipment to do so does not in itself help patients to fully know that you are offering new services. It is best practice to get the word out to as many people in the area as possible.
While there are many reasons why we do this, here are the three main reasons why.
Regenerative Medicine Was Founded Not Too Long Ago
Compared to many other medical practices, such as surgery and physical therapy, regenerative medicine is still fairly new. In fact, most people do not really know that PRP and stem cell therapy even exists, let alone can be used to manage chronic pain.
The fact that not many people even know about the existence of regenerative medicine, let alone what it can be used for, means that it would be difficult to get your patients to even understand what you are offering as a service. This can be addressed with marketing. Through marketing, a practice can not only let it become known that they are offering these new services, but also explain shortly what the service entails.
Marketing Is Like Dieting
Pretty much every doctor and dietitian knows that good nutrition is vital to great health down the line. Waiting until you’re sick and deficient to discuss nutrition is not the best way to address the issue. Marketing is similar in that instance. Marketing not only can be used to keep current patients informed, but can also be used to inform new patients about what you offer. Practices that don’t market often suffer in the same way as people who don’t get good nutrition.
There’s a lot of competition
Medicine has sadly become more and more like a business in the past years. This means that even doctors and practices need to have a good business sense if they are going to continue to be able to provide the type of services that patients need and desire. Not understanding business would only make any practice fail or at least prevent them from growing.
Because of this, private practices, as well as other medical groups are forced to compete. Marketing is a big way to make sure that you get patients instead of your competition. If you are utilizing PRP and stem cell therapies as a way to generate more income, then great! However, you will still have to market those services to get the word out, as well as compete.
We at Adimarket offer these services as a way to help the field of regenerative marketing succeed. We not only help your practice start to utilize regenerative medicine, but we also help you to promote your practice in the same way. This will help your patients know that you are using these methods, and what they are, so that you can get a leg up over the competition.
Stem cells from adults were found to save the lives of leukemia patients through bone marrow transplants more than 30 years ago. Since these stem cells were able to help treat leukemia and lymphoma, many scientists tested to see if this treatment can have other beneficial uses as well, such as treating other diseases and injuries. In the 80’s and 90’s, this started the Stem Cell debate, and although that has become much calmer of a debate, we are still waiting to see the boom of medical advancements promised by stem cell researchers.
While researchers may have over-exaggerated the exact benefits that stem cell therapy may have had, we at Adimarket knows that there are many more benefits of stem cells than we currently know. We just need to give it a little more time for researchers to understand the knicks and knacks of how stem cells interact with the human body.
What Are The Different Types of Stem Cells
The first while after stem cell research began, most of the time was spent learning about the two types of stem cells. These types are Adult, and Embryonic. Adult stem cells are used for bone marrow transplants and a few other treatments. Embryonic stem cells have proved to be too impractical to be useful.
A few decades later, in 2006, researchers in japan found a new way of using adult stem cells. They learned how to basically reprogram adult stem cells to act more like embryonic stem cells, and can become whatever cell type is needed at the time. These new cells were called Pluripotent, or iPS, stem cells.
While these cells were, in practice, viable, they did not come without complications. For instance, the new iPS cells became prone to mutation over time, leading to cancer in some instances.
Making The Research More Targeted
While the problems became a setback for some, it actually helped us to understand stem cells in the long term. Today, the focus of stem cell research is more about targeted therapies mainly used to help tissue damage, and this make sense.
Since cell reprogramming is no longer used as a method, stem cells taken from a tissue can only be used to create that same tissue. For instance, stem cells taken from a joint can only be used to make the tissue that the stem cells came from. This limits what stem cells can currently do at the present time. However, we believe that these limits are not permanent, and researchers will eventually find new and exciting ways to utilize stem cells.
Until then, Adimarket is happy to provide the equipment necessary to allow practices to utilize Platelet Rich Plasma and Stem Cell therapies. We hope that our equipment can be used to offer more treatment options for patients who are suffering from injuries and arthritis.
PRP and stem cell therapies seem to have a pretty bright future ahead of them. If you are a doctor or own a practice, you can be a part of this future by purchasing our equipment. If you have any questions for us, or want to know more, you can visit our website.
Hair loss is very common, with tens of millions, if not hundreds of millions of people all over the world suffering from it. Hundreds of thousands of people decide to utilize hair restoration therapy, as well as other procedures in order to try to get at least some of their former hair back. Although some are effective, most of the time, the treatments only move already existing hair from one place to another. However, with Stem Cell therapy, we try to help new hair grow by helping the follicles to regenerate.
Adimarket helps, alongside a few other companies, to help provide new and reliable uses for PRP and stem cell therapies. We provide the equipment and other services so that doctors and practices will be able to provide these services to their patients.
There’s a Lot of Promise
While the main people talking about PRP and stem cell therapies are smaller companies like us, many other people are also discussing and seeing potential in these therapies. These include doctors, and practices, such as a doctor from Miami known as Lazaro M Garcia Md. This doctor already utilized PRP and stem cell therapy for people who suffer from hair loss, and is currently conducting a study that is supported by the National Institutes of Health.
In order to participate in the study, patients pay a small fee, which changes based on what part of the study they are in. Afterwards, the receive 2 injections of PRP and stem cells that are made from their own body, over 3 months.
Dr. Garcia is utilizing the body’s own growth factors in order to increase the amount of blood and nutrients to the otherwise dead hair follicles. This makes the dead follicles more lively and allows them to create new hair growth.
The way to make Platelet Rich Plasma is to is to use the patients own blood, which can come from either bone marrow, or other sources of fat. They go into a centrifuge, which concentrates the composition, and then allows them to be injected into the treatment site. While it is an otherwise simple procedure, some training in still necessary to ensure that it is done safely.
We Provide Equipment
We at Adimarket do not perform stem cell and PRP therapies, but we do offer the equipment so that doctors and practices can do so themselves. These include amniotic tissue, stem cell and PRP kits, centrifuge devices, and many more. Practices and doctors can order directly from us.
It is good to note that not all PRP systems are equal. The system that we have uses the closed tabletop system that is able to process the PRP in under 10 minutes. For more information, contact us or visit our website.
Hair loss is a serious problem with many people suffering from it. Now, thanks for PRP and stem cell therapies, we no longer only have to rely on hair replacement surgery to help patients. PRP and stem cell therapies may be the best therapy out there for both your patients, as well as your practice.
Platelet Rich Plasma is a very important material, as it is be vital in treating bone and joint deterioration. Many patients have tried using PRP therapy as a treatment as an alternative to surgery and other procedures that can be invasive. This therapy relies on extracting platelets and other cell types, such as growth factors, from the patients blood, and concentrating them.
Many conditions have been treated by using this therapy, such as knees, hips, spines, shoulders, and pretty much any part of your body that has a joint or connective tissue.
What The Procedure Is Like
The procedure involves an injection of PRP at the point where treatment point. During the day, when the patient comes in, they wait while the PRP is processed. When it is done, the skin of the treatment site will be cleaned and sanitized much like a normal injection, such as a flu shot. Then, using ultrasound or fluoroscopy, the needed will be guided to the treatment area.
It generally takes less than 15 minutes for this procedure to take place. Then the physician or doctor in question will provide the patient with a list of things they should or should not do, such as not taking NSAIDs, such as Advil or Tylenol. If needed, other non-NSAID pain relievers may be prescribed.
What Should You Expect?
PRP brings platelets and growth factors in a concentrated form to the treatment area, as a result, your body reacts in a way that ultimately increases tissue repair. This bodily process will occur for weeks, even after one application of PRP.
After about a month to 6 weeks, most patterns will start to feel their pain decrease, and their mobility get better. This can occur for up to half a year. While most patients are satisfied with just one treatment, many will have more than one, depending on the severity of the defect. As a result of how well this treatment works many patients are able to avoid surgery altogether with just a couple of shots.