Role of Platelet-rich Plasma in the Management of Androgenetic Alopecia

Androgenetic alopecia (AGA), a hereditary and androgen-dependent progressive thinning of the scalp hair in a defined pattern, is a common dermatological disorder affecting more in men and occasionally in women, with significant negative impact on their social and psychological well being. It commonly begins by 20 years of age and affects nearly 50% of men by the age of 50 years.[1] Its etiopathogenesis is mainly androgen-dependent and modulated via the testosterone metabolite dihydrotestosterone, the expression of hair follicle-related androgen receptor; and genetic factors also have been implicated.[2]

Hair follicle has a very complex biologic structure and growth of the hair process is regulated by specific growth cycles. The mature follicle undergoes successive transformation from anagen (active hair shaft production) to catagen (apoptosis-driven regression) to telogen (resting phase with the involution of hair follicle).[3] Role of apoptosis (by the pathway of caspases cascade) in determining the passage from anagen to catagen is well known. Many growth factors play a fundamental role in the life-long cyclic transformation of the hair follicle functioning as biologic switches that are turned on and off during the different phases, controlling the active phase and promoting apoptosis to induce catagen and telogen.[4] The main growth factors involved in the establishment of hair follicle are vascular endothelial growth factor (VEGF), epidermal growth factor (EGF), insulin 1-like growth factor, and fibroblast growth factor (FGF). Platelets release large amounts of platelet-derived growth factor (PDGFaa, PDGFbb, and PDGFab), transforming growth factor beta (TGFβ1 and β2), EGF, and VEGF.[5]

Concerns about the efficacy and safety during the requisite long-term treatment of AGA with the FDA-approved oral finasteride and topical minoxidil therapy prompted the use of a newer modality of platelet-rich plasma (PRP) which has shown beneficial effect. PRP has been used in the past to prevent infection and speed up the wound healing process by reducing bleeding/swelling after surgery by the plastic-, dental-, general-, neuro-, and orthopedic surgeons. PRP, an autologous concentration of human platelets in a small volume of plasma has a higher platelet concentration (4-7 times) above the baseline. It is obtained from the patient’s own blood after processing in an automated centrifuge and it is injected subcutaneously into the area of alopecia.[6] Ubel in 2005 studied 23 patients of hair transplant after enriching the hair root grafts with PRP and without PRP. Two areas (2.5 cm2) each were marked on the scalp and planted with 20 grafts/cm2. After 1 year, the area implanted with the PRP-enriched grafts demonstrated a yield of 18.7 FU/cm2 versus 16.4 FU/cm2 of that without PRP, an increase in follicular density of 15.7%.[7] Li et al.[7] performed an in vivo study, where mice received subcutaneous injections of PRP, and their results were compared with control mice. Activated PRP increased the proliferation of dermal papilla (DP) cells and stimulated extracellular signal regulated kinase and Akt signaling. Fibroblast growth factors 7 (FGF-7) and beta-catenin, both potent stimuli of hair growth, where upregulated in the DP cells. The injection of mice with PRP induced faster telogen-to-anagen transition than that was seen in control mice.[8]

The beneficial effects of PRP in AGA can thus be attributed to various platelet-derived growth factors causing improvement in the function of hair follicle and promotion of hair growth. It is safe, cheap, and non-allergic and it appears to be a useful adjuvant in the management of AGA.

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