INTRODUCTION
Alopecia is characterized by the aberrant absence or loss of hair. The condition is intricately linked to the complex physiology of the hair follicle (HF), where numerous stem cell populations reside and participate in cycles of regeneration.1 In non-cicatricial alopecia (NCA), the HF stem cells are preserved and there is potential for regrowth whereas they are irreversibly destroyed in cicatricial alopecia (CA).2 Leveraging the HF's regenerative capacity to stimulate hair growth holds promising therapeutic potential.
In recent years, platelet-rich plasma (PRP) has garnered attention for its role in hair restoration (HR). PRP is an autologous preparation containing concentrated platelets comprising over 20 growth factors (GFs) and cytokines.2 Platelet GFs act on HF stem cells to stimulate new follicles, prolong the survival of dermal papilla cells, and promote vascularization.3 The efficacy of PRP has been evaluated across various forms of alopecia, presenting an innovative therapy for patients experiencing limited improvement with conventional hair-loss treatments.
Non-cicatricial Alopecia
Androgenic Alopecia
Androgenic alopecia (AGA) is a form of NCA, characterized by a progressively decreased ratio of terminal hairs to vellus hairs. The literature supporting the efficacy of PRP in HR is most established for this form of hair loss (Table 1),4-7 although the methodology of studies varies widely. In a recent randomized control trial (RCT) involving 72 participants with AGA, PRP treatment demonstrated a 91.7% reduction in hair pull rates after 12 weeks, significantly outperforming topical minoxidil, which achieved a 69.4% reduction.6 In an 80-patient randomized, double-blinded placebo-controlled trial, concurrent treatment with PRP and topical minoxidil yielded the highest improvement in hair density and patient satisfaction compared to each treatment in isolation, though PRP monotherapy demonstrated superior efficacy when compared to minoxidil monotherapy.7 A meta-analysis assessing 11 RCTs evaluating the use of PRP for treatment of AGA reported a significantly increased number of hair follicles, hair thickness, and hair density compared to placebo.8 Similar results have been reported in a meta-analysis evaluating activated-PRP.9 There is less rigorous data supporting the use of PRP in pediatric AGA patients, though a case series involving 4 pediatric patients treated with PRP found significant improvement of alopecia stabilization and regrowth with the use of global photographic assessments.10
Alopecia Areata
Alopecia area (AA) is the most common type of inflammatory hair loss, characterized by an unpredictable course of relapse and remission, lacking curative or preventative treatments. In a clinical trial randomizing 90 AA patients to 3-month treatment with topical minoxidil 5% twice daily, monthly PRP injections, or placebo, PRP resulted in earlier hair regrowth and reduction in short vellus and dystrophic hair compared to the minoxidil and control groups (P<0.05).11 A randomized, double-blind, placebo and active-controlled parallel-group study compared the efficacy of 3 intralesional injections of aPRP, triamcinolone acetonide, and placebo in 45 AA patients.12 PRP significantly increased hair regrowth and decreased hair dystrophy and associated burning/itching sensations when compared with triamcinolone and placebo. 60% of patients treated with PRP achieved complete remission 9 months after the final treatment cycle. The Ki-67 level, a marker for cell proliferation, was significantly higher with PRP treatment.12 Altogether, this data suggests that PRP may be superior to traditional alopecia treatments, particularly given the evidence of remission.
Cicatricial Alopecia
Data regarding the efficacy of PRP for the treatment of CA is largely anecdotal. A systematic review assessing 19 patients with CA reported that PRP was efficacious at alleviating disease progression in 100% of studies, though only case reports and small case series were evaluated.2 After three PRP sessions, a patient with central centrifugal CA and concomitant AGA achieved a normal temporal hairline follicular density and over 50% increased overall hair density.13 Another case report demonstrated stabilization of hair loss in a patient with FFA after 5 sessions of PRP in conjunction with standard therapies.14 PRP has also demonstrated efficacy in a handful of lichen planopilaris cases following 3-4 sessions,13,15,16 with one study noting complete regression of itching15 and another reporting no improvement in eyebrow hair density.16 The cumulative data supporting the use of PRP over standard treatment for CA is limited.
