878 Individual variation in balance between platelet-secreted growth factors causing contradictory effects on hair follicle could potentially impact response to PRP therapy in patients with scalp hair loss
J. Mohammed, M. Abedin, R. Farah, A. Wipf, M. Hordinsky
Platelets contain α-granules that are reservoirs of critical growth factors (GFs) regulating cellular proliferation, migration, differentiation and angiogenesis. Due to the ability of platelets to secrete GFs that play critical roles in the natural healing process, platelet-rich plasma (PRP) prepared from the blood is injected to sites of injury to deliver high concentrations of autologous GFs. Several studies published over the past few years have evaluated the effectiveness of PRP to treat hair loss disorders such as Androgenetic Alopecia. It is widely believed that GFs released from platelets upon PRP injection act on skin and hair follicle stem cells thereby promoting neovascularization and most likely, follicle differentiation. However, despite several promising results reported from clinical trials on the therapeutic potential of PRP, the response has been inconsistent and in some cases conflicting. Its likely that patient response to PRP depends on the balance between platelet-secreted GFs known to promote (PDGF-A, PDGF-B, VEGF, FGFb, EGF, IGF and HGF) versus inhibit hair follicle growth (TGFβ1). As PRP injection results in 300% to 700% enrichment of platelets secreting large quantities of GFs that can have contradictory roles in hair follicle differentiation, we analyzed platelet expression of GFs in PRP samples prepared from patient volunteers by quantitative PCR. Expression of TGFβ1 was highest followed by PDGF-A and PDGF-B while low to undetectable transcript levels were noticed for IGF and HGF. Variability in platelet expression between patients was highest for TGFβ1, PDGF-A and PDGF-B and lowest for VEGF. Consistently, we detected high TGFβ1 levels in PRP compared to other growth factors and its concentration relative to PDGF-BB in PRP varied highly between patients. Thus, balance between platelet-secreted TGFβ1 and other GFs in PRP that promote hair follicle differentiation could determine patient response to PRP therapy.