Q: How does PRP therapy for hair loss work? — B.T., Upper West Side, NYC

A: In theory, platelet rich plasma (PRP) stimulates the growth of hair follicles by reversing the hair miniaturization (thinning hair) process seen in androgenic alopecia (common baldness).

While it is not exactly known how PRP reverses miniaturization, researchers do have a few ideas. First, PRP may counteract miniaturization by prolonging the growth (anagen) phase of hair follicle. ((Z. J. Li, H.-I. Choi, D.-K. Choi et al., “Autologous platelet-rich plasma: a potential therapeutic tool for promoting hair growth.” Dermatologic Surgery, vol. 38, no. 7, part 11, pp. 1040–1046, 2012.)) Second, PRP has been observed to increase the number of stem cells in hair follicles. This is known to help protect a hair follicle from apoptosis, a natural process of programmed cell death. Researchers think that this anti-apoptotic effect could stimulate new hair growth. ((Takikawa M, Nakamura S, Nakamura S, et al. “Enhanced effect of platelet-rich plasma containing a new carrier on hair growth.” Dermatol Surg. 2011 Dec;37(12):1721-9.)) Finally, PRP treatment has been observed to promote growth of new blood vessels around treated hair follicles. Researchers have suggested that this could also stimulate new hair growth. ((L. Mecklenburg, D. J. Tobin, S.Muller-Rover, et al. “Active hair growth (anagen) is associated with angiogenesis.” Journal of Investigative Dermatology, vol. 114, no. 5, pp. 909–916, 2000.))

In sum, a number of factors may come into play to effect new hair growth during treatment with platelet rich plasma. Research is ongoing to further clarify the specific mechanisms involved.

• Read about the latest research into PRP therapy for hair loss
• Read more in our section on Platelet Rich Plasma