Could a hormone that plays a critical role in red blood cell production also play a critical role in hair follicle production? According to a 2010 research report published in the Journal of Dermatological Science, this may be the case.
Erythropoietin Implicated In Hair Growth Regulation
The hormone in question is called Erythropoietin (EPO). It is produced in the kidneys in order to regulate red blood cell production. Recent studies have shown that EPO is also produced in a structure that surrounds and protects a hair follicle, the outer root sheath (ORS). Moreover, other studies have found that the EOP secreted by the ORS seems to target dermal papilla (DP) cells. DP cells play a critical role in regulating hair growth.
Because of these results, researchers have speculated that EPO may affect hair growth by acting on DP cells, but no direct evidence for this had ever been found – until now.
Evidence That EPO Affects Hair Growth in Vitro (Cell Cultures)
Strong evidence of EPO’s direct involvement in hair growth would be the discovery of EPO receptor sites (EPOR) on DP cells and a clear mechanism of how EPO affects changes in a DP cell (called cell signaling); this is exactly what researchers in the Republic of Korea ((Kang BM, Shin SH, Kwack MH, Shin H, Oh JW, Kim J, Moon C, Moon C, Kim JC, Kim MK, Sung YK. Erythropoietin promotes hair shaft growth in cultured human hair follicles and modulates hair growth in mice. J Dermatol Sci. 2010 Aug;59(2):86-90. doi: 10.1016/j.jdermsci.2010.04.015. Epub 2010 May 19.)) have found. Not only did they find direct evidence of EPO receptive sites but they also discovered the critical cell signaling mechanism: phosphorylated EPOR signaling pathway mediators.
In addition to discovering the signaling mechanism, they also showed using cell cultures that EPO causes both dermal papilla to proliferate and hair shafts of human hair follicles to elongate.
While the effects of EPO on DP and hair follicles were compelling, they only occurred in vitro (in cell cultures outside the body) and it is known that cells cultured on a flat surface behave significantly differently than cells that exist in situ, inside the organism (see Higgins and Christiano, Regenerative Medicine And Hair Loss: How Hair Follicle Culture Has Advanced Our Understanding Of Treatment Options For Androgenetic Alopecia).
Evidence That EPO Affects Hair Growth In Situ (In The Body)
In order to better answer the questions of whether and how EPO might directly affect hair growth in situ, the Korean researchers implanted EPO treated DP cells into mice and found that these treated cells not only moved hair follicles from their resting (telogen) phase into an active hair growth (anagen) phase but also prolonged a follicle’s active growth phase.
This is a significant finding since one of the mechanisms of male pattern baldness is DHT susceptible hair follicles entering into progressively longer periods of a telogen (resting) phase relative to an anagen (hair growth) phase. EPO, having the opposite effect on hair follicles, opens the door to treating this type of hair loss with existing EPO analogs and/or developing new erythropoietin biopharmaceuticals.
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