Does erythropoietin modulate human hair follicle melanocyte activities in situ?

Erythropoietin (EPO) is now appreciated for not only drive erythopoiesis, but also to exert additional functions. Since we had previously shown that human hair follicles (HFs) are both an extra-renal source and an extra-medullary target of EPO, we have now studied whether one such function is the regulation of HF pigmentation. Human anagen VI HFs were treated with EPO (100 IU/ml) in serum-free organ culture. Unexpectedly, we noticed greatly divergent pigmentary effects of EPO, since both up- and down-regulation of HF melanin content and tyrosinase activity in situ was seen in HF derived from different individuals. These divergent effects could not be attributed to differences in skin regions, the total HF melanocyte number or specific traits of individual HF donors. Our pilot study provides first evidence suggesting that EPO may modulate normal human melanocyte functions under physiologically relevant conditions in situ.