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Molecular mechanism of male pattern alopecia

Male pattern alopecia is associated with a genetic predisposition and generally begins after adolescence following a specific pattern. Although it is colloquially called hair loss, male pattern alopecia is actually hair follicle miniaturization that occurs because of a shortened growth period and extended resting period. We have developed an in vitro hair growth model using dermal papilla cells and keratinocytes and investigated the effects of male hormones on hair growth. We have found paracrine mechanisms that operate through dermal papilla cells for hair growth. The secretion of IGF-1 (insulin-like growth factor-1) from dermal papilla cells was shown to stimulate facial hair growth, while the secretion of TGF-β (transforming growth factor β) is associated with male pattern baldness (Figure). It is known that oral ingestion of type II 5α-reductase inhibitors are effective for treating male pattern baldness, but we have also found that narrow-band LED can induce hair growth. Additionally, we have also shown that during the resting phase, dermal papilla cells secrete leptin, which induces transition to the growth phase and are investigating the clinical application of this effect.

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