Akkermansia muciniphila promotes testosterone-mediated hair growth inhibition in mice.

The beneficial effects of Akkermansia muciniphila ( Akk ) on gut health and inflammation reduction have been demonstrated; however, scientific evidence of hair growth enhancement by Akk has not been reported. Therefore, this study was undertaken to investigate the effect of Akk on improving testosterone-mediated hair growth inhibition. Hair growth inhibition was induced through subcutaneous injection of testosterone into the shaved dorsal skin of C57BL/6 male mice. Live and pasteurized Akk were orally administered at a concentration of 1 × 10 8 colony-forming unit. After 5 weeks, hair length and skin tissues were analyzed. The live and pasteurized Akk significantly stimulated hair growth, countering the inhibitory effect of testosterone compared to the testosterone-alone group. Hematoxylin and eosin staining revealed a significant increase in hair follicle size in the Akk -treated group. An increase in β-catenin levels, which are associated with hair growth and cell cycle progression, was also observed. Moreover, the Akk -treated group exhibited increased levels of fibroblast growth factors, including Fgf7 , Igf1 , Fgf7 , Fgf10 , and Fgf21 . However, no significant difference was observed between the live and pasteurized Akk groups. These results underscore the potential of live and pasteurized Akk in improving testosterone-mediated hair growth inhibition.