Development of in vitro hair pigmentation model using hair follicle organoids.

Hair color is formed through a series of processes such as melanin synthesis and storage in melanosomes, transfer from melanocytes, and reception by hair matrix cells in the hair bulb. Because gray hair is caused by the deterioration of a single or multiple of these processes, understanding the mechanisms responsible for these processes is crucial for developing therapeutic strategies. Recently, a robust approach for preparing hair follicle organoids (HFOs) was reported, in which hair follicle morphogenesis, including hair shaft elongation, was tracked in vitro. Here, we investigated whether HFOs could be used to assess genes involved in hair pigmentation. HFOs generated hair follicles and pigmented shafts during the in vitro culturing process. The knockdown of genes associated with melanosome production (Bcl2 and Mitf) and transport (MyoX, PAR2, and Rab11b) significantly increased the number of gray hairs in HFOs. This organoid model may be a promising platform for better understanding hair pigmentation and screening drugs for gray hair.