Preparation of hair follicle germs using centrifugal forces for hair regenerative medicine

Hair regenerative medicine presents a potential approach to treat hair loss. Mesenchymal and epithelial cells may be transplanted to regenerate de novo hair follicles, as epithelial–mesenchymal interactions are crucial for hair follicle morphogenesis. However, transplanting a mixture of the two cell types does not lead to efficient hair follicle formation, and engineering tissue grafts with these cell types before transplantation is necessary. Hair follicle germ-like aggregates (HFGs), which are found during hair follicle development, induced highly efficient de novo hair follicle formation. Although this is a sophisticated approach of mimicking in vivo hair follicle morphogenesis, further studies are required owing to its laborious and time-consuming nature. This study proposed a straightforward approach to prepare HFGs using centrifugal forces. We fabricated a centrifugal device consisting of tube tips that facilitate cell transplantation as a high cell dense aggregate, in contrast to conventional cell suspension injections. To prepare HFGs, mouse embryonic epithelial and mesenchymal cells were packed into the device using a two-step centrifugation method. Immediately after preparation, HFGs were directly injected into the back skin of nude mice, resulting in de novo hair follicle formation. This centrifugal approach significantly improved hair follicle regeneration efficiency compared with that of conventional cell suspension injection. Unlike previous studies, this approach does not require several days of culture, which could potentially facilitate rapid and cost-effective hair regenerative medicine.