Clinically applicable transplantation procedure of dermal papilla cells for hair follicle regeneration.

Dermal papilla cells (DPCs) interact with epithelial stem cells and induce hair folliculogenesis. Cell-based therapies using expanded DPCs for hair regeneration have been unsuccessful in humans. Two major challenges remain: first, expanded DPCs obtained from adult hair follicles have functional limitations; second, a clinically applicable method is needed for transplanting DPCs. This study aimed to identify an efficient, minimally invasive and economical DPC transplantation procedure for use in clinical settings. Five clinically applicable transplantation procedures were tested, termed the Pinhole, Laser, Slit, Non-vascularized sandwich (NVS) and Hemi-vascularized sandwich (HVS) methods. Labelled rat dermal papilla tissue was transplanted into rat sole skin, and hair follicle regeneration was evaluated histologically. Regenerated follicles and labelled DPCs were detected for all methods, although some follicles showed abnormal growth, i.e. a cystic or inverted appearance. The HVS method, pioneered here, resulted in significantly larger number of regenerated follicles that were more mature and regular than those observed using the other methods. Moreover, hair growth was detected after expanded adult-derived DPC transplantation using the HVS method. These results suggest that direct contact of epithelial and dermal components and better vascularization/oxygenation of the recipient site are critical for hair regeneration in cell-based therapies.