Effect of mesenchymal cells on human hair growth and death

−Animals have typically been used in efficacy tests, but there are a number of dissimilarities between humans and animals. To overcome the problems associated with animal testing, a model which is reproduced in vitro with longterm culture with cell growth with in vivo activity must be developed. We made a gel-type dermal equivalent (DE) that contained dermal papilla cells (DPCs) or dermal sheath cells (DSCs) isolated from human hair bulbs in order to mimic human scalp tissue. Hair follicles were organ-cultured on DE containing DPCs or DSCs. The DE used for organ culture was a reconstructed 3-dimensional contraction of collagen gel, and the cell density of the DE did not affect the increase in hair length. We tested the effects of cell types in DE on increases in hair length, and the results showed a large increase in hair length and long-term viability in the air-liquid interface culture on DE containing DSCs. We compared the submerged culture with the hair air-liquid interface culture on DE using immunohistochemical staining, and found that the hair follicles that were air-liquid interface cultured on DE maintained the growth phase (anagen) for a longer period of time than the hair follicles that were submerged. Since the hair follicles were cultured under an air-liquid interface condition, the increase in hair length was a reflection of the epithelial cell growth that resulted from the improved oxygen supply and paracrine factors secreted from hair origin cells.