The Investigation of Hair Follicle Regeneration Utilizing Human Interfollicular Dermal and Epidermal Stem Cells

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Dermal papilla cells (DPCs) in the mammalian hair follicles have been shown to have an ability to induce and develop hair follicles. It is theoretically possible to regenerate human hair by expanding DPCs and transplanting them in the bald skin.We performed a microarray analysis and RT-PCR comparing human dermal papilla cells and dermal fibroblasts both obtained from adult scalp skin, in order to elucidate the genetic factors responsible for hair induction in tissue engineered hair follicles. In the microarray analysis we found that TGFs gene was significantly upregulated compared to dermal fibroblasts and that it was one of the candidate genes involving in hair regeneration. RT-PCR analysis revealed significant and sustained upregulation of TGFs mRNA in cultured dermal papilla cells compared to dermal fibroblasts. Furthermore, we found soluble factors secreted by keratinocytes significantly upregulated TGF beta-2 mRNA.Immunohistochemistry (IHC) of human scalp skin and hair follicles for the biomarkers previously reported as specific for IFKC was performed. The expression of the biomarkers in cultured keratinocytes was also investigated by FACS analysis and immunostaining. Keratin 15 (K15) was expressed in the bulge area in IHC. CD34 was expressed in the lower area, which includes the sub-bulge area and outer root sheath (ORS). CD271 (p75 neurotrophin receptor) was expressed in the lower ORS that was negative for K15. All of them were expressed only in the outermost layer adhering to the basement membrane.We examined reproducibility of two of in vivo models for trichogenesis previously reported, including 'chamber models', grafting cultured human DPCs into silicone chambers on nude mice, and 'sandwich models', implanting cultured human DPCs with rat sole skin under the skin of nude mice. 'Sandwich models' were more useful than 'chamber models' and other in vivo models for testing the inductive viability of human DPCs in terms of reproducibility.