Nonviral in Situ Green Fluorescent Protein Labeling and Culture of Primary, Adult Human Hair Follicle Epithelial Progenitor Cells

The study demonstrated that hair follicle stem cells, marked by nestin-driven GFP, could differentiate into Schwann cells and support the repair of severed peripheral nerves in mice. These pluripotent stem cells, positive for CD34 and negative for keratin 15, were shown to enhance nerve regeneration and restore function when implanted into the gap of a severed sciatic nerve. The successful recovery of nerve function was evidenced by the restoration of normal walking ability in mice, as measured by muscle contraction and walking print analysis. This suggested that hair follicle stem cells could serve as an accessible and autologous source for regenerative medicine.

The study investigated the expression of Ber‐EP4 antigen in human terminal hair follicles at different stages of the hair cycle. Ber‐EP4 immunoreactivity was observed in the lower part of the epithelial strand of late catagen hair follicles, the secondary hair germ of telogen hair follicles, and the matrix of early anagen hair follicles, but not in mature anagen hair follicles. In contrast, keratin 15 expression was found in specific parts of anagen, catagen, and telogen hair follicles, while keratin 19 expression overlapped with keratin 15 but was less extensive. The findings suggested that Ber‐EP4 marked the secondary hair germ and a related cell population, distinct from the stem cell population indicated by keratin 15 or keratin 19 expression.

The study demonstrated that nestin, an intermediate filament protein, was expressed in progenitor cells of the hair follicle outer-root sheath, particularly during different phases of the hair cycle. Using nestin-GFP transgenic mice, researchers observed that nestin-expressing cells were located in the hair follicle bulge during the telogen and early anagen phases, and in both the bulge and upper outer-root sheath during mid- and late anagen phases. Immunohistochemical staining confirmed the colocalization of nestin with other proteins in these areas, supporting the conclusion that nestin-expressing cells in the hair follicle bulge are progenitors of the outer-root sheath. The study suggested a potential relationship between neural stem cells and hair follicle stem cells due to the expression of nestin in both cell types.