Towards expansion of human hair follicle stem cells in vitro

Objectives: Multipotential human hair follicle stem cells can differentiate into various cell lineages and thus are investigated here as potential autologous sources for regenerative medicine. Towards this end, we have attempted to expand these cells, directly isolated from minimal amounts of hair follicle explants, to numbers more suitable for stem-cell therapy. Materials and methods: Two types of human follicle stem cells, commercially available and directly isolated, were cultured using an in-house developed medium. The latter was obtained from bulge areas of hair follicles by mechanical and enzymatic dissociation, and was magnetically enriched for its CD200+ fraction. Isolated cells were cultured for up to 4 weeks, on different supports: blank polystyrene, laminin- and MatrigelTM-coated surfaces. Results: Two-fold expansion was found, highlighting the slow-cycling nature of these cells. Flow cytometry characterization revealed: magnetic enrichment increased the proportion of CD200+ cells from initially 43.3% (CD200+, CD34: 25.8%; CD200+, CD34+: 17.5%) to 78.2% (CD200+, CD34: 41.5%; CD200+, CD34+: 36.7%). Enriched cells seemed to have retained and passed on their morphological and molecular phenotypes to their progeny, as isolated CD200+ presenting cells expanded in our medium to a population with 80% of cells being CD200+: 51.5% (CD200+, CD34-) and 29.6% (CD200+, CD34+). Conclusions: This study demonstrates the possibility of culturing human hair follicle stem cells without causing any significant changes to phenotypes of the cells.