Functional characterization of highly adherent CD34+ keratinocytes isolated from human skin.

Compared to murine models, data on cells responsible for the homeostasis of human epidermis are scarce and often contradictory. Given the conflicting results and the availability of clinical grade protocols to purify CD34 cells from a given tissue, we pursued to phenotypically characterize human epidermal CD34+ population. After magnetic separation of whole skin CD34+ and CD34- cell fractions and selection for cells highly adherent to extracellular matrix, both CD34+/- fractions retained the ability to form a stratified epidermis in organotypic cultures and presented similar in vitro migratory phenotypes. However CD34- cells showed higher clonogenic potential and in vitro proliferative capacity. These results indicated that CD34- cell fraction contains stem/early progenitor cells, while CD34+ cells might be a transit-amplifying precursor for hair follicle (HF) sheath cells. The ability to isolate living cells using differential cell adhesion and surface markers provides an opportunity to study cells from different morphological regions of the HF.