Characterization of a melanocyte progenitor population in human interfollicular epidermis

It is still unknown whether the human interfollicular epidermis harbors a reservoir of melanocyte precursor cells. Here, we clearly distinguished between three distinct types of melanocytes in human interfollicular epidermis: (1) cKit+CD90-, (2) cKit+CD90+, and (3) cKit-CD90+. Importantly, we identified the Kit tyrosine kinase receptor (cKit) as a marker expressed specifically in mature, melanin-producing melanocytes. Thus, both cKit+CD90- and cKit+CD90+ cells represented polydendritic, pigmented mature melanocytes, whereas cKit-CD90+ cells displayed bipolar, non-dendritic morphology with reduced melanin content.Additionally, using tissue-engineered pigmented dermo-epidermal skin substitutes (melDESS), we revealed that the expression of cKit in human melanocytes is critical for the pigmentation of melDESS. Interestingly, cKit-CD90+ cells lacked the expression of markers such as HMB45, TYR, and TRP1 in vitro and in vivo. However, they co-expressed neural-crest progenitor markers and demonstrated multilineage differentiation potential in vitro.Hence, we propose that cKit-CD90+ cells constitute the precursor melanocyte reservoir in human interfollicular epidermis.