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 distinguish between three distinct types of melanocytes in human interfollicular epidermis: (1) cKitCD90, (2) cKitCD90, and (3) cKitCD90. Importantly, we identify the Kit tyrosine kinase receptor (cKit) as a marker expressed specifically in mature, melanin-producing melanocytes. Thus, both cKitCD90 and cKitCD90 cells represent polydendritic, pigmented mature melanocytes, whereas cKitCD90 cells display bipolar, non-dendritic morphology with reduced melanin content. Additionally, using tissue-engineered pigmented dermo-epidermal skin substitutes (melDESSs), we reveal that the cKit expression also plays an important role during melanogenesis in melDESS in vivo. Interestingly, cKitCD90 cells lack the expression of markers such as HMB45, TYR, and TRP1 in vitro and in vivo. However, they co-express neural-crest progenitor markers and demonstrate multilineage differentiation potential in vitro. Hence, we propose that cKitCD90 cells constitute the precursor melanocyte reservoir in human interfollicular epidermis.