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) cKit+CD90–, (2) cKit+CD90+, and (3) cKit−CD90+. Importantly, we identify the Kit tyrosine kinase receptor (cKit) as a marker expressed specifically in mature, melanin-producing melanocytes. Thus, both cKit+CD90– and cKit+CD90+ cells represent polydendritic, pigmented mature melanocytes, whereas cKit−CD90+ 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, cKit−CD90+ 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 cKit−CD90+ cells constitute the precursor melanocyte reservoir in human interfollicular epidermis. [Display omitted] •Human interfollicular epidermis harbors a reservoir of melanocyte precursor cells•Detection of melanocytes in human epidermis: cKit+CD90–, cKit+CD90+, and cKit−CD90+•Kit tyrosine kinase receptor (cKit) regulates melanin synthesis in melanocytes•Analysis of neural-crest markers and multilineage differentiation of cKit−CD90 Michalak-Mićka et al. investigate if human interfollicular epidermis harbors a reservoir of melanocyte precursor cells. They detect and characterize two polydendritic, pigmented mature melanocyte populations, cKit+CD90– and cKit+CD90+, as well as a bipolar, precursor population, cKit−CD90+, showing neural-crest characteristics and multilineage differentiation potential in vitro