Development of hTERT-Immortalized Neonatal Melanocytes for Toxicity Studies and Melanogenesis Regulation

Melanocytes are the cells that produce melanin and they are involved in the process of epidermal pigmentation, which involves two main steps. First, melanocytes perform a variety of complex biochemical and physiological steps to produce, package, and exocytose melanin-containing melanosomes. Secondly, the melanosomes are taken up by neighboring keratinocytes where the stored melanin protects the underlying tissues from damaging UV radiation.  In additional to playing an integral role in skin pigmentation, the dysfunction of melanocytes is associated with skin disease and skin cancer.  Therefore, it is important to have a reliable model system to study melanocytes and associated processes. Primary cells offer one model system to study pigmentation and dermal agents that may disrupt the melanogenesis; however, they are limited by lifespan, and donor-to-donor variability. Here, we created an immortalized melanocyte cell model—hTERT neonatal melanocytes—by retroviral transduction of human telomerase (hTERT) into primary cells. In addition to enhanced longevity (up to 35 doublings), physiologic marker expression (tyrosinase positive, fibroblast marker negative), and ability to create melanosomes in 3D organotypic co-cultures, the cell line also showed expected levels of responses to several stimulators and inhibitors of melanogenesis. In summary, immortalized melanocytes provide a versatile in vitro cell model for the study of skin toxicology and melanogenesis regulation.