hTERT-immortalized Neonatal Melanocytes – an Advanced In Vitro Cell-based Model for Pigmentation and Toxicity Studies

Pigmentation involves two main steps. First, melanocytes perform a myriad 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 underlying tissues from damaging UV radiation. This process of pigmentation involves a complex interplay between genetic, endocrine, and environmental factors. Primary cells offer one model system to study pigmentation and dermal agents that may disrupt the melanogenesis; however, they are hindered somewhat by donor-to-donor variability and limited lifespan. 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 the 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. The inhibitors hydroquinone and kojic acid showed dose-dependent decreases in melanin content and the stimulators stem cell factor and latanoprost showed a muted response. In summary, immortalized melanocytes provided a versatile in vitro cell model for the study of skin toxicology and melanogenesis regulation.