Cells of the Skin: Keratinocytes and Melanocytes

The skin has three layers, the epidermis (outermost), the dermis (middle), and the hypodermis (the innermost). The epidermis is largely composed of keratinocytes, which form a barrier against the external environment and play a role in wound repair. Melanocytes are another common cell type found in the skin. Melanocytes are the pigmented cells of the skin and are found in the basal layer of the epidermis. They produce the pigment melanin, which gives the skin color. Melanocytes are also the cell of origin for melanoma, which is most commonly caused by exposure to UV radiation.

Recent Studies Using Lifeline® Keratinocytes and Melanocytes

MicroRNAs (miRNAs) are small noncoding RNAs that are becoming well recognized for their roles in cancer. In a 2015 study, Sun et al. set out to discover the role of miR-1280 in melanoma. They first established that miR-1280 was downregulated in melanoma patient samples, as well as in melanoma cell lines. To begin to understand the consequences of miR-1280 downregulation, the authors identified target mRNAs using Lifeline® normal human melanocytes and confirmed Src as a miR-1280 target.

To validate miR-1280 regulation of Src, the researchers overexpressed miR-1280 in melanoma cells and found that Src expression decreased. Conversely, loss of miR-1280 in Lifeline® normal human melanocytes caused increased Src expression. Additionally, miR-1280-expressing melanoma cells exhibited decreased tumorigenic activity in vitro, which was due largely to Src inhibition. Finally, the group demonstrated that the suppression of Src by miR-1280 decreases melanoma cell xenograft tumor growth. Together, this study identifies Src as a target of miR-1280 and demonstrates that loss of miR-1280 in melanoma results in increased Src activity and protumorigenic effects.

Vitiligo is a condition that is caused by autoimmune destruction of melanocytes, resulting in large-scale loss of skin pigmentation. Vitiligo-inducing phenols (VIPs), such as 4-tertiary butyl phenol (4-TBP) and monobenzone (MBEH), can induce vitiligo, and in the case of MBEH, are used to treat the condition. In a new study this year, Arowojolu et al. investigated the response of normal melanocytes to MBEH to determine whether certain protective pathways that are activated might be dysregulated in vitiligo melanocytes. Their work focused on nuclear factor (erythroid-derived-2)-like 2 (NRF2), which they previously showed is increased in VIP-treated melanocytes to regulate oxidative stress.

In this study, the group used Lifeline® neonatal and adult epidermal melanocytes, as well as Lifeline® neonatal epidermal keratinocytes and dermal fibroblasts. They showed that NRF2 was expressed in unstressed melanocytes, and expressed at very low levels or absent in fibroblasts and keratinocytes. Importantly, downregulation of NRF2 targets decreased melanocyte viability, but not keratinocyte or fibroblast viability, except when exposed to oxidative stress. These results suggest that melanocytes uniquely rely on NRF2 for survival. Gene expression analysis indicated that the NRF2 antioxidant response is upregulated in response to VIP treatment, leading the researchers to determine how melanocytes respond to VIPs. They found that NRF2 and its targets were activated within 1-3 hours of TBP or MBEH treatment, which was also accompanied by upregulation of glutathione peroxidase I, suggesting activation of multiple antioxidant pathways.

To determine whether NRF2 could exert a protective effect against MBEH, the group treated normal melanocytes with MBEH in the setting of NRF2 activation and found that in this context, melanocytes had increased viability. To examine the effects of NRF2 in vitiligo melanocytes, the researchers first established that MBEH had a greater effect on vitiligo melanocytes than normal Lifeline® melanocytes, and demonstrated that vitiligo melanocytes had a weaker NRF2 response, as measured by NRF2 target expression. Importantly, however, treatment of vitiligo melanocytes with DMF, a drug that activates NRF2, resulted in greater NRF2 activation and NRF2-mediated protection from the effects of MBEH. Together, the results of this study define a critical role for the NRF2-mediated antioxidant response in protecting against the effects of VIPs and identify a target for vitiligo treatment.

Lifeline® offers a number of keratinocytes and melanocytes, including:

Neonatal epidermal melanocytes (primary, secondary, and highly pigmented)
Adult epidermal melanocytes (secondary and highly pigmented)
Neonatal epidermal keratinocytes
Adult epidermal keratinocytes
10-donor pool of adult epidermal keratinocytes

Our melanocytes and keratinocytes are optimized for growth in different DermaLife® media. Please use our DermaLife® Ma Melanocyte medium to culture Lifeline® adult melanocytes and DermaLife® M Melanocyte medium for neonatal melanocytes. All Lifeline® Keratinocytes are optimized for growth in DermaLife® K Keratinocyte medium.

Please let us know how you are using our cells and/or media to answer your research questions and your study could be featured here on our blog!