Cellular and Hormonal Regulation of Pigmentation in Human Ocular Melanocytes

Abstract

The purpose of this study was to examine some of the factors that may be relevant to regulating pigmentation in the human eye, specifically whether choroidal and iridial melanocytes are sensitive to regulation by epithelial and stromal cells and alpha-melanocyte stimulating hormone (alpha-MSH). Human choroidal and iridial melanocytes were established in culture and co-cultured with epithelial cells and stromal cells derived both from skin and from eye in order to determine their influence on choroidal and iridial melanocyte dopa oxidase activity. In all cases, co-culture of melanocytes with either epithelial cells or fibroblasts led to an increase in dopa oxidase activity during 5 days of co-culture. The extent of the increase ranged from 60% (non-significant) to as much as 185% when both fibroblasts and keratinocytes were present. The optimal ratio of fibroblasts to melanocytes was 1:10 (for dermal fibroblasts) or 1:2 (for iridial fibroblasts) and 1:1 for all epithelial cells to melanocytes. Both choroidal (three out of three cultures) and iridial (two out of three cultures) melanocytes showed increases in dopa oxidase activity to alpha-MSH when cultured in Green's media but the same cells cultured in MCDB153 were unresponsive to alpha-MSH. These in vitro studies suggest that ocular melanocytes have the capacity to be influenced by adjacent epithelial and stromal cells with respect to pigmentation.

Clinical, dermoscopy and histological correlation study of melanotic pigmentations in excision scars of melanocytic tumours

“…It has been demonstrated that fibroblasts influence dopa oxidase activity in melanocytes. [19][20][21] An additional source of signals for melanocyte proliferation and differentiation derives from extracellular matrix proteins. 22 Pigmented lesions that appear on excision scars of melanocytic tumours pose two main problems.…”

Ocular melanoma is not associated with CDKN2A or MC1R variants — a population-based study

“…Finally, the occurrence of ocular albinism, characterized by depigmentation of the eye but not the skin, suggests different melanogenesis pathways in ocular and cutaneous melanocytes [26]. To the contrary, however, recent evidence indicates that ocular melanocytes express melanocortin 1 receptors (MC1R) on their surface and are responsive to AE-melanocytestimulating hormone, the agonist for these receptors [28].…”

Serum-free cultivation of adult normal human choroidal melanocytes

“…They synthesise melanin, which has important protective functions such as absorption of UV light and binding of radicals and toxic substances [1,2]. In contrast to cutaneous melanocytes, choroidal melanocytes do not synthesise melanin in vivo, but they can do so in vitro [3][4][5][6]. Cultures of normal cutaneous or choroidal melanocytes are useful in vitro models for the study of melanocyte biology or melanocyte transformation into melanoma cells, and they can also be used for tissue engineering and the designing of tissues for transplantation purposes.…”