Keratinocytes Play a Role in Regulating Distribution Patterns of Recipient Melanosomes In Vitro

Abstract

Melanosomes in keratinocytes of Black skin are larger and distributed individually whereas those within keratinocytes of Caucasian skin are smaller and distributed in clusters. This disparity contributes to differences in skin pigmentation and photoprotection, but the control of these innate distribution patterns is poorly understood. To investigate this process, cocultures were established using melanocytes and keratinocytes derived from different racial backgrounds and were examined by electron microscopy. Melanosomes transferred to keratinocytes were categorized as individual or in various clusters. Melanosome size was also determined for individual and clustered melanosomes. Results indicate that, in our model system, melanosomes in keratinocytes from different racial backgrounds show a combination of clustered and individual melanosomes. When keratinocytes from dark skin were cocultured with melanocytes from (i) dark skin or (ii) light skin, however, recipient melanosomes were individual versus clustered in (i) 77% vs 23% and (ii) 64% vs 36%, respectively. In contrast, when keratinocytes from light skin were cocultured with melanocytes from (iii) dark skin or (iv) light skin, recipient melanosomes were individual versus clustered in (iii) 34% vs 66% and (iv) 39% vs 61%, respectively. These results indicate that recipient melanosomes, regardless of origin, are predominantly distributed individually by keratinocytes from dark skin, and in membrane-bound clusters by those from light skin. There were also differences in melanosome size from dark or light donor melanocytes. Melanosome size was not related to whether the melanosomes were distributed individually or clustered, however, in cocultures. These results suggest that regulatory factor(s) within the keratinocyte determine recipient melanosome distribution patterns.

Cellular senescence in naevi and immortalisation in melanoma: a role for p16?

“…Primary human melanocyte strains Nohm1 (Bennett et al, 1985), 830c (Scott et al, 2002) and HM303CN (Minwalla et al, 2001) were grown as described (Bennett et al, 1985), except in the following melanocyte medium (Sviderskaya et al, 2003): RPMI 1640 medium, 10% foetal calf serum, 200 nM 12-O-tetradecanoyl phorbol 13-acetate (Sigma Chemical Co., Poole, UK), 200 pM cholera toxin (Sigma), 10 ng ml À1 human stem cell factor (R&D Systems, Abingdon, UK) and 10 nM endothelin 1 (Sigma), gassed with 10% CO 2 . Supplements shortly after retroviral infection also included 1 mM insulin, 40 pM fibroblast growth factor 2 (R&D Systems, Abingdon, UK) and 1 mg ml À1 a-tocopherol.…”

Use of multiphoton tomography and fluorescence lifetime imaging to investigate skin pigmentationin vivo

“…6 Alternatively, keratinocyte-melanocyte cocultures are studied using electron ultrastructure microscopy, which relies on the ability to visualize melanin-filled melanosomes by incubation with l-dihydroxyphenylalanine (DOPA). 7 However, these methods fail to precisely define the quantitative profiling of the distribution patterns of melanin due to the inherent physical and chemical limitations of such techniques. For example, despite its simplicity, the nonlinear chemistry of Fontana-Masson staining may yield melanin content measurements that do not correlate with the visual register of skin complexion from different ethnic backgrounds.…”

A new Monte Carlo program for simulating light transport through Port Wine Stain skin

“…Although the spread of melanin through the simulated epidermis differed due to the differences in the initial skin models, the final prediction from the two experiments were similar overall ( Table 2). The melanosome diameters predicted from the two experiments were identical, although they were greater than expected these skin types [12][13][14][15][16].…”

“…The layer representing the living epidermis in Meglinski and Matcher's work was divided into two layers in the new programme in order to facilitate differences in melanin properties (Table 1). Estimations of representative melanosome concentrations and sizes were based upon an analysis of the literature [11][12][13][14][15][16]. [14].…”

“…During minimisation, stratum corneum granule diameter was limited to a minimum of 1 nm and a maximum of 20 nm [14,16] whilst melanosome size in the living epidermis was allowed to vary from 30 nm to 400 nm [12][13][14][15].…”