Long-term expression pattern of melanocyte markers in light- and dark-pigmented dermo-epidermal cultured human skin substitutes

Abstract

Purpose Transplantation of pigmented tissue-engineered human autologous skin substitutes represents a promising procedure to cover skin defects. We have already demonstrated that we can restore the patient's native light or dark skin color by adding melanocytes to our dermo-epidermal skin analogs. In this long-term study, we investigated if melanocytes in our skin substitutes continue to express markers as BCL2, SOX9, and MITF, known to be involved in survival, differentiation, and function of melanocytes. Methods Human epidermal melanocytes and keratinocytes, as well as dermal fibroblasts from light-and darkpigmented skin biopsies were isolated and cultured. Bovine collagen hydrogels containing fibroblasts were prepared, and melanocytes and keratinocytes were seeded in a 1:5 ratio onto the gels. Pigmented dermo-epidermal skin substitutes were transplanted onto full-thickness wounds of immuno-incompetent rats and analyzed for the expression of melanocyte markers after 15 weeks. ResultsEmploying immunofluorescence staining techniques, we observed that our light and dark dermo-epidermal skin substitutes expressed the same typical melanocyte markers including BCL2, SOX9, and MITF 15 weeks after transplantation as normal human light and dark skin. Conclusions These data suggest that, even in the long run, our light and dark dermo-epidermal tissue-engineered skin substitutes contain melanocytes that display a characteristic expression pattern as seen in normal pigmented human skin. These findings have crucial clinical implications as such grafts transplanted onto patients should warrant physiological numbers, distribution, and function of melanocytes.

UVB exposure of a humanized skin model reveals unexpected dynamic of keratinocyte proliferation and Wnt inhibitor balancing

“…We recently demonstrated for MelSkin the regular distribution of melanocytes in the basal layer with the protrusion of dendrites into lower and upper keratinocyte layers and the deposition of supranuclear melanin caps in the keratinocytes (Biedermann et al 2015b).…”

“…Moreover, the original color of the donor skin was restored after transplantation (Biedermann et al 2015b;Böttcher-Haberzeth et al 2013). Distinct MelSkin substitutes differing in color (light or dark) showed physiological melanocyte distribution and function even 15 weeks after transplantation (Biedermann et al 2015a;Böttcher-Haberzeth et al 2014).…”

“…Here we describe the first series of experiments investigating the effects of UVB irradiation on a novel type of pigmented bio-engineered dermo-epidermal skin substitutes of human origin, termed MelSkin. This new generation of skin equivalents, was investigated in vivo employing immuno-incompetent rats (Biedermann et al 2015b;Böttcher-Haberzeth et al 2014;Böttcher-Haberzeth et al 2013). Of note, basically identical but non-pigmented skin substitutes, are currently being tested in phase I and II clinical studies with highly encouraging results.…”

“…As in MelSkin the melanocyte compartment is biologically fully functional (Biedermann et al 2015b;Böttcher-Haberzeth et al 2014;Böttcher-Haberzeth et al 2013), we determined how MelSkin would compensate UV irradiation, in terms of skin pigmentation, cell proliferation and epidermal skin homeostasis. UVB irradiation can induce skin tanning as a protective mechanism to DNA damage.…”

Human Adipose Mesenchymal Cells Inhibit Melanocyte Differentiation and the Pigmentation of Human Skin via Increased Expression of TGF-β1

“…In human skin, epidermal melanocytes exist in distinct maturation states. We and others have shown that SOX9 is expressed in a subpopulation of melanocytes and that this correlates with the presence of MelanA þ and PMEL þ mature cells in the epidermis and in the hair matrix of normal (nonpalmoplantar) human skin (Biedermann et al, 2015a;Krahl and Sellheyer et al, 2010). In contrast, SOX10 plays an important role during the early development of melanocytes in the neural crest and is still expressed in immature melanocytes in the epidermis (Greenhill et al, 2011;Harris et al, 2013).…”