The Influence of Stromal Cells on the Pigmentation of Tissue-Engineered Dermo-Epidermal Skin Grafts

Abstract

It has been shown in vitro that melanocyte proliferation and function in palmoplantar skin is regulated by mesenchymal factors derived from fibroblasts. In this study, we investigated in vivo the influence of mesenchymal-epithelial interactions in human tissue-engineered skin substitutes reconstructed from palmarand nonpalmoplantar-derived fibroblasts. Tissue-engineered dermo-epidermal analogs based on collagen type I hydrogels were populated with either human palmar or nonpalmoplantar fibroblasts and seeded with human nonpalmoplantar-derived melanocytes and keratinocytes. These skin substitutes were transplanted onto fullthickness skin wounds of immunoincompetent rats. Four weeks after transplantation the development of skin color was measured and grafts were excised and analyzed with regard to epidermal characteristics, in particular melanocyte number and function. Skin substitutes containing palmar-derived fibroblasts in comparison to nonpalmoplantar-derived fibroblasts showed (a) a significantly lighter pigmentation; (b) a reduced amount of epidermal melanin granules; and (c) a distinct melanosome expression. However, the number of melanocytes in the basal layer remained similar in both transplantation groups. These findings demonstrate that human palmar fibroblasts regulate the function of melanocytes in human pigmented dermo-epidermal skin substitutes after transplantation, whereas the number of melanocytes remains constant. This underscores the influence of sitespecific stromal cells and their importance when constructing skin substitutes for clinical application.

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

“…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). We show here that MelSkin can adapt its melanin content as a reaction to UVB exposure, namely by an increased production of melanin and its transfer to the upper layers of epidermal keratinocytes.…”

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

“…This was of particular interest because ASCs represent an abundant cell source and can be used as a substitute for dermal Fbs, especially if the latter are limited in number. To gain more insight into this matter, we bioengineered pigmented dermo-epidermal skin substitutes (melDESS) containing epidermal melanocytes and keratinocytes and differing in the distinct types of stromal cells in the dermal part (Biedermann et al, 2015b). The overall results showed an anti-melanogenic effect of ASCs.…”

“…Previously we showed that the composition and properties of a particular stroma also varies significantly with respect to its body site (Biedermann et al, 2015b). As a consequence, we need to consider both from which dermal layer the stromal cells are derived and from which area of the body stromal cells are isolated to bioengineer a skin graft that optimally matches the color of the particular skin region.…”

“…Increasing evidence suggests that, in addition to keratinocytes, stromal cells present in the human dermis are significantly involved in the regulation of skin pigmentation (Biedermann et al, 2015b). Yamaguchi et al (2004Yamaguchi et al ( , 2008 suggested that DKK1, an inhibitor of the Wnt signaling pathway produced by Fbs in the palms and soles, has an inhibitory effect on melanocyte proliferation and function, leading to a hypopigmentation of these body sites (Yamaguchi et al, 2004(Yamaguchi et al, , 2008.…”

Negative Regulation of Skin Pigmentation in Three-Dimensional Reconstructs by Adipose-Derived Mesenchymal Cells

“…Skin pigmentation is regulated by crosstalk between melanocytes and adjacent skin cells such as epidermal keratinocytes and dermal fibroblasts (Yamaguchi and Hearing, 2009). Variation of skin color among different body sites is incompletely understood, although increasing evidence shows that mesenchymal cells, especially dermal fibroblasts, might play important roles through a paracrine mechanism (Biedermann et al, 2015;Cario-André et al, 2006;Choi et al, 2010;Yamaguchi et al, 2004). It is less certain if other skin mesenchymal cells such adipocytes or endothelial cells, which are normally not in direct contact with epidermal melanocytes, might influence pigmentation in certain clinically relevant circumstances, such as in engineered skin reconstructs.…”