Melanin Transfer in Human 3D Skin Equivalents Generated Exclusively from Induced Pluripotent Stem Cells.

Karl Gledhill,Angela M Christiano,Claire A Higgins,Munenari Itoh,Zongyou Guo,Noriko Umegaki-Arao,Johanna M Brandner

doi:10.1371/journal.pone.0136713

Abstract

The current utility of 3D skin equivalents is limited by the fact that existing models fail to recapitulate the cellular complexity of human skin. They often contain few cell types and no appendages, in part because many cells found in the skin are difficult to isolate from intact tissue and cannot be expanded in culture. Induced pluripotent stem cells (iPSCs) present an avenue by which we can overcome this issue due to their ability to be differentiated into multiple cell types in the body and their unlimited growth potential. We previously reported generation of the first human 3D skin equivalents from iPSC-derived fibroblasts and iPSC-derived keratinocytes, demonstrating that iPSCs can provide a foundation for modeling a complex human organ such as skin. Here, we have increased the complexity of this model by including additional iPSC-derived melanocytes. Epidermal melanocytes, which are largely responsible for skin pigmentation, represent the second most numerous cell type found in normal human epidermis and as such represent a logical next addition. We report efficient melanin production from iPSC-derived melanocytes and transfer within an entirely iPSC-derived epidermal-melanin unit and generation of the first functional human 3D skin equivalents made from iPSC-derived fibroblasts, keratinocytes and melanocytes.

Highlights

Human 3D skin equivalents (HSEs) are in vitro models used to conduct experiments on processes involving the skin e.g. disease progression and drug discovery
Even at this early stage of the differentiation protocol, a small proportion of Induced pluripotent stem cells (iPSCs)-derived cells were positive for gp-100 expression (Fig 1k) and had begun to adapt a typical melanocyte morphology (Fig 1m) suggesting that some melanoblasts had begun to mature into normal melanocytes
We reported generation of 3D skin equivalents composed exclusively of human iPSC-derived keratinocytes and fibroblasts demonstrating that iPSCs can provide the basis for modeling a human organ derived entirely from two different types of iPSC-derived cells [14]

Summary

Introduction

Human 3D skin equivalents (HSEs) are in vitro models used to conduct experiments on processes involving the skin e.g. disease progression and drug discovery. They are widely used for several reasons, but mainly because many studies report differences in phenotype, cellular signaling, cell migration, and drug responses when the same cells are grown under 2D vs 3D conditions [1,2,3,4]. One major reason for this is that these models consist of cells isolated from freshly discarded tissue following surgery. In order to isolate large numbers of these cells to include these cells in HSEs and accurately model cutaneous disorders, biopsies are required from patients who often are unwilling to undergo any procedure that may exacerbate their condition

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