Bioengineered human skin from embryonic stem cells

Both murine ESC and hESC lines (H9 and H1) can be converted to K14-positive epidermal cells in culture.3-5 An important advance6 was the ability to reconstitute skin tissue complete with a dermal and epidermal component from murine ESCs, by culturing with extracellular matrix proteins and bone morphogenetic protein 4 (BMP4) in a three-dimensional organotypic culture model. A legitimate concern with therapies based on ESCs is the tumorigenic capacity of these cells, restricting their potential usefulness for patients.10,11 However, no tumours were seen in Guenou and colleagues' study, as reported previously for keratinocytes derived from murine ESCs,6 consolidating the idea that a longlasting predifferentiation protocol for hESCs in vitro reduces the incidence of tumour formation after transplantation.12 The replacement of skin connective tissue, or the under lying dermis and associated epidermal appendages (ie, sweat glands and hair follicles), frequently lost in patients with full thickness burns, needs to be studied in more detail.