Multipotent skin-derived precursors: adult neural crest-related precursors with therapeutic potential

Abstract

We previously made the surprising finding that cultures of multipotent precursors can be grown from the dermis of neonatal and adult mammalian skin. These skin-derived precursors (SKPs) display multi-lineage differentiation potential, producing both neural and mesodermal progeny in vitro, and are an apparently novel precursor cell type that is distinct from other known precursors within the skin. In this review, we begin by placing these findings within the context of the rapidly evolving stem cell field. We then describe our recent efforts focused on understanding the developmental biology of SKPs, discussing the idea that SKPs are neural crest-related precursors that (i) migrate into the skin during embryogenesis, (ii) persist within a specific dermal niche, and (iii) play a key role in the normal physiology, and potentially pathology, of the skin. We conclude by highlighting some of the therapeutic implications and unresolved questions raised by these studies.

Figure 1

Isolation and differentiation of skin-derived precursors. (a) Isolation of SKPs. (i) Fluorescence micrograph of post-natal mouse skin, with nuclei labelled by Hoechst (blue) and epithelial cells of the epidermis and hair follicles labelled with anti-cytokeratin (green). Non-specific cytokeratin staining also illuminates the subcutaneous muscle layer. (ii) Enzymatically and mechanically dissociated mouse skin. (iii) Growth of SKP spheres in suspension cultures when dissociated skin cells are exposed to the mitogens FGF2 and EGF. (b) Differentiation of SKP spheres. Under appropriate conditions, SKP spheres differentiate into neurons that express βIII tubulin, glial cells that express S100β, smooth muscle cells that express smooth muscle SMA and adipocytes containing characteristic intracellular lipid droplets. FGF2, fibroblast growth factor-2; EGF, epidermal growth factor; SMA, smooth muscle actin.

Figure 2

SKPs from the facial skin of Wnt1-cre;R26R compound transgenic mice. Spheres generated from the facial skin of Wnt1-cre;R26R transgenic mice, which indelibly express β-galactosidase in neural crest derivatives, react positively with the β-galactosidase substrate X-gal.

Figure 3

Characterization and differentiation of precursors isolated from the rodent olfactory epithelium. (a) Immunocytochemical comparison of spheres grown from embryonic rodent cortex, post-natal rodent olfactory epithelium and post-natal rodent skin. Note that olfactory epithelium-derived spheres have an immunocytochemical phenotype intermediate to cortical and skin-derived spheres. For example, while only very rare cells from SKP spheres were positive for the p75 neurotrophin receptor (p75NTR) and many cells from CNS cortical neurospheres were positive, a significant fraction of cells from the olfactory epithelium also expressed this receptor. (b) Cells differentiating for 1 day from olfactory epithelium-derived spheres co-express nestin and fibronectin, similar to SKPs. (c) After 2–3 weeks of differentiation, olfactory epithelium-derived spheres generate neurons that express βIII tubulin, MAP2 and NFM, smooth muscle cells that express SMA, and glial cells that express CNPase and GFAP. MAP2, microtubule-associated protein-2; NFM, medium neurofilaments; SMA, smooth muscle actin; CNPase, cyclic nucleotide phosphohydrolase; GFAP, glial fibrillary acidic protein.