Mesodermal Differentiation of Skin-derived Precursor cells

Neural crest stem cells (NCSCs) are embryonic multipotent cells that give rise to a wide range of cell types that include those forming the peripheral neural cells and the mesodermal cells of the face including the facial bones. In neonatal and adult skin, skin-derived precursor cells (SKPs) are multipotent dermal precursors that share similarities with NCSCs and can differentiate into peripheral neural and mesodermal cells, such as adipocytes. Based on the similarities between SKPs and NCSCs, I asked, in this thesis, whether rodent or human SKPs can differentiate into skeletal mesodermal cell types by determining their ability to differentiate into osteoblasts and chondrocytes. In culture, rodent and human SKPs differentiated into alkaline phosphatase-, osteopontin- and type-I collagen-positive osteoblasts that produced mineral deposits and into type-II collagen expressing chondrocytes. Clonal analysis showed that SKPs are multipotent for the osteogenic and chondrogenic lineages. To ask whether SKPs can generate these cells in vivo, genetically-tagged naïve rat SKPs were transplanted into a tibia bone fracture model. Six weeks post-transplantation, SKP-derived osteoblasts and osteocytes were present in the newly formed bone, showing their osteogenic differentiation in vivo. At three weeks post-transplantation, some of the injected cells differentiated into hypertrophic chondrocytes in the callus and others into perivascular cells in areas just outside the callus. To test whether it is the local environment that dictates the phenotype of transplanted SKPs, GFP-tagged undifferentiated rat SKPs were injected into the hypodermis of the skin, an adipogenic environment. Four weeks post-transplantation, SKPs differentiated into adipocytes, but not in inappropriate cell types. These results further the known differentiation potential of SKPs, show that local environment of a bone fracture or the hypodermis of the skin is sufficient to induce the differentiation of undifferentiated SKPs into appropriate cell types and suggest the use of SKPs as source of mesodermal precursor cells for cell therapy.Ph