This illustration shows various tissue sources of stem cells, including NSPCs, iPSCs, SKPs, MSCs, ES cells (ESC), and direct conversion methods to yield neural cells for transplantation. NSPCs can be isolated from the fetal and adult brain and spinal cord and differentiated into progenitor cells, such as OPCs and mature oligodendrocytes, or astrocytes or neurons depending on culture conditions and exposure to growth factors. ES cells follow a default pathway to neural cells, and specific conditions can promote OPC generation. MSCs can be derived from a variety of tissues, including BM, umbilical cord, adipose tissue, muscle, and dental pulp from deciduous baby teeth. In culture, MSCs have shown properties of neural cells. Fibroblasts from the skin can be reprogrammed using various methods into iPSCs,which are then directed along a neural lineage. Recent studies have directly converted fibroblasts to neurons and NSPCs, bypassing the pluripotent stage.