NPC1 and metabolic disease: In the CNS, transplantation of mesenchymal stem cells (MSCs) into the cerebellum of a mouse model of a metabolic disease, Niemann-Pick disease type C (NPC1), led to fusion of MSCs with compromised Purkinje cells in vivo, partially correcting the impaired sphingolipid metabolism associated with NPC1 transgenic mice, resulting in a mild motoric improvement [24,25].