Specification Of Midbrain Dopamine Neurons From Primate Pluripotent Stem Cells And Their Implications In Parkinson’s Diseases

Degeneration of dopamine(DA)-producing neurons in the midbrain, especially the substantia nigra, underlies the pathophysiology of Parkinson’s disease(PD). At present, there has been no effective treatment for such disease. Human pluripotent stem cells, including human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs), can differentiate to any cell types of the human body, including DA neurons. These DA neurons may be used to study pathological processes of neural degeneration, which in turn may become a target for therapeutic discovery. These DA procursors may also become a source of cell based therapy for the Parkinson’s diseases.Autologous transplantation via induced pluripotent stem cells (iPSCs) is a potential strategy to have readily available matching donor cells and therefore, minimize host immune response. A recent study with iPSC transplants showed rejection of teratomas by syngenic host mice, casting doubt on the utility of reprogrammed cells for autologous transplant therapy. Clinical translation of cell replacement strategies will rely upon iPSC-differentiated progenies instead of iPSCs themselves. Here we show that transplantation of rhesus monkey iPSC-derived neural progenitors survive for up to6months without immune suppression and differentiate into neurons, astrocytes, and oligodendrocytes in the striatum of MPTP-induced hemiparkinsonian rhesus monkeys with minimal presence of inflammatory cells. This finding raises hopes of personalized regenerative therapies.By sequentially applying sonic hedgehog (C25II) and CHIR99021(GSK3□inhibitor) to induce the midbrain floor plate progenitors and fibroblast growth factor8(FGF8) to promote dopaminergic differentiation in a chemically defined medium, we have established a robust system for generation of midbrain dopamine (DA) neurons from human and rhesus monkey embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs).We found that CHIR99021specifies diencephalon to hindbrain fates in a concentration-dependent manner and only a narrow concentration range of CHIR99021at a particular window is necessary to induce the midbrain floor plate progenitors, expressing Corin, Enl, FoxA2and Lmxla. FGF8enhances the dopaminergic fate of the progenitors, thus generating DA neurons with midbrain characteristics, including expression of TH, Lmxla/b, FoxA2, FoxPl, Nurr1and Enl as well as typical electrophysiological properties. More than half of these DA neurons expressed A9DA neuron markers Girk2and ALDHlal. The new strategy will allow generation of enriched populations of functional midbrain DA neurons from both human and monkey PSCs for disease modeling, drug testing, and potential cell therapy.