CD200-based cell sorting results in homogeneous subpopulations of transplantable postmitotic striatal progenitors

Neurodegenerative diseases (NDDs) are characterized by a selective and irreversible loss of neurons in a specific brain area. These diseases are incurable and debilitating, becoming the greatest unmet clinical need of our time. Cell replacement therapies (CRTs) are distinguished by their potential to replace cells lost to the degenerative process and have shown a great potential to replace degenerated neurons in animal models and in clinical trials in Parkinson's Disease (PD) and Huntington's Disease (HD) patients. In fact, CRT is the only approach currently focused on the structural and functional restoration of atrophied tissue in HD (a powerful NDD paradigm in which to establish principles for safe and efficient CRT translation), by replenishing the degenerating striatal projection neuron (SPN) population. In recent years, human pluripotent stem cells (hPSCs) have become a key cell source for CRTs given the scarcity and heterogeneity of previously used fetal-derived neural progenitors. However, directing hPSCs into specific neuronal types is complex and the clinical translation of hPSC-derived neural progenitors is limited by the heterogeneity of cell products obtained using existing differentiation protocols. Here, we describe that CD200 is a cell surface marker suitable for the enrichment of hPSC-derived striatal neuroblasts (NBs). We set up and optimize an immunomagnetic sorting pipeline which allows for high-yield enrichment of striatal neuroblasts in heterogenous cell populations resulting from in vitro differentiation, and demonstrate that implementation of this approach leads to a reduction of the heterogeneity and batch-to-batch variation of the final cell population. Furthermore, we show that sorted cell populations are composed of correctly specified, SPN-committed progenitors with the potential to generate different SPN subtypes, which result in a higher yield of neurons with an SPN phenotype upon terminal in vitro differentiation. Finally, we demonstrate that transplanted selected neuroblasts survive upon intrastriatal transplantation in adult mice with no evidence of graft overgrowth in vivo. CD200-based sorting before transplantation has the potential to enable the development of more effective, safer, and more reproducible cell products to be used for clinical CRT strategies in HD and other NDDs.