Therapeutic efficacy of intracerebral hematopoietic stem cell gene therapy in an Alzheimer’s disease mouse model

The conditions supporting the generation of microglia-like cells in the central nervous system (CNS) after transplantation of hematopoietic stem/progenitor cells (HSPC) have been extensively studied to advance the treatment of neurodegenerative disorders. Here, we challenge the HSPC transplantation paradigm by exploring different cell subsets and delivery routes with the goal of favoring the establishment of a robust and exclusive engraftment of HSPCs and their progeny in the CNS of transplant recipients. In this setting, we show that the CNS environment uniquely drives the expansion, distribution and myeloid differentiation of the locally transplanted cells towards a microglia-like phenotype. Importantly, intra-CNS transplantation of engineered HSPCs benefit 5xFAD Alzheimer’s disease mice, a finding that provides not only the first example of efficacy of HSPC gene therapy in this indication, but also a proof of the therapeutic potential of this novel approach that determines a CNS-restricted engraftment of the transplant progeny cells. The experimental design involved assessing the effects of different delivery methods and hematopoietic cell subsets on competitive transplantation outcomes in mice. CD34+-equivalent lineage-negative (Lin-) murine hematopoietic stem and progenitor cells (HSPCs) were delivered into the cerebroventricular space (ICV), followed by intravenous (IV) administration of various hematopoietic cell subsets, including total bone marrow (BM), Lin- cells, and c-kit+ Sca-1+ stem cell-enriched Lin- (KSL) cells. The IV delivery was either simultaneous with or delayed by 5 days after the ICV delivery. Additionally, the study explored a novel intrathecal lumbar (ITL) delivery method as an alternative to the ICV route. The outcomes were evaluated based on hematopoietic reconstitution and competitive transplantation efficiency.