Transplanting Directly Reprogrammed Human Neural Precursor Cells to Promote Functional Recovery Following Stroke

Vonderwalde, Ilan 1; Rolvink, Gabrielle 2; Azimi, Ashkan 3; Ahlfors, Jan-Eric 4; Shoichet, Molly 1; Morshead, Cindi 1, 2, 3

1. Institute of Biomaterials and Biomedical Engineering, University of Toronto, Ontario; 2. Department of Surgery, University of Toronto, Ontario; 3. Institute of Medical Science, University of Toronto, Ontario; 4. New World Laboratories Inc, Laval, Quebec

Current treatment strategies for stroke offer limited success, making it one of the leading causes of acquired long-term disability worldwide. Cell transplantation is a promising therapeutic intervention. However, several hurdles, including the identification of an optimal cell type and source, still exist. Herein, we explore the efficacy of a novel population of directly reprogrammed human neural precursor cells (drNPCs) to treat the stroke-injured brain. Briefly, somatic cells were isolated and transformed via transient expression of Musashi-1 (Msi1), Neurogenin-2 (Ngn2), and Methyl-CpG Binding Domain Protein 2 (MBD2), generating drNPCs within 2 weeks of transfection. These cells afford the benefit of using patient specific somatic cells and directly reprogramming them to NPCs, without the use of viral constructs, thereby providing a safe and ethically sound source of autologous cells that can avoid immune rejection and bypass risks associated with pluripotency. Using immunohistochemistry and PCR, we confirmed drNPCs comprise a population of stem and progenitor cells committed to the neural lineage. To examine the potential of drNPCs to promote neural repair and functional recovery following ischemia, we established an endothelin-1 model of stroke in the sensorimotor cortex of immunocompromised SCID/Beige mice that results in long term motor deficits, which permits us to examine functional recovery and avoid immunorejection of drNPCs following transplantation. The drNPCs were transplanted into the lesion site 4 days post-stroke in artificial cerebrospinal fluid (aCSF) or a hyaluronan methylcellulose (HAMC) hydrogel that has been shown to promote cell survival. Stroke-injured mice that received aCSF alone, HAMC alone, drNPCs+aCSF, and drNPCs+HAMC were compared. Sensorimotor behavioural assays, immunostaining, and lesion volume outcomes were used to measure functional recovery, cell survival and differentiation, and tissue regeneration. Although we found that lesion volume was not significantly different in any treatment group 32 days post-stroke, we did find that transplanted human cells survive up to 32 days post-stroke in the SCID/Beige mouse cortex. Interestingly, at 32 days post-stroke we observed significant functional recovery in mice that received drNPCs. These findings reveal that drNPCs are a promising cell source for neuroregenerative strategies to treat the stroke-injured brain.