Human iPSC-derived cell grafts promote functional recovery by molecular interaction with stroke-injured brain

Stroke is a leading cause of disability and death due to the brain’s limited ability to regenerate damaged neural circuits. To date, stroke patients have only few therapeutic options and are often left with considerable disabilities. Induced pluripotent stem cell (iPSC)-based therapies are emerging as a promising therapeutic approach for stroke recovery. In this study, we demonstrate that local transplantation of good manufacturing practice (GMP)-compatible iPSC-derived neural progenitor cells (NPCs) improve long-term recovery-associated brain tissue responses and reduce neurological deficits after cerebral ischemia in mice. Using in vivo bioluminescence imaging and post-mortem histology, we showed long-term graft survival over the course of five weeks and preferential graft differentiation into mature neurons without signs of pluripotent residuals. Transplantation of NPCs led to a set of recovery-associated tissue responses including increased vascular sprouting and repair, improved blood-brain barrier integrity, reduced microglial activation, and increased neurogenesis compared to littermate control animals receiving sham transplantation. Employing deep learning-assisted behavior analysis, we found that NPC-treated mice displayed improved gait performance and complete fine-motor recovery in the horizontal ladder rung walk, five weeks post-injury. To dissect the molecular graft composition and identify graft-host interactions, single nucleus profiling of the cell transplants and host stroke tissue was performed. We identified graft differentiation preferentially towards GABAergic cells with remaining cells acquiring glutamatergic neuron, astrocyte, and NPC-like phenotypes. Interaction between graft and host transcriptome indicated that GABAergic cell grafts were primarily involved in graft-host communication through the regeneration-associated NRXN, NRG, NCAM and SLIT signalling pathways. In conclusion, our study reveals that transplanted iPSC-derived NPCs primarily differentiate into GABAergic neurons contributing to long-term recovery, and further delineates the regenerative interactions between the graft and the stroke-injured host tissue.