Identification of allogeneic and xenogeneic neural stem cells' immunogenicity in the brain and strategies to alleviate transplantation rejection

Neural stem cells (NSCs) are a promising therapy for central nervous system (CNS) disorders, yet post-transplant immune rejection critically compromises their survival and efficacy. In this study, we demonstrated the neuroinflammatory responses triggered by syngeneic, allogeneic, and xenogeneic NSCs transplantation, and evaluated the immunosuppressive effects of cyclosporine A (CyA) and methylprednisolone (MP) on graft rejection. Our findings revealed that xenogeneic NSCs transplantation induced infiltration of neutrophils (p < 0.0001), microglia/macrophages (p < 0.0001), CD4⁺ and CD8⁺ T cells (p < 0.0001), while allogeneic transplantation primarily triggered microglia/macrophages (p < 0.0005) recruitment. Both transplantation types caused a sharp decline in grafted cell numbers (p < 0.005). Combinatorial CyA and MP treatment significantly attenuated xenogeneic immune rejection and markedly increased surviving graft cells in the brain. Similarly, MP monotherapy effectively reduced allogeneic rejection and enhanced transplanted cell survival. Overall, allogeneic NSCs transplantation primarily triggers innate immunity, while xenogeneic transplantation causes both innate and adaptive immune responses. Accordingly, xenogeneic transplantation required combined CyA and MP therapy, whereas MP monotherapy mitigated rejection in allogeneic transplantation. Our findings may offer a strategy to mitigate transplantation rejection of allogeneic and xenogeneic NSCs in the brain, thereby optimizing the microenvironment for NSC-based therapies in preclinical and clinical applications for various CNS disorders.