BMSCs overexpressing hBcl2 can resist myelin-induced apoptosis and promote repair after spinal cord injury in rats

Abstract After spinal cord injury (SCI), the production of myelin debris at the lesion core worsens parenchymal cell death and hinders axonal regrowth. BMSCs are susceptible to apoptosis after transplantation, and it remains unclear if this process is associated with myelin debris. we constructed BMSCs overexpressing hBcl2 (hBcl2group), BMSCs overexpressing hBcl2 with an endoplasmic reticulum-anchored segment (hBcl2-cb) (cb group), and a negative control group (NC group) for this study. Immunocytochemistry staining showed that hBcl2 was more stably and significantly higher in BMSCs of the hBcl2 group. All BMSCs from each group exhibited the ability to phagocytize Dil-myelin debris. However, only BMSCs from the hBcl2 group demonstrated resistance to apoptosis and sustained survival for up to 5 days in the presence of myelin debris. This process appeared to be associated with the efficient degradation of myelin debris through the Lamp1 + lysosomal pathway in the hBcl2 group. In the in vivo transplantation experiments, the hBcl2 group exhibited significantly higher numbers of surviving cells and fewer apoptotic cells compared to the cb and NC groups following BMSCs transplantation. Additionally, the hBcl2 group showed a remarkable reduction in GFAP + glial scarring and significantly greater preservation of NF200 + axons in the lesion regions of SCI rats. This study revealed that myelin debris induces apoptosis in BMSCs, providing a potential explanation for the low survival rate of transplanted BMSCs after SCI. Interestingly, it was observed that the overexpression of hBcl2 protein, rather than its endoplasmic reticulum-anchored counterpart, significantly enhances the resistance of BMSCs against myelin debris-induced apoptosis. Consequently, the survival rate of transplanted BMSCs is improved, and there is an enhancement in axonal preservation within the injured spinal cord.