| Background:Traumatic Brain Injury(TBI),is a disease caused by external mechanical forces that can lead to brain dysfunction.Its pathophysiology mainly includes disruption of the Blood Brain Barrier(BBB),extensive neuroinflammation,diffuse axonal injury and neurodegenerative lesions.The current main treatment methods include symptomatic and rehabilitation management,but it is difficult to address the problem of brain tissue regeneration and repair effectively,thus new strategies need to be explored.Stem Cells(SCs),with their proliferative and differentiation advantages,offer the possibility of brain tissue regeneration and repair following TBI,and bring hope for a cure for TBI.Numerous basic and clinical studies have shown that SCs transplantation following TBI is effective.However,it is not yet fully clarified that the treatment with allogeneic SCs following TBI(e.g.,bone marrow mesenchymal stem cells(BMSCs)transplantation between young donors and aged TBI recipients,umbilical cord-derived stem cells(BMSCs)transplantation between young donors and aged TBI recipients,and the treatment with allogeneic stem cells(BMSCs)is not yet fully clarified.Umbilical cord derived stem cells(UCSCs)transplantation,etc.),whether there are safety risks in terms of genetic information,survival and distribution after transplantation into the host need to be explored in depth,and this experiment has thus conducted a preliminary exploration study.Objective:To track the survival and distribution of BMSCs transplanted into the host brain,to explore whether phagocytosis occurs between BMSCs and microglia,and to detect changes in microglia after phagocytosis of BMSCs,so as to provide experimental data support for the new cell therapy strategy of allogeneic BMSCs transplantation for TBI.Methods:To simulate continuous and adequate transplantation of stem cells in the clinical setting,a guide cannula was implanted for intracerebroventricular injection was implanted into the left ventricle of female rats 5 days before being subjected to controlled cortical impact injury in vivo.Next,the rats received an injection of 2.5 ×105 BMSCs 4 hours and every 3 days following TBI.The cerebral cortex was harvested and sliced,and the RNA scope technique was used to identify whether the transplanted male BMSCs would fuse with astrocytes and neurons of the female host following TBI in vivo.Then,to verify whether microglia cells would phagocytize BMSCs in vitro,we pr-labeled BMSCs with a pH-sensitive dye,and co-cultured them with GFP-BV2 cells for 36h and 72h.Finally,to identify the phagocytosis of BMSCs that activate MGs and induce polarization in vitro,flow cytometry was used to detect CD86(Ml marker)and CD206(M2 marker)expression in lipopolysaccharide-treated microglia.Results:Flow cytometry showed that the primary primary BMSCs conformed to the international stem cell standard.The results of cellular immunofluorescence showed that the primary glial cells were astrocytes.In vivo,no fusion of BMSCs with astrocytes and neurons was found,however,microglia were activated and migrated to or near the ventricle at 10d and 14d,which was most likely because BMSCs were phagocytosed by microglia.In vitro,the co-cultures of the BV2 cell line and BMSCs showed that the BMSCs were engulfed by BV2 cells.Flow cytometry data showed that the expression of CD206 in co-cultured cells was significantly higher than that in lipopolysaccharide-treated microglia cultured alone,while the expression of CD86 did not change between the two groups.Conclusion:Allogeneic BMSCs did not genetically integrate with cells in the TBI host brain after transplantation;however,allogeneic BMSCs were phagocytosed by microglia/macrophages during transplantation for TBI and promoted the development of microglia from a pro-inflammatory phenotype to an anti-inflammatory phenotype.Allogeneic BMSCs transplantation for TBI is safe. |
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