Depletion of microglia combined with transplantation of bone marrow mesenchymal stem cells for repairing spinal cord injury / 中华骨科杂志

ABSTRACT

Objective:To study the effect of microglia depletion combined with bone marrow mesenchymal stem cells (BMSC) transplantation for spinal cord injury (SCI) repair.Methods:GFP-BMSCs were cultured, identified and detected for expression levels of growth factors. The effects of BMSCs ondorsal root ganglion (DRG) axon outgrowth were observed by the co-culture of BMSCs with DRGs. Mice were depleted of microglia by administrating the colony stimulating factor 1 receptor (CSF1R) inhibitor PLX3397. The spinal cords of these microglia-depleted mice were subjected to crush injury. BMSCs were transplanted into SCI area after microglia depletion. Mice were randomly divided into control group (SCI+BMSCs) and experimental group (PLX3397+SCI+BMSCs). Mice were sacrificed at corresponding time points after transplantation for observing the survival of transplanted BMSCs and the repair of spinal cord. BMS score was used for evaluation of motor function recovery.Results:BMSCs secreted a large number of neurotrophic factors and promoted the growth of DRG axons when co-cultured with DRGs. Depletion of microglia significantly improved the survival of transplanted BMSCs. Compared with BMSCs transplantation alone, the combined treatments slightly but non-significantly reduced the area of the lesion ( t=2.141, P=0.065). Immunofluorescence staining showed that both BMSC transplantation alone and the combined treatments did not cause the corticospinalaxons across the lesion and into distal spinal cord. BMS scores were (1.20±0.45), (3.20±0.45), (3.80±0.45), (4.20±0.45), and (4.60±0.55) points in control group at 1, 7, 14, 21 and 28 d after injury. The experimental groups were(0.60±0.55), (3.00±0.71), (3.80±0.84), (4.20±0.84), and (4.40±0.89) points, respectively. Conclusion:Depletion of microglia improves the survival of transplanted cells, depletion of microglia combined with BMSC transplantation did not result in a significant reduction in lesion area. At the same time, the damaged CST axons were notregenerated. Thus, combining cell transplantation with axon-promoting strategy may be necessary for SCI repair.