Transplantation of rat-derived microglial cells promotes functional recovery in a rat model of spinal cord injury

This study evaluated the effect of microglia transplantation on neurological functional recovery in rats subjected to traumatic spinal cord injury (SCI). The rat model of SCI was established using a weight drop device. Forty SCI rats were randomly divided into the microglia group and the saline group. Then, rat-derived microglial cells or normal saline was injected into the injured site 7 days after surgery. The Basso-Beattie-Bresnahan (BBB) score, inclined plate test, and motor-evoked potentials (MEPs) were applied to assess the recovery of motor function. Hematoxylin and eosin (H&E) staining was used to assess the therapeutic effect. Microglia transplantation significantly improved BBB scores and functional scores at 2, 3, 4, 6, and 8 weeks after surgery compared to saline injection (P<0.05). Meanwhile, a prolonged MEP latency and decreased MEP amplitude were observed at 4 and 8 weeks in the microglia group (P<0.05). Histological analysis showed less damage and better prognosis in SCI rats of the microglia group. BrdU(+) cell tracing experiments showed that microglia were recruited to the injured area of the spinal cord at 7 and 14 days after transplantation. The intensity of immunofluorescence was increased in CD68(+) and OX42(+) microglia at 2 days, 1 week, and 2 weeks, and then decreased at 3 and 4 weeks after transplantation in the microglia group. The transplantation of activated microglia played a key role in promoting the recovery of spinal cord function in a rat model of SCI.