OBJECTIVETo study the effect of activated microglia grafting on rats' hind limb motor function recovery after spinal cord injury.

METHODSMicroglia were separated from primary culture and subcultured for 3 generations. Lipopolysaccharide was added to the culture medium with the terminal concentration of 10 microl/L for microglia activation 3 days before transplantation. Totally 80 adult Wistar rats were divided into transplantation group and control group, with 40 rats in each group. Spinal cord injury model of rats was set by hitting onto the spinal cord using a modified Allen impactor. With a 5 microl micro-syringe, the activated microglia suspension was injected into the injured area 7 days after the first operation. Basso, Beattie and Bresnahan (BBB) scoring for hind limb motor function was taken on the 1st, 7th, 14th, 21st, and 28th day after microglia transplantation, and 8 rats were sacrificed at each time point mentioned above, respectively. Frozen sections of the spinal cord were made for haematoxylin-eosin (HE) and Naoumenko-Feigin stainings. SPSS 11.0 software was used for statistical analysis.

RESULTSBBB scores for hind limb motor function on the 14th, 21st, and 28th day were significantly higher compared with the control group. Most liquefaction necrosis areas disappeared and only a few multicystic cavities surrounded by aggregated microglia remained in the transplantation group. Naoumenko-Feigin staining for microglia showed that the transplantation group had significantly more positive cells (P < 0.05).

CONCLUSIONSGrafting of activated microglia into the injured spinal cord can significantly promote the hind limb motor function recovery in rats with spinal cord injury and reduce the size of liquefaction necrosis area. The extent of lower limb motor function improvement has a positive correlation with the number of aggregated microglia.