Locomotor improvement of spinal cord-injured rats through treadmill training by forced plantar placement of hind paws

Abstract

Study design: Experimental training model of rats with spinal cord injury (SCI). Setting: Osaka, Japan Objective: To investigate the effect of forced treadmill training by plantar placement (PP), as compared with dorsal placement (DP), of the dorsal paws on the locomotor behaviors of spinal cord-injured rats. Methods: The spinal cord was contusion-injured at the thoracic level. Rats were divided into three groups: forced training involving stepping by PP and DP and non-forced training/assistance (nT). Training began 1 week after injury and was conducted for 4 weeks. Locomotor behaviors were estimated using Basso-Beattie-Bresnahan (BBB) scores, dorsiflexion of the hind paws and footprints of the hind paws. Histological and immunohistochemical examinations of the spinal cord lesions were conducted after 4 weeks of training. Results: The values, respectively, of PP, DP and nT groups at 4 weeks of training were as follows: BBB scores were 15.6±0.8, 7.7±1.3 and 10.3±0.4. The paw dorsiflexion angles were 34.1±5.2, 16.4±2.4 and 23.6±3.0 degrees, respectively. The stride angles were 5.1±0.9, 13.7±4.9 and 17.8±4.0 degrees for the left paws. Cavity volumes were 10.3±2.1, 31.0±2.0 and 28.2±4.9%. In addition to cavities, there were astrocyte-devoid areas containing some loose tissues, through which many axons extended longitudinally. Conclusions: The BBB score, dorsiflexion angle and stride angle were consistently improved in the PP group. Cavity formation was more reduced, and many axons extended through coarse tissues formed in astrocyte-devoid areas at the lesion in the PP group. Forced training by PP of the hind paws promoted the behavioral and histological improvement of rats with SCI.