The effects of weight- and non-weight-bearing exercise on corticospinal axon sprouting, regeneration-related proteins and functional recovery after spinal cord contusion

The purpose of this study was to investigate the effects of weight- and non-weight-bearing exercises on the Basso-Beattie-Bresnahan (BBB) locomotor rating scale, corticospinal axon regrowth and regeneration-related proteins following spinal cord injury (SCI). Twenty-four male Sprague-Dawley rats were randomly divided into four groups: control group (n=6), SCI+sedentary group (SED, n=6), SCI+treadmill exercise group (TREAD, n=6), and SCI+swimming exercise group (SWIM, n=6). All rats in the SCI group were given the rest for 2 weeks after SCI, and then they were allowed to engage in low-intensity exercise for 6 weeks on treadmill device. Motor function (BBB score) was improved more in the SWIM group compared to the SED group at 3 and 6 weeks after SCI. The SWIM group also showed higher levels of axonal outgrowth in corticospinal tract and increased expression of phosphorylated extracellular signal-regulated kinase, a marker of axonal regeneration in the dorsal horn of the caudal region, compared to the TREAD group. Additionally, the SWIM group significantly upregulated the expression of regeneration-related proteins. Our findings suggest that non-weight-bearing exercise may be one of several rehabilitation methods for improving locomotor function and corticospinal axon regeneration after SCI.