The Efficacy of Immediate Implantation of Macroporous Poly(N-[2-Hydroxypropyl]-Methacrylamide) Hydrogel after Laceration Spinal Cord Injury in Young Rats

Abstract

Spinal cord regeneration after mechanical injury is one of the most difficult biomedical problems. This article evaluates the effect of poly(N-[2-hydroxypropyl]-methacrylamide) hydrogel (PHPMA-hydrogel) on spinal cord regeneration in young rats after lateral spinal cord hemi-excision (laceration) at the level of segments T12–T13 (TrGel group). The locomotor function score (FS) and the paretic hindlimb spasticity score (SS) were assessed according to Basso–Beattie–Bresnahan (BBB) and Ashworth scales, respectively, and compared to a group of animals with no matrix implanted (Tr group). Regeneration of nerve fibers at the level of injury was evaluated at ~5 months after spinal cord injury (SCI). One week after the SCI induction, the FS on the BBB scale was 0.9±0.5 points in the Tr group and 3.6±1.2 points in the TrGel group. In the Tr group, the FS in 5 months was significantly lower than in 2 weeks after SCI, while no significant changes in FS were detected in the TrGel group over the entire observation period. The final FS was 0.8±0.3 points in the Tr group and 4.5±1.8 points in the TrGel group. No significant changes in SS have been observed in the TrGel group throughout the experiment, while the Tr group showed significant increases in SS at 2nd week, 6th week, 3th month and 5th month. The SS in 5 months was 3.6±0.3 points on the Ashworth scale in the Tr group and 1.8±0.7 points in the TrGel group. Throughout the observation period, significant differences in FS between groups were observed only in 5 weeks after SCI, whereas significant differences in SS were observed in 2, 3 and 6–8 weeks post-injury. Glial fibrous tissue containing newly formed nerve fibers, isolated or grouped in small clusters, that originated from the surrounding spinal cord matter have been found between the implanted hydrogel fragments. In conclusion, PHPMA-hydrogel improves recovery of the hindlimb locomotor function and promotes regenerative growth of nerve fibers. Further research is needed to clarify the mechanism of this PHPMA-hydrogel effect.