Morphological changes in the sciatic nerve in experimental modeling of contusion injury of the spinal cord in rats

Objective. To analyze morphological and morphometric changes in the sciatic nerve of rats after the spinal cord injury.

Material and Methods. The Т9 moderately severe contusion injury of the spinal cord was simulated in 12 Wistar female rats. Functions of the pelvic limbs were assessed according to the standardized BBB scale. The animals were withdrawn from the experiment after nine and 13 weeks. Epoxy semi-thin (1 µm) sections were used to study sciatic nerve at the light-optical level.

Results. Significant recovery of pelvic limb functions was observed within four weeks after surgery, the plateau was achieved by Week 5 (9.5 ± 0.28 points according to the BBB scale), the deterioration in the motor activity was observed by Week 9 (8.67 ± 0.33), its recovery was achieved by Week 13 of the experiment (9.5 ± 0.87). After 9 and 13 weeks, reactive-destructive changes were detected in the sciatic nerve in 9 % and 8 % of nerve conductors, an increase in the number density of myelin fibers by 28 % and 27 % (p < 0.05) and myelin-free fibers by 20 % and 49 % (p < 0.05), and a decrease in axon diameters by 8 % and 10 % (p < 0.05), respectively.

Conclusions. The morphological and morphometric changes in the sciatic nerve revealed after the spinal cord injury in the form of destruction of a part of the fibers, axonal atrophy and a decrease in the proportion of large fibers negatively affect its conductive properties. The leveling of peripheral nerve damage, possibly, will accelerate the regression of the motor deficit caused by the spinal cord injury; therefore, it is necessary to develop a set of preventive measures aimed at preventing the reorganization of the peripheral nerve tissue.

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