Structural and molecular changes in the epicenter of injury and distant segments of the rat spinal cord in response to rehabilitative motor training

Background . Spinal cord injury (SCI) leads to partial or complete loss of sensory and/or motor functions below the injury site due to neuron and glial cell death, axonal degeneration, and disruption of the blood-spinal cord barrier (BSCB). Motor rehabilitation presents a promising strategy for recovery after SCI, but its molecular and cellular mechanisms remain poorly understood, particularly in regions distant from the injury epicenter within the central pattern generator. The aim of the study . To assess structural and molecular changes occurring in regions proximal (Th9) and distal (L 2 ) to the epicenter of SCI in rats (Th 8 ) during rehabilitation motor load. Materials and methods . SCI was induced in rats at the Th 8 level. Animals were divided into a control group (SCI) and a group subjected to motor rehabilitation (SCI + Rehab). Structural and molecular changes were evaluated in the thoracic (Th 9 ) and lumbar (L 2 ) regions. The number of preserved myelinated fibers was assessed using methylene blue staining, and BSCB disruption was evaluated through the epifluorescence of Evans blue dye. Quantitative PCR was used to analyze the mRNA expression of genes encoding proteins specific to perisynaptic astrocytic processes. Results . In the lumbar region (L 2 ), motor rehabilitation led to a greater number of myelinated fibers in the corticospinal tract compared to the control group. Astrong negative correlation (r = –0.761) was observed between Evans blue fluorescence and the area of preserved tissue in the Th 7 –Th 9 region in rehabilitated animals; however, this relationship is not statistically significant. Molecular analysis revealed that rehabilitation did not affect astrocyte polarization into aneurotoxic phenotype or the alteration of perisynaptic processes in both proximal and distal regions. Conclusion . Motor rehabilitation promotes the preservation of myelinated fibers in the lumbar region and reduces BSCB damage in the area proximal to the SCI. However, rehabilitation does not affect astrocyte polarization or the expression of mRNA genes encoding proteins characteristic of perisynaptic astrocyte processes.