Avaliação dos efeitos da fotobiomodulação vascular no reparo neuromuscular e recuperação funcional após a lesão medular por compressão em ratos

Abstract

Introduction: Spinal Cord Injury (SCI) is an impairment of the spinal cord that promotes the discontinuity of the spinal canal, leading to functional and sensory losses in the areas below the lesion, which are often irreversible. The effects of photobiomodulation (PBM) in the neuromuscular repair process show positive results, especially considering peripheral nerve injuries, however, in the recovery of spinal cord injuries, its effects are still poorly known and described in the literature, especially with regard to non-invasive systemic application, called vascular PBM (VPBM). Objective: Analyze the effects of VPBM in the immediate, acute and intermediate phases on functional (motor) recovery, tissue morphological aspects of neuromuscular repair, on the differential white blood cell count and on the protein expression of Brain Derived Neurotophic Factor (BDNF) after induction of SCI by compression. Methodology: 125 Wistar rats were used, divided into 5 groups: control group (n=5), SCI group (n=35), SCI+VPBM-I group (n=35), SCI+VPBM-2h group (n= 35) and SCI+VPBM-14d group (n=15). The VPBM was applied in the region of the caudal artery with the low-level laser (LLLT) AsGaAl (780 nm, 80 J/cm², 40 mW, for 80 seconds, totaling 3.2J energy in a single point) for 14 consecutive days. During the analysis periods (1, 3, 7, 14, 21, 28 and 35 days after SCI), the animals were evaluated for functionality using the Basso-Beattie- Bresnahan Index (BBB). At the end of each experimental period, blood samples were collected to evaluate the differential count of peripheral leukocytes and to evaluate the circulating concentration of BDNF by ELISA technique and for morphological and histological evaluation, muscle and nervous tissue samples were also extracted. Results: Treatment with VPBM-I and VPBM-2h led to the recovery of motor function, observed from the 7th day after injury (p<0.05), to an increase in the Cross-Sectional Area (CSA) in the second week of evaluation and to the diameter of the muscle fiber, observed from the 21st evaluation (p<0.05), it was also observed that early irradiation has more effect in reducing the cavity size with stabilization of the same being observed on the 28th day of treatment. evaluation (p<0.05), there was maintenance of baseline neutrophil values on the 1st day after SCI with a significant increase on the 3rd day after injury in the SCI+VPBM-2h group. In addition, an increase in BDNF expression was observed on the 7th day for the SCI+VPBM-I and SCI groups (p=0.0045 and p=0.0011 respectively), after 35 days the irradiated groups SCI+VPBM-I and SCI+VPBM- 2h showed BDNF levels that did not differ from the control. Conclusion: The results showed that VPBM was able to modulate the morphological and functional recovery after SCI, especially when applied early, showing positive effects on functional recovery evaluated by the BBB index and horizontal ladder, reestablishment of muscle tissue structure (diameter and AST) and nervous tissue (reduction of the cavity size in the spinal cord) and reduction of BDNF levels close to the values of the control group in the later phases evaluated, which can therefore be an important ally in the treatment of SCI.