Potencial terapêutico das células mononucleares da medula óssea em um modelo experimental de esclerose lateral amiotrófica

Abstract

Lateral amyotrophic sclerosis (ALS) is a neurodegenerative disease characterized by the selective loss of both lower and upper motoneurons in the spinal cord, brain stem and motor cortex. Loss of motoneurons leads to progressive paralysis, and death in 2 to 5 years. Treatment is based on symptomatic measures and pharmacological therapy available is not curative. Thus, it is of great importance to develop new therapeutic strategies to manage this disease. Alternatively, stem cells to replace could be used to replace degenerating neurons or to stop/delay neuronal death. The aim of this study was to verify if bone marrow mononuclear cells (BMMC) have therapeutic potential in transgenic mice superexpressing SOD1G93A. These animals phenotypic and physiopathological characteristics mimic those of ALS. Seventy-day-old or 110-day-old mice were administered with 107 BMMC in the tail vein. BMMC were obtained from C57BL/6-EGFP or SOD1G93A donors. Control animals received saline. In order to determine disease onset and progression, animals were evaluated in the Rotarod test, by electromyography and had their body weight measured. Survival was also evaluated. Tissue samples were collected for PCR analysis of cell migration. Additional groups of animals were euthanized at 120-days-old for histological analysis and the alkaline comet assay. Our results indicate that EGFPBMMC transplantation in 70-day-old mice (pre-symptomatic) mice prolong survival, preserve motor function and preserve motoneurons in the ventral horn of the spinal cord. However, for mSOD1BMMC the observed effect is intermediary. Furthermore, in 110-day-old (symptomatic) mice, only EGFPBMMC prolonged survival. This effect was more discrete than the one observed for pre-symptomatic-treated animals. Finally, systemically administered BMMC migrate into the spinal cord where fragments of their DNA were identified by PCR. There were no differences between the experimental groups in the electromyographical evaluation or DNA integrity measured by the alkaline comet assay. Our results suggest that BMMC have therapeutic potential in ALS since we observed improved motor performance and prolonged survival in animals that received the transplant. Nonetheless, outcomes were better when intervention was early and the transplanted cells did not express the mutated SOD1. Thus, our data represent a step forward in making cell-based therapy available for ALS patients. However, questions associated to the time of intervention and the source of the cells should be carefully addressed.