| Summary: | 碩士 === 南台科技大學 === 生物科技系 === 100 === Background: Spinal cord injury(Sci) results in damage to the vasculature and blood supply and in destruction of the brain-spinal cord fiber connectivity, leading to progressive tissue decay at the damage site and paralysis below the lesion site. Lack of wound repair and chronic tissue decay accompanied by enlarging cavitation at the lesion site are characteristic of the pathology of spinal cord injury. Induction of HSP72 expression in the rat spinal cord after progressive exercise training for 3 weeks has not been studied. It also remains unclear whether physical exercise protects rats against spinal cord injury-induced neuronal damage.
Aim: The aims of this study were first to ascertain whether heat shock protein (HSP) 72 in the spinal cord tissue can be induced by exercise in rats and second to assess whether neuron degeneration and motor deficit in Sci can be prevented by pre-injury exercise training induced HSP72 expression.
Materials and methods: Rats were divided into four groups: (1)Sedentary group (Sed): no exercise training; (2)Exercise group (Exe):exercise pre-training for 3 weeks; (3) Sham operation (Sham): laminectomy only; (4)Spinal cord injury group (Sci): sedentary for 3 weeks and then induced laminectomy +Sci; and (5) Exercise pre-training and induced Sci group (Exe+Sci): exercise precondition for 3 weeks and then induced laminectomy + Sci. Spinal cord injury was induced by compressing the spinal cord for 1 min with an aneurysm clip calibrated to a closing pressure of 55 g. Behavioral tests of motor function measured by CBS and BBB score were conducted at day 1 to day 14, after spinal cord injury. To elucidate whether HSP72 can be secreted in spinal cord injured area by the exercise pre-training, analysis of spinal cord homogenate’s supernatants by specific immunofluorescence stain and western blotting for HSP72 was conducted respectively. The triphenyltetrazolium chloride (TTC), NeuN staining and terminal deoxynucleotidyl transferase (TdT)-mediated deoxyuridine triphosphate (dUTP)-biotin nick end labeling (TUNEL) assay, HSP72 and neuron or astrocyte double immunofluorescence staining were conducted at day 1-14 days after spinal cord injury to evaluate spinal cord infarction, neuron apoptosis, and neuron express with HSP72 respectively.
Results: We demonstrated that, at 1, 3, 7, 14 days after spinal cord injury, exercise pre-training significantly reduced the total lesion volume, neuron apoptosis and increased HSP72 expression as compared to the sedentary Sci group. Qualitative examination of injury site morphology indicated that microcystic cavitation and robust astrogliosis (GFAP-labeled astrocyte accumulation) were characteristic of rat response to clip compressive Sci. Since Sci induces apoptotic neuron death, we also studied the co-expression of HSP72 with markers of apoptosis. No HSP72-positive neurons were found to be apoptotic, as assessed by both TUNEL, DAPI and HSP72 immunoreactivity. Therefore, it is possible that the upregulation of HSP72 observed in injured neurons may play a role in protecting neurons from apoptotic cell death following Sci.
Conclusions: Exercise pre-training is a simple and effective modality protecting the spinal cord against subsequent prolonged periods of compression injury. It was found that exercise pre-training significantly attenuated the Sci -induced motor function defect, infarction, and apoptosis by stimulating HSP72 in a spinal cord compression model.
Key words: spinal cord injury, motor function, heat shock protein 72, neuron apoptosis
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