Electric Axonal Plasticity Research On Stem Cells And SCI Rats And Related Mechanism

Neuronal regeneration in the central nervous system (CNS) has been studied as a hot topic in neuroscience and even whole life science field. Spared neurons and axons after spinal cord injury (SCI) have functional plasticity. How can we activate and enlarge the endogenous potentials for our use? In this thesis, we focused on corticospinal tract (CST) and investigated whether electroacupuncture (EA) can enhance CST sprouting and resulting functional synaptogenesis by using a nerve-tracing technique. We examined whether EA increased proliferation, differentiation, and remyelination of endogenous neural stem cells by using immunofluorescent labeling, and our data provide scientific evidence for the enhancement of SCI repair by EA.In the first part of this thesis, we investigated whether EA enhanced the development of neural plasticity and functional recovery following unilateral CST injury in rats.36adult Long Evans female rats were randomly assigned into two groups, sham group (n=18) and EA group (n=18). Pyramidotomy was used to produce unilateral CST injury. EA was carried out one week after CST injury at GB30and HTJJ-T630min per day for3weeks. By using a biotinylated dextran amin (BDA)-mediated neural-tracing technique combined with foot-print and Horizontal ladder test, we observed the effect of EA on morphological alteration of CST projection and behavioral recovery in the injured limb; by using immunohistochemical staining, we calculated the percentage of vGlutl+/BDA+double-labeling nerves and observed the effect of EA on formation of functional synapses between regenerated axons and targeted neurons; by using Western blotting, we examined the expression of spinal brain-derived neurotrophic factor (BDNF) to address the mechanisms underlying CST sprouting. We found that1) EA significantly enhanced CST sprouting and synaptic formation (p<0.05);2)the expression of BDNF in L5spinal cord of EA group was significantly higher than that in the control group (p<0.05);3) EA significantly increased the percentage of vGlutl+/BDA+double-labeling nerves (p<0.05);4) Foot-print and cat-walk testing showed that EA promoted functional recovery in the first4weeks after surgery (p<0.01). These results indicate that EA can enhance CST sprouting and the subsequent formation of functional synapses, and that EA can increase the expression of BDNF in the ipsilateral motor neurons. Therefore, our data provide experimental evidence for the enhancement of CST plasticity by EA. Our study demonstrates that EA can enhance CST sprouting and provides scientific evidence for neural injury and repair in the CNS.In the second part of this thesis, we investigated the effect of EA on proliferation of endogenous stem cells, differentiation of oligodendrocytes and functional recovery after SCI. In this part, contusive SCI at T8-9level was performed in adult SD rats. EA was carried out one week after SCI at GB30and HTJJ-T630min per day for3weeks. Spinal cord tissues were harvested in the fourth week following SCI. By using5-bromo-2’-deoxyuridine (BrdU) labeling and immunohistochemical staining, we observed co-localization of BrdU+/NG2+and BrdU+/GFAP+in the injured spinal cord15mm rostral (R-15) and caudal (C-15). By using Basso, Beattie and Bresnahan (BBB) scale scoring, we assessed the effect of EA on recovery of motor function after SCI. We found that EA significantly increased the number of BrdU+/NG2+double-labeling cells in both R-15and C-15of the injured spinal cord (p<0.01), but EA had no effect on the number of BrdU+/GFAP+double-labeling cells in both R-15and C-15of the injured spinal cord (p>0.05).We also found that EA significantly increased BBB scores from2weeks to4weeks after SCI (p<0.05), and of which the effect of EA reached maximal in the fourth week (p<0.01). These results suggest that EA can promote the proliferation and differentiation of endogenous oligodendrocytes and improve functional recovery after contusive SCI.Based on our data, we conclude that1) EA can enhance neuronal plasticity in the CNS by upregulating the expression of BDNF, thereby regenerating neural circuits through axon sprouting and reconnection with target neurons in the injured spinal cord and2) EA can promote the proliferation and differentiation of endogenous stem cells and then improve functional recovery after SCI.