Effect Of Retrograde Gene Transfer Of Brain-derived Neurotrophic Factor In The Spinal Cord Injury Of Rat

Background:Spinal cord injury(SCI) can be divided into two types-primary and secondary injury. Primary injury is a kind of irreversible injury, however, there are seldom cases whose spinal cord is directly cut off. In most of the injury cases, the injury of spinal cord is contusion and compression, which means there is still intact nervous tissue. Previous researches indicate that the shortage of neurotrophic factors may be one of the main problems during recovery of SCI. And Brain-derived Neurotrophic Factor(BDNF) is one of the most researched factors in SCI.ObjectiverUsing Adv-BDNF up-regulate the expression of BDNF in a rat SCI model, therefore promoting recovery of nervous tissue and motor function.Method:Rats are divided into4groups:G1-4, rats in group G1-3are induced spinal cord injury, while in group G4underwent a laminectomy only. G1group and G2group are respectively inject adenoviral vector encoding BDNF(Adv-BDNF) or eGFP(Adv-eGFP) in the rostral5mm of the injured spinal cord, while G3is injected PBS instead. Spinal cord sample is gathered at1,3,7,14and28days after injury. We use RT-PCR and Western blot to detect expression of BDNF, and use immunohistochemistry to evaluate degree of injury of nervous tissue. The Basso, Beattie, and Bresnashan (BBB) scale system is used for motor function.Result:Immunohistochemistry of spinal cord sample from G2group shows that GFP distributes throughout the rostral spinal cord, mainly in anterior horn motor neurons, whereas GFP is distributed in the interneurons of the gray matter near the central canal in the transverse sections of the injured spinal cord. The results of RT-PCR and western blot indicate that:In group G3, the expression of BDNF is increased24h after injury, but is reduced at3days. And BDNF expression remains low for up to1week. In group G1, the down-regulation of BDNF following SCI is milder, there is an obvious recovery of expression at14and28days. Both G1and G2group exhibit more BDNF than G3group do. G1group shows a smaller cyst cavity compares with G3group, and G2group exhibit the smallest cavity at4week post-surgery. However, more normal spinal parenchyma is observed in G1group compares G2group. Rats in all groups exhibit a gradual improvement in BBB scores, G1group has a higher BBB scores than G2and G3group at7,14and28days after injury.Conclusion:1. Using adenovirus-mediated BDNF can up-regulate the expression of BDNF in a rat SCI model.2. In the rat SCI model, up-regulation of BDNF can promote nervous tissue and motor function.