The experimental study of hypoxia-inducible factor-1 alpha and its target genes in spinal cord injury

Study design: Animal model of compressive spinal cord injury (SCI), reverse transcription-polymerase chain reaction (RT-PCR), in situ hybridization (ISH), immunohistochemistry (IHC) and enzymehistochemistry (EHC) were used to test the hypothesis that hypoxia- inducible factor-1 alpha (HIF-1 alpha) and the target genes activated by HIF-1 alpha are involved in cell hypoxia tolerance and tissue vascularity to help injured tissue to go through the stress disease. Objective: To determine whether HIF-1 alpha and its target genes associated with hypoxia tolerance and neovascularization take part in the pathophysiological procedure of SCI in rats. Setting: Yunnan University, China. Methods: Random-bred adult male Sprague-Dawley (SD) rats weighing 250 +/- 750 g were prepared for compressive SCI models. After receiving compressive injury at T-10, rats were sacrificed at different times from 6 h to 1 week after injury. The injured cords were removed, and HIF-1 alpha and its target genes were assayed by RT-PCR, ISH, IHC and EHC. The data were statistically analyzed. Results: An increase in HIF-1 alpha mRNA expression was observed 12 h postinjury, reached a maximum at 3 days, and reduced gradually thereafter. HIF-1 alpha protein expressed earlier than HIF-1 alpha mRNA. Additionally, two glycolytic enzymes and vascular endothelial growth factor (VEGF), which are regulated by HIF-1 alpha, also increased after an interval postinjury, and their expression patterns shared a same trend with that of HIF-1 alpha protein. Conclusion: The. findings suggested that the most important hypoxic regulatory factor HIF-1 alpha was upregulated in involved cells by activating the transcription and increasing protein stability, and subsequently activated the expression of HIF-1 alpha target genes, including glycolytic enzymes and VEGF in SCI. Combined with the pathologic observation, it suggested that overexpression of HIF-1 alpha and its target genes might take part in hypoxia tolerance and vascularity of the injured spinal cord.