Effects of hyperglycemia and cerebral ischemia on VEGF expression in different subfield of cerebral cortex in tree shrews / 中国病理生理杂志

ABSTRACT

AIM: To observe the changes of VEGF expression in different subfield of brain in tree shrews during hyperglycemia and focal cerebral ischemia, in order to explore the relationship between cerebral ischemia, hyperglycemia and VEGF. METHODS: High blood glucose in tree shrews was induced by intraperitoneal injection of streptozotoctin. Focal cortical thrombotic cerebral ischemia was induced by photochemical method in tree shrews. At 4 h, 24 h and 72 h after cerebral ischemia, the histopathological changes and hippocampal neuronal density were examined. VEGF expressions in the ischemic core, penumbra and contralateral cerebral cortex were detected by immunohistochemistry technique at different times after cerebral ischemia. RESULTS: The results of histopathological study showed that there was infarction zone in the exposured cerebral cortex at 4 h after photochemical reaction, and the damage was most severe at 24 h, subsequently accompanied with the glia multiplication and rehab reaction at 72 h. The animals in hyperglycemic ischemic group suffered from greater neurological lesion than the normoglycemic stroke animals, especially at 24 h (P<0.01) and 72 h (P<0.05) after cerebral ischemia. Immunohistochemical analyses of VEGF expression revealed that it started to increase at 4 h after brain ischemia in the penumbra, reached a peak at 24 h, and weakened at 72 h. The stimulated VEGF production was also observed in hyperglycemic only group. When hyperglycemia and brain ischemia were combined, the VEGF expression was higher than that in hyperglycemic only group (P<0.05). Compared to normoglycemic ischemic group, no additivity of the effects of hyperglycemia combined with brain ischemia was observed. CONCLUSION: (1) The model of experimental hyperglycemia and cerebral ischemia is replicated successfully by applying the method combined in vivo injection of streptozotocin in the lower primate tree shrew with thrombotic focal cerebral ischemia. (2) This study shows that hyperglycemia aggravates the focal cerebral ischemia damage. (3) Cerebral ischemia and hyperglycemia both can independently up-regulate VEGF expression, but there is no additional increase in VEGF expression when hyperglycemia combined with brain ischemia is applied.