The Development Of Rat Model Of Intracerebral Hemorrhage And The Roles Of VEGF Dynamic Expression Following Intracerebral Hemorrhage

Objective: Cerebral vascular diseases (CVD) are common in current societies. Among which, intracerebral hemorrhage (ICH) is an emergent disease endangering the people's life and work because of its high mortality and serious disability. The most important pathological changes after ICH are the hemotoma itself and the secondary edema, which causes herniation-related death and severe neurological deficits. Although lots of improvements have been made on the prevention and treatment of ICH, the mechanism of brain edema formation and secondary neuron injury are not clear now. So the researches on ICH become the focus of clinical and primary studies. Vascular endothelial growth factor (VEGF) plays important roles in increasing the vascular permeability, promoting the proliferation of endothelial cells and the angiogenesis, as well as protecting the nerve tissues. Many studies have testified that VEGF is closely associated with the onset and development of brain edema in cerebral diseases, such as cerebral ischemia and brain tumor, and so on. And it has some relations with the volume and prognosis of cerebral ischemia. But the relationship of VEGF and ICH is poorly understood. The purposes of this study are to develop a reliable and reproducible animal model of ICH, to observe the changes of behavioral function and brain water content, to confirm the VEGF expression and cell location in brain tissues and to analyze the relations among the neurological function, brain edema and VEGF expression on the basis of the ICH rat model. Methods: Adult male Sprague-Dawley rats were fixed to the stereotactic frame after anesthesia, and then the ICH model was induced by the injection of 50μl autologous caudate artery blood into the right basal ganglia of rats stereotactically. And the rats of control group underwent intracranial needle insertion but without blood injection. At 6 h,12 h,24 h,48 h,72 h and 7 d after operation, all the rats were tested for neurological behavior using four different methods. And then rats were sacrificed, the brain tissues were quickly moved from the skull and the cerebrum was coronally cut through the needle entry site. The frontal part (almost 3 mm thick ) was for brain water content measurement, which was calculated as the percentage changes between wet weight and dry weight using the following formula:(WW-DW)/WW×100%. The postal parts were used for histological examination. They were dealed after several procedures, including fixed in 4% formalin, dehydrated by different concentrations of ethanol and then embedded in paraffin. Then the brain tissues were cut into 5μm slices. Parts of slices were stained with hematoxylin and eosin to observe the edema around hematoma, the inflammatoryinfiltration, the microgliocyte proliferation and overall brain morphology. Other parts of slices were stained by routine immunohistochemical methods using primary antibodies of VEGF to observe the kinds of positive cells; the expression of VEGF in and around hematoma, and the changes of its expression with time went on. All the observations were done in both ipsilateral and contralateral of the hematoma. Results: All rats had different neurological deficit scores at different time points after ICH. As the consequences of anesthesia and operation injury, the neurological deficit there was severe at 6 h, but there was no significant difference between the ICH group and the control group, P>0.05. During the 12 h to 72 h, there were significant differences between two groups, P<0.05. At 7 d, the neurological function recovered. At 6 h and 7 d, the brain water content of the ICH and control group had no significant difference, P>0.05. At 48 h and 72 h, significant differences existed, P<0.05, and it was highest at 48 h. Significant differences also existed between the ipsilateral and contralateral at 48 h and 72 h, P<0.05. The HE stain of the ICH group indicated that at 6 h,around the periphery of hematoma there were a few scattered neutrophils and the shape of neurons had no obvious changes. At 48 h and 72 h, brain tissues around the hematoma were obviously swollen and necrotic, and there were a compact band of cells including inflammatory cells, clusters of intact erythrocytes...