| Objective To investigate the neuroprotective mechanism of recombinant human erythropoietin (RhEPO) and its effect on the expression of aquaporin4(AQP-4) in brain tissue of neonatal rats with hypoxic-ischemic brain damage (HIBD)Methods100seven-day-old Sprague-Dawley (SD) rats were randomly divided into sham-operated group(n=20), control group(n=20), RhEPO-treated group{low dose group(n=20), medium dose group(n=20), high dose group (n=20)}. The right carotid arteries of rats in sham-operated group were only isolated, without ligation, ischemia, hypoxia and medication, while the other four groups were made by shearing right carotid arteries communis and breathing8%oxygen for two hours. Then low dose group, medium dose group, high dose group received an intraperitoneal injection of EPO at dose of1000IU/kg,2500IU/kg,5000IU/kg,every other day,four times in a row. While the other two groups received equivalent saline at the same time.10of each group rats were randomly executed on the3th and7th day after the HI operation (n=10).Cerebral pathomorphological changes was observed by HE staining. The AQP-4expression in neonatal rats brain was examined by immunohistochemical technique and image quantitative analysis after the operation.Results l.The number of AQP-4positive cells in RhEPO-treated groups was significantly less than control group on the3th day (26.6±4.67,36.6±3.97,20.8±7.9,23.0±9.6,P<0.05). The number of AQP-4positive cells of medium dose group and high dose group were less than those of low dose group (P<0.05). The number of AQP-4positive cells in control group was more than those of sham-operated group (P<0.05).2. The number of AQP-4positive cells in medium dose group, high dose group was less than control group on the7th day.(33.2±4.38,25.6±7.63,43.8±4.76,P<0.05). These of high dose group were less than those of medium dose group, and Those of medium dose group was less than the low dose group’s, too (P<0.05). The number of AQP-4positive cells in RhEPO-treated groups and control group were higher than those of sham-operated group (P<0.05).3. In control group and RhEPO-treated group, brain edema, degeneration, apoptosis and necrosis of the neurons in the right hemispheres was obvious by HE staining on the3th day, to lessen on the7th day.The cerebral pathomorphological changes of RhEPO-treated group was lessen than control group. Compare with low dose group,the cerebral cortex and hippocampus pathology of medium dose group and high dose group was more pyramidal cell layers,the cell boundary more clealy,significantly reduced the number of cell apoptosis and necrosis of the neurons. There was no cerebral pathomorphologieal changes in sham-operated group and the right hemisphere of control group.Conclusion The expression of AQP-4was significantly increased in brain tissue of neonatal rats with hypoxic-ischemic brain damage (HIBD),closely related to the severity of brain edama. EPO has neuroprotective effect on neonatal rats with HIBD by down regulating of AQP-4expression, so as to alleviate brain edema. The effect of high dose and medium dose EPO are better than that of low dose with dose dependent manner. |
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