| Objective In this study we investigate the effects of erythropoietin (EPO) on the expression of 5-bromo-deoxyuridine (BrdU) in subgranular zone (SGZ) and Nestin in dentate gyrus (DG) after hypoxic-ischemic brain damage (HIBD) in neonatal rats, to explore the neuroprotective effects of erythropoietin according to the regeneration of neurocytes and the improvement of learning and memory capability by using the Morris water maze, in order to obtain the experimental evidences of the suitable therapeutic dose of the EPO for hypoxic-ischemic encephalopathy of neonates.Methods One hundred sixty neonatal Wistar rats were divided into five groups randomly: the group of the HIBD, the control group of normal sodium and the trial group of EPOⅠ,Ⅱ,Ⅲ, each group were thirty-two, the HIBD models of neonatal Wistar rats were made by shearing right arteria carotis communis and then breathing 8%02+92%N2 for two hours. the trial groups of EPOⅠ,Ⅱ,Ⅲwere injected intraperitonally separate rhEPO 5u/g,10u/g,15u/g for fourteen days since operation, the control group of the HIBD was injected intraperitonally 0.5ml NS as a pair, the other forty rats were taken into the sham operation group. Before every rat was sacrificed,5-bromodeoxyuridine (BrdU) was injected intraperitonally three times in order to label newly generated neurocytes exclude the rats for spatial cognitive capability by using the Morris water maze in each groups. The expressions of BrdU and Nestin in dentate gyrus (SGZ) were examined with immunohistochemical staining and image quantitative analysis 14d,21d,28d after the operation. Pathological change of brain was investigated with microscope. Each of five group's spatial cognitive capability was evaluated by using the Morris water maze also.Results 1. the expression of 5-bromo-deoxyuridine (BrdU) in subgranular zone(SGZ): The number of BrdU-positive cells in SGZ of hippocampal region was gradually decreasing accompany with the increasing age in each groups (P<0.05); The BrdU-positive cells were a significantly difference of the five groups(P<0.05), The expression of BrdU-positive cells of the EPO trial groups were higher than the control group, and the sham operation group was least compare with other groups (there is a significantly difference in five groups at the 14th and 21th days after the operation, but no significantly difference at the 28th days after the operation); The number of BrdU-positive cells in subgranular zone (SGZ) had decreasing tendency accompany with the increase therapeutic dose of the EPO at all points in the trial groups, but there is no significantly difference (P>0.05).2. the expression of nestin in dentate gyrus (DG):The number of nestin in dentategyrus (DG) was gradually decreasing accompany with the increasing age, there is a significantly difference(P<0.05); The expression of nestin-positive cells was the most in the trial group of EPO, second is the control group of HIBD, the sham operation group was least (there is a significantly difference in five groups at the 14th and 21th days after the operation, but no significantly difference at the 28th days after the operation); 3. Determination of Morris water maze:①Learning ability:The latency to escape was significantly difference in five groups (P<0.05), the sham group is the shorter compared with the EPOⅠ,Ⅱ,Ⅲtreated groups, the control group of HIBD is the longest.②Memory capacity:the frequency of passing the platform was a significantly difference in five groups; there is a significantly difference in the sham operation group and the EPOⅠ,Ⅱ,Ⅲtreated group compared with the control group of HIBD (P<0.05), but there was no significant difference between the sham operation group and the EPOⅠ,Ⅱ,Ⅲtreated group(P>0.05). and also no significant difference in the EPOⅠ, the EPOⅡand the EPOⅢgroups too (P>0.05).Conclusions 1. Exogenous EPO could increases the expression of BrdU and Nestin in hippocampal region of neonatal rats with HIBD, it means that EPO promotes the regeneration of neurocytes damaged by hypoxia-ischemia and it may be involved in the regeneration of neurocytes and play an important role of neuroprotective effects in neonatal rats with HIBD; 2. EPO early intervention can improve the ability of learning and memory in the neonatal rats with HIBD; 3. EPO could improve the proliferation, differentiation and regeneration of the endogenous neural stem cells in the neonatal rats with HIBD; 4.The result show there is a decreasing tendency of the marks that represents the regeneration of neurocytes accompany with increased therapeutic dose of the EPO in the neonatal rats with HIBD, it could not improve the neuroprotective effects by increasing dose of EPO. |
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