Effects of basic fibroblast growth factor on beta-catenin protein and mRNA expression during the proliferation of endogenous neural stem cells following focal cerebral ischemia

Xuesong Xing; Weili Lü; Liguang Sun

摘要

BACKGROUND:The Wnt/β-catenin signaling pathway plays an important role in neural development.β-catenin is an important component of the Wnt/β-catenin signaling pathway.The Wnt signaling pathway has been shown to regulate the interaction of neural stem cells with the extracellular matrix. OBJECTIVE:To investigate the effects of basic fibroblast growth factor(bFGF) onβ-catenin protein and mRNA expression,and on hippocampal neural stem cell proliferation in a rat model of cerebral ischemia/reperfusion. DESIGN,TIME AND SETTING:A randomized,controlled,neurobiology experiment was performed in Shenyang Medical College between August 2006 and August 2008. MATERIALS:A total of 72 healthy male Wistar rats,aged 3 months,were used in this study. bFGF was provided by Beijing SL Pharmaceutical Co.,Ltd.,China. METHODS:Rats were randomly divided into 3 groups:sham-operated,ischemia/reperfusion,and bFGF-treated(n=24 per group).Focal cerebral ischemia/reperfusion was induced in rats from the ischemia/reperfusion group and the bFGF-treated group by 2 hour right middle cerebral artery occlusion and 2 hour restoration of blood flow using the suture method.The ischemia/reperfusion and bFGF-treated groups were intraperitoneally administered 500 IU/mL of bFGF,or the same volume of physiological saline,once a day at postoperative days 1-3,and once every 3 days thereafter.Simultaneously,the sham-operated group underwent experimental procedures identical to the ischemia/reperfusion and bFGF-treated groups,with the exception of ischemia/reperfusion induction and drug administration.At 2 hours,2,6,13,and 20 days after ischemia/reperfusion induction,50 mg/kg bromodeoxyuridine(BrdU) was administered to each group,twice daily,to label proliferating neural stem cells. MAIN OUTCOME MEASURES:The effects of bFGF on BrdU labeling,andβ-catenin mRNA and protein expression,in neural stem cells were examined by immunohistochemistry,Western blot, RT-PCR,and in situ hybridization techniques. RESULTS:In the sham-operated group,only a few BrdU-immunoreactive neural stem cells were found.In the ischemia/reperfusion group,BrdU-immunoreactive cells began to increase from 3 days after ischemia/reperfusion induction,reached a peak level at 7 days,and gradually reduced from 21 days.At 3,7,14,and 21 days after ischemia/reperfusion induction,the numbers of BrdU-immunoreactive cells were significantly greater in the bFGF-treated group than in the ischemia/reperfusion group.The sham-operated group exhibited slight expression ofβ-catenin andβ-catenin mRNA.In the ischemia/reperfusion group,the expression ofβ-catenin andβ-catenin mRNA gradually increased with reperfusion time,peaked at 14 days after reperfusion, and gradually decreased thereafter;by 21 days,the expression was markedly lower.Following bFGF injection,the expression of hippocampal BrdU,β-catenin,andβ-catenin mRNA had apparently increased in each group. CONCLUSION:bFGF promotes neural stem cell proliferation,and the expression ofβ-catenin andβ-catenin mRNA in the ischemic brain tissue.These findings indicate that bFGF promotion of neural stem cell proliferation may be mediated by Wnt/β-catenin signaling pathway.

Effects of basic fibroblast growth factor on beta-catenin protein and mRNA expression during the proliferation of endogenous neural stem cells following focal cerebral ischemia

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