The experimental study of murine cytomegalovirus inhibits the differentiation and the differentiation genes expression of neural stem cells in vitro

Abstract

Objective To investigate the influence of murine cytomegalovirus(MCMV) infection on differentiation and differentiation gene expression of neural stem cells (NSCs) in vitro for studying the mechanisms of brain abnormalities calmed by congenital cytomegalovirns infection. Methods NSCs were separated from fetal BALB/c mouse and cultured and identified in vitro. The differentiation potency of NSCs was observed by immunnfluorescence. The NSCs infected by MCMV at dosage of multiplicity of infection (MOI) equaled to 5, I and 0. 1, respectively, were cultured in differentiation medium. The morphological changes of the cells were observed by inverted microscope. The ratios of NSCs and its differentiated cells were detected by flow cytometry. The expression changes of nestin, GFAP and NSE, markers of NSCs and its differentiated cells, were studied by immunofluorescence ( MOI = 1 ). The expression of early antigen (EA) of MCMV was detected to observe the infection process. Real-time RT-PCR method was employed to measure the expression levels of the key differentiation genes Wnt-3 and Wnt-7a in Wnt signal pathway of NSCs at early phage of differentiation culture. Results NSCs isolated from embryonic mouse brains could proliferate to form neurnspheres and strongly express Nestin and differentiate into NF-200 positive neurons or GFAP positive astrocytes. The NSCs of the infected groups couldn't adhere to the wall and appear differentia-tion growth, but showed swollen gradually after differentiation culture. The nostin expression of the infected groups downregulated slowly and was higher than that of the control groups ( P < 0.05 ). The GFAP and NSE expression of the infected groups were lower than that of the control groups (P <0.05). The EA of MCMV could be always detected in the cells of the infected groups. The ratios of nestin positive cells of the infected groups were higher than that of the control groups, but the ratios of GFAP and NSE positive cells of the for-mer were lower than that of the latter from 3rd to 9th day after differentiation culture ( P < 0.05 ). The levels of Wnt-3 mRNA and Wnt-7a mRNA of the infected groups were markedly lower than that of the control groups from 1st to 2nd clay and from 12th hour to 2nd day after differentiation culture respectively ( P < 0.05 ) . These changes of the infected groups became more obvious as MCMV MOI increased . Conclusion MCMV could inhibit significantly NSCs differentiate to neurons and astrocytes and lead to the decrease of dif-ferentiated cells. MCMV could inhibit or interfere with the gene expression of Wnt-3 and Wnt-7a in Wnt sig-nal pathway of NSCs. The effect that MCMV inhibited the differentiation and the differentiation gene expres-sion of NSCs showed dose-dependent with MCMV MOI. The inhibitory effect of MCMV on the differentiation of NSCs might be induced by interfering the differentiation gene expression of NSCs, which is possibly the one of primary causes of brain development disorders caused by congenital CMV infection. Key words: Cytomegalovirus; Neural stem cells; Differentiation; Wnt-3; Wnt-7a