不同浓度Wnt-11诱导骨髓间充质干细胞向心肌样细胞定向分化的实验研究

Inducing bone marrow mesenchymal stem cells to differentiate into cardiomyocyte-like cells via Wnt-11 in vitro

目的探讨Wnt-11体外诱导骨髓间充质干细胞(BMMSCs)分化为心肌样细胞的最适浓度。方法采用全骨髓贴壁法分离培养SD大鼠BMMSCs,取第2代BMMSCs培养48h后进行定向诱导,根据Wnt-11终浓度的不同分为A组(100ng/mL),B组(200ng/mL),C组(400ng/mL)和D组(空白对照组),诱导72h后更换为完全培养液继续培养4周,D组仅用完全培养液培养。倒置相差显微镜下观察培养细胞的形态学变化。运用流式细胞仪检测技术对BMMSCs表面联合标记物进行鉴定。各组细胞培养至第4周时,运用免疫细胞化学染色技术检测结蛋白(Desmin)、间隙连接蛋白43(Connexin43)及心肌肌钙蛋白I(cTnI)的表达情况。运用透射电镜观察分化细胞的超微结构变化。实时荧光定量多聚核苷酸链式反应(real-time quantitative polymerase chain reaction,RT-qPCR)检测各组细胞在诱导后培养第1、2、4周时心肌早期转录因子GATA-4、Nkx2.5及α-MHC的表达。结果 1原代BMMSCs于第2周形成集落,多呈梭形、星形,少数形状不规则。传代后细胞体积变大,诱导后细胞多为长梭形,呈一致性生长。2流式细胞仪检测技术对BMMSCs表面联合标记物的鉴定结果显示CD29、CD45、CD90的阳性表达率分别为97.9%、0.4%和99.5%。3免疫细胞化学染色技术检测结果显示:诱导后常规培养至第4周,A组、B组、C组细胞胞质均呈阳性表达Desmin、Connexin43和cTnI,而D组细胞呈弱阳性或阴性表达,B组细胞的阳性表达率均最高,差异具有统计学意义(P<0.05)。4透射电镜结果显示:各诱导组细胞于诱导后常规培养至第4周,胞质内可见平行排列的肌丝及亚细胞结构如线粒体、粗面内质网和核糖体。5RT-qPCR检测结果显示:BMMSCs经诱导后,常规培养第1周时各诱导组细胞均表达GATA-4及Nkx2.5基因,在第2周时表达减弱,在第4周时表达增强,就基因表达而言,三个诱导组相比较,B组明显优于其他两组(P<0.05)。α-MHC基因在诱导后常规培养期间均不表达。对照组细胞在常规培养期间GATA-4及Nkx2.5基因的表达量为1,而不表达α-MHC基因。结论 Wnt-11可在体外诱导SD大鼠BMMSCs定向分化为心肌样细胞,其诱导分化最适浓度为200ng/mL。

Objective To probe into the optimal concentration of Wnt-11 to induce the differentiation of bone marrow mesenchymal stem cells（BMMSCs）into cardiomyocyte-like cells in vitro.Methods BMMSCs were isolated from the bone marrow of SD rats using whole bone marrow culture method.After cultured for 48 h,BMMSCs of the second generation were utilized for directed induction.Based on the final concentration of Wnt-11,BMMSCs were divided up into Group A（100 ng/mL）,Group B（200 ng/mL）,Group C（400 ng/mL）and Group D（blank control）.After 72-hour induction,the cells were cultured in complete medium for 4 weeks while cells in Group D were cultured only in the complete medium.The morphological changes were observed under the phase contrast microscope.Surface antigen expression of BMMSCs was identified by flow cytometry.When cells were cultured for 4 weeks,the expressions of Desmin,Connexin43 and cTnI were detected by immunocytochemistry.Meanwhile,the ultrastructural changes were observed using transmission electron microscope. The mRNA expressions of cardiac transcription factors GATA-4,Nkx2.5 andα-MHC in BMMSCs were detected by RT-qPCR at1,2 and 4 weeks after induction.Results Primary BMMSCs formed cell colonies at 2 weeks;the cells were mainly fusiform or star-shape,and a few irregularly-shaped ones were also visible.The passaged cells were larger than those of primary culture.After induction,the cells exhibited long shuttle-shape and were aligned in parallel.Flow cytometery displayed that the positive rate of the surface antigens of BMMSCs CD29,CD45,and CD90 was97.9%,0.4% and 99.5%,respectively.When BMMSCs-induced via Wnt-11 were cultured for 4 weeks,Desmin,cTnI and Connexin43 were all positively expressed in induction groups.Whereas in the blank control group they were slightly positive or negative;the positive rate in Group B was the highest（P〈0.05）.Transmission electron microscopy exhibited that organelles such as rough endoplasmic reticulum,mitochondria,as well as some ribosomes were visible in the cytoplasm of these cells in each induction group.In addition,myofilaments were arranged in parallel in the cytoplasm.The cells in induction groups could express GATA-4 and Nkx2.5 in the first week,and then the expression of them decreased in the second week,but then increased in the fourth week;gene expression in induction Group B was significantly higher than in the other two induction groups（P〈0.05）.The expression of GATA-4 and Nkx2.5 in Group D was 1,α-MHC was not expressed in the four groups during the culture period.Conclusion Wnt-11 can induce the differentiation of BMMSCs into cardiomyocyte-like cells in vitro,and the optimal concentration of Wnt-11 is 200 ng/mL.