目的:探讨生理性拉应力对软骨细胞分化的调控作用,并阐明其相关信号通路机制.方法:体外培养软骨ATDC5细胞,应用四点弯曲细胞力学加载仪对其施加生理性拉应力,首先分为对照组和拉应力组(2 000 μstrain/2 h组),另分为不同力值(1 000、2 000和3 000 μstrain)加力时间为2 h和力值为2 000 μstrain不同加力时间(1、2和4 h)组,同时设未加力的细胞为对照组,采用实时荧光定量PCR(RT-qPCR)法检测各组细胞中Ⅱ型胶原(Col-Ⅱ)、Ⅹ型胶原(Col-Ⅹ)、聚集蛋白聚糖(Aggrecan)、性别决定区Y框蛋白9(SOX9)、血管内皮生长因子(VEGF)、增殖细胞核抗原(PCNA)、Nel样1型分子(Nell-1)、Runt相关转录因子2(Runx2)、印度刺猬因子(Ihh)、补缀同源物1(Ptch-1)、GLI家族锌指蛋白1(Gli-1)和刺猬因子相互作用蛋白1(Hhip-1)mRNA表达水平,采用Western blotting法检测各组细胞中Nell-1、Runx2和Ihh蛋白表达水平.ATDC5细胞分为对照组、环巴胺组、拉应力组和环巴胺+拉应力组,采用 RT-qPCR法检测各组细胞中 Nell-1、Ihh、Ptch-1、Gli-1和Hhip-1 mRNA表达水平,采用Western blotting法检测各组细胞中 Nell-1和Ihh蛋白表达水平.结果:与对照组比较,2 000 μstrain/2 h组细胞中Col-Ⅱ、Col-Ⅹ、Aggrecan、SOX9、VEGF和PCNA mRNA表达水平均明显升高(P<0.01).在对细胞施加2 000 μstrain不同加力时间(1、2和4 h)或不同力值(1 000、2 000和3 000 μstrain)2 h的拉应力后,与对照组比较,随时间的延长或力值的增加其他各组细胞中Runx2 mRNA表达水平逐渐升高(P<0.01),Nell-1、Ihh、Ptch-1、Gli-1 和Hhip-1 mRNA表达水平逐渐升高(P<0.01),且在2 000 μstrain/2 h时达到最高,随后出现回落但仍明显高于对照组(P<0.01).Western blotting检测,各组细胞中Nell-1、Runx2和Ihh蛋白表达水平与mRNA表达水平变化趋势一致.环巴胺预处理后,与对照组比较,环巴胺组细胞中Ihh、Ptch-1、Gli-1和Hhip-1 mRNA表达水平均明显降低(P<0.01),拉应力组和环巴胺+拉应力组细胞中Nell-1、Ihh、Ptch-1、Gli-1和Hhip-1 mRNA表达水平明显升高(P<0.01);与环巴胺组比较,环巴胺+拉应力组细胞中Nell-1、Ihh、Ptch-1、Gli-1和Hhip-1 mRNA表达水平明显升高(P<0.01);与拉应力组比较,环巴胺+拉应力组细胞中Ihh、Ptch-1、Gli-1和Hhip-1 mRNA表达水平明显降低(P<0.01).与对照组比较,环巴胺组细胞中Ihh蛋白表达水平明显降低(P<0.01),Nell-1蛋白表达水平差异无统计学意义(P>0.05),拉应力组和环巴胺+拉应力组细胞中Nell-1 和Ihh蛋白表达水平明显升高(P<0.01);与环巴胺组比较,拉应力组和环巴胺+拉应力组细胞中Nell-1和Ihh蛋白表达水平明显升高(P<0.01);与拉应力组比较,环巴胺+拉应力组细胞中Nell-1和Ihh蛋白表达水平差异均无统计学意义(P>0.05).结论:在生理性拉应力刺激下,Nell-1可在上游激活Ihh信号通路,进而调控ATDC5软骨细胞的分化.
Objective:To discuss the regulatory effect of physiological tensile stress on the differentiation of chondrocytes,and to clarify the associated signaling pathway mechanism.Methods:The ATDC5 chondrocytes were cultured in vitro and subjected to physiological tensile stress by four-point bending cell mechanical loading device.Initially,the cells were divided into control group and tensile stress group(2 000 μstrain/2 h group),and further divided into different stress magnitudes(1 000,2 000,and 3 000 μstrain)for 2 h,and 2 000 μstrain for different duration time(1,2,and 4 h)groups;the cells without tensile stress were used as control group.Real-time fluorescence quantitative PCR(RT-qPCR)method was used to detect the expression levels of type Ⅱ collagen(Col-Ⅱ),type Ⅹ collagen(Col-Ⅹ),aggregated proteoglycom(Aggrecan),sex-determining region Y-box protein 9(SOX9),vascular endothelial growth factor(VEGF),proliferating cell nuclear antigen(PCNA),Nel-like molecule tyep 1(Nell-1),Runt-related transcription factor 2(Runx2),Indian hedgehog(Ihh),patched homolog 1(Ptch-1),GLI family zinc finger protein 1(Gli-1),and hedgehog interacting protein 1(Hhip-1)mRNA in the cells in various groups;Western blotting method was used to detect the expression levels of Nell-1,Runx2,and Ihh proteins in the cells in various groups.The ATDC5 cells were divided into control group,cyclopamine group,tensile stress group,and cyclopamine + tensile stress group.RT-qPCR method was used to detect the expression levels of Nell-1,Ihh,Ptch-1,Gli-1,and Hhip-1 mRNA in the cells in various groups;Western blotting method was used to detect the expression levels of Nell-1 and Ihh proteins in the cells in various groups.Results:Compared with control group,the expression levels of Col-Ⅱ,Col-Ⅹ,Aggrecan,SOX9,VEGF,and PCNA mRNA in the cells in 2 000 μstrain/2 h group were significantly increased(P<0.01);after treated with 2 000 μstrain tensile stress for different duration time(1,2,and 4 h)or different tensile stresses(1 000,2 000,and 3 000 μstrain)for 2 h,compared with control group,the expression levels of Runx2 mRNA in the cells in other groups were increased with the prolongation of time or the increasing of tensile stress(P<0.01),and the expression levels of Nell-1,Ihh,Ptch-1,Gli-1,and Hhip-1 mRNA were gradually increased(P<0.01),the expression levels reached the peaking at 2 000 μstrain/2 h,and then decreased but remained significantly higher than that in control group(P<0.01).The Western blotting results showed that the expression levels of Nell-1,Runx2,and Ihh proteins in the cells were consistent with the change trend of mRNA expression levels.After pre-treated with cyclopamine,compared with control group,the expression levels of Ihh,Ptch-1,Gli-1,and Hhip-1 mRNA in the cells in cyclopamine group were significantly decreased(P<0.01),and the expression levels of Ihh,Ptch-1,Gli-1,and Hhip-1 mRNA in the cells in tensile stress and cyclopamine+tensile stress groups were significantly increased(P<0.01);compared with cyclopamine group,the expression levels of Nell-1,Ihh,Ptch-1,Gli-1,and Hhip-1 mRNA in the cells in cyclopamine+tensile stress group were significantly increased(P<0.01);compared with tensile stress group,the expression levels of Ihh,Ptch-1,Gli-1,and Hhip-1 mRNA in the cells in cyclopamine + tensile stress group were significantly decreased(P<0.01).Compared with control group,the expression level of Ihh protein in the cells in cyclopamine group was significantly decreased(P<0.01),but there was no significant difference in expression level of Nell-1 protein in the cells between control group and cyclopamine group(P>0.05),while the expression levels of Nell-1 and Ihh proteins in the cells in tensile stress group and cyclopamine + tensile stress group were significantly increased(P<0.01);compared with cyclopamine group,the expression levels of Nell-1 and Ihh proteins in the cells in tensile stress group and cyclopamine + tensile stress group were significantly increased(P<0.01);compared with tensile stress group,in the expression levels of Nell-1 and Ihh proteins in the cells in cyclopamine + tensile stress group had no significant differences(P>0.05).Conclusion:After stimulated with physiological tensile stress,Nell-1 can activate the Ihh signaling pathway upstream,and regulate the differentiation of the ATDC5 chondrocytes.