Liu Limin, Chen Lin, Mai Zhihui, Peng Zhuli, Yu Kafung, Liu Guanqi, Ai Hong
Department of Stomatology, The Third Affiliated Hospital of Sun Yat‑sen University, Guangzhou, Guangdong 510630, P.R. China.
Mol Med Rep. 2016 Nov;14(5):4293-4300. doi: 10.3892/mmr.2016.5788. Epub 2016 Sep 26.
The role of myosin light chain II (MLC‑II) in cellular differentiation of rat mandibular condylar chondrocytes (MCCs) induced by cyclical uniaxial compressive stress (CUCS) remains unclear. In the current study, a four‑point bending system was used to apply CUCS to primary cultured MCCs from rats. It was identified that CUCS stimulated features of cellular differentiation including morphological alterations, cytoskeleton rearrangement and overproduction of proteoglycans. Furthermore, CUCS promoted runt‑related transcription factor‑2 (RUNX2) expression at mRNA (P<0.01) and protein levels (P<0.05) and elevated alkaline phosphatase (ALP) activity (P<0.01), which are both markers of osteogenic differentiation. Under conditions of stress, western blotting indicated that the ratio of phosphorylated MLC‑II to total MLC‑II was increased significantly (P<0.05). Silencing MLC‑II by RNA interference reduced ALP activity (P<0.01), and eliminated RUNX2 mRNA expression (P<0.01). Addition of the MLC kinase inhibitor, ML‑7, reduced the CUCS‑associated upregulation of RUNX2 expression (P<0.01) and ALP activity (P<0.01). The data indicated that CUCS promoted cellular differentiation of rat primary MCCs, and this was suggested to be via the phosphorylation of MLC‑II.
肌球蛋白轻链II（MLC-II）在周期性单轴压缩应力（CUCS）诱导的大鼠下颌髁突软骨细胞（MCCs）细胞分化中的作用仍不清楚。在本研究中，使用四点弯曲系统对原代培养的大鼠MCCs施加CUCS。结果发现，CUCS刺激了细胞分化的特征，包括形态改变、细胞骨架重排和蛋白聚糖的过量产生。此外，CUCS促进了与成骨分化相关的转录因子2（RUNX2）在mRNA水平（P<0.01）和蛋白水平（P<0.05）的表达，并提高了碱性磷酸酶（ALP）活性（P<0.01），这两者都是成骨分化的标志物。在应激条件下，蛋白质印迹法表明磷酸化的MLC-II与总MLC-II的比例显著增加（P<0.05）。通过RNA干扰沉默MLC-II可降低ALP活性（P<0.01），并消除RUNX2 mRNA表达（P<0.01）。添加MLC激酶抑制剂ML-7可降低CUCS相关的RUNX2表达上调（P<0.01）和ALP活性（P<0.01）。数据表明，CUCS促进了大鼠原代MCCs的细胞分化，这可能是通过MLC-II的磷酸化实现的。
