[Regulation of cell deformation induced by RhoA/ROCK signaling pathway in osteogenic differentiation of human mesenchymal stem cells].

Objective: To investigate whether the cell deformation induced by RhoA/ROCK signaling pathway plays a regulatory role in the osteogenic differentiation in human mesenchymal stem cells (hMSCs). Methods: The primary hMSCs were cultured until the P3 generation was added to the osteogenic induction solution for 14 days, and the expression levels of RhoA and ROCK-1 proteins were detected by immunofluorescence. Another P3 generation hMSCs cells were divided into induction group, blank plus drug group and medicated group, and the induction group was induced by simple osteogenic induction; the blank drug-added group was added to the osteogenic induction solution and the solvent dimethyl sulfoxide (DMSO) for induction culture; the medicinal group was added with osteogenic induction solution and Y-27632 (RhoA/ROCK signaling pathway inhibitor) dissolved in DMSO for induction culture. The proliferation of the cells was detected by CCK-8 methods. The changes of cytoskeleton in each group were observed by fluorescence microscope. The expression changes of osteogenic genes alkaline phosphatase (ALP), osteocalcin (OCN) and runt-relatedtranscriptionfactor-2 (RUNX-2) in each group were detected by real time polymerase chain reaction (RT-PCR) and ALP staining. The t test was used for data comparison between the two groups. Results: There were significant differences in the expression of RhoA and ROCK-1 protein before and after osteogenic induction of hMSCs (22.7±2.1 vs 14.7±0.6 and 24.3±1.5 vs 20.3±0.6, t=- 6.414, -4.243, both P< 0.05). Mesenchymal stem cell proliferation on day 1, 5, 9 and day 14 in the medicated group were comparable with those in the induction group ( F= 0.427, 1.000, 0.298, 1.314, all P> 0.05). The cytoskeleton of the medicated group showed obvious spindle-shaped changes, and the cell spreading area became smaller. From the three groups of ALP staining on the 14th day, it can be seen that the color of the medicated group was significantly lighter than that of the induction group. The results of RT-PCR showed that the expression of osteogenic phenotypic genes increased with the induction time in the induction group and the blank drug-treated group, the expression levels of osteogenic phenotype genes ALP, OCN and RUNX-2 in the drug-treated group were gradually decreased with the induction time. The expression of ALP in the drug-treated group was significantly lower than those in the other two groups at 14th day ( F= 25.891, P= 0.001); the expression of OCN in the drug-treated group was significantly lower than those in the other two groups at 11th and 14th days ( F= 5.773, 25.382, both P< 0.05); the expression of RUNX-2 in the drug group was significantly lower than those in the other two groups at 11th and 14th days ( F= 34.972,10.808, both P< 0.05). Conclusion: The RhoA/ROCK signaling pathway may play a role in promoting osteogenic differentiation of hMSCs through mediating cytoskeletal deformation.