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Objective: To investigate the effect of different mechanical tensions on the expressions of RhoA/Rho associated protein kinases (ROCK) in rat tendon stem cells (TSCs)., Methods: TSCs were isolated from the tendon tissue of male Sprague Dawley rats (aged, 2-3 months; weighing, 200-250 g) by enzymatic digestion method and cultured for 2-3 passages, then seeded on micro groovdishes. The 4% (4% stretch group) and 8% (8% stretch group) mechanical stretching was performed for 4 hours every day at 1 Hz. After 1, 2, and 3 days, the protein and mRNA expressions of RhoA and ROCK were measured by Western blot and real-time quantitative PCR. The cell proliferation was measured by cell counting kit 8. The cells were not stretched as control group., Results: The TSCs at passage 2 showed a cobble-stone shape and aggregation growth; TSCs seeded on micro groovdishes showed random growth, and the cells grew along the stretching direction after mechanical stretching. The mRNA expressions of RhoA and ROCK in control group, 4%, and 8% stretch groups showed an increasing tendency at 1, 2, and 3 days, showing significant difference between groups (P < 0.05). The protein expressions of RhoA and ROCK in 4% and 8% stretch groups were similar to those in control group at 1 day (P > 0.05), but the expressions in 4% and 8% stretch groups showed an increasing tendency at 2 and 3 days, which were significantly higher than those in control group (P < 0.05). The cell proliferation of 8% stretch group was significantly lower than that of 4% stretch group and control group at each time point (P < 0.05), but no significant difference was found between 4% stretch group and control group (P > 0.05)., Conclusion: The expressions of RhoA and ROCK of rat TSCs are positively correlated with stretch intensity. So RhoA/ROCK may be an important molecule in TSCs after mechanical stretching.

This study was intended to observe the biological properties of primary human embryonic skeletal myoblasts cultured in vitro and to inquire about the possible differentiation mechanism. Isolated human embryonic myoblasts were identified by morphology and myosin immunohischemical staining. The proliferating myoblasts were shifted to DM (DMEM supplemented with 3% fetal bovine serum) to induce differentiation. The control group was cultured in GM (DMEM supplemented with 10% fetal bovine serum). The differentiation was tested by the rate of myotube formation (RMF); The change of cell cycle was tested by flow cytometry; the morphological features were observed by use of inverted microscope and TEM. The myogenic regulatory factors (MRFs) such as MyoD, Myogenin and Myf5 were assayed by RT-PCR. Results showed that the primary myoblasts cultured in DM, in comparison with those cultured in GM, had higher rate of myotube formation (RMF) and myofilament formation, and more of the myoblasts cultured in DM exited the S phase. The expression level of Myogenin mRNA was obviously higher than that of the control group, the increase of MyoD mRNA expression level was not so high, however, the expression of Myf5 mRNA was decreased. These data indicate that there is a possible mechanism between differentiation and cell cycle. Besides, the mRNA expression of myogenic regulatory factors (MRFs) occurs in different phase of differentiating myoblastes and implicates the diverse biological function.