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Objective @#To investigate the activation of the mammalian target of rapamycin complex 1 (mTORC1) signaling pathway molecules during the process by which kaempferol (Kae) promotes osteogenic differentiation of mouse bone marrow mesenchymal cells (BMMCs) under cyclic and uniaxial tension.@*Methods @#BMMCs isolated and cultured in vitro were subjected to uniaxial dynamic tension with a 10% shape variable. The appropriate concentration of Kae was selected by cytotoxicity testing. The endogenous mTOR signal was inhibited by pp242. Four hours after traction, alkaline phosphatase (ALP) and osteocalcin (OCN) were detected by chemical colorimetry and ELISA, and the relative concentration of intracellular calcium was detected by flow cytometry. Phosphorylation of mTOR, 4E/BP1, and ribosomal protein S6 kinases (S6K), which are the main molecules of the endogenous mTORC1 signaling pathway, and expression of osteogenic transcription factors (Runx2 and Osterix) were detected by western blotting (WB), and mRNA expression levels of the above factors were detected by qRT-PCR.@*Results @# The cytotoxicity test showed that 10 μmol/L Kae had little inhibitory effect on cell proliferation but had the strongest osteogenic ability. Four hours after stretching, Kae effectively promoted the osteogenic differentiation of BMMCs. The expression of ALP was （153.04 ± 18.72） U/mg, the expression of OCN was （1.64 ± 0.25） U. The mRNA and protein levels of Runx2 and Osterix were upregulated, and the intracellular calcium content was decreased. The mRNA and protein phosphorylation of mTOR and S6K was upregulated, and the opposite effect was observed with 4E/BP1. After pp242 was added to inhibit mTOR signaling, mTOR and S6K mRNA and protein phosphorylation were downregulated, but 4E/BP1 mRNA and protein phosphorylation was upregulated. The osteogenic differentiation of BMMCs was also significantly inhibited, mRNA and protein expression of Runx2 and Osterix were significantly downregulated, ALP and OCN expression were downregulated, and intracellular calcium content was increased. @* Conclusion@#Kae promotes osteogenic differentiation of mouse BMMCs under uniaxial dynamic tension through the mTORC1 signaling pathway.
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Objective@# To investigate the expression of the mTORC1 signaling pathway during the osteogenic differentiation of mouse bone marrow mesenchymal cells (BMMSCs) under cyclic uniaxial tension and explore its possible role.@*Methods @# The BMMSCs of mice were affected by uniaxial dynamic tensile force. Western blot was used to detect the expression changes of major molecules (mTOR, Raptor, S6K) in the endogenous mTORC1 signaling pathway at 0, 1, 2, 4, and 8 hours after stretching. Chemical colorimetry, ELISA and PCR were used to detect alkaline phosphatase (ALP), osteocalcin (OCN) and Runx2 mRNA, respectively. Then, inhibition, activation and control groups were established by administration of the drugs PP242, MHY1485 and PBS, respectively. Two hours after the stress, the expression of S6K was detected by western blot, and the expression of the osteogenic signal was continuously detected by the above methods.@*Results @#Western blot analysis showed that the main molecules of the mTORC1 signaling pathway were all expressed within 8 hours after traction, and the highest expression was 2 hours after the stress. Compared with those in the control group, the ALP activity and OCN expression decreased and the Runx2 mRNA levels increased after the mTORC1 signal pathway was inhibited (P ＜ 0.001); ALP activity and OCN expression increased after the mTORC1 signal pathway was activated, while the Runx2 mRNA levels decreased (P ＜ 0.001). @*Conclusion @#The mTORC1 signaling pathway participates in the osteogenic differentiation of mouse BMMSCs under tension. The osteogenesis of BMMSCs under cyclic uniaxial tension would be enhanced if the mTORC1 signaling pathway was activated.
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Objective To study the mechanical properties of porcine descending aorta. Methods The porcine descending aortas were divided into 5 groups by the distance from the heart, and tissues in each group were subdivided into ventral-quadrant part and lateral-quadrant part. Stress-stretch curves were obtained by using uniaxial tension test. The moduli of elastic and collagen fiber and collagen fiber recruitment parameter of tissues in 5 groups (Position 1-5) were first analyzed by a classical mathematical model. Then the mechanical differences between tissues of ventral quadrant and lateral quadrant were compared. Results The modulus of circumferential collagen fibers increased gradually away from the heart. The modulus of circumferential elastic fibers had the same trend except for tissues at Position 5 (the most distal one). The elastic fibers modulus of tissues decreased at Position 5. At the most distal position, the circumferential and axial elastic fiber modulus of the lateral quadrant was lower than that of ventral quadrant by 19% and 33%, respectively. The axial and the elastic fiber modulus of the ventral quadrant was similar with that of tissues at Position 4 and 5. For the whole descending aorta, the circumferential collagen fiber modulus of the lateral quadrant was higher than that of ventral quadrant by 26% and the circumferential elastic fiber modulus of the lateral quadrant was higher than that of ventral quadrant by 16% at the proximal 4 positions. Conclusions The circumferential mechanical properties of porcine descending aorta were related with regions. The ventral quadrant of the most distal aorta showed abnormally soft trend. The research findings can be used to better understand the mechanism of aorta and improve the spatial accuracy of computer models.
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BackgroundIt has been proved that,after being forced,the biological soft tissue has stable biomechanical characteristics.However,there is rare study on corneal biomechanics.Rabbit is a main animal for experimental study in ophthalmology.But the biomechanical study of cornea in normal rabbit has not been reported.ObjectiveThis study was to investigate the biomechanical properties of normal rabbit central cornea and acquire the parameter. Methods Ten rabbits were sacrificed and the whole corneas were obtained and 20 central cornea specimens with 7 mm×5 mm of rabbit were prepared and tested on BOSE electroforce 3220-AT biomechanics machine under the room temperature and suitable humidity environment.Uniaxial tension,stress between strain,relaxation and creep were performed and the curves were drawn.The data was collected by wintest system to evaluate the biomechanical parameters of rabbit corneal tissue. ResultsThe maximum distortion intension of rabbit cornea was (7.7432±0.6099)MPa.After three cyclic loading,the stress gradually attenuated and the stress and strain flattened as the time change with the relaxation rate 30.33％.The deformation of the specimens enhanced with time decrease with the creep rate 24.33％. ConclusionsThe biomechanical characteristics of normal rabbit cornea are revealed in this study,which offer the basis for the experimental research of rabbit model aimed at corneal disease.