ABSTRACT
BACKGROUND: Changes in extracellular of chondrocyte can reflect influence of external force on temporomandibular joint and adaptability of body to external force. OBJECTIVE: To study the effect of cyclic tensile stress on main extracellular matrix of condylar chondrocyte.METHODS: The cyclic tensile stress was exposed to the third passage condylar chondrocyte for 0, 1, 6, 12 and 24 hours, respectively, using a Flexcell Strain Unit-5000T system (10% surface elongation, 6 cycles/min). After mechanical loading, total RNA was extracted from the cells harvested from Six-well BioFlex flexible cell Petri Dish, reverse transcribed, and reverse trabscription-PCR was performed to quantify mRNA levels for type Ⅱ collagen and aggrecan.RESULTS AND CONCLUSION: Compared with the control group (0 hour group), both type Ⅱ collagen and aggrecan mRNA expression was significantly increased after loading for 6 hours (P < 0.05), but began to decrease since 12 hours, and significantly decreased at 24 hours (P < 0.05). Results showed that cyclical tensile stress stimuli can affect the synthesis of main extracellular matrix of condylar cartilage, i.e. the synthesis was gradually enhanced with prolonged stimulation duration, but significantly inhibited in response to further stress stimuli.
ABSTRACT
BACKGROUND: Because of complicated physiological environment and difficulty to control experimental conditions, it is difficult to get satisfactory results from in vivo studies of cell mechanics.OBJECTIVE: To study the action and mechanism of p38MAPK signaling pathways on myoblast apoptosis based on successful construction of in vitro mechanical stimulation models.METHODS: The C2C12 cells cultured in vitro were divided into control group and SB203580 treatment group. Cyclic tensile stress was applied on the C2C12 myoblast cells for 0, 6, 12 and 24 hours in each group. The Flexcell Strain Unit-5000T was used to expose C2C12 myoblast cell to an equiaxial cyclic of 15% magnitude and a frequency of 10 cycles/min, each cycle including the 3 s stretch and 3 s relaxation. Hoechst 33258 fluorescent staining and optical microscope were used to detect cell apoptosis. RT-PCR, flow cytometric analysis were used to observe the apoptosis of C2C12 myoblast cells and Western blotting were used to detect the activity of p38MAPK and p-p38MAPK. RESULTS AND CONCLUSION: The optical microscope tested the change in the morphology. Hoechst 33258 staining showed that after treatment with cyclic stress, the cell took the typical appearance of apoptosis with chromatin condensation and apoptotic bodies. RT-PCR and flow cytometry showed that with the extension of time the rate of the apoptosis of C2C12 myoblast cell increased. And cells imposed SB203580 before imposing cyclical tensile stress, the results showed that the apoptosis was markedly affected, and the p-p38MAPK expression declined apparently. These findings demonstrate that p38MAPK signaling pathways in stress mediated into C2C12 myoblast cell apoptosis plays an important role.