Integrin-ß1, not integrin-ß5, mediates osteoblastic differentiation and ECM formation promoted by mechanical tensile strain

BACKGROUND: Mechanical strain plays a great role in growth and differentiation of osteoblast. A previous study indicated that integrin-ß (ß1, ß5) mediated osteoblast proliferation promoted by mechanical tensile strain. However, the involvement of integrin-ß; in osteoblastic differentiation and extracellular matrix (ECM) formation induced by mechanical tensile strain, remains unclear. RESULTS: After transfection with integrin-ß1 siRNA or integrin-ß5 siRNA, mouse MC3T3-E1 preosteoblasts were cultured in cell culture dishes and stimulated with mechanical tensile strain of 2500 microstrain (µÎµ) at 0.5 Hz applied once a day for 1 h over 3 or 5 consecutive days. The cyclic tensile strain promoted osteoblastic differentiation of MC3T3-E1 cells. Transfection with integrin-ß1 siRNA attenuated the osteoblastic diffenentiation induced by the tensile strain. By contrast, transfection with integrin-ß5 siRNA had little effect on the osteoblastic differentiation induced by thestrain. At thesametime, theresultofECM formation promoted by the strain, was similar to the osteoblastic differentiation. CONCLUSION: Integrin-ß1 mediates osteoblast differentiation and osteoblastic ECM formation promoted by cyclic tensile strain, and integrin-ß5 is not involved in the osteoblasts response to the tensile strain.

Effects of mechanical stimulus on mesenchymal stem cells differentiation toward cardiomyocytes.

Background: Mesenchymal stem cells (MSCs) known to be sensitive to mechanical stimulus. This type of stimulus plays a role in cellular differentiation, so that it might affect MSCs differentiation toward cardiomyocytes. Objectives: Investigate the effect of mechanical stimulus on MSCs differentiation toward cardiomyocytes. Methods: The adipose tissue-derived MSCs were induced to differentiate with 5-azacytidine, and stimulated by one Hz mechanical stretching up to 8%. After 10 days, the cell’s cardiac markers and cardiogenesis-related genes were detected by immumohistochemistrical staining and reverse transcriptase-polymerase chain reaction, and the cell’s ATPase activity was detected. Results: The cyclic mechanical stretching enhanced the expression of cardiogenesis-related genes and cardiac markers, and stimulated the activity of Na+-K+-ATPase and Ca2+-ATPase in the MSCs treated with 5-azacytidine. Without 5-azacytidine pre-treatment, cyclic mechanical stretch alone has little effect. Conclusion: Mechanical stretch combined with 5-azacytidine treatment could accelerate MSCs differentiation toward cardiomyocytes.