The Mechanism Of Signal Transduction In Cyclic Strain-induced Proliferation Of Vascular Smooth Muscle Cells

Objective: This current study is to investigate the pathway of mechanotransduction in vascular smooth muscle cells under cyclic strain condition and the related mechanisms underlying cyclic strain-induced proliferation of vascular smooth muscle cells. Materials and methods: A pulsatile membrane cyclic stress system was used to perform cyclic strain on the VSMCs of adult SD rats. (1)Morphological changes were observed microscopically, and proliferation and DNA synthesis of VSMCs were indicated by 3HTdR method. (2)Change of microfilament skeleton was observed by Coomassie Brilliant Blue staining; Expression of cytoskeleton proteins, such as talin and paxillin was observed by immunofluorescence staining and confocal laser scanning microscope; Phosphorylation of talin and paxillin was shown by immunocytochemistry. (3) After blocking the interaction of integrin and extracellular matrix by RGD, the spacial structure of microfilaments, the phosphorylation of talin and paxillin and the proliferation of VSMCs were studied; Cytochalasin B and Genistein were used to block the formation of contractile microfilament and inhibit cytoskeleton protein tyrosine kinases respectively, then the proliferation of VSMCs was measured. Results: (1)The growth and 3H thymidine incorporation of VSMCs under 8% cyclic strain were arrested; but accelerated under 14% cyclic strain, the 3H thymidine incorporation had a significant difference in 12 hours and increased by 1.4-fold and 1.8-fold in 24 and 48 hours respectively compared with control group. (2)Under 14% cyclic strain,VSMCs re-aligned gradually, and finally were vertical to the direction of stress; The shape index was decreased. However, the spreadingarea, perimeter and long axis of stretched VSMCs were increased within 6 hours, then decreased to a relatively stable level from 12 to 24 hours. The microfilaments were decreased and the alignment was disordered, companying with a shift towards the cellular membrane. The expression of talin and paxillin were increased with a short and quick phosphorylation. (?RGD blocked the proliferation of VSMCs, the expression and phosphorylation of talin and paxillin, and the microfilament rearrangement; Cytochalasin B and Genistein inhabited the proliferation of VSMCs under cyclic strain. Conclusion: Extracellular matrix -integrin - cytoskeleton protein-cytoskeleton is a key signaling pathway in cyclic strain- induced proliferation of VSMCs.