Mechanical influences on human vascular smooth muscle cell growth

The leading cause of death in Western countries is cardiovascular disease with over 1 million people dying each year as a result in the United States alone. One condition identified as a risk factor for cardiovascular disease is an increased blood pressure or "hypertension" which has been shown to result in morphological changes in blood vessels at different sites around the body, including narrowing of pre-capillary "resistance" vessels. This thesis has sought to investigate whether or not this narrowing of resistance vessels might result from the increased physical forces of hypertension exerted upon the vascular smooth muscle cells of the vessel wall and to investigate the intracellular signalling mechanisms initiating this cellular response. Results indicate that cultured human vascular smooth muscle cells undergo cellular proliferation in response to chronic cyclical mechanical strain but only in the presence of suitable concentrations of soluble growth factors. Furthermore, these growth factors do not originate from the cells in response to the mechanical strain. Therefore, the proliferation is a direct response proportional to the strain applied but dependent upon the concentration of growth factors in the overlying media. In addition the magnitude of human vascular smooth muscle cell proliferation in response to mechanical strain is dependent upon interactions between the cells and specific extracellular matrix proteins and involves activation of the mitogen-activating protein kinase intracellular signalling cascade. In conclusion, these results suggest that the narrowing of resistance vessels observed in hypertension subjects may be a direct result of the increased physical forces exerted upon the vascular smooth muscle cells in conjunction with circulating growth factors. This biological response is mediated via specific cell/matrix interactions and involves specific intracellular signalling pathways, which may provide new targets for the effective treatment and/or management of these structural alterations observed in hypertension individuals.