Cellular response to mechanical stimulation is a balance between contractile elements of the cytoskeleton and cell-matrix (focal) adhesions. This study investigates the effect of the extracellular matrix on mechanical signaling through integrins, which controls actin organization and focal adhesion formation. Vascular smooth muscle cells (VSMC) were plated on different matrix proteins used as substrate (fibronectin, collagen IV, collagen I, and laminin), or have been mechanically stimulated by an atomic force microscope (AFM) probe functionalized with matrix proteins. Matrix-induced cellular characteristic morphology and the specific cellular adaptive responses to mechanical stimulation were recorded by total internal reflection fluorescence (TIRF) and confocal microscopy. Adhesion assays and western blot analysis were used as complementary approaches to determine protein expression. In addition, integrin-matrix adhesion force measurements using the AFM were performed on cells in which the pre-existing cytoskeletal tension has been modulated by drugs affecting actomyosin contractility. Our results showed that matrix has an important role in cell spreading, adhesion and morphology with a direct effect on modulating cell response to external mechanical cues. Protein recruitment at focal adhesions as initiated by fibronectin, induced early maturation of these adhesion sites anchoring the cell to the matrix. Fibronectin-functionalized AFM probes sustained long-termed interactions with the VSMC by inducing a functional focal adhesion. In contrast, laminin-functionalized and uncoated probes detached from the cell surface at very low forces. Taken together, our results show that matrix has an important role in modulating VSMC response to mechanical stimuli inducing key signaling pathways involved in cellular adaptation to the local extracellular microenvironment.

Extracellular matrix modulates mechanical characteristics of cell-matrix adhesions

247th National Meeting (2014)

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