Question: 

The focal adhesion protein zyxin is involved in mechanotransduction in vascular smooth muscle cells (SMC). Here we characterize phenotype changes in SMC deficient in zyxin.

Methods: 

Using primary cultured (stretchable Flexercell membranes) aortic SMC derived from wild type and zyxin-deficient mice cultured, we performed a microarray (n = 3; Mouse Genome 430 2.0; Affymetrix) analysis to characterize stretch-induced (10% elongation, 0.5 Hz for 6 h) changes in gene expression by pathway (KEGG, GO) analysis. Proliferation was estimated by counting DAPI-stained nuclei from fixed cells at various time points. Contractility in response to various agonists was tested with a collagen-gel assay. Analytical methods such as real time RT-PCR, Western blotting and immunofluorescence analysis were performed according to standard protocols.

Results: 

Approximately 600 gene products were stretch-regulated in wild type SMC. Comparing these gene products to the stretch-induced gene expression in zyxin-deficient SMC revealed that 70% of the normal stretch-response in SMC is zyxin-dependent. Pathway analysis revealed that zyxin-induced gene expression, generally seems to strengthen the contractile capacity of SMC and to suppress proliferation. In accordance, SMC proliferation, migration, contractility, also in response to agonists such as epinephrine and endothelin-1, as well as the organization of the cytoskeleton are strongly altered when compared to SMC derived from wild type mice.

Conclusion: 

Zyxin appears to be an important factor in the stretch-induced changes in SMC phenotype. Besides its role in gene expression, also its capacity to organize the actin cytoskeleton may play a role in this process.