The role of valvular interstitial cell (VIC) architecture in regulating cardiac valve function and pathology is not well understood. VICs are known to be more elongated in a hypertensive environment compared to those in a normotensive environment. We have previously reported that valve tissues cultured under hypertensive conditions are prone to acute pathological alterations in cell phenotype and contractility. We therefore aimed to rigorously study the relationship between VIC shape, contractile output and other functional indicators of VIC pathology. We developed an in vitro model to engineer VICs to take on the same shapes as those seen in normal and hypertensive conditions. VICs with longer cellular and nuclear shapes, as seen in hypertensive conditions, had greater contractile response to endothelin-1 that correlated with increased anisotropy of the actin architecture. These elongated VICs also demonstrated altered cell metabolism through a decreased optical redox ratio, which coincided with increased cellular proliferation. In the presence of actin polymerization inhibitor, however, these functional responses were significantly reduced, suggesting the important role of cytoskeletal actin organization in regulating cellular responses to abnormal shape. Overall, these results demonstrate the relationship between cell shape, cytoskeletal and nuclear organization, with functional output including contractility, metabolism, and proliferation.

Valve interstitial cells are dispersed throughout the heart valve and play an important role in maintaining its integrity, function, and phenotype. While prior studies have detailed the role of external mechanical and biological factors in the function of the interstitial cell, the role of cell shape in regulating contractile function, in the context of normal and diseased phenotypes, is not well understood. Thus, the aim of this study was to elucidate the link between cell shape, phenotype, and acute functional contractile output. Valve interstitial cell monolayers with defined cellular shapes were engineered via constraining cells to micropatterned protein lines (10, 20, 40, 60 or 80µm wide). Samples were cultured in either normal or osteogenic medium. Cellular shape and architecture were quantified via fluorescent imaging techniques. Cellular contractility was quantified using a valve thin film assay and phenotype analyzed via western blotting, zymography, and qRT-PCR. In all pattern widths, cells were highly aligned, with maximum cell and nuclear elongation occurring for the 10μm pattern width. Cellular contractility was highest for the most elongated cells, but was also increased in cells on the widest pattern (80μm) that also had increased CX43 expression, suggesting a role for both elongated shape and increased cell-cell contact in regulating contractility. Cells cultured in osteogenic medium had greater expression of smooth muscle markers and correspondingly increased contractile stress responses. Cell phenotype did not significantly correlate with altered cell shape, suggesting that cellular shape plays a significant role in the regulation of valve contractile function independent of phenotype.

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Background Duchenne muscular dystrophy (DMD) associated cardiomyopathy is a major cause of morbidity and mortality. In an in vitro DMD cardiomyocyte model, nicorandil reversed stress-induced cell injury through multiple pathways implicated in DMD. We aimed to test the efficacy of nicorandil on the progression of cardiomyopathy in mdx mice following a 10-day treatment protocol. Methods A subset of mdx mice was subjected to low-dose isoproterenol injections over 5 days to induce a cardiac phenotype and treated with vehicle or nicorandil for 10 days. Baseline and day 10 echocardiograms were obtained to assess cardiac function. At 10 days, cardiac tissue was harvested for further analysis, which included histologic analysis and assessment of oxidative stress. Paired student’s t test was used for in group comparison, and ANOVA was used for multiple group comparisons. Results Compared to vehicle treated mice, isoproterenol decreased ejection fraction and fractional shortening on echocardiogram. Nicorandil prevented isoproterenol induced cardiac dysfunction. Isoproterenol increased cardiac fibrosis, which nicorandil prevented. Isoproterenol increased gene expression of NADPH oxidase, which decreased to baseline with nicorandil treatment. Superoxide dismutase 2 protein expression increased in those treated with nicorandil, and xanthine oxidase activity decreased in mice treated with nicorandil during isoproterenol stress compared to all other groups. Conclusions In conclusion, nicorandil is cardioprotective in mdx mice and warrants continued investigation as a therapy for DMD associated cardiomyopathy.