Cytoskeletal structure and recovery in single human cardiac myocytes

Background: Mechanical support of the failing human heart with a left ventricular assist device (LVAD) normalizes many components of myocyte structure and function. We hypothesized that recovery of the cytoskeleton, a major site of mechanotransduction in cardiac myocytes, is crucial for sustained improvement of myocardial function. We therefore measured the effects of LVAD support on 4 cytoskeletal proteins in single human heart cells. Methods: Myocytes were isolated from non-failing (NF), hypertrophied (H), failing (F) and LVAD-supported failing (L) human hearts. Protein quantitation was performed using Western blot analysis and cellular distribution was determined by immunolabeling and confocal microscopy. Results: alpha-actinin did not differ in cells from H or F as compared with NF, and L had no effect. Vinculin was not quantitatively different in H or F vs NF, but localization at the intercalated disks was significantly decreased in H and absent in F, and this pattern was consistently reversed in L. Desmin protein was significantly increased in F vs NF, both in quantity and distribution, and these increases were reversed in L. beta-tubulin was increasingly polymerized in H and F, and the hyperpolymerization was reversed in L. Conclusions: On the level of the single cardiomyocyte, major proteins of the cytoskeleton are significantly altered in hypertrophied and failing human hearts. These alterations are reversed by mechanical unloading with an LVAD, suggesting that the cytoskeleton is not the limiting factor in determining full cardiac recovery.