Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, PCB029

Poster Communications

Does collagen drive transverse tubule remodelling in human heart failure?

D. Crossman1

1. Physiology, University of Auckland, Auckland, Select State, New Zealand.

In heart failure remodelling of the transverse (t) tubules leads to disrupted Ca2+ release and contraction. In the failing human heart the t-tubules have elevated levels of glycosylation as demonstrated by labelling with the lectin wheat germ agglutinin (WGA). Notably, WGA can bind to the dystrophin-associated glycoprotein complex leading us to postulate that increases in this complex may contribute to the increased WGA labelling and play a role in t-tubule remodelling. In this work we aimed to identify the glycosylated proteins responsible for increased WGA labelling of t-tubules. Samples of left ventricle (LV) were obtained from age and sex matched healthy human donors and patients with idiopathic dilated cardiomyopathy in end-stage heart failure. All human tissue was obtained with written and informed consent following national guide- lines. Western blot was used to probe LV homogenates. This analysis identified 1.7 fold increase in total WGA positive proteins in heart failure samples (0.64 ± 0.05 AU vs 0.37 ± 0.02 n = 11 failing, and n = 8 donor hearts, P=0.001***). In particular, 140 kDa WGA positive band was elevated 5.7 fold in heart failure (0.61 ± 0.06 AU vs 0.11 ± 0.04 AU n as above, P=0.001***). Mass spectrometry indicated the 140 kDa band was collagen VI. Interestingly mutations in this protein are associated with Ulrich congenital muscular dystrophy and Bethlam myopathy suggesting an important role in muscle physiology. Subsequent westerns confirmed the 140 kDa band was collagen VI with 2.4 fold increase in expression in heart failure (0.55 ± 0.08 AU vs 0.23 ± 0.02 AU n as above, P=0.01**). Calculation of WGA / protein ratio indicated a 3.2 fold increase in glycosylation of collagen VI in heart failure (0.45 ± 0.07 AU vs 0.14 ± 0.04 AU n as above, P=0.001***). Notably, glycosylation of collagen VI is essential for fibril formation. Confocal microscopy of LV tissue sections showed that collagen VI was located at the t-tubules and that label diameter was increased in heart failure (328 ± 11 nm vs 272 ± 15 nm, n=7 failing hearts, n=5 donor hearts, P = 0.014*). Super-resolution microscopy demonstrated collagen VI was located within the t-tubule lumen and that in heart failure its diameter increased (374 ± 43 nm vs 231 ± 18 nm, n=5 failing hearts, n=5 donor hearts, *P=0.018) alongside a displacement in the cytoskeletal protein dystrophin (Fig1). Subsequent confocal and super-resolution imaging of Collagens I, III and IV showed that these proteins were also located within the t-tubule lumen and diameters increased in sections from the failing human heart. Conclusion: Increased expression and labelling of collagens suggest that fibrosis contributes to t-tubule remodelling in human heart failure. For further methodological details, including statistical design, refer to the study publication (1).

Where applicable, experiments conform with Society ethical requirements