Abstract 237: Noncanonical WNT Activation in Human Right Ventricular Heart Failure

Abstract

Background: Drivers of adaptive and pathologic human right ventricular (RV) remodeling are poorly defined, but there is some evidence that WNT signaling contributes to these processes. Methods: Using a candidate gene approach, we sought to identify genes specifically expressed in RV failure by assessing the expression of 28 WNT-related genes in the RVs of three groups: human explanted nonfailing donor hearts (NF, n = 29), pre-transplant cardiomyopathy hearts with preserved RV function (pRV, n = 78), and pre-transplant cardiomyopathy hearts with RV failure (RVF, n = 35). Results: We identified the noncanonical WNT receptor ROR2 as transcriptionally strongly upregulated in RVF compared to pRV and NF (p < 0.05, adjusted for multiple hypothesis testing using Benjamin-Hochberg). By western blot, ROR2 protein expression correlated to mRNA expression (R 2 = 0.41, p = 8.1 x 10-18) and increased linearly with higher right atrial to pulmonary capillary wedge ratio in RVF (R 2 =0.40, p = 3.0 x 10-5). Using trichrome, immunohistochemistry, and RNAscope, we identified preferential ROR2 mRNA and protein expression in fibrotic regions by both cardiomyocytes and noncardiomyocytes. High ROR2 expression correlated with increased expression of a known ROR2 target, the WNT/Ca2+ responsive protease calpain and its target FLNA (R 2 0.25 and 0.67, respectively, p < 0.05), as well as with increased relative phosphorylation of FLNA (R 2 0.62, p < 0.05), a marker of its activation by ROR2. Finally, mice with a range of RVF severity, generated by pulmonary artery constriction, demonstrated a robust increase in ROR2 and FLNA expression compared to sham-treated animals, and ROR2 and FLNA expression correlated strongly with each other (R 2 0.89, p = 6.9 x 10-5) and with increasing RV weight normalized to body weight (R 2 ~0.8, p < 0.001, both). Conclusion: ROR2 expression in the RV is dramatically increased in humans and mice with severe RVF, and ROR2 expression correlates with worsening RV hemodynamics, calpain expression, FLNA cleavage, and FLNA phosphorylation. Taken together, the data reveal the robust activation of noncanonical WNT signaling in human RVF, and identify ROR2-mediated cytoskeleton protein cleavage as a potential novel target of human pathologic RV remodeling.