C-Type Natriuretic Peptide Attenuates Aortic Valvular Interstitial Cell Myofibrogenesis Through Natriuretic Peptide Receptor 2

Adams, Rachel 1, 2; Blaser, Mark 1, 2; Tam, Richard 2, 3; Wei, Kuiru 2, 3; Caruso, Laura-lee 1, 2; Simmons, Craig 1, 2, 3

1. Translational Biology & Engineering Program, Ted Rogers Centre for Heart Research; 2. Institute of Biomaterials and Biomedical Engineering, University of Toronto; 3. Mechanical and Industrial Engineering, University of Toronto

Aortic valve (AV) fibrosis occurs when valve interstitial cells (VICs) are activated to contractile myofibroblasts that express a-smooth muscle actin (SMA). Previously we showed that C-type natriuretic peptide (CNP) inhibits VIC myofibroblast differentiation in vitro and is associated with valve homeostasis in vivo. CNP mediates vascular homeostasis through natriuretic peptide receptors 2 (Npr2) and 3 (Npr3), but the receptor through which CNP mediates AV myofibrogenesis is unknown. To identify the roles of Npr2 and Npr3 in VICs, SMA expression was measured in porcine VICs treated with CNP and receptor inhibitors. CNP inhibited myofibrogenesis (58±6% SMA+ cells vs. untreated cells, p<0.05), with blockage of Npr2 (89±4%, p>0.05) more effectively abrogating the protective effect of CNP than Npr3 (77±10%, p<0.05). To further assess the functional role of Npr2, we compared the effects of CNP on SMA expression and traction force generation in heart and lung myofibroblasts from male C57Bl/6J (WT) and heterozygous Npr2 (Hets) mice. As expected, Npr2 expression in heart and lung was significantly lower in Hets (relative to WTs: heart 0.34±0.11, p<0.002 and lung 0.44±0.12, p<0.01). In myofibroblasts isolated from WT mice, CNP treatment reduced SMA expression (31±4% SMA+ cells compared with 55±10% of untreated cells, p<0.05) and traction forces (2.5±1.2 Pa/µm2 vs. 4.4±3.3 Pa/µm2, p<0.1), but had no effect on SMA expression (p=0.98) or traction force generation (p=0.36) in Hets. These data support that CNP attenuates VIC myofibrogenesis through Npr2, suggesting a therapeutic pathway to target fibrosis in AV disease progression.