Cardio-omentopexy requires a cardioprotective innate immune response to promote myocardial angiogenesis in mice

Abstract

Objective: The pedicled greater omentum, when applied onto stressed hearts using omentopexy, has been shown to be protective in humans and animals. The mechanisms underlying cardioprotection using omentopexy remain elusive. This study examined whether macrophage-mediated angiogenesis accounts for the cardioprotective effect of omentopexy in mice.

Methods: C57BL/6 mice were subjected to minimally invasive transverse aortic constriction for 6 weeks and subsequent cardio-omentopexy for 8 weeks. Control mice underwent the same surgical procedures without aortic constriction or cardio-omentopexy.

Results: Transverse aortic constriction led to left ventricular concentric hypertrophy, reduced mitral E/A ratio, increased cardiomyocyte size, and myocardial fibrosis in the mice that underwent sham cardio-omentopexy surgery. The negative effects of transverse aortic constriction were prevented by cardio-omentopexy. Myocardial microvessel density was elevated in the mice that underwent aortic constriction and sham cardio-omentopexy surgery, and cardio-omentopexy further enhanced angiogenesis. Nanostring gene array analysis uncovered the activation of angiogenesis gene networks by cardio-omentopexy. Flow cytometric analysis revealed that cardio-omentopexy triggered the accumulation of cardiac MHCII^loLyve1+TimD4+ (Major histocompatibility complex class II^low lymphatic vessel endothelial hyaluronan receptor 1+ T cell immunoglobulin and mucin domain conataining 4+) resident macrophages at the omental-cardiac interface. Intriguingly, the depletion of macrophages with clodronate-liposome resulted in the failure of cardio-omentopexy to protect the heart and promote angiogenesis.

Conclusions: Cardio-omentopexy protects the heart from pressure overload-elicited left ventricular hypertrophy and dysfunction by promoting myocardial angiogenesis. Cardiac MHCII^loLyve1+TimD4+ resident macrophages play a critical role in the cardioprotective effect and angiogenesis of cardio-omentopexy.

Keywords: AXL, AXL receptor tyrosine kinase; Akt, protein kinase B; CD45, lymphocyte common antigen; CD64, cluster of differentiation 64; COP, cardio-omentopexy; Calm1, calmodulin 1; Cdh5, cadherin 5; Clodro, clodronate-liposomes; Crk, proto-oncogene c-Crk; Ctnnb1, catenin β1; Ctnnd1, catenin delta 1; Cybb, cytochrome B-245 beta chain; Cyfip1, cytoplasmic FMR1 interacting protein 1; ECM, extracellular matrix; F4/80, F4/80 antigen; HCM, hypertrophic cardiomyopathy; HSP89aa1, heat shock protein 89aa1; Hippo, hippocampal; Itpr2, inositol 1,4,5-trisphosphate receptor type 2; Kdr, kinase insert domain receptor; Kras, kirsten rat sarcoma virus; LV, left ventricle; Ly6Clo, lymphocyte antigen-6Clow; Ly6G, lymphocyte antigen 6 complex locus G6D; Lyve1, lymphatic vessel endothelial hyaluronan receptor 1; MHCIIlo, major histocompatibility complex class IIlow; Ncf1, neutrophil cytosolic factor 1; Nck2, NCK adaptor protein 2; Nckap1H, NCK-associated protein 1H; Nos3, nitric oxide synthase 3; PBS, phosphate-buffered saline; PDGF, platelet-derived growth factor; PI3K, phosphoinositide-3-kinase; Plcg1, phospholipase Cγ1; Plcg2, 1-phosphatidylinositol-4,5-bisphosphate phosphodiesterase γ2; Prkaca, protein kinase cAMP-activated catalytic subunit α; Prkacb, protein kinase cAMP-activated catalytic subunit β; Prkca, protein kinase Cα; Ptk2, protein tyrosine kinase 2; Ptk2b, protein tyrosine kinase 2β; Rac1, Rac family small GTPase 1; Rock2, Rho associated coiled-coil containing protein kinase 2; Src, proto-oncogene tyrosine-protein kinase Src; TAC, transverse aortic constriction; TGF, transforming growth factor; TimD4, T cell immunoglobulin and mucin domain conataining 4; VEGF-A, vascular endothelial growth factor A; Vav1, Vav guanine nucleotide exchange factor 1; WGA, wheat germ agglutinin; angiogenesis; cardiac hypertrophy; cardio-omentopexy; iB4, biotinylated-isolectin B4; mTOR, mammalian target of rapamycin; macrophages.