Abstract 223: Yap and Its Homolog Wwtr1 Are Regulators of Myofibroblast Activation Following Ischemic Injury

Introduction: Following ischemic injury in adult mammals, cardiac fibroblasts differentiate into myofibroblasts and promote secretion of matrix fibers. Myofibroblast activation is critical for initial scar formation and preventing heart rupture, however, extended activity can lead to heart failure progression. Thus, there is a need to identify the mechanisms mediating persistent activation of myofibroblasts to prevent excessive fibrosis and adverse cardiac remodeling. Here we demonstrate that Hippo-Yap pathway offers a target for modulating myofibroblast activation and thus the fibrotic response. Methods and Results: We tested the hypothesis that Yap and its homolog Wwtr1 (known as ‘Taz’) are regulators of myofibroblast activation following ischemic injury. We implemented a Cre-lox system whereby Yap alone or both Yap and Wwrt1 were depleted using an inducible Cre expressed under a myofibroblast specific promoter ( Postn MCM ). Following permeant ligation of the left anterior descending artery in adult mice, we found that myofibroblast depletion of Yap alone resulted in a significant reduction in left ventricular dilation 28 days post injury (dpi) and decreased proliferation of scar associated cells. Strikingly, myofibroblast specific depletion of Yap and one copy of Wwrt1 resulted in further attenuation of left ventricular dilation as well as improved fractional shortening and ejection fraction at 28 and 60 dpi. Histological assessment revealed that depletion of both Yap and Wwrt1 resulted in greater than 50% reduction in scar size (by midline) at 60 dpi. RNAseq of whole hearts collected at 4 dpi suggested that Hippo-Yap pathway expression specifically in myofibroblasts facilitates immune cell recruitment in the heart. Collectively These data illustrate a role for Hippo-Yap signaling mediating myofibroblast activity and immune cell coordination following injury and therefore cardiac fibrosis and remodeling. Conclusions: Our data demonstrate that endogenous Yap and Wwrt1 deletion in myofibroblasts suppresses the fibrotic response, mediates inflammation, and improves cardiac function after ischemic injury. These results therefore offer a regulatory pathway that can be targeted therapeutically to prevent progressive heart failure.

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Regulation and impact of cardiac lymphangiogenesis in pressure-overload-induced heart failure

10.1101/2021.04.27.441616 ◽

2021 ◽

Author(s):

C Heron ◽

A Dumesnil ◽

M Houssari ◽

S Renet ◽

A Lebon ◽

...

Keyword(s):

Heart Failure ◽

Dilated Cardiomyopathy ◽

Cardiac Fibrosis ◽

Immune Cell ◽

Pressure Overload ◽

Wall Stress ◽

Myocardial Edema ◽

Selective Inhibition ◽

Left Ventricular ◽

Ventricular Dilation

AbstractRationaleLymphatics are essential for cardiac health, and insufficient lymphatic expansion (lymphangiogenesis) contributes to development of heart failure (HF) after myocardial infarction. However, the regulation and impact of lymphatics in non-ischemic cardiomyopathy induced by pressure-overload remains to be determined.ObjectiveInvestigate cardiac lymphangiogenesis following transverse aortic constriction (TAC) in adult male or female C57Bl/6J or Balb/c mice, and in patients with end-stage HF.Methods & ResultCardiac function was evaluated by echocardiography, and cardiac hypertrophy, lymphatics, inflammation, edema, and fibrosis by immunohistochemistry, flow cytometry, microgravimetry, and gene expression analysis, respectively. Treatment with neutralizing anti-VEGFR3 antibodies was applied to inhibit cardiac lymphangiogenesis in mice.The gender- and strain-dependent mouse cardiac hypertrophic response to TAC, especially increased ventricular wall stress, led to lymphatic expansion in the heart. Our experimental findings that ventricular dilation triggered cardiac lymphangiogenesis was mirrored by observations in clinical HF samples, with increased lymphatic density found in patients with dilated cardiomyopathy. Surprisingly, the striking lymphangiogenesis observed post-TAC in Balb/c mice, linked to increased cardiac Vegfc, did not suffice to resolve myocardial edema, and animals progressed to dilated cardiomyopathy and HF. Conversely, selective inhibition of the essentially Vegfd-driven capillary lymphangiogenesis observed post-TAC in male C57Bl/6J mice did not significantly aggravate cardiac edema. However, cardiac immune cell levels were increased, notably myeloid cells at 3 weeks and T lymphocytes at 8 weeks. Moreover, while the TAC-triggered development of interstitial cardiac fibrosis was unaffected by anti-VEGFR3, inhibition of lymphangiogenesis increased perivascular fibrosis and accelerated the development of left ventricular dilation and cardiac dysfunction.ConclusionsWe demonstrate for the first time that endogenous cardiac lymphangiogenesis limits pressure-overload-induced cardiac inflammation and perivascular fibrosis, thus delaying HF development. While these findings remain to be confirmed in a larger study of HF patients, we propose that under settings of pressure-overload poor cardiac lymphangiogenesis may accelerate HF development.

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