Temporary, Systemic Inhibition of the WNT/β-Catenin Pathway promotes Regenerative Cardiac Repair following Myocardial Infarct

Abstract

Aims The WNT/β-catenin pathway is temporarily activated in the heart following myocardial infarction (MI). Despite data from genetic models indicating both positive and negative roles for the WNT pathway depending on the model used, the effect of therapeutic inhibition of WNT pathway on post-injury outcome and the cellular mediators involved are not completely understood. Using a newly available, small molecule, GNF-6231, which averts WNT pathway activation by blocking secretion of all WNT ligands, we sought to investigate whether therapeutic inhibition of the WNT pathway temporarily after infarct can mitigate post injury cardiac dysfunction and fibrosis and the cellular mechanisms responsible for the effects. Methods and Results Pharmacologic inhibition of the WNT pathway by post-MI intravenous injection of GNF-6231 in C57Bl/6 mice significantly reduced the decline in cardiac function (Fractional Shortening at day 30: 38.71 ± 4.13% in GNF-6231 treated vs. 34.89 ± 4.86% in vehicle-treated), prevented adverse cardiac remodeling, and reduced infarct size (9.07 ± 3.98% vs. 17.18 ± 4.97%). WNT inhibition augmented proliferation of interstitial cells, particularly in the distal myocardium, inhibited apoptosis of cardiomyocytes, and reduced myofibroblast proliferation in the peri-infarct region. In vitro studies showed that WNT inhibition increased proliferation of Sca1+ cardiac progenitors, improved survival of cardiomyocytes, and inhibited collagen I synthesis by cardiac myofibroblasts. Conclusion Systemic, temporary pharmacologic inhibition of the WNT pathway using an orally bioavailable drug immediately following MI resulted in improved function, reduced adverse remodeling and reduced infarct size in mice. Therapeutic WNT inhibition affected multiple aspects of infarct repair: it promoted proliferation of cardiac progenitors and other interstitial cells, inhibited myofibroblast proliferation, improved cardiomyocyte survival, and reduced collagen I gene expression by myofibroblasts. Our data point to a promising role for WNT inhibitory therapeutics as a new class of drugs to drive post-MI repair and prevent heart failure.

Blockade to pathological remodeling of infarcted heart tissue using a porcupine antagonist

“…Another study using a precursor compound of WNT-974 (GNF-6231) given at a comparable drug concentration recently reported similar proregenerative effects in heart tissue, including improvements in heart function following Porcn inhibition and reduced scarring (38). The immediate delivery of a Porcn inhibitor following LAD ligation in that study suggests that suppression of Wnt responses during the inflammatory phase does not contribute to the improvements in heart recovery seen in WNT-974-treated animals.…”

“…At the same time, the success of our approach (a 1-wk delay in drug delivery following injury) reveals at a minimum a 1-wk window in which initiation of Porcn inhibitor delivery following myocardial infarction (MI) might be beneficial. Finally, we acknowledge that changes in the expression of Col6 may be only one proregenerative consequence of Porcn inhibition and that other molecular changes (38,39) may also be factors that influence heart function outcome.…”

“…Suppression of Porcn activity may blunt this phenomenon, in addition to influencing the activity of resident fibroblasts in the heart. A recent study using GNF-6231 also revealed potential increased doubling in the cardiac progenitor population following injury (38). Thus, activation of stem/progenitor cells by direct/indirect action of Porcn inhibitors may also contribute to improvements in regeneration in some tissues.…”

Wnt/β‐catenin pathway in tissue injury: roles in pathology and therapeutic opportunities for regeneration

“…One of the Porcupine inhibitors identified in those screens, LGK974, is currently in phase I dose‐escalation studies for malignancies driven by WNT ligands (http://Clinicaltrials.gov: NCT01351103). We reported a significant improvement in cardiac recovery from infarction by temporary systemic treatment with an analog of LGK974 (167). Intravenous administration of a Porcupine inhibitor GNF‐6231 for 6 d after experimental infarction in mice results in reduced adverse remodeling, improved function, and decreased infarct size.…”

Wnt signaling in cardiovascular disease: opportunities and challenges

“…For example, GNF-6231 is an inhibitor of porcupine, the endoplasmic reticulum protein that is required for Wnt palmitoylation. GNF-6231 inhibits the secretion of both canonical and noncanonical Wnt ligands, and transient porcupine inhibitioin limits pro-fibrotic myocardial injury and enhances recovery in preclinical models of myocardial infarction[141]. Similarly, antagonists of tankyrase – a poly ADP-ribose polymerase that reduces the canonical pathway inhibitor Axin (Figure 1) – increase Axin levels, reduce canonical Wnt signaling and mechanical injury-induced neointima formation[142].…”