A Bioengineered Neuregulin-Hydrogel Therapy Reduces Scar Size and Enhances Post-Infarct Ventricular Contractility in an Ovine Large Animal Model

Abstract

The clinical efficacy of neuregulin (NRG) in the treatment of heart failure is hindered by off-target exposure due to systemic delivery. We previously encapsulated neuregulin in a hydrogel (HG) for targeted and sustained myocardial delivery, demonstrating significant induction of cardiomyocyte proliferation and preservation of post-infarct cardiac function in a murine myocardial infarction (MI) model. Here, we performed a focused evaluation of our hydrogel-encapsulated neuregulin (NRG-HG) therapy's potential to enhance cardiac function in an ovine large animal MI model. Adult male Dorset sheep (n = 21) underwent surgical induction of MI by coronary artery ligation. The sheep were randomized to receive an intramyocardial injection of saline, HG only, NRG only, or NRG-HG circumferentially around the infarct borderzone. Eight weeks after MI, closed-chest intracardiac pressure-volume hemodynamics were assessed, followed by heart explant for infarct size analysis. Compared to each of the control groups, NRG-HG significantly augmented left ventricular ejection fraction (p = 0.006) and contractility based on the slope of the end-systolic pressure-volume relationship (p = 0.006). NRG-HG also significantly reduced infarct scar size (p = 0.002). Overall, using a bioengineered hydrogel delivery system, a one-time dose of NRG delivered intramyocardially to the infarct borderzone at the time of MI in adult sheep significantly reduces scar size and enhances ventricular contractility at 8 weeks after MI.

Keywords: hydrogel; ischemic heart failure; myocardial infarction; neuregulin.

Figure 1

Ovine myocardial infarction model using a mini left thoracotomy approach. (A) The left ventricle is exposed through a fifth interspace mini left thoracotomy incision. (B) Diagonal branches of the left anterior descending coronary artery are ligated using 5-0 or 6-0 polypropylene sutures (arrow), producing a consistently-sized pale and hypokinetic infarct zone (bounded by dotted line). The infarct borderzone lies immediately beyond the dotted yellow line.

Figure 2

Cardiac function at 8 weeks after myocardial infarction, measured by analyzing closed-chest left ventricular pressure-volume hemodynamics data. Data regarding (A) ejection fraction (%) and (B) the slope of the end-systolic pressure–volume relationship (ESPVR, mmHg/mL) are compared among sheep receiving saline (n = 6), hydrogel only (HG, n = 4), neuregulin only (NRG, n = 4), and hydrogel-encapsulated neuregulin (NRG-HG, n = 6). Data are presented as mean ± standard error. * indicates statistically significant (p < 0.05) compared to the NRG-HG group.

Figure 3

Representative pressure–volume loops for the (A) saline, (B) hydrogel only (HG), (C) neuregulin only (NRG), and (D) hydrogel-encapsulated neuregulin (NRG-HG) groups are shown. The slope of the end-systolic pressure-volume relationship (ESPVR, red line) is quantified.

Figure 4

Left ventricular endocardial scar size at 8 weeks after myocardial infarction. Representative photographs of sheep hearts from the (A) saline, (B) neuregulin only (NRG), and (C) hydrogel-encapsulated neuregulin (NRG-HG) groups are shown. (D) Quantified scar size for the saline (n = 6), hydrogel only (HG, n = 4), NRG only (n = 4), and NRG-HG groups (n = 7). Data are presented as mean ± standard error. ** indicates statistically significant (p < 0.01) compared to the NRG-HG group.