AAV9.I-1c delivered via direct coronary infusion in a porcine model of heart failure improves contractility and mitigates adverse remodeling

Abstract

Background: Heart failure is characterized by impaired function and disturbed Ca2+ homeostasis. Transgenic increases in inhibitor-1 activity have been shown to improve Ca2 cycling and preserve cardiac performance in the failing heart. The aim of this study was to evaluate the effect of activating the inhibitor (I-1c) of protein phosphatase 1 (I-1) through gene transfer on cardiac function in a porcine model of heart failure induced by myocardial infarction.

Methods and results: Myocardial infarction was created by a percutaneous, permanent left anterior descending artery occlusion in Yorkshire Landrace swine (n=16). One month after myocardial infarction, pigs underwent intracoronary delivery of either recombinant adeno-associated virus type 9 carrying I-1c (n=8) or saline (n=6) as control. One month after myocardial infarction was created, animals exhibited severe heart failure demonstrated by decreased ejection fraction (46.4±7.0% versus sham 69.7±8.5%) and impaired (dP/dt)max and (dP/dt)min. Intracoronary injection of AAV9.I-1c prevented further deterioration of cardiac function and led to a decrease in scar size.

Conclusions: In this preclinical model of heart failure, overexpression of I-1c by intracoronary in vivo gene transfer preserved cardiac function and reduced the scar size.

Figure 1. Study design

Twenty one pigs underwent myocardial infarction and fourteen survived one month following myocardial infarction. Eight pigs received AAV9.I-1c while six pigs received saline. All animals receiving AAV9.I-1c survived until sacrifice after 3months, while there was one death in the control group. Referenced time points are indicated on the right.

Figure 2. Cardiac output

Cardiac output was measured before MI creation, at the time of gene transfer and before sacrifice at three months.

Figure 3. Ejection fraction

Global functional analysis shows long-term improvements in AAV9.I-1c-treated animals as determined by ejection fraction.

Figure 4. Differences in the adjusted peak LV pressure rate of rise and the time constant isovolumic relaxation

(dP/dt)max as a measure of cardiac contractility was normalized to the average Pressure: (dP/dt)max /P.

Figure 5. Heart Weight to Body Weight Ratio

Weight of the left ventricle was determined after explanation at sacrifice and the ratio to animal’s body weight was calculated.

Figure 6. Left Ventricular Scar Size

Quantification of scar volume by tetrazolium chloride (TTC) staining.

Figure 7. Expression of I-1c

a) Western blot for I-1 and I-1c in left ventricular tissues following gene transfer of I-1c or injection with saline. b) RTPCR of I-1c in left ventricular tissues following gene transfer of I-1c. Border: Viable tissue adjacent to scar tissue. Inferior: Myocardium supplied by RCA at mid-papillary muscle level.