BackgroundIt remains unclear whether abnormal systolic function and relaxation are essential for developing heart failure in pathophysiology of severe aortic stenosis.Methods and ResultsYorkshire pigs underwent surgical banding of the ascending aorta. The animals were followed for up to 5 months after surgery, and cardiac function was assessed comprehensively by invasive pressure–volume measurements, 3-dimensional echocardiography, echocardiographic speckle-tracking strain, and postmortem molecular and histological analyses. Pigs with aortic banding (n=6) exhibited significant left ventricular hypertrophy with increased stiffness compared with the control pigs (n=7) (end-diastolic pressure–volume relationship β: 0.053±0.017 versus 0.028±0.009 mm Hg/mL, P=0.007); however, all other parameters corresponding to systolic function, including ejection fraction, end-systolic pressure–volume relationship, preload recruitable stroke work, echocardiographic circumferential strain, and longitudinal strain, were not impaired in pigs with aortic banding. Relaxation parameters were also similar between groups. Sarcoplasmic reticulum calcium (Ca2+) ATPase protein levels in the left ventricle were similar. There were significant increases in 3-dimensional echocardiographic left atrial volumes, suggesting the usefulness of these indexes to detect increased stiffness. Right atrial pacing with a heart rate of 120 beats per minute induced increased end-diastolic pressure in pigs with aortic banding in contrast to decreased end-diastolic pressure in the control pigs. Histological evaluation revealed that increased stiffness was accompanied by cardiomyocyte hypertrophy and increased perimysial and perivascular fibrosis.ConclusionIncreased stiffness is the major early pathological process that predisposes to congestive heart failure without abnormalities in systolic function and relaxation in a clinically relevant animal model of aortic stenosis.

Background Stem cell factor (SCF), a ligand of the c-kit receptor, is a critical cytokine which contributes to cell migration, proliferation, and survival. It has been shown that SCF expression increases after myocardial infarction (MI) and may be involved in cardiac repair. The aim of this study was to determine whether gene transfer of membrane-bound human SCF improves cardiac function in a large animal model of MI. Methods and Results A transmural MI was created by implanting an embolic coil in the left anterior descending artery in Yorkshire pigs. One week after the MI, the pigs received direct intramyocardial injections of either a recombinant adenovirus encoding for SCF, (Ad.SCF, n=9) or β-gal (Ad.β-gal, n=6) into the infarct border area. At three months post-MI, ejection fraction increased by 12% relative to baseline after Ad.SCF therapy, whereas it decreased by 4.2% (P=0.004) in pigs treated with Ad.β-gal. Preload-recruitable stroke work was significantly higher in pigs after SCF treatment (Ad.SCF, 55.5±11.6 mmHg vs Ad.β-gal, 31.6±12.6 mmHg, P=0.005), indicating enhanced cardiac function. Histological analyses confirmed the recruitment of c-kit+ cells as well as a reduced degree of apoptosis one week after Ad.SCF injection. In addition, increased capillary density compared to pigs treated with Ad.β-gal was found at three months and suggests an angiogenic role of SCF. Conclusions Local over-expression of SCF post-MI induces the recruitment of c-kit+ cells at the infarct border area acutely. In the chronic stages, SCF gene transfer was associated with improved cardiac function in a pre-clinical model of ischemic cardiomyopathy.

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