Adverse remodeling of the left ventricle (LV) after myocardial infarction (MI) results in abnormal tissue biomechanics and impaired cardiac function, often leading to heart failure. We hypothesized that intramyocardial delivery of engineered stromal cell-derived factor 1a analog (ESA), our previously-developed supra-efficient pro-angiogenic chemokine, preserves biaxial LV mechanical properties after MI. Male Wistar rats (n?=?45) underwent sham surgery (n?=?15) or permanent left anterior descending coronary artery ligation. Rats sustaining MI were randomized for intramyocardial injections of either saline (100?µL, n?=?15) or ESA (6?µg/kg, n?=?15), delivered at four standardized borderzone sites. After 4 weeks, echocardiography was performed, and the hearts were explanted. Tensile testing of the anterolateral LV wall was performed using a displacement-controlled biaxial load frame, and modulus was determined after constitutive modeling. At 4 weeks post-MI, compared to saline controls, ESA-treated hearts had greater wall thickness (1.68?±?0.05?mm vs 1.42?±?0.08?mm, p?=?0.008), smaller end-diastolic LV internal dimension (6.88?±?0.29?mm vs 7.69?±?0.22?mm, p?=?0.044), and improved ejection fraction (62.8?±?3.0% vs 49.4?±?4.5%, p?=?0.014). Histologic analysis revealed significantly reduced infarct size for ESA-treated hearts compared to saline controls (29.4?±?2.9% vs 41.6?±?3.1%, p?=?0.021). Infarcted hearts treated with ESA exhibited decreased modulus compared to those treated with saline in both the circumferential (211.5?±?6.9?kPa vs 264.3?±?12.5?kPa, p?=?0.001) and longitudinal axes (194.5?±?6.5?kPa vs 258.1?±?14.4?kPa, p?
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