Introduction : Regenerative therapy for heart failure (HF) points to bone marrow mesenchymal stem cell (BM-MSC) as a promising cell source. High mobility group box 1 (HMGB1) is a nuclear protein involved in tissue homeostasis. In this study, we developed an HMGB1 fragment containing a BM-MSC mobilization domain. Hypothesis: We hypothesize that the HMGB1 fragment improves cardiac function by activating a tissue healing pathway of BM-MSC within a porcine ischemic cardiomyopathy (ICM) model as a pre-clinical study. Methods: Gottingen mini pigs weighing 15-25 kg were used. An ICM model was generated by placing an ameroid constrictor ring (internal diameter; 3.5 mm) on the left anterior descending artery (LAD). After 4 weeks, either the HMGB1 fragment (HMGB1 group; 3 mg/kg, n=6) or normal saline (control group; n=5) was administered intravenously with one dose every 48 h for five times. We examined cardiac function before and 8 weeks post treatment through echocardiography, cardiac magnetic resonance imaging (cMRI) with late gadolinium enhancement (LGE), and a fluoroscopy-guided pressure wire study. Then, histological analysis was performed. Results: In echocardiography, ejection fraction significantly improved in the HMGB1 group compared with the control (+11.1% vs -4.8%, p=0.0003). cMRI with LGE demonstrated that the areas of damaged myocardium (core infarct zone + border zone) in the LAD region was reduced in the HMGB1 group compared with the control group (-11.9% vs +17.9%, p=0.0090). Coronary flow reserve (CFR) and resistive reserve ratio (RRR) were evaluated through pressure wire study; they improved in the HMGB1 group compared with the control group (ΔCFR; +0.38 vs +0.01, p=0.0249, ΔRRR; +0.42 vs +0.07, p=0.0275). Histological analysis showed that cardiomyocyte size (26.6 μm vs 38.0 μm, p=0.0339) and areas of fibrosis were smaller (9.8% vs 11.6%, p=0.1649), and the density of CD31-positive endothelial cells was higher (1033/mm 2 vs 640/mm 2 , p=0.0339) in the HMGB1 group than in the control group. Conclusions: Systemic administration of the HMGB1 fragment improved cardiac function, coronary flow reserve, and reduced cardiac fibrosis in an ICM model. This drug-induced activation of inner tissue repair and regeneration is a novel approach to treat HF.