ABSTRACT: BACKGROUND: Tissue engineering scaffold constitutes a new strategy of myocardial repair. Here, we studied the contribution of a patch using autologous mesenchymal stem cells (MSCs) seeded on collagen-1 scaffold on the cardiac reconstruction in rat model of chronic myocardial infarction (MI). METHODS: Patches were cultured with controlled MSCs (growth, phenotype and potentiality). Twenty coronary ligated rats with tomoscingraphy (SPECT)-authenticated transmural chronic MI were referred into a control group (n = 10) and a treated group (n = 10) which beneficiated an epicardial MSC-patch engraftment. Contribution of MSC-patch was tested 1-mo after using non-invasive SPECT cardiac imaging, invasive hemodynamic assessment and immunohistochemistry. RESULTS: 3D-collagen environment affected the cell growth but not the cell phenotype and potentiality. MSC-patch integrates well the epicardial side of chronic MI scar. In treated rats, one-month SPECT data have documented an improvement of perfusion in MI segments compared to control (64 +/- 4% vs 49 +/- 3% p = 0.02) and a reduced infarction. Contractile parameter dp/dtmax and dp/dtmin were improved (p < 0.01). Histology showed an increase of ventricular wall thickness (1.75 +/- 0.24 vs 1.35 +/- 0.32 mm, p <0.05) and immunochemistry of the repaired tissue displayed enhanced angiogenesis and myofibroblast-like tissue. CONCLUSION: 3D-MSC-collagen epicardial patch engraftment contributes to reverse remodeling of chronic MI.