Figure 1.

BM Sca-1⁺ cells homed to the epicardium and increased proliferation of host epicardial cells after MI. Sca-1⁺ and Sca-1^- bone marrow (BM, 2×10⁶) cells from young (Y) GFP (green fluorescent protein) transgenic mice were used to reconstitute irradiated old (O, 9.5 Gy) wild type mice, generating Y(Sca1⁺)-O and Y(Sca1^-)-O chimeras, respectively. Twelve weeks after BM reconstitution, coronary occlusion was performed to induce myocardial infarction (MI). To detect cell proliferation after MI, BrdU (50 mg/kg) was administered to mice by intraperitoneal injection for 3 consecutive days. Coronary artery ligation was performed 1 day later. (A) Immunofluorescent staining of GFP and WT1 in chimeric hearts at baseline, 3 and 7 days post-MI. (B) Quantification of GFP⁺ in the epicardium, myocardium, and endocardium of chimeric hearts at baseline and in the infarcted region at 3 and 7 days post-MI. (C) Quantification of WT1⁺ cells in the epicardium, myocardium, and endocardium of the infarct area in the chimeric hearts. (D) Quantification of WT1⁺GFP^- or WT1⁺GFP⁺ cells in the infarcted region of the chimeric hearts. (E) Immunofluorescent staining of GFP, WT1, and BrdU in chimeric hearts at baseline, 3 and 7 days post-MI. Yellow arrows indicate GFP, WT1, and BrdU triple-positive cells. White arrows indicate WT1 and BrdU double-positive cells. (F) Quantification of WT1⁺BrdU⁺ (proliferating epicardial cells) cells in the infarcted region of the chimeric hearts at 3 and 7 days post-MI. Quantification of WT1⁺BrdU⁺GFP^- (host-derived proliferating epicardial cells) and WT1⁺BrdU⁺GFP⁺ cells (donor-derived proliferating epicardial cells) in the infarcted region of the chimeric hearts at 3 (G) and 7 (F) days post-MI. n= 6/group, mean ± SD; *P<0.05, **P<0.01. BrdU: bromodeoxyuridine; WT1: wilms tumor 1.