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Background— Cardiac cell transplantation is limited by poor graft viability. We aimed to enhance the survival of transplanted cardiomyoblasts using growth factor-supplemented collagen matrices. Methods and Results— H9c2 cardiomyoblasts were lentivirally transduced to express firefly luciferase and green fluorescent protein (GFP). Lewis rats underwent ligation of the left anterior descending artery (LAD) ligation to induce an anterior wall myocardial infarction. Hearts (n=9/group) were harvested and restored ex vivo with 1×10 6 genetically labeled H9c2 cells either in (1) saline-suspension, or seeded onto (2) collagen-matrix (Gelfoam [GF];), (3) GF/Matrigel (GF/MG), (4) GF/MG/VEGF (10 μg/mL), or (5) GF/MG/FGF (10 μg/mL). Hearts were then abdominally transplanted into syngeneic recipients (working heart model). Controls (n=6/group) underwent infarction followed by GF implantation or saline injection. Cell survival was evaluated using optical bioluminescence on days 1, 5, 8, 14, and 28 postoperatively. At 4 weeks, fractional shortening and ejection fraction were determined using echocardiography and magnetic resonance imaging, respectively. Graft characteristics were assessed by immunohistology. Bioluminescence signals on days 5, 8, and 14 were higher for GF-based grafts compared with plain H9c2 injections ( P <0.03). Signals were higher for GF/MG grafts compared with GF alone ( P <0.02). GFP-positive, spindle-shaped H9c2 cells were found integrated in the infarct border zones at day 28. Left ventricular (LV) function of hearts implanted with collagen-based grafts was better compared with controls ( P <0.05). Vascular endothelial growth factor or fibroblast growth factor did not further improve graft survival or heart function. Conclusions— Collagen matrices enhance early survival of H9c2 cardiomyoblasts after transplantation into ischemic hearts and lead to improved LV function. Further optimization of the graft design should make restoration of large myocardial infarctions by tissue engineering approaches effective.

The db/db mouse is a well-established model of diabetes. Previous reports have documented contractile dysfunction (i.e., cardiomyopathy) in these animals, although the extant literature provides limited insights into cardiac structure and function as they change over time. To better elucidate the natural history of cardiomyopathy in db/db mice, we performed cardiac magnetic resonance (CMR) scans on these animals. CMR imaging was conducted with a 4.7-T magnet on female db/db mice and control db/ϩ littermates at 5, 9, 13, 17, and 22 wk of age. Gated gradient echo sequences were used to obtain cineographic short-axis slices from apex to base. From these images left ventricular (LV) mass (LVM), wall thickness, end-diastolic volume (LVEDV), and ejection fraction (LVEF) were determined. 18 F]FDG metabolic imaging showed a 40% decrease in glucose uptake in db/db mice. Furthermore, contractile dysfunction was observed in 15-wk db/db mice undergoing pressure-volume loops. Finally, real-time quantitative PCR revealed an age-dependent recapitulation of the fetal gene program, consistent with a myopathic process. In summary, as assessed by CMR, db/db mice develop characteristic structural and functional changes consistent with cardiomyopathy. diabetes mellitus; insulin resistance; heart failure; metabolism CONGESTIVE HEART FAILURE (CHF) is a significant yet often underappreciated complication of diabetes mellitus (25). While atherosclerotic coronary artery disease is highly prevalent and likely responsible for CHF in many diabetic patients, findings from several large-scale heart failure clinical trials reveal a 16 -20% prevalence of diabetes in patients with nonischemic cardiomyopathy (9). Moreover, an analysis of hospital discharge data showed a 27% prevalence of diabetes in patients discharged with idiopathic cardiomyopathy, compared with 18% for control subjects (13). Collectively these data suggest an alternative mechanism for CHF in diabetics-one independent of the effects of epicardial coronary disease. However, studies investigating this unique form of "diabetic cardiomyopathy" (51) have failed to establish a unifying mechanistic basis for this phenomenon.The C57BL/KLS-lepr db /lepr db (db/db) mouse, which has a mutation in the leptin receptor, is a well-established animal model of Type 2 diabetes mellitus (19). Leptin resistance results in hyperphagia and weight gain from birth. Homozygous db/db mice become noticeably obese by 3-4 wk of age and develop hyperglycemia at 4 -8 wk. Serum insulin levels increase as early as 10 -14 days, peak at 6 -8 wk, then decrease precipitously afterward (although db/db mice continue to be hyperinsulinemic throughout life). This drop, which is believed to be secondary to pancreatic islet cell dysfunction, further exacerbates the hyperglycemia.In addition to these characteristic phenotypic changes, db/db mice also develop cardiomyopathy. Metabolic experiments using cultured db/db cardiomyocytes have shown impaired glucose oxidation as early as 6 wk of age (1). Echocardiographic studie...

Cell therapy has demonstrated the potential to restore injured myocardium. A reliable in vivo imaging method to localize transplanted cells and monitor their restorative effects will enable a systematic investigation of this therapeutic modality. The dual MRI capability of imaging both magnetically labeled mouse embryonic stem cells (

Background-Cell transplantation for myocardial repair is limited by early cell death. Gene therapy with human Bcl-2 (hBcl-2) has been shown to attenuate apoptosis in the experimental setting. Therefore, we studied the potential benefit of hBcl-2 transgene expression on the survival of cardiomyoblast grafts in ischemic rat hearts. Methods and Results-H9c2 rat cardiomyoblasts were genetically modified to express both firefly luciferase and green fluorescent protein (mH9c2). The cells were then transduced with adenovirus carrying hBcl-2 (AdCMVhBcl-2/mH9c2). Lewis rats underwent ligation of the left anterior descending artery (LAD) to induce a sizable left ventricular (LV) infarct. Hearts were explanted and the infarcted region was restored using collagen matrix (CM) seeded with 1ϫ10 6 mH9c2 cells (nϭ9) or AdCMVhBcl-2/mH9c2 cells (nϭ9). Control animals received CM alone (nϭ6) or no infarct (nϭ6). Restored hearts were transplanted into the abdomen of syngeneic recipients in a "working heart" model. Cell survival was evaluated using optical bioluminescence imaging on days 1, 5, 8, 14, and 28 after surgery. The left heart function was assessed 4 weeks postoperatively using echocardiography and magnetic resonance imaging. During 4 weeks after surgery, the optical imaging signal for the AdCMVhBCL2/mH9c2 group was significantly (PϽ0.05) higher than that of the mH9c2-control group. Both grafts led to better fractional shortening (AdCMVhBcl-2/mH9c2: 0.

This study validates in vivo magnetic resonance imaging as an effective means of evaluating the restorative potential of mouse embryonic stem cells.

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