Scaffold Delivery of Neonatal Cardiomyocyte Results in Prolonged Cellular Survival and Improvements in Left Ventricular Function in Rats with Chronic Heart Failure

Abstract

Tissue engineered scaffolds used for cell delivery enhance improvements in cardiac function by providing structural and nutrient support for transplanted cell survival, integration, and re-population of injured tissues. Previously, our laboratory reported improvements in left ventricular (LV) function in rats with chronic heart failure (CHF) after placement of a neonatal cardiomyocyte seeded 3-dimensional fibroblast construct (NCM-3DFC). The current report focuses on NCM survival and LV improvements out to 7 weeks post NCM-3DFC implantation. Implantation of a neonatal cardiomyocyte scaffold promotes transplanted cell survival and prolongs improvements in left ventricular function in rats with chronic heart failure. Cardiomyocytes were isolated from neonatal rat hearts. Briefly, hearts were excised, atria removed and ventricles minced, and digested in a pancreatin/collagenase solution. Cardiomyocytes were collected and re-suspended in DMEM with 10% FBS. The NCM-3DFC were cultured in 10% FBS in DMEM-LG, maintained under standard culture conditions. We evaluated NCM-3DFC in vitro for cellular organization and the presence of functional gap junctions, which demonstrated extensive cell-to-cell connectivity. At 5 days in culture, the seeded patch contracted spontaneously in a rhythmic and directional fashion, beating at 43±3 beats/min with a mean displacement of 1.3±0.3 mm and contraction velocity of 0.8±0.2 mm/sec. The seeded patch could be electrically paced at 270±30 beats/min while maintaining coordinated, directional contractions. For in vivo evaluation, NCM-3DFC were implanted 3 weeks after ligation and evaluated 3 and 7 weeks later (6 and 10 weeks after ligation respectively). Live cell tracking of implanted NCM revealed ∼9% survival of transplanted cells 3 weeks after implantation and improved LV function by increasing (p<0.05) ejection fraction 26% and cardiac index 33%, while decreasing (p<0.05) LV end diastolic pressure 38%. Improvements in LV function continued at 7 weeks after implantation of the NCM-3DFC by increasing (p<0.05) ejection fraction 37%. A multicellular, electromechanically organized, cardiomyocyte scaffold, engineered in vitro can improve LV function when implanted directly on the hearts of rats with CHF; the transplanted cells survive and improve LV function chronically.