579 Aged Human Cells Rejuvenated by Cytokine-Enhancement of Biomaterials for Surgical Ventricular Restoration

Abstract

BackgroundAge-related stem cell exhaustion contributes to the increased risk of heart failure following a myocardial infarction (MI) in the elderly. New therapies are urgently needed to prevent ventricular decompensation in older patients and rejuvenate their dysfunctional stem cells. We created a cell-seeded, cytokine-enhanced biodegradable cardiac patch that can be employed for surgical ventricular restoration (SVR) to normalize the size and shape of the ventricle. The sustained cytokine release is intended to rejuvenate the stem cells of aged patients, prevent remodeling, and improve the recovery of ventricular function.Methods/ResultsWe covalently immobilized two pro-angiogenic cytokines, vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF), onto porous collagen scaffolds. The efficiency of immobilization for VEGF was 42% and bFGF was 24%. Scaffolds were seeded with human mesenchymal stem cells (hMSCs) isolated from young (50.0±8.0 years, N=4) or old (74.5±7.4 years, N=4) cardiac patients. Old MSCs seeded in cytokine-free scaffolds in vitro had the fewest cells at both day 2 and 4 after seeding, but cytokine enhancement significantly increased proliferation of the old hMSCs (p<0.05 day 2, p<0.01 day 4) to the level seen with young cells and modulated two aging-related genes (p16 and RGN), converting the old phenotype to a young cell phenotype. We then evaluated the potential of the patches to improve recovery of ventricular function after SVR in a rat MI model. In vivo cell survival 28 days after patch implantation was significantly lower in patches seeded with old hMSCs; however, cytokine enhancement significantly increased old cell survival (p<0.05). Vascular density (determined by immunostaining of heart sections) was lowest in the old hMSC group but increased significantly with the addition of cytokines (p<0.05) to a density similar to the young hMSC group. Patch dilatation on day 28 was most dramatic in the old hMSC group. Cytokine enhanced patches seeded with old hMSCs preserved patch area similar to patches seeded with young cells (p<0.05). Cardiac function was assessed by echocardiography and pressure-volume loops. Rats implanted with cytokine-enhanced patches had better cardiac function. Ejection fraction was significantly lower (p<0.05) in rats implanted with old hMSC patches (24.08±3.96%) vs. cytokine-enhanced old hMSC patches (30.65±1.86%). With immobilized cytokines, the old hMSCs were rejuvenated and the patch became elastic tissue.ConclusionThis sustained-release, cytokine-conjugated system provides a promising platform for engineering myocardial tissue to restore ventricular function for aged patients and prevent progressive heart failure. BackgroundAge-related stem cell exhaustion contributes to the increased risk of heart failure following a myocardial infarction (MI) in the elderly. New therapies are urgently needed to prevent ventricular decompensation in older patients and rejuvenate their dysfunctional stem cells. We created a cell-seeded, cytokine-enhanced biodegradable cardiac patch that can be employed for surgical ventricular restoration (SVR) to normalize the size and shape of the ventricle. The sustained cytokine release is intended to rejuvenate the stem cells of aged patients, prevent remodeling, and improve the recovery of ventricular function. Age-related stem cell exhaustion contributes to the increased risk of heart failure following a myocardial infarction (MI) in the elderly. New therapies are urgently needed to prevent ventricular decompensation in older patients and rejuvenate their dysfunctional stem cells. We created a cell-seeded, cytokine-enhanced biodegradable cardiac patch that can be employed for surgical ventricular restoration (SVR) to normalize the size and shape of the ventricle. The sustained cytokine release is intended to rejuvenate the stem cells of aged patients, prevent remodeling, and improve the recovery of ventricular function. Methods/ResultsWe covalently immobilized two pro-angiogenic cytokines, vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF), onto porous collagen scaffolds. The efficiency of immobilization for VEGF was 42% and bFGF was 24%. Scaffolds were seeded with human mesenchymal stem cells (hMSCs) isolated from young (50.0±8.0 years, N=4) or old (74.5±7.4 years, N=4) cardiac patients. Old MSCs seeded in cytokine-free scaffolds in vitro had the fewest cells at both day 2 and 4 after seeding, but cytokine enhancement significantly increased proliferation of the old hMSCs (p<0.05 day 2, p<0.01 day 4) to the level seen with young cells and modulated two aging-related genes (p16 and RGN), converting the old phenotype to a young cell phenotype. We then evaluated the potential of the patches to improve recovery of ventricular function after SVR in a rat MI model. In vivo cell survival 28 days after patch implantation was significantly lower in patches seeded with old hMSCs; however, cytokine enhancement significantly increased old cell survival (p<0.05). Vascular density (determined by immunostaining of heart sections) was lowest in the old hMSC group but increased significantly with the addition of cytokines (p<0.05) to a density similar to the young hMSC group. Patch dilatation on day 28 was most dramatic in the old hMSC group. Cytokine enhanced patches seeded with old hMSCs preserved patch area similar to patches seeded with young cells (p<0.05). Cardiac function was assessed by echocardiography and pressure-volume loops. Rats implanted with cytokine-enhanced patches had better cardiac function. Ejection fraction was significantly lower (p<0.05) in rats implanted with old hMSC patches (24.08±3.96%) vs. cytokine-enhanced old hMSC patches (30.65±1.86%). With immobilized cytokines, the old hMSCs were rejuvenated and the patch became elastic tissue. We covalently immobilized two pro-angiogenic cytokines, vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF), onto porous collagen scaffolds. The efficiency of immobilization for VEGF was 42% and bFGF was 24%. Scaffolds were seeded with human mesenchymal stem cells (hMSCs) isolated from young (50.0±8.0 years, N=4) or old (74.5±7.4 years, N=4) cardiac patients. Old MSCs seeded in cytokine-free scaffolds in vitro had the fewest cells at both day 2 and 4 after seeding, but cytokine enhancement significantly increased proliferation of the old hMSCs (p<0.05 day 2, p<0.01 day 4) to the level seen with young cells and modulated two aging-related genes (p16 and RGN), converting the old phenotype to a young cell phenotype. We then evaluated the potential of the patches to improve recovery of ventricular function after SVR in a rat MI model. In vivo cell survival 28 days after patch implantation was significantly lower in patches seeded with old hMSCs; however, cytokine enhancement significantly increased old cell survival (p<0.05). Vascular density (determined by immunostaining of heart sections) was lowest in the old hMSC group but increased significantly with the addition of cytokines (p<0.05) to a density similar to the young hMSC group. Patch dilatation on day 28 was most dramatic in the old hMSC group. Cytokine enhanced patches seeded with old hMSCs preserved patch area similar to patches seeded with young cells (p<0.05). Cardiac function was assessed by echocardiography and pressure-volume loops. Rats implanted with cytokine-enhanced patches had better cardiac function. Ejection fraction was significantly lower (p<0.05) in rats implanted with old hMSC patches (24.08±3.96%) vs. cytokine-enhanced old hMSC patches (30.65±1.86%). With immobilized cytokines, the old hMSCs were rejuvenated and the patch became elastic tissue. ConclusionThis sustained-release, cytokine-conjugated system provides a promising platform for engineering myocardial tissue to restore ventricular function for aged patients and prevent progressive heart failure. This sustained-release, cytokine-conjugated system provides a promising platform for engineering myocardial tissue to restore ventricular function for aged patients and prevent progressive heart failure.