775 Encapsulation of Ex Vivo Proliferated Human Cardiac Stem Cells Within Matrix Supplemented Hydrogel Enhances Survival by Preventing Detachment Induced Apoptosis

Abstract

Cellular cardiomyoplasty using ex vivo proliferated cardiac stem cells (CSC) is an emerging treatment option in the management of heart failure; however, regeneration is limited by cell acute engraftment and survival. Using other cell types, it is well established that biomaterials may enhance engraftment with salutary effects on functional outcomes. Therefore we explored the ability of CSC encapsulation to prevent apoptosis and cell death with the ultimate goal of boosting engraftment after myocardial injection. Human atrial appendages were obtained from patients undergoing clinically-indicated surgery. Resident CSC cultures were established and CSCs were encapsulated in hydrogel capsules with immobilized matrix proteins to enhance cell-matrix survival signals. Supplemented CSC capsules increased viability compared to adherent and suspension culture (1.7±0.7 vs. 1.3±0.1 and −0.9±0.1 fold increase in cell numbers over 24 hours, respectively; p<0.05). To mimic the natural matrix microenvironment of stem cell niches within the native heart, type IV collagen was added to CSC capsules and, while this strategy improved encapsulation efficiency (+1.7±1.0 fold increase in encapsulated cell vs. standard encapsulation, p<0.05), collagen did not further improve proliferation of CSCs within the capsule (1.2±0.3 fold increase in cell numbers over 24 hours, p=ns). Activation of cell-matrix interactions within matrix supplemented CSC capsules sustained downstream expression of gene targets (BCL-2, FOS, and JUN) within three complimentary pro-survival pathways (AKT, ERK, and JNK). Decreasing the capsular hydrogel content provided a means of engineering early CSC migration from the capsule (52.3±6.5% vs. 5.0±3.4% extra-capsular CSCs 24 hours after encapsulation with 2.5% and 3.5% hydrogel, respectively; p<0.05). Finally, acute retention of encapsulated human cells is increased following intra-myocardial injection into an in vivo immunodeficient mouse model of myocardial ischemia. Encapsulation of CSCs in supplemented hydrogel boosts proliferation/survival by providing vital extra cellular matrix cues that prevent detachment induced apoptosis. Manipulation of capsule constituents supplies a means of altering CSCs migration from the capsule - potentially altering the kinetics of CSC delivery to the myocardium after transplantation.