Abstract 427: In Vivo Integration of Tissue-Engineered Human Vascularized Cardiac Muscle
Background: Myocardial cell replacement strategies have been hampered by the lack of sources for human cardiomyocytes and by the significant donor cell loss and death following grafting. We aimed to assess the ability of 3D engineered human vascularized cardiac muscle constructs to engraft in the in vivo rat heart, induce cardiomyocyte maturation, and promote functional vascularization.
Methods and Results: Human embryonic stem cell-derived cardiomyocytes, alone (C) or in combination with human vascular precursor cells and embryonic fibroblasts (CHM), were seeded on degradable biopolymer scaffolds. Synchronously contracting cardiac tissue constructs were formed in vitro that contained a dense endothelial vessel network (in the CHM constructs). Grafting of the engineered tissue in the rat heart resulted in the formation of long-term stable grafts, which showed gradual structural maturation of the human cardiomyocytes. Electromechanical integration of the human cardiac tissue was suggested by positive immunostaining for Cx43. Next, the formation of human and rat-derived vasculature within the scaffold was confirmed by immunostaining with anti-smooth muscle actin and anti-human specific CD31 antibodies. Intraventricular injection of fluorescent microspheres and lectin resulted in their incorporation into blood vessels within the scaffolds, confirming their functional perfusion capabilities. Finally, the number of vessel lumens per mm2 was significantly increased in the CHM-containing scaffolds (33 ± 3, p<0.01) when compared to those containing cardiomyocytes alone (17 ± 3).
Tissue-engineered human cardiac constructs, containing a dense vascular network, can be successfully established ex vivo and grafted in vivo to form stable cell grafts.
The grafted tissue-constructs showed significant vascularization, consisting of both pre-existing human- and newly formed rat vessels.
The presence of pre-existing human vessels in the CHM scaffolds significantly increased tissue vascularity and resulted in the generation of functional vessels that became integrated with host vascular network.
The establishment of this unique model may have important implications for cardiovascular regenerative medicine.