Tissue Engineering of Vascularized Cardiac Muscle From Human Embryonic Stem Cells

TLDR

Tissue‑engineered heart muscle transplantation is a promising therapy for myocardial disease, yet its success is limited by scarce human cardiomyocyte sources and inadequate vasculature, which are essential for oxygen delivery and may influence cell survival and proliferation. This study aims to generate synchronously contracting human cardiac tissue from embryonic stem cells that incorporates endothelial vessel networks. The engineered 3D muscle comprised cardiomyocytes, endothelial cells, and embryonic fibroblasts, with the latter providing mural cells that stabilize the formed vessels. Embryonic fibroblasts reduced endothelial cell death, promoted endothelial and cardiomyocyte proliferation without disrupting alignment, and the constructs displayed cardiac‑specific molecular, ultrastructural, and functional properties with synchronous activity mediated by gap junctions, marking the first report of vascularized human cardiac tissue for developmental and therapeutic research.

Abstract

Transplantation of a tissue-engineered heart muscle represents a novel experimental therapeutic paradigm for myocardial diseases. However, this strategy has been hampered by the lack of sources for human cardiomyocytes and by the scarce vasculature in the ischemic area limiting the engraftment and survival of the transplanted muscle. Beyond the necessity of endothelial capillaries for the delivery of oxygen and nutrients to the grafted muscle tissue, interactions between endothelial and cardiomyocyte cells may also play a key role in promoting cell survival and proliferation. In the present study, we describe the formation of synchronously contracting engineered human cardiac tissue derived from human embryonic stem cells containing endothelial vessel networks. The 3D muscle consisted of cardiomyocytes, endothelial cells (ECs), and embryonic fibroblasts (EmFs). The formed vessels were further stabilized by the presence of mural cells originating from the EmFs. The presence of EmFs decreased EC death and increased EC proliferation. Moreover, the presence of endothelial capillaries augmented cardiomyocyte proliferation and did not hamper cardiomyocyte orientation and alignment. Immunostaining, ultrastructural analysis (using transmission electron microscopy), RT-PCR, pharmacological, and confocal laser calcium imaging studies demonstrated the presence of cardiac-specific molecular, ultrastructural, and functional properties of the generated tissue constructs with synchronous activity mediated by action potential propagation through gap junctions. In summary, this is the first report of the construction of 3D vascularized human cardiac tissue that may have unique applications for studies of cardiac development, function, and tissue replacement therapy.