Optimizing Engineered Heart Tissue for Therapeutic Applications as Surrogate Heart Muscle

Abstract

Background— Cardiac tissue engineering aims at providing heart muscle for cardiac regeneration. Here, we hypothesized that engineered heart tissue (EHT) can be improved by using mixed heart cell populations, culture in defined serum-free and Matrigel-free conditions, and fusion of single-unit EHTs to multi-unit heart muscle surrogates. Methods and Results— EHTs were constructed from native and cardiac myocyte enriched heart cell populations. The former demonstrated a superior contractile performance and developed vascular structures. Peptide growth factor-supplemented culture medium was developed to maintain contractile EHTs in a serum-free environment. Addition of triiodothyronine and insulin facilitated withdrawal of Matrigel from the EHT reconstitution mixture. Single-unit EHTs could be fused to form large multi-unit EHTs with variable geometries. Conclusions— Simulating a native heart cell environment in EHTs leads to improved function and formation of primitive capillaries. The latter may constitute a preformed vascular bed in vitro and facilitate engraftment in vivo. Serum- and Matrigel-free culture conditions are expected to reduce immunogenicity of EHT. Fusion of single-unit EHT allows production of large heart muscle constructs that may eventually serve as optimized tissue grafts in cardiac regeneration in vivo.

Physiological function and transplantation of scaffold-free and vascularized human cardiac muscle tissue

“…1A). Several recent studies indicate that formation of vascular networks in tissueengineered constructs is augmented by inclusion of mesenchymal cells that provide key paracrine factors and serve as supporting mural cells (9,19,20). We therefore constructed ''tri-cell'' cardiac patches containing hESC-derived cardiomyocytes, HUVECs, and mouse embryonic fibroblasts (MEFs) in 1:1:0.5 ratios, respectively (cardio-HUVEC-MEF patches).…”

“…Delivery of cells in tissue-like structures that preserve cellular attachments could increase cell delivery efficiency and reduce cell death (4). Most heart tissue engineered in vitro to date has focused on creating tissues by seeding neonatal rat or chick cardiomyocytes into polymer or extracellular matrix scaffolds and gels (5)(6)(7)(8)(9)(10)(11). Creation of 3D tissues that are composed only of cells and the matrix they secrete (12)(13)(14)(15), which we refer to as ''scaffoldfree'' tissue engineering, addresses limitations associated with polymer and exogenous matrix-based tissues (e.g., unfavorable host response to biomaterials).…”

Adhesion Proteins, Stem Cells, and Arrhythmogenesis

“…Furthermore, the presence of fibroblasts has been shown to decrease endothelial cell death and increase cell proliferation in vitro, which suggests that these cells can also promote vascularization of the injured myocardium [20]. Additional evidence of the benefits of a heterogeneous cell population has been documented in studies of engineered heart tissue, where the constructs made from mixed cell populations improved cardiac function to a greater extent than the ones made from a purified myocyte populations [66].…”

“…1c, d), and then use it to surgically repair the diseased myocardium. Several laboratories are successfully moving toward this goal [48,66,[73][74][75][76]. For example, engineered heart tissue grafts (EHTs) have been developed by seeding neonatal cardiomyocytes in circular molds with collagen and Matrigel, and then culturing the formed rings in a mechanical stretch device [73].…”

“…Moreover, echocardiograph and MRI indicated reduced left ventricular dilation and end diastolic volume. Recent modifications to EHT generation, using a mixed cell population with fibroblasts, smooth muscle cells, and endothelial cells, have resulted in superior contractile performance over cardiomyocyte samples alone [66]. Moreover, the creation of EHT from ESC and successful engraftment of these ESC-EHT into the working myocardium has also been reported [74].…”