Although heart failure continues to be the leading cause of death in the U.S., research into safer and more reliable methods for replacing dead cardiac cells has become more promising. Instead of a human donor transplant, we can engineer a patient-specific heart to be used in the transplant that will lower risk of rejection by the receiver. Our research at BYU has focused on strengthening the beating function of engineered cardiac tissue and layering the engineered tissue to create transplantable patches to be inserted on damaged hearts. Beating human heart tissue was created in vitro using non-immunogenic scaffolds generated from decellularized porcine hearts combined with cardiomyocytes (CMs) derived from human induced pluripotent stem cells (hiPSCs). Whole porcine hearts were decellularized to create 3D scaffolds capable of supporting the human cells mechanically and biochemically. From the left ventricle of the decellularized hearts, 300 µm thick, 10 mm round slices were prepared and mounted on glass coverslips. Human iPSCs were differentiated into cardiac progenitors and 4 days after differentiation, these cells were seeded onto the decellularized tissue samples. Ten days after recellularization, clusters of differentiated CMs started to beat spontaneously. Immunofluorescence images showed confluent coverage of CMs on the decellularized slices and the effect of the scaffold was evident in the alignment of the CMs in the direction of the collagen fibers. A resazurin-based viability assay showed attachment and survival of 75% of the seeded cells up to 14 days after recellularization. The clusters continued to beat for 60 days. To improve the beating function of the CMs implanted in the tissue scaffold, we will use mechanical, electrical and pharmacological stimulation. By combining mechanical stimulation through a mechanical stretching device, electrical stimulation through transmitting electrical frequencies ranging from 1 to 1.6 Hz, and pharmacological stimulation through drugs, such as epinephrine, we hypothesize that we will increase the beating function of the cardiac tissue from 10 beats per minute (current rate) to 60 beats per minute. We will also layer sheets of CMs into a patch, and insert them onto hearts of induced-infarction rats on top of the dead cardiac tissue. By using these strengthened CMs and layering them through chemical binding factors and centrifugation, we hypothesize that the CM patch will attach securely to the patch of dead cardiac tissue in the rats and replace it in function without being rejected by the host.
