Engineering of functional cardiac tubes by stepwise transplantation of cardiac cell sheets onto intestinal mesentery

Implantable organ-like grafts made using tissue engineering techniques could potentially be used as circulatory assist devices in people with heart failure. The aims of this study were to engineer implantable, thick cardiac tubes by the stepwise transplantation of cardiac cell sheets onto intestinal mesentery and confirm that these cardiac tubes exhibited pulsatile activity and generated an internal pressure. Cell sheets were created by culturing neonatal rat cardiac cells on temperature-responsive dishes. After harvesting, three cell sheets were stacked, and the triple-layered cell sheet was rolled around a section of endotracheal tube. The resulting construct was cultured to generate a cardiac tube. In the single-step group (n = 6), a cardiac tube was implanted onto the intestinal mesentery of a rat. In the double-step group (n = 6), a cardiac tube was implanted onto the intestinal mesentery of a rat, and another new cardiac tube was inserted into the original cardiac tube one day later. The pulsations and internal pressures of the implanted cardiac tubes were evaluated 1, 2 and 4 weeks after transplantation. Histology and immunohistochemistry were used to confirm whether vasculature was present in the cardiac tubes at 4 weeks after transplantation. We found that the cardiac tubes developed spontaneous pulsations from 1 week after transplantation. The average internal pressures of the cardiac tubes at 4 weeks after transplantation were 1.8 ± 1.0 mmHg in the single-step group and 2.5 ± 0.3 mmHg in the double-step group. The cardiac tubes in the double-step group contracted in response to electrical stimulation at 4 weeks after transplantation. Histological and immunohistochemical analyses revealed engraftment of the transplanted cardiac cell sheets and neovascularization of the cardiac tubes in both groups. Our findings demonstrate that it is feasible to generate functional cardiac tubes using the mesentery as a vascular bed. Further development of this technique will include the creation of a thicker tube, transplantation of the tube into major vessels and evaluation of the function of the tube under physiological conditions.