Although the extracellular matrix (ECM) plays essential roles in heart tissue engineering, the optimal ECM components for heart tissue organization have not previously been elucidated, and most of the commercially available collagen is skin-derived and type I collagen. Here, we focused on the main ECM component, fibrillar collagen, and analyzed the effects of collagens on heart tissue engineering, by comparing the use of porcine heart-derived collagen and other organ organs (kidney, liver, lung, skin, and spleen) derived collagens in generating engineered heart tissue (EHT). We demonstrate that heart-derived collagen induces better contraction and relaxation of human-induced pluripotent stem cell-derived EHT (hiPSC-EHT) and that hiPSC-EHT with heart-derived collagen exhibit more mature profiles than those with collagens from other organs. Further, we found that collagen fibril formation and gel stiffness influence the contraction, relaxation, and maturation of hiPSC-EHT, suggesting the importance of collagen types III and type V, which are relatively abundant in the heart. Furthermore, mRNA expression related to maturation was highest in EHTs with crude collagen compared with EHTs with purified type collagen, indicating that the component of each type of collagen in the appropriate distribution has significant effects on tissue maturation. Thus, we demonstrated the potency of heart-derived collagen in heart tissue engineering and drug discovery.

The long-term maintenance of graft function following organ transplantation is a crucial issue for future consideration. Recently, donor-derived cell-free DNA has emerged as a non-invasive and sensitive serum biomarker for monitoring graft failure. Its effectiveness in early diagnosis of acute rejection, evaluating therapeutic efficacy, reducing invasive diagnostic procedures, and facilitating safe outpatient monitoring has been well-established. Moreover, it is expected to enhance long-term graft survival when used in conjunction with conventional biomarkers.

In donating from deceased donors, proper temperature control of procured organs is important. It should be noted that not only temperature rise but also ice-up may damage the organs. In July 2021, the Japanese Society for Transplantation published a standard packing protocol for organ transport using a dual-liquid phase to prevent organ freeze damage. We tested the scientific validity of this protocol using bovine livers. The surface temperature and pathology of bovine livers were examined after 6 hours of storage in a cooler box with ice of which the temperature was -20°C or -80°C. In the -80°C-ice group, the organ surface temperature decreased below -0.7°C, the freezing point of the organ preservation fluid, University of Wisconsin solution (UW solution) regardless of the use of the standard packaging protocol. Eventually, the solution and the organ were frozen. On the other hand, according to the standard packing protocol with -20°C-ice, the temperature of the UW solution did not fall below -0.7°C and no icing was observed either in the solution or the organ. Histologically, the normal structure was maintained. The standard packing protocol of the Japan Transplantation Society prevents the icing of the transplanted organs. In this review, we discuss the importance of organ packaging to prevent freeze damage during transportation.

Collaboration between medicine and engineering is indispensable for the advancement of healthcare. However, there are many challenges associated with this interdisciplinary partnership. One of the important issues is the lack of sufficient opportunities for medical professionals and engineers to collaborate on developing medical devices. In particular, innovation in medical technology related to transplantation requires a new system for development. This should involve not only medical professionals, engineers, and pharmacologists but also citizens, patients, and other societal members. In this report, the current state of medical-engineering collaboration in the machine perfusion is explained and the potential for future developments of medical devices is discussed.