A review article published in Engineering delves into the crucial field of organ preservation, exploring its history, current techniques, and future prospects. The shortage of donor organs remains a significant global challenge, with only about 10% of the global demand for organ transplantation being met, as stated by the World Health Organization. This shortage is further exacerbated by the limitations of current organ preservation methods.
Currently, the main clinical methods for organ preservation are static cold storage (SCS) and machine perfusion (MP). SCS, which involves storing organs in a preservation solution at low temperatures (usually 4 °C), is simple and cost-effective. It has been widely used, for example, in Japan for kidney preservation. However, it can only maintain the function of organs for a limited time. For kidneys, the preservation time is 12–24 hours; for lungs, 6–8 hours; and for hearts, 4–6 hours. Prolonged SCS can lead to issues such as adenosine triphosphate (ATP) depletion, metabolite accumulation, and subsequent ischemia-reperfusion injury (IRI), which can cause organ damage and transplant failure.
MP, on the other hand, can extend the preservation time. Hypothermic machine perfusion (HMP) can maintain organ function for several days by providing a continuous supply of oxygen and nutrients. Normothermic machine perfusion (NMP), which simulates normal body temperature, has shown superior transplant survival rates in some cases, like in liver transplantation. But it also has its own problems, such as non-anastomotic biliary strictures in liver transplants.
In recent years, cryopreservation techniques have emerged as promising alternatives. Vitrification, in particular, is regarded as a potentially effective long-term organ preservation method. It involves replacing a portion of the water in organs with solutes to form a glass-like state, avoiding ice crystal formation. However, high concentrations of cryoprotective agents (CPAs) are required for vitrification, which can cause toxicity issues in cells. To address this, researchers are exploring various strategies, such as using isochoric preservation to reduce the required concentration of CPAs and developing new rewarming techniques.
The paper also discusses the preservation of different major organs. For kidneys, in addition to SCS and MP, vitrification cryopreservation has shown potential, with successful transplantation of cryopreserved rat kidneys after 100 days. For livers, MP techniques are being developed to address the high discard rate due to IRI. Hearts face challenges in preservation due to high ATP consumption, but MP and vitrification-based methods are being explored. Lungs, currently preserved mainly by SCS for a short time, may benefit from ex vivo lung perfusion (EVLP) and cryopreservation in the future. Intestine preservation is crucial but challenging due to its large bacterial reservoir, and MP techniques are being investigated to improve outcomes.
Significant progress has been made in organ preservation, yet there remains a long journey ahead. Going forward, future research ought to center on devising more efficient preservation strategies, minimizing the toxicity of CPAs, and enhancing rewarming techniques. By doing so, it will be possible to achieve long-term, high-quality organ preservation, thus ultimately resolving the organ shortage issue.
The paper "Organ Preservation: History, Advancements, and Perspectives," authored by Xinmeng Liu, Zhiquan Shu, Liming Zhang, Haoyue Li, Jing Yang, Lei Zhang. Full text of the open access paper: https://doi.org/10.1016/j.eng.2024.12.020
