In a groundbreaking advancement from China's research institutions, scientists have developed a system that cryopreserves transplant organs in liquid nitrogen for up to seven days and revives them for successful transplantation. This innovation, detailed in a peer-reviewed study published in the Journal of Medical Devices, promises to revolutionize organ transplantation by dramatically extending preservation times beyond the current few hours. Led by Wei Rao from the State Key Laboratory of Cryogenic Science and Technology at the Technical Institute of Physics and Chemistry (TIPC) under the Chinese Academy of Sciences (CAS), the team includes researchers affiliated with the University of Chinese Academy of Sciences (UCAS), highlighting the pivotal role of China's higher education sector in cutting-edge biomedical engineering.

The Multithermic Machine Perfusion (MTMP) system enables precise control of temperature, pressure, and flow rates across a wide range—from normothermic 37°C to supercooling below 0°C—facilitating stepwise loading of cryoprotectants (CPAs) essential for vitrification. Vitrification transforms biological tissues into a glass-like state, preventing damaging ice crystal formation during freezing. Experiments demonstrated stable perfusion on rat hearts, rabbit kidneys, and pig kidneys, with kidneys preserved at -150°C in liquid nitrogen for seven days before revival and transplantation.

🔬 The Organ Transplant Crisis in China

China faces one of the world's most acute organ shortages, with demand far outstripping supply. In 2025, over 300,000 patients awaited transplants, but only about 20,000 procedures were performed annually, primarily kidneys and livers. Heart transplants are particularly challenging, viable for just six hours under static cold storage, leading to high discard rates during transport. Thousands die yearly on waiting lists, exacerbated by a low voluntary donation rate of around 4 per million population—far below Spain's 48 or the US's 36. Chinese universities and research institutes like UCAS and TIPC-CAS are at the forefront, training the next generation of bioengineers to address this through innovations like cryogenic preservation.

Reforms since 2015 have shifted to voluntary donation, boosting numbers but not enough. High-speed rail enables rapid transport, yet time limits persist. Extended preservation could clear backlogs, reduce waste, and enable scheduled transplants, potentially saving tens of thousands of lives annually.

The Research Institutions Driving Innovation

The State Key Laboratory of Cryogenic Science and Technology at TIPC-CAS, established decades ago, specializes in low-temperature physics and biology. Wei Rao, a full professor, focuses on cryomedicine, tumor cryoablation, and nanomaterial-enhanced preservation. Co-authors Fan Yang and Zixin Li, from UCAS's School of Future Technology, exemplify how graduate programs bridge fundamental science and applied biotech.

UCAS, as CAS's graduate university, plays a crucial role, enrolling thousands in interdisciplinary programs. Its Beijing campus hosts cryo research labs, fostering PhD students in bioheat transfer and organ engineering. This CAS-UCAS synergy underscores China's higher education emphasis on national priorities like health tech, with funding from the National Natural Science Foundation supporting such projects.

How the MTMP System Works: Step-by-Step Breakdown

The MTMP integrates dual-channel temperature control, closed-loop perfusion with pressure feedback, and scalable chambers for organs 1-200 cm³. Here's the process:

• Normothermic Perfusion (37°C): Mimics body conditions to assess viability, flushing out blood and loading initial protectants.
• Hypothermic Shift (4°C): Slows metabolism, reducing energy needs; standard for short-term storage.
• Supercooling (<0°C): Cools to -5°C to -10°C without freezing, minimizing injury.
• CPA Stepwise Loading: Gradually infuses high-concentration cryoprotectants (e.g., dimethyl sulfoxide, ethylene glycol) to replace water, preventing osmotic shock.
• Vitrification and Cryostorage: Rapid immersion in liquid nitrogen (-150°C or lower) forms glass state; stored up to 7 days.
• Rewarming and Revival: Controlled nanowarming reverses process, restoring function.

This automation ensures uniform perfusion, unlike manual methods prone to errors.

Experimental Results and Proof of Viability

Rat hearts preserved up to 24 hours (from 6 hours baseline), showing restored contractility post-rewarming. Rabbit and pig kidneys—closer to human size—endured 7 days at -150°C LN2. Post-transplant, recipients survived without rejection signs, with kidneys filtering waste effectively. Physiological monitoring confirmed stable hemodynamics, no edema or necrosis.

Compared to controls, MTMP organs exhibited 80-90% viability retention, per hemodynamic and histological data. This multiscale success (small to large organs) positions it for human trials.

Photo by Spencer Gu on Unsplash

Overcoming Key Challenges in Cryopreservation

Ice recrystallization, CPA toxicity, and uneven rewarming have stymied organ cryo. MTMP's precise control mitigates these: stepwise CPA gradients reduce toxicity (from 50% cell death to <10%), supercooling avoids initial crystals, and feedback loops ensure homogeneity. Vitrification solutions, optimized at TIPC, achieve glass transition without fracturing.

Wei Rao notes: “Extending heart preservation to 24 hours provides larger time windows, saving more lives.” Global parallels include US nanowarming kidneys (100 days rat-scale), but MTMP's perfusion-vitrification integration is novel.Read the full study here.

Implications for Global and Chinese Transplant Systems

In China, where 1.4 billion people drive massive demand, this could halve discards, easing waits. Hearts, discarded 40-50% due to time, become viable for rail transport nationwide. Globally, if US adopted similar for half-discarded hearts, waiting lists clear in 2-3 years. Enables organ banks, international sharing via air freight.

Challenges: scaling to human organs (e.g., 500g liver vs 200g pig kidney), CPA optimization for humans. Ethical risks include smuggling, as WHO warns shortages fuel trafficking (e.g., SE Asia black market kidneys ~US$40k pair).

Chinese Higher Education's Role in Biotech Leadership

UCAS and CAS labs exemplify China's “Double First-Class” initiative, investing billions in universities for sci-tech self-reliance. Programs in bioengineering produce 10,000+ PhDs yearly, many in cryo. TIPC-UCAS collaborations train interdisciplinary talent; Fan Yang/Zixin Li's involvement shows graduate impact.

Other unis like Tsinghua (cryobiology prof elected society president 2026) advance parallel tech. Government funds via NSFC/863 Program prioritize organ eng, positioning China as cryo leader.

Future Outlook and Clinical Translation

Next: human-scale trials, perhaps porcine hearts/livers. Integration with xenotransplants (pig organs) amplifies impact. UCAS plans AI-optimized CPA delivery. Regulatory path via NMPA fast-tracked for national need.

Experts predict 5-10 year clinical use, transforming transplants into elective procedures. For patients, hope amid shortages; for researchers, new careers in cryo-biotech.

Ethical and Societal Considerations

Extended viability raises equity: access for rural poor? Costs? Past controversies (prisoner organs pre-2015) demand transparency. Universities emphasize ethics training; UCAS curricula include bioethics. Balanced views from stakeholders ensure benefits outweigh risks.

Photo by Eric Prouzet on Unsplash

Career Opportunities in Cryogenic Research

China's push creates demand for PhDs/postdocs in cryo-eng at UCAS, Tsinghua. Roles: perfusion techs, CPA chemists. Salaries ~200k-500k RMB/year, with grants. Global collaborations welcome international talent.