Pig blood can heal and preserve injured human donor lungs for long durations

Pigs and their blood have the power to save humanity, and if not humanity, at least they can save injured human lungs and make lung transplants more accessible.
Rupendra Brahambhatt
Pigs stock image.
Pigs stock image.

Ledernase/iStock 

A report from Stanford Healthcare reveals that the average waiting period for a lung transplant in the US is two years for a patient who needs only one lung and three years if they seek two lungs. There is always a shortage of lungs available for transplants, and even out of the total donated lungs, only 30 percent are finally accepted.

About 70 percent of donated lungs either get damaged or undergo injuries during preservation, turning them unsuitable for use. Unfortunately, this is why many patients listed by the United Network for Organ Sharing (UNOS) for lung transplants die before their number comes. A team of researchers has proposed a unique solution to this serious problem.

In their recently published study, they claim that a donated injured human lung can be turned into a healthy, transplant-worthy lung using blood from a pig host. If successful, this technique could drastically increase the number of lungs that can be accepted for transplants.

How can a pig host save injured human lungs?   

The donated lungs are preserved in clinical facilities using the ex-vivo lung perfusion (EVLP) method. This process involves keeping the donated lung active outside the human body on an ex-vivo organ support system using human blood. However, it is not possible to completely replicate human body-like conditions.   

“These isolated single-organ support systems lack the ability to replicate the complex hematologic, metabolic, endocrine, biochemical, and other homeostatic processes that enable long-term ex vivo organ support,” the researchers note.

Therefore, most clinical facilities are able to preserve the donated lungs for up to six hours, and after that, the health of the lungs starts to deteriorate. Due to the lack of a suitable environment, the organs undergo several injuries and eventually become unusable. 

Pig blood can heal and preserve injured human donor lungs for long durations
Cross blood circulation between a pig host and injured human lungs.

According to the study authors, using blood from a pig host in an EVLP drastically increases the organ preservation time and makes injured lungs usable for transplant. They even tested this method on injured lungs received from four cadavers. 

They set up a cross-blood circulation platform that allowed them to perfuse pig blood in injured but otherwise healthy human lungs. 

The results were surprising —- “We showed that this system not only enabled multiday maintenance and recovery of injured porcine lungs but also supported the viability and functional recovery of human donor lungs that declined for transplantation,” said the researchers.

Is this approach viable?

Since human lungs could’ve discarded pig blood due to immunity issues, the authors monitored immunologic interactions taking place as a result of this exchange to check the feasibility of this method. Interestingly, they noticed that although pig immune cells and immunoglobulin made their way into human lungs, they didn’t affect perfusion and lung recovery.  

The authors explained, “We demonstrate that a porcine xenogeneic XC (cross circulation) system is capable of supporting the viability and physiologic improvement of human donor lungs despite substantial and complex human-swine immunologic interactions.”

However, the effect of foreign blood on human lung functions is still unknown. The authors don’t know whether or not the human lungs which were exposed to pig blood will function the same way as normal lungs. Therefore, further research is required to understand and optimize the long-term outcomes of this method.  

The study is published in the journal Science Advances.

Study Abstract:

Improved approaches to expanding the pool of donor lungs suitable for transplantation are critically needed for the growing population with end-stage lung disease. Cross-circulation (XC) of whole blood between swine and explanted human lungs has previously been reported to enable the extracorporeal recovery of donor lungs that declined for transplantation due to acute, reversible injuries. However, immunologic interactions of this xenogeneic platform have not been characterized, thus limiting potential translational applications. Using flow cytometry and immunohistochemistry, we demonstrate that porcine immune cell and immunoglobulin infiltration occurs in this xenogeneic XC system, in the context of calcineurin-based immunosuppression and complement depletion. Despite this, xenogeneic XC supported the viability, tissue integrity, and physiologic improvement of human donor lungs over 24 hours of xeno-support. These findings provide targets for future immunomodulatory strategies to minimize immunologic interactions on this organ-support biotechnology.

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