CD38 Drives Cellular Senescence and Ischemia-Reperfusion Injury in Donor Lungs
This study identifies CD38 as a critical mediator linking donor aging and ischemic stress to cellular senescence and ischemia-reperfusion injury in donor lungs, demonstrating that its inhibition preserves NAD⁺ levels, attenuates inflammatory damage, and improves graft outcomes.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
Every year, thousands of people with failing lungs wait for a transplant, a life-saving procedure that remains the only option for end-stage disease. Yet, a severe shortage of donor organs means many patients die while waiting. The problem is not just a lack of donors, but a lack of usable lungs. Many potential organs are discarded because they come from older donors or have been exposed to stress during the donation process, making them too fragile to survive the transplant. When a lung is removed from a donor and placed into a recipient, it suffers a specific type of trauma known as ischemia-reperfusion injury. This occurs when blood flow is cut off during the surgery and then suddenly restored, causing a surge of inflammation and oxidative stress that damages the delicate tissue. If this damage is too severe, the new lung fails to function, leading to early death or long-term complications. Scientists have long suspected that the aging process itself makes lungs more vulnerable to this injury, but the exact biological mechanism linking age, stress, and organ failure has remained a mystery.
A team of researchers at The Ohio State University has now identified a key molecule that acts as a bridge between donor aging, cellular stress, and lung injury. They focused on a protein called CD38, which is found on the surface of cells and plays a major role in managing the cell's energy and chemical balance. In healthy cells, CD38 helps regulate calcium and energy molecules, but when cells are under stress—such as during the aging process or the trauma of organ donation—CD38 becomes overactive. The researchers discovered that this overactivity triggers a chain reaction that depletes the cell's essential energy reserves and forces the cells into a state of "senescence." Senescence is a biological condition where cells stop dividing and become damaged, yet they refuse to die. Instead of disappearing, these senescent cells begin to pump out harmful inflammatory signals that damage their neighbors, turning a local injury into a widespread failure of the organ.
To understand how this works in real patients, the team first examined lung tissue from human donors who had passed away. They compared lungs from younger donors with those from older donors, and also looked at lungs from donors who died after their heart stopped beating, a situation that involves longer periods of stress for the organ. They found that CD38 levels rose significantly as the donors got older and as the time without blood flow increased. The highest levels of this protein were found in the lungs of older donors who had experienced the most stress. In these same lungs, the researchers also found high levels of markers for cellular senescence and inflammation, along with a depletion of the energy molecules that cells need to repair themselves. This suggested that CD38 was not just a bystander but a driver of the damage, linking the age of the donor and the stress of the procedure to the failure of the organ.
To prove that CD38 was actually causing the injury, the researchers moved to experiments using mice. They created a model where they temporarily blocked blood flow to a mouse's lung and then restored it, mimicking the injury that happens during a human transplant. In mice that had been genetically engineered to lack the CD38 protein, the lungs suffered far less damage. These mice maintained better lung function, had less fluid buildup, and showed fewer signs of inflammation compared to normal mice with the same injury. The researchers also tested a drug that specifically blocks the activity of CD38. When they gave this drug to normal mice before the injury, it produced the same protective effect as the genetic deletion. The lungs stayed healthier, the energy levels in the cells remained stable, and the harmful inflammatory signals were kept in check. This confirmed that stopping CD38 activity could directly prevent the cascade of damage that leads to organ failure.
The team then explored whether natural compounds found in food could achieve the same result. They tested two plant-based molecules, quercetin and fisetin, which are known to have anti-inflammatory properties. When they treated mice with these compounds before inducing the lung injury, the results were strikingly similar to the genetic and drug-based approaches. The lungs of the treated mice were preserved, showing less structural damage and fewer signs of the cellular aging that usually follows such trauma. To see if this mechanism worked directly on the blood vessels inside the lung, they grew human blood vessel cells in a dish and subjected them to low oxygen followed by a return to normal oxygen. When they blocked CD38 in these cells, either with genetic tools or the natural compounds, the cells survived the stress much better and did not enter the harmful senescent state. This provided strong evidence that CD38 acts directly on the cells lining the blood vessels to determine whether they survive the transplant or succumb to injury.
The findings suggest that CD38 is a central switch that turns donor aging and surgical stress into cellular damage. By consuming the cell's energy reserves and triggering a toxic inflammatory response, this protein makes older or stressed lungs much more likely to fail after transplantation. The study indicates that targeting CD38 could be a powerful new strategy to protect donor lungs. If doctors could temporarily block this protein during the time an organ is being prepared or preserved, they might be able to keep the lungs healthier and more resilient. This approach could potentially allow surgeons to use lungs from older donors or those from donors who died after their heart stopped, organs that are currently often discarded. By preserving the quality of these extended-criteria lungs, the pool of available organs could expand significantly, saving more lives and offering hope to the many patients currently waiting on the list. The research points to a future where managing the molecular stress of an organ before it is transplanted could become a standard part of the process, turning previously unusable lungs into life-saving gifts.
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