Prolonged Warm Ischemia Drives Graft Injury in cDCD Lung Transplantation
Controlled donation after circulatory death has become an important route to expand the donor pool in lung transplantation, but the interval between circulatory arrest and organ preservation remains a major source of injury. In this preclinical study, investigators built a rat model to reproduce the agonal phase seen in controlled donation after circulatory death and then used it to test whether necroptosis could be therapeutically targeted during the ischemic window.
The biology is unforgiving. Warm ischemia deprives the graft of oxygen and perfusion at the same time that inflammatory signaling begins to intensify, setting the stage for ischemia-reperfusion injury once circulation is restored. In this model, longer warm ischemic time progressively worsened graft function, with lower oxygenation, more pulmonary edema, and stronger necroptosis-related signals in pretransplant samples. Those changes fit the expected trajectory of a graft that is already injured before it ever reaches the recipient.
The study design was deliberately sequential. First, the team established a donor phase that mirrored the agonal period. Next, they extended warm ischemia to determine how graft quality deteriorated over time. Finally, they tested whether blocking receptor-interacting protein kinase 1 with necrostatin-1 could blunt the injury cascade before and around transplant.
RIPK1 Inhibition Reduced Necroptosis-Related Signaling Before Transplant
Necroptosis is a regulated form of cell death that sits between apoptosis and uncontrolled necrosis. In transplantation, that distinction matters because necroptotic signaling can amplify tissue damage, recruit inflammatory cells, and intensify reperfusion injury in a graft that has already suffered ischemic stress. The investigators focused on RIPK1, a key upstream driver of this pathway, and used necrostatin-1 across the pre-mortem, graft-flushing, and peri-transplant periods.
The intervention improved graft quality. It also reduced neutrophil infiltration after reperfusion, a biologically coherent finding because neutrophils are among the earliest effector cells to arrive in injured pulmonary tissue and can worsen endothelial and alveolar damage. In pretransplant samples, the ratio of phosphorylated mixed lineage kinase domain-like protein to total MLKL, or pMLKL/MLKL, fell with necrostatin-1 treatment, consistent with attenuation of necroptosis-related signaling.
One sentence captures the central signal from the entire experiment: longer ischemic exposure worsened the graft, and RIPK1 blockade partially reversed that trajectory.
A Preclinical Framework for Primary Graft Dysfunction Risk
The implications extend beyond rodent physiology. In human transplantation, primary graft dysfunction remains one of the most feared early complications after lung transplant, and the ischemic interval before implantation is a major contributor to that risk. A model that reproduces the agonal phase of controlled donation after circulatory death offers a more realistic platform than generic ischemia-reperfusion systems for testing injury biology in the lung.
This is especially relevant because cDCD lungs face a unique sequence of insults. The organ is exposed to warm ischemia before procurement, then cold preservation, then reperfusion after implantation. Each phase can compound injury, but the pre-mortem and immediate procurement window may be the most modifiable. By placing necrostatin-1 in the donor, flushing, and peri-transplant periods, the study addresses that narrow biologic window directly.
The pattern observed here suggests that necroptosis is not just a downstream marker of damage; it may be part of the machinery that converts warm ischemia into structural graft injury. Reduced oxygenation and pulmonary edema are the bedside-facing expression of that process. At the tissue level, worsening injury signals the failure of the alveolar-capillary barrier, while the drop in pMLKL/MLKL points to fewer activated necroptotic pathways in the treated grafts.
Why Necroptosis Matters in the Ischemic Lung
The appeal of targeting necroptosis lies in its position within the injury cascade. Unlike broad immunosuppression, a RIPK1 inhibitor aims at a more specific cell-death pathway that may be active before the recipient even receives the organ. If a graft enters reperfusion with less intracellular injury and less inflammatory priming, the downstream inflammatory burst may be smaller.
That logic aligns with the observed reduction in neutrophil infiltration after reperfusion. Neutrophils do not arrive in a vacuum; they are drawn into tissue shaped by danger signals, endothelial activation, and cellular debris. A graft with less necroptotic signaling may therefore present a less hostile microenvironment at the moment blood flow returns.
The study does not claim clinical proof, and it does not need to. Its value lies in establishing a controlled model that connects prolonged warm ischemia to measurable necroptosis-related injury and shows that RIPK1 inhibition can modify that biology in a living transplant system.
What This Rat Model Can and Cannot Answer
Several details make the model useful. It reproduces the agonal phase of controlled donation after circulatory death, it tracks injury across ischemic time, and it measures both functional and molecular endpoints. The combination of oxygenation, pulmonary edema, neutrophil infiltration, and pMLKL/MLKL creates a coherent preclinical picture rather than a single isolated biomarker.
At the same time, the model remains preclinical. Rodent physiology does not fully recapitulate human donor management, recipient comorbidity, or the procedural complexity of clinical lung transplantation. The study also does not establish whether necrostatin-1 would be safe, durable, or effective in people, nor does it define an optimal dosing strategy for clinical use.
Even so, the translational signal is clear enough to matter for future work. Prolonged warm ischemia was associated with worse graft quality, and inhibition of RIPK1 dampened the necroptosis-related signature in the injured lung. For transplant researchers trying to preserve marginal cDCD organs, that combination points to a plausible therapeutic target, but the next step has to move from a rat graft to a validated clinical strategy with human safety data.