Beyond Immune Rejection: Lymphatic Disruption as a Key Factor in Chronic Organ Failure

For decades, chronic organ rejection following transplantation has been largely attributed to the recipient’s immune system attacking the donor organ. However, groundbreaking research published on February 25, 2026, in Science Translational Medicine suggests a surprising culprit: disruption of the donor organ’s lymphatic vessels. This discovery, led by researchers at Washington University School of Medicine in St. Louis, offers a recent understanding of chronic rejection and potential therapeutic targets.

The Lymphatic System and Organ Rejection

The lymphatic system is a crucial drainage network throughout the body, responsible for removing waste and fluid. Researchers found that damage to these vessels during organ removal and transplantation initiates a cascade of events leading to fibrosis – the slow replacement of healthy tissue with scar tissue – and organ failure. This process can occur even in the presence of ongoing immunosuppression, a long-standing puzzle in the field of transplantation.

How Lymphatic Disruption Leads to Fibrosis

The study revealed that when lymphatic vessels are disrupted, a sugar molecule called hyaluronan accumulates in the transplanted organ. This buildup occurs given that the lymphatic system is unable to effectively drain it. The accumulation of hyaluronan drives the fibrotic process, contributing to chronic organ rejection. This was observed in both analyses of transplanted human organs and in mouse models of lung and heart transplantation.

Potential Therapeutic Strategies

The research team identified three promising strategies to prevent or reverse this process in mouse models:

• Blocking Hyaluronan Production: Inhibiting the protein responsible for manufacturing hyaluronan kept the lymphatic vessels unclogged during healing.
• Stimulating Lymphatic Vessel Growth: Promoting the growth of new lymphatic vessels improved drainage and reduced hyaluronan accumulation.
• Blocking Hyaluronan Production Signal: Targeting the signal that triggers hyaluronan production could also prevent its buildup.

All three interventions successfully halted hyaluronan accumulation and prevented chronic fibrosis in the transplanted lungs of mice. In many cases, the treated organs appeared indistinguishable from healthy ones.

Implications for Treatment and Future Research

Interestingly, the treatment that blocked hyaluronan production, 4-methylumbelliferone (4-MU), is already approved for use in Europe and Asia for treating biliary disorders and has a favorable safety profile. This suggests a potentially rapid path to clinical trials for transplant patients.

Although the study focused on lung and heart transplants, the presence of lymphatic vessels in all organs suggests that lymphatic disruption could contribute to chronic rejection in any transplanted organ. Researchers also suggest exploring these strategies as treatments to administer directly to the organ before or during transplantation, potentially reducing the necessitate for lifelong immunosuppression.

Lung Transplantation: A Unique Challenge

Research from Washington University’s Thoracic Immunobiology Lab highlights that lungs are more immunogenic than other organs, meaning they are more likely to trigger an immune response. Combined heart-lung transplants, in particular, demonstrate a rapid onset of lung rejection [1]. However, this new research suggests that even beyond the immune response, lymphatic disruption plays a critical role.

The Role of Inflammation and Cell Death

Post-transplant inflammation is a significant factor in both acute and chronic rejection. Recent studies indicate that regulated cell death, specifically ferroptosis, contributes to this inflammation and activates both innate and adaptive immune cells [3]. Addressing lymphatic drainage may facilitate mitigate this inflammatory response.

Looking Ahead

This research represents a significant paradigm shift in our understanding of chronic organ rejection. By focusing on the lymphatic system, scientists are opening up new avenues for treatment and potentially improving the long-term outcomes for transplant recipients. Further research is needed to refine these strategies and translate them into effective clinical therapies.