Extended Cold Ischemia and Indirect Alloimmunity Are Fundamental for the Development of Chronic Lung Allograft Dysfunction

Background: Lung transplantation has the worst long-term survival in solid-organ transplantation due to the chronic lung allograft dysfunction (CLAD). Lymphatic vessels play crucial role in alloimmunity by bridging innate and adaptive immune response. However, their functions in CLAD development are unknown.

Method: Single mismatch orthotopic left lung transplantation (left lungs from HLA-A2 knock-in mice on a C57BL/6J background or C57BL/6J as donor mice were orthotopically transplanted to C57BL/6J recipient mice) was used as a CLAD model. Donor lungs were induced to 6 hours of cold ischemia at 4°C. CLAD development was analyzed by Masson's trichrome staining. Lymphatic vessels were stained by anti-podoplanin and anti-LYVE-1 antibodies. Proinflammatory macrophages were stained by anti-iNOS antibody, and anti-inflammatory macrophages were stained by anti-CD206 antibody. VEGFC source in macrophages were identified by dual immunofluorescence.

Results: Short cold allograft ischemia (1 h, +4°C) resulted in the development of lymphocytic bronchiolitis (LB) 8 weeks after the surgery. Prolonged cold allograft ischemia resulted in the development of lymphocytic bronchiolitis (LB) already one week after the surgery and led to the late stage CLAD 8 weeks after reperfusion. All histological features of bronchiolitis obliterate syndrome and restrictive allograft syndrome (RAS) were observed in 8-week allogeneic lungs and were similar to human findings. The lungs from syngeneic recipients showed no pathological changes. In the allogeneic recipients, the lymphatic density increased during the CLAD development. VEGFC expression was observed in iNOS and CD206 positive macrophages.

Conclusion: Prolonged cold lung ischemia seems to facilitate the development of experimental late stage CLAD. Indirect alloimmunity and deteriorated ischemia-reperfusion injury are fundamental for the late stage CLAD development. Experimental allogeneic lung transplantation with prolonged cold ischemia leads to a lymphatic phenotype similar to human RAS. Proinflammatory and anti-inflammatory macrophages are likely to drive lymphangiogenesis by increased VEGFC expression.

Publication History

Article published online:
03 February 2022