Linking CLAD in Lung Transplant Recipients after 3 Years Follow Up with Transplant Arteriosclerosis in Humanized Mice

Purpose Chronic lung allograft dysfunction (CLAD) is a severe complication of lung transplantation (LTX) limiting long term survival. Here, we studied correlations between CLAD after clinical LTX and leukocyte-mediated development of transplant arteriosclerosis (TA) in a humanized mouse model. Methods The pericardiophrenic artery was procured from surplus tissue of 27 donor lungs transplanted in our clinical program and was implanted into the abdominal aorta of immune deficient mice. The experimental mice were then divided into four groups. Negative control mice received no human leukocyte reconstitution (neg. co). PBMC group mice received 5 × 10 6 allogeneic human peripheral blood mononuclear cells (PBMC) from the respective lung recipients (LR). A further group of animals was reconstituted with the respective PBMC additionally enriched with autologous CD4+CD25high cells (putative regulatory T cells, Treg). Human leukocyte engraftment was monitored by FACS and development of TA was histologically assessed 28 days after PBMC reconstitution. The 27 LR were divided into two groups at least 3 years post transplantation according to their development of chronic rejection. Nine patients (33.3%) developed CLAD 36.2± 4.16 month after LTX. The remaining eighteen patients (66,6%) did not develop CLAD within 35.9± 5.1 month after LTX. Results The neg. co group showed only mild thickening of the intima (6.38±5.70%). In the PBMC CLAD+ group, intimal thickening obliterating the vessel lumen was significantly more severe than in the PBMC CLAD- group (33.19 ± 7.02% vs. 13.37 ± 2.99%, p= 0.011). Then, intimal thickening was significantly inhibited in the PBMC+Treg CLAD+ group as compared to the PBMC CLAD+ group (0.39 ± 3.69% vs 33.19 ± 7.02%, p=0.012). In the experiments using PBMC from lung recipients without CLAD, enriching Treg also further suppressed the development of transplant arteriosclerosis (13.37 ± 2.99% PBMC CLAD- vs. 0.69 ± 5.88% PBMC+Treg CLAD-, p=0.007). Conclusion Lung transplant recipients, who later developed CLAD, had peripheral leukocytes already at the time of transplant that transfered pro-inflammatory properties leading to TA into a humanized mouse model. TA remained sensitive to inhibition by autologous regulatory T cells, suggesting a cell therapy-based approach for the prevention and treatment of CLAD after LTX.