Correlation of CLAD in Lung Transplant Recipients with Transplant Arteriosclerosis in Humanized Mice: A 5-years Follow Up Analysis

Abstract

Chronic lung allograft dysfunction (CLAD) is the leading cause of long-term mortality after LuTX. We studied correlations between CLAD five years after clinical LuTX and leukocyte-mediated development of transplant arteriosclerosis (TA) in a humanized mouse model. The pericardiophrenic artery was procured from surplus tissue of 25 donor lungs transplanted in our clinical program and each was implanted into the abdominal aorta of cohorts of at least four immune deficient mice. The mice from each experiment were then divided into four groups. Negative control mice received no human leukocyte reconstitution (neg. co). PBMC group mice received 5 × 106 allogeneic human peripheral blood mononuclear cells (PBMC) from the respective lung recipients. 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 25 lung recipients were divided into two groups at least 5 years post LTX according to their development of chronic rejection. Sixteen patients (64%) developed CLAD 74.5± 7.01 months after LuTX. The remaining nine patients (36%) did not develop CLAD within 67.81± 2.24 months after LuTX RESULTS: The neg. co group showed only mild thickening of the intima (7.78±4.60%). In the PBMC CLAD+ group, intimal thickening obliterating the vessel lumen was significantly more severe than in the PBMC CLAD- group (41.91 ± 6.12% vs. 15.45 ± 3.22%, p= 0.001). Then, intimal thickening was significantly inhibited in the PBMC+Treg CLAD+ group as compared to the PBMC CLAD+ group (0.29 ± 2.99% vs 41.91 ± 6.12%, p=0.012). In the experiments using PBMC from lung recipients without CLAD, enriching Treg also further suppressed the development of TA (12.77 ± 2.59% PBMC CLAD- vs. 0.39 ± 4.11% PBMC+Treg CLAD-, p=0.012). Lung transplant recipients, who later developed CLAD, had peripheral leukocytes already at the time of LTX that transferred 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 LuTX.