Molecular signatures of chronic antibody-mediated rejection in human liver transplants
Authors: Engel Bastian , Alaswad Ahmed , Campos-Murguia Alejandro , Zoodsma Martijn , Klingbeil Anne , Chihab Kinan , Bosselmann Emily A. , Heinrich Sophia , Hartleben Björn , Jonigk Danny D. , Verboom Murielle , Hallensleben Michael , Geffers Robert , Falk Christine S , Ruff Sergej , Lauber Chris , Skovgaard Emilie Toft , Karsdal Morten , Leeming Diana Julie , Wedemeyer Heiner , Xu Cheng-Jian , Jaeckel Elmar , Li Yang , Taubert Richard 
Published: February 2024

Background&Aims

The role of antibody-mediated rejection (ABMR) after liver transplantation (LT) remains controversial. Chronic ABMR (cABMR) is often subclinical and potentially missed without surveillance biopsies (svLbx). Transcriptome analysis previously characterized molecular changes in T cell-mediated rejection (TCMR) after solid organ transplantation. We aimed to identify molecular cABMR signatures after LT.

Methods

We retrospectively identified indication and svLbx from our prospective institutional biorepository (n=1207 over 12 years). We performed RNA-sequencing on liver biopsies (discovery cohort: n=71; validation cohort: n=58). Downstream analyses explored the molecular features of cABMR, clinical (clinTCMR),subclinical TCMR (subTCMR) and chronic ductopenic rejection compared to no histological rejection (NHR).

Results

Nineteen percent of LT recipients with donor-specific antibodies had cABMR. Eighty-one percent of cABMR patients had ALT and AST ≤2x the upper limit of normal, recognized only by svLbx. CABMR was associated with subsequent cirrhosis development in 40%. The cABMR group displayed differentially expressed genes (DEGs) uniquely enriched in fibrogenesis-, complement activation- and TNFα-signaling-related pathways. ClinTCMR showed DEGs uniquely enriched in antigen presentation-, interferon-signaling-, and T cell receptor-signaling-related pathways. Common cABMR and clinTCMR DEGs were enriched in chemokine-signaling- and cytokine response-related pathways. Gene set enrichment scores of interferon-signaling and extracellular matrix remodeling pathways discriminated cABMR and clinTCMR. Molecular signatures of clinTCMR correlated with histological TCMR-patterns. Molecular cABMR-signatures correlated with lobular graft injury and liver fibrosis scores. SubTCMR was molecularly almost indistinguishable from NHR. There was a high degree of correlation in the DEGs for both the training and validation cohorts.

Conclusions

We report transcriptome-unique features of cABMR that is a unique molecular identity associated with inflammation and fibrogenesis.

Lay summary

Antibody mediated rejection (ABMR) is a rare rejection type after liver transplantation and its chronic form often presents subclinical, i.e. without abnormal liver function test, which may be missed without histological surveillance of the grafts. Nonetheless it is associated with the development of liver cirrhosis in 40% of patients. We performed RNA-sequencing from liver graft biopsies of chronic ABMR, clinical T cell mediated rejection (TCMR), chronic ductopenic rejection and subclinical TCMR and compared these to healthy grafts without signs of graft injury. These analyses revealed cABMR to be associated with TNF-signaling, fibrogenesis and complement activation and cTCMR with interferon-signaling, antigen presentation and T cell receptor-signaling related pathways. These patterns were consistently found in an independent validation cohort. Hence, we firstly report unique transcriptome-features of cABMR discriminating it from all other types of rejection.

Impact and Implications

- Chronic antibody-mediated rejection (ABMR) is a recognized relevant cause of graft injury and unfavorable patient outcomes after kidney, heart and lung transplantation but the role of chronic ABMR after liver transplantation (LT) remains controversial, despite a recirrhosis rate of 40% in the present study

- We aimed to characterize chronic ABMR after LT on a molecular basis to identify unique features compared to three other rejection entities.

- Our findings highlight chronic ABMR to be a distinct clinical phenotype of rejection after LT. Furthermore, we demonstrate chronic ABMR to present mostly with normal liver enzymes, therefore only being detected if surveillance biopsies are performed for graft monitoring.

- Therefore, our work emphasizes the usage of surveillance graft biopsies for the detection of a fibrosis associated phenotype of chronic ABMR. Pending external validation, the molecular signature may be used in the future to discriminate chronic ABMR from graft injury of other causes.