Background: Graft function post liver transplantation (LT) depends on donor quality and the degree of hepatocyte post-ischemia reperfusion injury (IRI). Hereby, we evaluated early-deregulated molecular processes immediately after LT by integrating gene expression (GE) and microRNA (miRNA) profiles.

Patients and Methods: LT patients were studied (n=41). Paired biopsies (n=82) were collected at pre-implantation (Pre-I) and 90 min post-reperfusion (Post-R), and grouped as Training (n=48) and Validation (n=34) sets. Total RNA was isolated. RNA samples from training set were used for miRNA and GE microarrays hybridization. Human miRNA and GE expression summaries were obtained using RMA algorithm. Post-R vs. Pre-I comparisons were fit using two-sample t-test. A p-values ≤ 0.01 were considered significant. FDRs ≤ 10% and ≤ 1% were controlled for miRNA and GE, respectively. MiRNA target genes identification and pathway analysis were performed using IPA tool. Top significant molecules were assessed by qPCR in the validation set.

Results: Donor data included: mean age 47 yo, caucasian 79%, and 47% male, mean CIT 6.8 hrs and mean WIT 33 min. No significant differences were observed between study sets. Overall, 32 miRNAs were significantly differentially expressed Post-R (15 upregulated and 17 downregulated). Inflammatory response and apoptosis represented top network functions. Seven miRNAs were associated with hepatic parenchymal disorders: malignancies (miR-139), steatosis (miR-451, miR-331), and fibrosis (miR-27a, miR-27b, miR-29b, miR-192). Eight miRNAs were found to respond to amino acids and hypoxia as post reperfusion stimuli. GE analysis revealed 3168 genes significantly differentially at Post-R time. After validated target analysis, 1999 genes predicted to be regulated by the here identified set of miRNAs. Molecular pathway analyses identified anti-apoptotic hepatocytes profiles, cell cycle arrest, and cell survival. Increased expression of leukocyte adhesion molecules (ICAM-1), prostaglandin synthases (Cox-2), and inflammatory cytokines (CXCL3, TNFAIP3, SERPINE1) indicated initial inflammation steps. Top five differentially expressed miRNAs and genes were independently validated.

Conclusions: Molecular pathways at early IRI post LT denotes hepatocyte salvage profiles, connoted by cell proliferation arrest and apoptosis inhibition as hallmark. Moreover, activation of inflammatory processes occurs as an early event after IRI.

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