Transcriptional Analysis of Liver Tissue Identifies Distinct Phenotypes of Indeterminate Pediatric Acute Liver Failure

Many patients with indeterminate pediatric acute liver failure (PALF) have evidence of T‐cell driven immune injury; however, the precise inflammatory pathways are not well defined. We have characterized the hepatic cytokine and transcriptional signatures of patients with PALF. A retrospective review was performed on 22 children presenting with indeterminate (IND‐PALF; n = 17) or other known diagnoses (DX‐PALF; n = 6) with available archived liver tissue. Specimens were stained for clusters of differentiation 8 (CD8) T cells and scored as dense, moderate, or minimal. Measurement of immune analytes and RNA sequencing (RNA‐seq) was performed on whole‐liver tissue. Immune analyte data were analyzed by principal component analysis, and RNA‐seq was analyzed by unsupervised hierarchical clustering, differential gene expression, and gene‐set enrichment analysis. Most patients with IND‐PALF (94%) had dense/moderate CD8 staining and were characterized by Th1 immune analytes including tumor necrosis factor α, interferon γ (IFN‐γ), interleukin (IL) 1β, IL‐12, C‐X‐C motif chemokine ligand (CXCL) 9, and CXCL12. Transcriptional analyses identified two transcriptional PALF phenotypes. Most patients in group 1 (91%) had IND‐PALF and dense/moderate CD8 staining. This group was characterized by increased expression of genes and cell subset–specific signatures related to innate inflammation, T‐cell activation, and antigen stimulation. Group 1 expressed significantly higher levels of gene signatures for regulatory T cells, macrophages, Th1 cells, T effector memory cells, cytotoxic T cells, and activated dendritic cells (adjusted P < 0.05). In contrast, patients in group 2 exhibited increased expression for genes involved in metabolic processes. Conclusion: Patients with IND‐PALF have evidence of a Th1‐mediated inflammatory response driven by IFN‐γ. Transcriptional analyses suggest that a complex immune network may regulate an immune‐driven PALF phenotype with less evidence of metabolic processes. These findings provide insight into mechanisms of hepatic injury in PALF, areas for future research, and potential therapeutic targets.