SINGLE-CELL ANALYSIS OF PATIENT LIVER TISSUE CHARACTERIZES AN ALTERED CELLULAR LANDSCAPE IN PRIMARY SCLEROSING CHOLANGITIS (PSC) AND IDENTIFIES INTERCELLULAR COMMUNICATION NETWORKS ACTIVE IN THE PSC LIVER.

Background: PSC is a chronic inflammatory condition of the biliary epithelium characterized by concentric periductal fibrosis. As opposed to inflammatory bowel disease (IBD), a frequently overlapping trait, there are currently no drugs that definitively slow disease progression. This study aims to define cellular abundances and pathogenic cross-talk driving periductal fibrosis in PSC using single-cell analysis.

Methods: scRNA-seq was performed on tissue sections from 4 FFPE blocks that included tissue from 2 PSC patients undergoing liver transplant and 2 patients with secondary liver cancer undergoing resection (controls, tumor-free margin). scRNA-seq was performed using the 10X Genomics Next GEM platform. Cells were projected onto reference datasets within CellTypist. Ligand-receptor interactions were assessed with CellChat.

Results: We recovered 34,183 cells from the 4 samples. PSC samples were enriched for T cells, mast cells, and monocyte-derived macrophages and depleted for zone 1 and zone 2 hepatocytes compared to controls as determined by a two-sample proportion test. PSC samples were enriched for an “intestinal macrophage”-like subset defined by expression of CD209, IGF1, and TNFSF13, predicted to interact with memory B cells and plasma cells via TNFSF13B & TNFSF17 (p=2.3x10^-7). 64% of collagen-producing fibroblasts (CPFs) and 30% of ACTA2-expressing myofibroblasts (MFs) in PSC samples expressed the portal fibroblast (PF) marker elastin (ELN). PDGF-PDGFR signaling between portal endothelial cells and CPFs was determined to be active in PSC samples but not in controls (p=5.7x10^-7).

Conclusion: ELN expression in CFPs and MFs in PSC samples implicate PFs as key effectors of periductal fibrosis in PSC. Predicted cell-cell interactions will be validated in intact tissues of selected protein analytes, focusing on periportal regions. The increased abundance of intestinal-like macrophages implicates a shared pathophysiology with IBD, possibly involving aberrant myeloid-stromal cell differentiation and cross-talk.