Targeting Hepatic Stellate Cell PD-L1 Alters Liver Inflammation and Fibrosis in CCl4 Liver Injury Mouse Model
Bing Bai, Wenming Bao, Yuanguo Wang, Aurpita Shaha, Tatiana Kisseleva, Lianping He, Liankang Sun, Sofía Jerez, Vijay H. Shah, Xianghu Wang, Ningling Kang
Abstract
Background & Aims Programmed death-ligand 1 (PD-L1) on hepatic stellate cells (HSCs) is required for HSC activation and suppressing T and B lymphocytes. We tested whether targeting HSC PD-L1 influenced liver inflammation and fibrosis in a carbon tetrachloride (CCl 4 ) injury mouse model. Methods HSC-specific PD-L1 knockout (PD-L1 HSCKO ) mice were created by crossing Cd274 floxed mice to Collagen1A1- Cre mice. CCl 4 was injected into PD-L1 HSCKO and PD-L1 HSCWT mice twice weekly for 6 weeks. Liver fibrosis was assessed by Trichrome and Picrosirius Red staining; HSC activation was determined by immunofluorescence and Western blot for HSC activation markers; liver inflammation was studied by multiplex immunofluorescence and cytokine profiling. Multiomics was leveraged to determine how targeting PD-L1 altered HSC producing collagens and cytokines/chemokines. Results Collagen deposition was reduced in CCl 4 -injured PD-L1 HSCKO livers compared with CCl 4 -injured PD-L1 HSCWT livers; myofibroblast density was lower in CCl 4 -injured PD-L1 HSCKO livers compared with CCl 4 -injured PD-L1 HSCWT livers. CCl 4 -injured PD-L1 HSCKO livers had higher lymphocyte densities (GranzymeB+, CD8a+, CD20+) but lower Kupffer and myeloid cell densities (F4/80+ and CD11b+) compared with CCl 4 -injured PD-L1 HSCWT livers. Serum aspartate aminotransferase and alanine aminotransferase, however, were similarly elevated by CCl 4 in both groups. Spatial and bulk-cell transcriptomics revealed a global transcriptomic change of HSCs induced by PD-L1 targeting. A targeted proteomics identified that HSC secretion of a group of cytokines/chemokines, including growth/differentiation factor 15, granulocyte-macrophage colony-stimulating factor, C-X-C motif and C-C motif chemokines, was altered upon PD-L1 targeting, highlighting the role of HSC PD-L1 in HSC/Kupffer and HSC/myeloid cell interactions during HSC activation and fibrosis development. Conclusions Targeting HSC PD-L1 altered HSC transcriptome and liver inflammation, and suppressed liver fibrosis, representing a potential therapeutic strategy for liver fibrosis.