Unbiased Spatial Proteomics Uncovers Hepatic in Situ Regulation in Alcohol-Associated Hepatitis.

Alcohol-associated hepatitis (AH) is an acute inflammatory form of alcohol-associated liver disease. Previous studies have explored molecular mechanisms associated with AH pathogenesis through bulk liver tissue analysis; however, the heterogeneity of liver tissue and hence the spatial regulation within the AH liver microenvironment remained unaddressed. Here, an unbiased spatial proteomics analysis on the pathologic regions (PRs) of AH liver tissue is presented, including immune cell infiltration foci, lipid droplets, chicken-wire fibrosis, and fibrotic bands. Through combining a highly efficient nanodroplet processing in one pot for trace samples platform with ultrasensitive liquid chromatography-mass spectrometry, this study identified and quantified a total of 5186 unique proteins from PRs isolated in 200-μm-long × 200-μm-wide × 10-μm-thick areas. This in-depth spatial proteome coverage allowed us to discover mechanistic regulations within individual PRs, including compromised resolution of inflammation with infiltrated neutrophils at infiltration foci, increase of mitochondrial and peroxisomal fatty acid β-oxidation at lipid droplets, and differential cellular and extracellular regulations between chicken-wire fibrosis and fibrotic bands. Overall, this study demonstrated a new capability for AH research, revealed the significance of understanding spatial regulation within AH liver tissue, and further facilitated the development of therapeutic strategies at high resolution.