Reprogramming macrophages to treat liver diseases

Cutting-edge research has expanded our understanding of the macrophage activation programs in liver diseases making this immune cell type a therapeutic target. Clinical data on macrophage infiltration and polarization states have been used to help predict mortality or poor prognosis in patients with liver cirrhosis and/or HCC. The latest single-cell and spatial transcriptomics studies have dissected unforeseen aspects depicting the immense heterogeneity of macrophages and their multifaceted role in both promoting and resolving hepatic inflammation, injury, and fibrosis. Hepatic macrophages (resident tissue KCs and monocyte-derived macrophages) display such plasticity and phenotypic diversity that macrophages with antagonistic functions may coexist in adjacent regions of the liver. In this scenario, the analysis of macrophage-derived inflammatory and anti-inflammatory circulating soluble markers in patients with liver disease only offers a partial picture of the full complexity of the hepatic macrophage subsets. The reprogramming of macrophages involves understanding the multiple regulatory mechanisms and diverse populations of hepatic macrophages and the design of macrophage-targeted therapeutic interventions to restore hepatic homeostasis. Here we review the potential targets to modulate macrophage behavior in liver diseases and nanoscale therapeutics that aim to target and treat macrophages. We will summarize current knowledge on the diverse macrophage programs activated in chronic liver inflammation, cirrhosis, and HCC that may be of therapeutic interest for precision medicine.