AbstractBackground & Aims Metabolic dysfunction-associated steatotic liver disease (MASLD) is characterized by profound remodeling of hepatic macrophages, including the emergence of lipid-associated macrophages (LAMs). However, the mechanisms through which LAMs promote fibrosis and their key molecular drivers remain elusive. Methods Macrophage-specific CD36 knockdown was achieved using AAV8-delivered shRNA. A suite of experimental systems—including co-culture models, lipid trafficking assays, ChIP-qPCR, and lipidomics—was employed to dissect the CD36-PPARγ-SPP1 axis. Genetic and pharmacological tools were used for mechanistic and therapeutic studies. Clinical relevance was assessed in well-characterized patient cohorts. Results We identified a unique CD36+ macrophage subpopulation that aligns with LAMs and expands markedly in human and murine MASLD livers, strongly correlating with fibrosis severity. Macrophage-specific CD36 deletion attenuated steatosis, transaminases (ALT and AST reduced by > 30%, p p SPP1 promoter, stimulating SPP1 secretion. SPP1 in turn activates hepatic stellate cells. Clinically, the CD36-PPARγ-SPP1 gene signature was independently associated with both fibrosis stage (p = 0.009) and steatosis grade (p = 0.03) in patients (n = 48). Importantly, pharmacological inhibition of CD36 suppressed lipid uptake and SPP1 release, attenuating fibrogenesis, while combination therapy with a PPARγ agonist yielded synergistic anti-steatotic and anti-fibrotic effects. Conclusion Our study identifies the CD36-PPARγ-SPP1 axis as a core mechanism whereby lipid-loaded macrophages drive liver fibrosis in MASLD. Therapeutic co-targeting of CD36 and PPARγ presents a novel and promising strategy to counteract fibrosis progression in advanced disease. Impact and implications Our study provides an investigation of the features and signals of lipid-associated macrophages (LAMs) that are present in MASLD liver and express a specific protein called CD36. We find that these cells internalize hepatocyte-derived lipids via CD36 and activate PPARγ-SPP1 axis, contributing to exacerbating liver fibrosis. More importantly, targeting CD36 effectively improves serum aminotransferases, liver steatosis and liver fibrosis. Understanding the novel signal in LAMs and discovering the diverse roles of PPARγ in different cell populations that may be therapeutically targeted to treat MASLD-related liver fibrosis.
Dai et al. (Thu,) studied this question.