Serum amyloid P (PTX2) attenuates hepatic fibrosis in mice by inhibiting the activation of fibrocytes and HSCs

Background: Liver fibrosis is caused by chronic toxic or cholestatic liver injury. Fibrosis results from the recruitment of myeloid cells into the injured liver, the release of inflammatory and fibrogenic cytokines, and the activation of myofibroblasts, which secrete extracellular matrix, mostly collagen type I. Hepatic myofibroblasts originate from liver-resident mesenchymal cells, including HSCs and bone marrow-derived CD45⁺ collagen type I⁺ expressing fibrocytes. Recombinant human serum amyloid P (hSAP), a natural inhibitor of fibrocyte activation into myofibroblasts, was shown to ameliorate experimental renal, lung, skin, and cardiac fibrosis. We investigated if hSAP can ameliorate the development of liver fibrosis of different etiologies. Methods: Reporter Collagen-α(1)I-GFP mice were subjected to cholestatic liver injury (by ligation of the common bile duct) or toxic liver injury (by carbon tetrachloride administration) and treated prophylactically or therapeutically with hSAP (12.5 μg/g). Primary cultures of mouse fibrocytes and HSCs were stimulated to activate with or without incubation with hSAP. Results: We demonstrate that treatment with hSAP suppressed hepatic fibrosis by ≈50% through dual mechanisms. hSAP prevented the recruitment of fibrocytes into the injured liver and their differentiation into myofibroblasts. Remarkably, hSAP also inhibited the activation of HSCs into myofibroblasts. Conclusions: Since HSCs serve as a major source of collagen type I-producing myofibroblasts and fibrocytes stimulate fibrosis, hSAP may become part of the therapy of liver fibrosis of different etiologies.