Placental growth factor silencing ameliorates liver fibrosis and angiogenesis and inhibits activation of hepatic stellate cells in a murine model of chronic liver disease

Abstract

Placental growth factor (PlGF) is a member of the vascular endothelial growth factor (VEGF) family and is involved in pathological angiogenesis associated with chronic liver diseases. However, the precise mechanisms underlying PlGF signalling contributing to liver fibrosis and angiogenesis remain largely unexplored. This study aimed to assess the effect of reducing PlGF expression using small interfering RNA (siRNA) on experimental liver fibrosis and angiogenesis, and to elucidate the underlying molecular mechanisms. Fibrosis was induced in mice by carbon tetrachloride (CCl 4 ) for 8 weeks, and mice were treated with PlGF siRNA or non-targeting control siRNA starting two weeks after initiating CCl 4 injections. The results showed that PlGF was highly expressed in cirrhotic human and mice livers; which mainly distributed in activated hepatic stellate cells (HSCs). PlGF silencing robustly reduced liver inflammation, fibrosis, intrahepatic macrophage recruitment, and inhibited the activation of HSCs in vivo. Moreover, PlGF siRNA-treated fibrotic mice showed diminished hepatic microvessel density and angiogenic factors, such as hypoxia-inducible factor-1a (HIF-1a), VEGF and VEGF receptor-1. Moreover, down-regulation of PlGF with siRNA in HSCs inhibited the activation and proliferation of HSCs. Mechanistically, overexpression of PlGF in activated HSCs was induced by hypoxia dependent on HIF-1a, and PlGF induces HSC activation and proliferation via activation the phosphatidylinositol 3-kinase (PI3K)/Akt signalling pathways. These findings indicate that PlGF plays an important role in liver fibrosis-associated angiogenesis and that blockage of PlGF could be an effective strategy for chronic liver disease.

Placental Growth Factor Contributes to Liver Inflammation, Angiogenesis, Fibrosis in Mice by Promoting Hepatic Macrophage Recruitment and Activation

“…In this study, our findings lend support for the notion that PlGF plays a critical role in the pathogenesis of fibrotic liver disease and provide evidence that PlGF is a potential therapeutic target in chronic inflammatory liver diseases (22, 23). Moreover, knockdown of PlGF by siRNA in BDL mice ameliorates hepatic inflammation, angiogenesis, and fibrogenesis.…”

“…Protein extraction from macrophage cells was as previously described (22). The protein concentration was measured using the Bicinchoninic Acid Protein Colorimetric Assay kits (BMI, Shanghai, China) with BSA as standard.…”

Placental growth factor inhibition targets pulmonary angiogenesis and represents a therapy for hepatopulmonary syndrome in mice†

“…We and others have reported on the therapeutic effects of PlGF blockade on liver fibrosis in CCl 4 ‐induced mice . Although HPS develops on a background of liver fibrosis, this could only be confirmed following CBDL .…”

“…Finally, we and others have reported on the potential of PlGF as a therapeutic target in chronic liver disease using the CCl 4 model . Based on these results, one could postulate that the beneficial effects of αPlGF on HPS originate from a favorable primary effect on the liver.…”

Interplay Between Macrophages and Angiogenesis: A Double-Edged Sword in Liver Disease

“…PlGF is expressed by macrophages, ECs, and HSCs and specifically binds to VEGFR1. It is upregulated in fibrosis, cirrhosis, and hepatocellular carcinoma (39). Silencing PlGF in mice reduces tumor associated macrophage (TAM)-related chemokines and receptors (CXCL10, ICAM-1, VCAM, and CCR2), pro-inflammatory molecules (TNF-α, IL-1β, CCL2), and even anti-microbial receptors (TLR4 and TLR9), emphasizing the crucial role of this molecule and thus its potential as a therapeutic target (40).…”