Foxf1 +/− mice exhibit defective stellate cell activation and abnormal liver regeneration following CCl4 injury

Abstract

Previous studies have shown that haploinsufficiency of the splanchnic and septum transversum mesoderm Forkhead Box (Fox) f1 transcriptional factor caused defects in lung and gallbladder development and that Foxf1 heterozygous (؉/؊) mice exhibited defective lung repair in response to injury. In this study, we show that Foxf1 is expressed in hepatic stellate cells in developing and adult liver, suggesting that a subset of stellate cells originates from septum transversum mesenchyme during mouse embryonic development. Because liver regeneration requires a transient differentiation of stellate cells into myofibroblasts, which secrete type I collagen into the extracellular matrix, we examined Foxf1 ؉/؊ liver repair following carbon tetrachloride injury, a known model for stellate cell activation. We found that regenerating Foxf1 ؉/؊ liver exhibited defective stellate cell activation following CCl 4 liver injury, which was associated with diminished induction of type I collagen, ␣-smooth muscle actin, and Notch-2 protein and resulted in severe hepatic apoptosis despite normal cellular proliferation rates. Furthermore, regenerating Foxf1 ؉/؊ livers exhibited decreased levels of interferon-inducible protein 10 (IP-10), delayed induction of monocyte chemoattractant protein 1 (MCP-1) levels, and aberrantly elevated expression of transforming growth factor ␤1. T he Forkhead Box (Fox) family of transcription factors shares homology in the winged helix DNA binding domain, 1 and its members play important roles in cellular proliferation, differentiation, and metabolic homeostasis. [2][3][4][5][6] Haploinsufficiency of the Foxf1 gene (previously known as HFH-8 or Freac-1) in heterozygous (ϩ/Ϫ) mice causes perinatal lethality from pulmonary hemorrhage and severe defects in alveolarization, vascularization, and fusion of lung lobes. 7-9 Lung hemorrhage was observed in one half of newborn Foxf1 ϩ/Ϫ mice that had an 80% reduction in pulmonary Foxf1 levels (low Foxf1 ϩ/Ϫ) and reduced expression of genes involved in lung morphogenesis. 7 Interestingly, expression of these lung developmental genes was unchanged in 40% of the newborn Foxf1 ϩ/Ϫ mice that had near wildtype (WT) pulmonary levels of Foxf1 messenger RNA (mRNA) (high Foxf1 ϩ/Ϫ mice) without pulmonary hemorrhage, but they exhibited diminished alveolar septation. 7 Moreover, the high Foxf1 ϩ/Ϫ mice had normal life spans and adult lung morphology, suggesting that these mice compensated for the alveolar septation defect but exhibited defective lung repair in response to injury. 10 Liver development initiates at 9 days postcoitum (dpc) of mouse embryogenesis, when the cardiac mesenchyme induces the hepatic primordium to emerge from the foregut endoderm that invades the septum transversum mesenchyme. 6 Previous expression studies have shown

Prominent contribution of portal mesenchymal cells to liver fibrosis in ischemic and obstructive cholestatic injuries

“…To a large extent, these phenotypic changes caused by acute injury are reversible, as indicated here by the demonstration that in the same model, desmin overexpression in HSCs was significantly reduced at the end of follow-up. One may postulate that this response of HSCs has beneficial effects on the repair of wounded hepatocytes, a possibility supported by previous studies 20,[33][34][35][36] and here by the fact that all signs of liver injury had disappeared at the end of follow-up in the model of arterial liver ischemia. In both models, the accumulation of fibrosis coincided with that of a-SMA-labeled myofibroblasts, confirming that the vast majority of liver fibrogenic cells are a-SMA positive.…”

Mechanisms of Hepatic Fibrogenesis

“…Deletion of one Foxf1 allele reduces stellate cell activation and fibrosis. 82 Similarly, knockout of JunD, a member of the AP-1 transcription factor complex, 83 protects mice from CCl 4 induced hepatic fibrosis, which is associated with reduced numbers of activated stellate cells and diminished expression of hepatic TIMP-1. 84 Finally, phosphorylation of the transcription factor C/EBPβ by the RSK kinase promotes stellate cell survival.…”

Induction of Gas6 protein in CCl4-induced rat liver injury and anti-apoptotic effect on hepatic stellate cells

“…This is supported by the defective regeneration observed in Foxf Ϫ/ϩ mice associated with a reduced HSC activation, a diminished induction of type I collagen, and a delayed induction of MCP-1. 16 Pathways controlling HSC/MFB transformation and survival are therefore important issues in liver regeneration, 17 and their understanding might provide new options in the treatment of hepatocellular insufficiency.…”