Hepatocellular carcinoma in a mouse model fed a choline‐deficient,L‐amino acid‐defined,high‐fat diet

Hepatocellular carcinoma (HCC) is a common cancer worldwide and represents the outcome of the natural history of chronic liver disease. The growing rates of HCC may be partially attributable to increased numbers of people with non‐alcoholic fatty liver disease (NAFLD) and non‐alcoholic steatohepatitis (NASH). However, details of the liver‐specific molecular mechanisms responsible for the NAFLD–NASH–HCC progression remain unclear, and mouse models that can be used to explore the exact factors that influence the progression of NAFLD/NASH to the more chronic stages of liver disease and subsequent HCC are not yet fully established. We have previously reported a choline‐deficient, L‐amino acid‐defined, high‐fat diet (CDAHFD) as a dietary NASH model with rapidly progressive liver fibrosis in mice. The current study in C57BL/6J mice fed CDAHFD provided evidence for the chronic persistence of advanced hepatic fibrosis in NASH and disease progression towards HCC in a period of 36 weeks. When mice fed CDAHFD were switched back to a standard diet, hepatic steatosis was normalized and NAFLD activity score improved, but HCC incidence increased and the phenotype of fibrosis‐associated HCC development was observed. Moreover, when mice continued to be fed CDAHFD for 60 weeks, HCC further developed without severe body weight loss or carcinogenesis in other organs. The autochthonous tumours showed a variety of histological features and architectural patterns including trabecular, pseudoglandular and solid growth. The CDAHFD mouse model might be a useful tool for studying the development of HCC from NAFLD/NASH, and potentially useful for better understanding pathological changes during hepatocarcinogenesis.     

An improved mouse model that rapidly develops fibrosis in non‐alcoholic steatohepatitis

Non‐alcoholic steatohepatitis (NASH) is a progressive fibrotic disease, the pathogenesis of which has not been fully elucidated. One of the most common models used in NASH research is a nutritional model where NASH is induced by feeding a diet deficient in both methionine and choline. However, the dietary methionine‐/choline‐deficient model in mice can cause severe weight loss and liver atrophy, which are not characteristics of NASH seen in human patients. Exclusive, long‐term feeding with a high‐fat diet (HFD) produced fatty liver and obesity in mice, but the HFD for several months did not affect fibrosis. We aimed to establish a mouse model of NASH with fibrosis by optimizing the methionine content in the HFD. Male mice were fed a choline‐deficient, L‐amino acid‐defined, high‐fat diet (CDAHFD) consisting of 60 kcal% fat and 0.1% methionine by weight. After 1–14 weeks of being fed CDAHFD, the mice were killed. C57BL/6J mice maintained or gained weight when fed CDAHFD, while A/J mice showed a steady decline in body weight (of up to 20% of initial weight). In both strains of mice, plasma levels of alanine aminotransferase increased from week 1, when hepatic steatosis was also observed. By week 6, C57BL/6J mice had developed enlarged fatty liver with fibrosis as assessed by Masson's trichrome staining and by hydroxyproline assay. Therefore, this improved CDAHFD model may be a mouse model of rapidly progressive liver fibrosis and be potentially useful for better understanding human NASH disease and in the development of efficient therapies for this condition.     

JNK1 and JNK2 regulate α‐SMA in hepatic stellate cells during CCl4‐induced fibrosis in the rat liver

Following liver injuries, hepatic stellate cells (HSCs) express α‐SMA. Mitogen activated protein kinase (MAPK) signaling pathways mediate α‐SMA expression in distinct cell types. However, the regulation of α‐SMA expression by MAPKs in HSCs has been rarely studied. We aimed to study the role of MAPKs in the activation of HSCs during liver fibrosis. Liver fibrosis of rats was induced by carbon tetrachloride. HSC‐T6 cells, murine embryonic fibroblasts, JNK1^?/? and JNK2^?/? cells were used for in vitro studies. Immunohistochemistry and immunoblot analysis were used. We have found that the expression of JNK and α‐SMA co‐localized in HSCs during liver fibrosis, but ERK and p38 expressed in macrophages. The expression of α‐SMA was up‐regulated by JNK1 and JNK2 in non‐stress condition. Under TGF‐β stimulation, however, the level α‐SMA expression was increased by only JNK1, but not significantly changed by JNK2. We suggest that JNKs are responsible for α‐SMA regulation, and especially JNK1 has a major role in up‐regulation of α‐SMA expression in HSCs under stress condition induced by TGF‐β during liver fibrosis.     

Silymarin suppresses hepatic stellate cell activation in a dietary rat model of non-alcoholic steatohepatitis: analysis of isolated hepatic stellate cells

Non-alcoholic steatohepatitis (NASH) is characterized by hepatocellular injury and initial fibrosis severity has been suggested as an important prognostic factor of NASH. Silymarin was reported to improve carbon tetrachloride-induced liver fibrosis and reduce the activation of hepatic stellate cells (HSC). We investigated whether silymarin could suppress the activation of HSCs in NASH induced by methionine- and choline-deficient (MCD) diet fed to insulin-resistant rats. NASH was induced by feeding MCD diet to obese diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats. Non-diabetic Long-Evans Tokushima Otsuka (LETO) rats were fed with standard chow and served as the control. OLETF rats were fed on either standard laboratory chow, or MCD diet or MCD diet mixed with silymarin. Histological analysis of the liver showed improved non-alcoholic fatty liver disease (NAFLD) activity score in silymarin-fed MCD-induced NASH. Silymarin reduced the activation of HSCs, evaluated by counting α-smooth muscle actin (SMA)-positive cells and measuring α-SMA mRNA expression in the liver lysates as well as in HSCs isolated from the experimental animals. Although silymarin decreased α(1)-procollagen mRNA expression in isolated HSCs, the anti-fibrogenic effect of silymarin was not prominent so as to show significant difference under histological analysis. Silymarin increased the nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) and decreased tumor necrosis factor (TNF)-α mRNA expression in the liver. Our study suggested that the possible protective effect of silymarin in diet induced NASH by suppressing the activation of HSCs and disturbing the role of the inflammatory cytokine TNF-α.     

Novel non‐alcoholic steatohepatitis model with histopathological and insulin‐resistant features

Although several non‐alcoholic steatohepatitis (NASH) models have been reported to date, few of these models fully reflect the histopathology and pathophysiology of human NASH. The aim of this study was to establish a novel NASH model by feeding a high‐fat (HF) diet and administering both carbon tetrachloride (CCl₄) and the Liver X receptor agonist T0901317. Male C57BL/6J mice were divided into four groups (each n = 5): HF, HF + CCl₄, HF + T0901317, and the novel NASH model (HF + CCl₄ + T0901317). CCl₄ (0.1 mL/kg) and T0901317 (2.5 mg/kg) were intraperitoneally administered four times and five times, respectively. The livers of the novel NASH model group presented a whitish colour. The serum levels of TNF‐α and IL‐6 were significantly increased in the novel NASH model group, and mice in this group exhibited histopathological features and insulin resistance reflective of NASH, i.e., macrovesicular hepatic steatosis, ballooning hepatocytes, Mallory‐Denk bodies, lobular inflammation and fibrosis. The novel NASH model group presented significantly upregulated expression levels of mRNAs related to lipogenesis, oxidative stress, fibrosis and steatosis and significantly downregulated expression levels of mRNAs related to triglyceride export. We successfully established a novel experimental NASH model that exhibits similar histopathology and pathophysiology to human NASH.     

Interleukin‐23 promotes intestinal T helper type17 immunity and ameliorates obesity‐associated metabolic syndrome in a murine high‐fat diet model

We addressed the role of interleukin‐23 (IL‐23) in driving the intestinal T helper type 17 (Th17) response during obesity and metabolic syndrome progression induced by a high‐fat diet (HFD). Diet‐induced obese and lean mice received HFD or control diet (CTD), respectively, for 20 weeks. The nutritional, metabolic and immune parameters were examined at weeks 9 and 20. Gene and protein IL‐23p19 and IL‐23 receptor expression was increased in the ileum of obese wild‐type mice (WT) fed the HFD for 9 weeks. Mice lacking IL‐23 and fed the HFD exhibited greater weight gain, higher fat accumulation, adipocyte hypertrophy and hepatic steatosis. Notably, these mice had more glucose intolerance, insulin resistance and associated metabolic alterations, such as hyperinsulinaemia and hyperlipidaemia. IL‐23 deficiency also significantly reduced protein levels of IL‐17, CCL20 and neutrophil elastase in the ileum and reduced Th17 cell expansion in the mesenteric lymph nodes of the HFD mice. Of importance, IL‐23‐deficient mice exhibited increased gut permeability and blood bacterial translocation compared with WT mice fed HFD. Finally, metagenomics analysis of gut microbiota revealed a dramatic outgrowth of Bacteroidetes over Firmicutes phylum with the prevalence of Bacteroides genera in the faeces of IL‐23‐deficient mice after HFD. In summary, IL‐23 appears to maintain the Th17 response and neutrophil migration into the intestinal mucosa, minimizing the gut dysbiosis and protecting against obesity and metabolic disease development in mice.     

PKCη deficiency improves lipid metabolism and atherosclerosis in apolipoprotein E‐deficient mice

Genomewide association studies have shown that a nonsynonymous single nucleotide polymorphism in PRKCH is associated with cerebral infarction and atherosclerosis‐related complications. We examined the role of PKCη in lipid metabolism and atherosclerosis using apolipoprotein E‐deficient (Apoe^?/?) mice. PKCη expression was augmented in the aortas of mice with atherosclerosis and exclusively detected in MOMA2‐positive macrophages within atherosclerotic lesions. Prkch^+/+Apoe^?/? and Prkch^?/?Apoe^?/? mice were fed a high‐fat diet (HFD), and the dyslipidemia observed in Prkch^+/+Apoe^?/? mice was improved in Prkch^?/?Apoe^?/? mice, with a particular reduction in serum LDL cholesterol and phospholipids. Liver steatosis, which developed in Prkch^+/+Apoe^?/? mice, was improved in Prkch^?/?Apoe^?/? mice, but glucose tolerance, adipose tissue and body weight, and blood pressure were unchanged. Consistent with improvements in LDL cholesterol, atherosclerotic lesions were decreased in HFD‐fed Prkch^?/?Apoe^?/? mice. Immunoreactivity against 3‐nitrotyrosine in atherosclerotic lesions was dramatically decreased in Prkch^?/?Apoe^?/? mice, accompanied by decreased necrosis and apoptosis in the lesions. ARG2 mRNA and protein levels were significantly increased in Prkch^?/?Apoe^?/? macrophages. These data show that PKCη deficiency improves dyslipidemia and reduces susceptibility to atherosclerosis in Apoe^?/? mice, showing that PKCη plays a role in atherosclerosis development.     

Regulatory role of DC‐derived osteopontin in systemic allergen sensitization

Osteopontin (OPN) is a secreted phosphoglycoprotein with a wide range of functions, and is involved in various pathophysiological conditions. However, the role of OPN in IgE and Th2‐associated allergic responses remains incompletely defined. The aim of this study was to elucidate the role of OPN in systemic allergen sensitization in mice. When compared with OPN^+/+ mice, significantly increased levels of OVA‐induced IgE were found in OPN^?/? mice. OPN^?/? DC demonstrated an increased capacity to enhance Th2 cytokine production in CD4⁺ T cells from sensitized OPN^+/+ mice. Furthermore, significantly reduced levels of IL‐12p70 expression were seen in LPS‐stimulated OPN^?/? DC as compared with the WT DC, and the reduction was reversible by the addition of recombinant OPN (rOPN). rOPN was able to suppress OVA‐induced IL‐13 production in the cultures of CD4 and OPN^?/? DC, but this inhibitory activity was neutralized by the addition of anti‐IL‐12 Ab. In addition, administration of rOPN in vivo suppressed OVA‐specific IgE production; however, this suppressive effect was abrogated in IL‐12‐deficient mice. These results indicate that DC‐derived OPN plays a regulatory role in the development of systemic allergen sensitization, which is mediated, at least in part, through the production of endogenous IL‐12.     

Synectin‐dependent regulation of arterial maturation

Synectin, a ubiquitously expressed PDZ scaffold protein, has been shown to be a key regulator in the formation of arterial vasculature. Examination of the retinal vasculature in synectin^?/? mice demonstrated poor mural cell coverage of and attachment to the forming arterial tree, a defect reminiscent of retinal abnormalities observed in platelet derived growth factor (PDGF) ‐B^?/? mice. Primary cultures of synectin^?/? smooth muscle cells had normal expression of PDGFR‐β and migrated normally in response to PDGF‐BB. However, expression of PDGF‐BB protein, but not mRNA, was reduced in lysates from arterial, but not venous, primary synectin^?/? endothelial cells (EC), that was restored by inhibition of proteosomal degradation. Transduction of synectin^?/? and ^+/+ EC with a bicistronic Pdgfb/gfp construct, resulted in comparable expression of green fluorescent protein in both EC populations while PDGF‐BB expression was severely reduced in synectin^?/? EC. Finally, synectin expression in synectin^?/? arterial EC restored PDGF‐BB protein levels. These results suggest that synectin deficiency results in increased degradation of PDGF‐BB protein in arterial EC and, consequently, reduced recruitment of mural cells to newly forming arteries. This observation may explain the selective reduction in arterial morphogenesis observed in synectin knockout mice. Developmental Dynamics 238:604–610, 2009. © 2009 Wiley‐Liss, Inc.     

Divergent roles of Toll‐like receptor 2 in response to lipoteichoic acid and Staphylococcus aureus in vivo

The response of leukocytes to lipoteichoic acid (LTA), a TLR2‐dependent major cell wall component of Staphylococcus aureus, is linked to the outcome of an infection. In this study we investigated the role of nonhematopoietic TLR2 in response to LTA and S. aureus by creating bone marrow chimeras. Significant leukocyte recruitment in response to LTA required IFN‐γ priming in WT C57BL/6 and TLR2^?/??WT mice, but was not observed in TLR2^?/? or WT?TLR2^?/? animals. LTA also induced a proinflammatory response in IFN‐γ primed primary human microvascular endothelial cells leading to leukocyte recruitment in vitro. When mice were infected with S. aureus, the most profound elevation of TNF‐α and IL‐6 was seen in TLR2^?/? and TLR2^?/??WT mice. TLR2^?/?, but not chimeric mice, demonstrated increased IL‐17, blood leukocytosis and pulmonary neutrophilia compared to WT mice. Collectively, the results suggest an essential role for IFN‐γ and nonhematopoietic TLR2 for leukocyte recruitment in response to LTA. In contrast, TLR2 on both hematopoietic and nonhematopoietic cells appears to orchestrate an inhibitory response to S. aureus such that in complete TLR2 deficiency, there is an exaggerated proinflammatory response and/or skewing of the immune response towards a Th17 phenotype that may contribute to the decreased survival of TLR2^?/? mice.     

Chemokine receptor Ccr5 deficiency induces alternative macrophage activation and improves long‐term renal allograft outcome

The chemokine (C‐C motif) receptor 5 (CCR5) has been implicated in experimental and clinical allograft rejection. To dissect the function of CCR5 in acute and chronic renal allograft rejection, bilaterally nephrectomized WT and Ccr5^?/? C57BL/6 mice were used as recipients of WT BALB/c renal allografts and analyzed 7 and 42 days after transplantation. Lesion scores (glomerular damage, vascular rejection, tubulointerstitial inflammation) and numbers of CD4⁺, CD8⁺, CD11c⁺ and alpha smooth muscle actin (αSMA)⁺ cells were reduced in allografts from Ccr5^?/? recipients during the chronic phase. Increasing creatinine levels indicated deterioration of allograft function over time. While mRNA expression of Th1‐associated markers decreased between 7 and 42 days, Th2‐associated markers increased. Markers for alternatively activated macrophages (arginase 1, chitinase 3‐like 3, resistin‐like α, mannose receptor, C type 1), were strongly upregulated (mRNA and/or protein level) only in allografts from Ccr5^?/? recipients at 42 days. Ccr5 deficiency shifted intragraft immune responses during the chronic phase towards the Th2 type and led to accumulation of alternatively activated macrophages. Additionally, splenocytes from unchallenged Ccr5^?/? mice showed significantly increased arginase 1 and mannose receptor 1 mRNA levels, suggesting constitutive alternative activation of splenic macrophages. We conclude that Ccr5 deficiency favors alternative macrophage activation. This finding may be relevant for other inflammatory diseases that involve macrophage activation and may also influence future therapeutic strategies targeting CCR5.     

Differential TM4SF5‐mediated SIRT1 modulation and metabolic signaling in nonalcoholic steatohepatitis progression

Nonalcoholic fatty liver disease is a chronic condition involving steatosis, steatohepatitis and fibrosis, and its progression remains unclear. Although the tetraspanin transmembrane 4 L six family member 5 (TM4SF5) is involved in hepatic fibrosis and cancer, its role in nonalcoholic steatohepatitis (NASH) progression is unknown. We investigated the contribution of TM4SF5 to liver pathology using transgenic and KO mice, diet‐ or drug‐treated mice, in vitro primary cells, and in human tissue. TM4SF5‐overexpressing mice exhibited nonalcoholic steatosis and NASH in an age‐dependent manner. Initially, TM4SF5‐positive hepatocytes and liver tissue exhibited lipid accumulation, decreased Sirtuin 1 (SIRT1), increased sterol regulatory‐element binding proteins (SREBPs) and inactive STAT3 via suppressor of cytokine signaling (SOCS)1/3 upregulation. In older mice, TM4SF5 promoted inflammatory factor induction, SIRT1 expression and STAT3 activity, but did not change SOCS or SREBP levels, leading to active STAT3‐mediated ECM production for NASH progression. A TM4SF5‐associated increase in chemokines promoted SIRT1 expression and progression to NASH with fibrosis. Suppression of the chemokine CCL20 reduced immune cell infiltration and ECM production. Liver tissue from high‐fat diet‐ or CCl₄‐treated mice and human patients exhibited TM4SF5‐dependent steatotic or steatohepatitic livers with links between TM4SF5‐mediated SIRT1 modulation and SREBP or SOCS/STAT3 signaling axes. TM4SF5‐mediated STAT3 activation in fibrotic NASH livers increased collagen I and laminin γ2. Both collagen I α1 and laminin γ2 suppression resulted in reduced SIRT1 and active STAT3, but no change in SREBP1 or SOCS, and abolished CCl₄‐mediated mouse liver damage. TM4SF5‐mediated signaling pathways that involve SIRT1, SREBPs and SOCS/STAT3 promoted progression to NASH. Therefore, TM4SF5 and its downstream effectors may be promising therapeutic targets to treat nonalcoholic fatty liver disease. © 2020 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Loss of glutathione S‐transferase A4 accelerates obstruction‐induced tubule damage and renal fibrosis

Glutathione transferase isozyme A4 (GSTA4) exhibits high catalytic efficiency to metabolize 4‐hydroxynonenal (4‐HNE), a highly reactive lipid peroxidation product that has been implicated in the pathogenesis of various chronic diseases. We investigated the role of 4‐HNE in the mechanisms of unilateral ureteral obstruction (UUO)‐induced fibrosis and its modulation by GSTA4‐4 in a mouse model. Our data indicate that after UUO, accumulation of 4‐HNE and its adducts were increased in renal tissues, with a concomitant decrease in the expression of GSTA4‐4 in mice. As compared to wild‐type (WT) mice, UUO caused an increased expression of fibroblast markers in the interstitium of GSTA4 KO mice. Additionally, increased autophagy and tubular cell damage were more severe in UUO‐treated GSTA4 KO mice than in WT mice. Furthermore, GSK‐3β phosphorylation and expression of Snail, a regulator of E‐cadherin and Occludin, was found to be significantly higher in UUO‐inflicted GSTA4 KO mice. GSTA4 over‐expression prevented 4‐HNE‐induced autophagy activation, tubular cell damage and Snail nuclear translocation in vitro. The effects of long‐term expression of GSTA4 in restoration of UUO‐induced damage in mice with the GSTA4 inducible transposon system indicated that release of obstruction after 3 days of UUO resulted in the attenuation of interstitial SMAα and collagen I expression. This transposon‐delivered GSTA4 expression also suppressed UUO‐induced loss of tubular cell junction markers and autophagy activation. Together, these results indicate that 4‐HNE significantly contributes to the mechanisms of tubule injury and fibrosis and that these effects can be inhibited by the enhanced expression of GSTA4‐4. Copyright © 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

IFN‐γ‐producing NKT cells exacerbate sepsis by enhancing C5a generation via IL‐10‐mediated inhibition of CD55 expression on neutrophils

A role for NKT cells has been implicated in sepsis, but the mechanism by which NKT cells contribute to sepsis remains unclear. Here, we examined WT and NKT‐cell‐deficient mice of C57BL/6 background during cecal ligation and puncture‐induced sepsis. The levels of C5a, IFN‐γ, and IL‐10 were higher in the serum and peritoneal fluid of WT mice than in those of CD1d^?/? mice, while the mortality rate was lower in CD1d^?/? mice than in WT mice. C5a blockade decreased mortality of WT mice during sepsis, whereas it did not alter that of CD1d^?/? mice. As assessed by intracellular staining, NKT cells expressed IFN‐γ, while neutrophils expressed IL‐10. Upon coculture, IL‐10‐deficient NKT cells enhanced IL‐10 production by WT, but not IFN‐γR‐deficient, neutrophils. Meanwhile, CD1d^?/? mice exhibited high CD55 expression on neutrophils during sepsis, whereas those cells from WT mice expressed minimal levels of CD55. Recombinant IL‐10 administration into CD1d^?/? mice reduced CD55 expression on neutrophils. Furthermore, adoptive transfer of sorted WT, but not IFN‐γ‐deficient, NKT cells into CD1d^?/? mice suppressed CD55 expression on neutrophils, but increased IL‐10 and C5a levels. Taken together, IFN‐γ‐producing NKT cells enhance C5a generation via IL‐10‐mediated inhibition of CD55 expression on neutrophils, thereby exacerbating sepsis.     

IL‐1β activation in response to Staphylococcus aureus lung infection requires inflammasome‐dependent and independent mechanisms

Maintaining balanced levels of IL‐1β is extremely important to avoid host tissue damage during infection. Our goal was to understand the mechanisms behind the reduced pathology and decreased bacterial burdens in Ifnlr1^?/? mice during lung infection with Staphylococcus aureus. Intranasal infection of Ifnlr1^?/? mice with S. aureus led to significantly improved bacterial clearance, survival and decrease of proinflammatory cytokines in the airway including IL‐1β. Ifnlr1^?/? mice treated with recombinant IL‐1β displayed increased bacterial burdens in the airway and lung. IL‐1β levels in neutrophils from Ifnlr1^?/? infected mice lungs were decreased when compared to neutrophils from WT mice. Mice lacking NLRP3 and caspase‐1 had reduced IL‐1β levels 4 h after infection, due to reductions or absence of active caspase‐1 respectively, but levels at 24 h were comparable to WT infected mice. Ifnlr1^?/? infected mice had decreases in both active caspase‐1 and neutrophil elastase indicating an important role for the neutrophil serine protease in IL‐1β processing. By inhibiting neutrophil elastase, we were able to decrease IL‐1β levels by 39% in Nlrp3^?/? infected mice when compared to WT mice. These results highlight the crucial role of both proteases in IL‐1β processing, via inflammasome‐dependent and ‐independent mechanisms.     

肝星状细胞SCAP特异性敲除对小鼠肝纤维化的影响

目的:探讨固醇调节元件结合蛋白裂解活化蛋白(SCAP)在肝星状细胞中缺失能否延缓小鼠肝纤维化进程.方法:将SCAPloxP/loxP小鼠与Lrat-Cre工具鼠繁殖得到Lrat-Cre+/+SCAPfl/fl、Lrat-Cre+/?SCAPfl/fl和Lrat-Cre?/?SCAPfl/fl小鼠,并用PCR法对小鼠基因...     

Enhanced protection from fibrosis and inflammation in the combined absence of IL‐13 and IFN‐γ

Persistent or dysregulated IL‐13 responses are key drivers of fibrosis in multiple organ systems, and this identifies this cytokine as an important therapeutic target. Nevertheless, the mechanisms by which IL‐13 blockade leads to the amelioration of fibrosis remain unclear. Because IFN‐γ exhibits potent anti‐fibrotic activity, and IL‐4Rα signalling antagonizes IFN‐γ effector function, compensatory increases in IFN‐γ activity following IL‐13/IL‐4Rα blockade might contribute to the reduction in fibrosis. To investigate the role of IFN‐γ, we developed novel IL‐13^?/?/IFN‐γ^?/? double cytokine‐deficient mice and examined disease progression in models of type 2‐driven fibrosis. As predicted, we showed that fibrosis in the lung and liver are both highly dependent on IL‐13. We also observed increased IFN‐γ production and inflammatory activity in the tissues of IL‐13‐deficient mice. Surprisingly, however, an even greater reduction in fibrosis was observed in IL‐13/IFN‐γ double deficient mice, most notably in the livers of mice chronically infected with Schistosoma mansoni. The increased protection was associated with marked decreases in Tgfb1, Mmp12, and Timp1 mRNA expression in the tissues; reduced inflammation; and decreased expression of important pro‐inflammatory mediators such as TNF‐α. Experiments conducted with neutralizing monoclonal antibodies to IL‐13 and IFN‐γ validated the findings with the genetically deficient mice. Together, these studies demonstrate that the reduction in fibrosis observed when IL‐13 signalling is suppressed is not dependent on increased IFN‐γ activity. Instead, by reducing compensatory increases in type 1‐associated inflammation, therapeutic strategies that block IFN‐γ and IL‐13 activity simultaneously can confer greater protection from progressive fibrosis than IL‐13 blockade alone. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.