Kazuhiko Bessho

Growth Inhibition and Apoptosis in Liver Myofibroblasts Promoted by Hepatocyte Growth Factor Leads to Resolution from Liver Cirrhosis

Liver cirrhosis is characterized by hepatic dysfunction with extensive accumulation of fibrous tissue in the liver. In response to chronic hepatic injury, hepatic portal myofibroblasts and activated hepatic stellate cells (HSCs) play a role in liver fibrosis. Although administration or gene expression of hepatocyte growth factor (HGF) leads to improvement in hepatic fibrosis/cirrhosis, the related mechanisms are not fully understood. We investigated mechanisms involved in resolution from liver cirrhosis by HGF, focusing on growth regulation and apoptosis in portal myofibroblasts. Cultured rat HSCs could not proliferate, were withdrawn after passage, and were replaced by proliferating portal myofibroblasts during the passages. In quiescent HSCs, c-Met receptor expression was undetected whereas c-Met receptor expression was detected in activated HSCs and liver myofibroblasts expressing alpha-smooth muscle actin (alpha-SMA), suggesting that activated HSCs and portal myofibroblasts are targets of HGF. For cultured rat portal myofibroblasts, HGF counteracted phosphorylation of extracellular signal-regulated kinase (Erk) 1/2 and mitogenic stimulus induced by platelet-derived growth factor, induced c-jun N-terminal kinase (JNK) 1 phosphorylation, and promoted apoptotic cell death. In the dimethylnitrosamine rat model of liver cirrhosis, administration of HGF suppressed proliferation while promoting apoptosis of alpha-SMA-positive cells in the liver, events that were associated with reduced hepatic expressions of alpha-SMA and histological resolution from liver cirrhosis. Growth inhibition and enhanced apoptosis in portal myofibroblasts by HGF are newly identified mechanisms aiding resolution from liver fibrosis/cirrhosis by HGF.

Clinical phenotype and endocrinological investigations in a patient with a mutation in the MCT8 thyroid hormone transporter

Thyroid hormones are known to be essential for growth, development, and metabolism. Recently, the monocarboxylate transporter 8 (MCT8) was identified as a thyroid hormone transporter, and MCT8 mutations have been associated with Allan-Herndon-Dudley syndrome, an X linked condition characterized by severe mental retardation, dysarthria, athetoid movements, muscle hypoplasia, and spastic paraplegia. Here we describe in detail the clinical and biochemical features and the response to thyroid hormone (L-thyroxine (LT4)) administration in a boy with an MCT8 mutation (c.1649delA) that truncates the protein in the twelfth transmembrane domain. It is of note that brain magnetic resonance imaging (MRI) revealed delayed myelination from infancy. Endocrine functions other than thyroid hormone regulation and metabolism were intact, resulting in normal hypothalamic/pituitary function tests. While LT4 administration suppressed thyrotropin (TSH) secretion, no significant changes in thyroid hormone values or clinical symptoms were observed. Conclusion: the characteristic thyroid hormone function tests and brain MRI findings may allow screening of high-risk populations for a better understanding of MCT8 pathophysiology.

Recombinant hepatocyte growth factor accelerates cutaneous wound healing in a diabetic mouse model.

We examined effects of recombinant hepatocyte growth factor (HGF) on cutaneous wound healing, using a full-thickness cutaneous excision model in diabetic mice. Topical administration of HGF, as well as basic fibroblast growth factor (bFGF), promoted the rate of wound closure and re-epithelialization. Both HGF and bFGF enhanced expansion of the granulation tissue and stimulated neovascularization on day 7 postwounding, wherein the increase in microvessel density in HGF-treated wounds was higher than that in bFGF-treated wounds. Matrix metalloproteinases (MMP-2 and MMP-9) activities involved in cell migration, angiogenesis, and extracellular matrix (ECM) remodeling, were enhanced by HGF-treatment on day 7. On day 28 postwounding (later stages of wound healing), granulation tissue in bFGF-treated wounds remained to a greater extent than that seen in saline- and HGF-treated wounds. Likewise, bFGF- but not HGF-treatment stimulated DNA synthesis of fibroblasts in granulation tissue, suggesting that HGF stimulates wound healing with lesser degree of susceptibility to cutaneous scarring. We propose that supplement of HGF may be a potential therapeutic approach for treatment of cutaneous ulcer.

Biliary Atresia: Will Blocking Inflammation Tame the Disease?

Biliary atresia is the most common cholangiopathy of childhood. With complete obstruction of segments or the entire length of extrahepatic bile ducts, the timely pursuit of hepatoportoenterostomy is the best strategy to restore bile drainage. However, even with prompt surgical intervention, ongoing injury of intrahepatic bile ducts and progressive cholangiopathy lead to end-stage cirrhosis. The pace of disease progression is not uniform; it may relate to clinical forms of disease and/or staging of liver pathology at diagnosis. Although the etiology of disease is not yet defined, several biological processes have been linked to pathogenic mechanisms of bile duct injury. Among them, there is increasing evidence that the immune system targets the duct epithelium and disrupts bile flow. We discuss how careful clinical phenotyping, staging of disease, and basic mechanistic research are providing insights into clinical trial designs and directions for development of new therapies to block progression of disease.

Th2 signals induce epithelial injury in mice and are compatible with the biliary atresia phenotype

Biliary atresia (BA) is a destructive cholangiopathy of childhood in which Th1 immunity has been mechanistically linked to the bile duct inflammation and obstruction that culminate in liver injury. Based on reports of decreased Th1 cytokines in some patients and the development of BA in mice lacking CD4+ T cells, we hypothesized that Th1-independent mechanisms can also activate effector cells and induce BA. Here, we tested this hypothesis using Stat1-/- mice, which lack the ability to mount Th1 immune responses. Infection of Stat1-/- mice with rhesus rotavirus type A (RRV) on postnatal day 1 induced a prominent Th2 response, duct epithelial injury and obstruction within 7 days, and atresia shortly thereafter. A high degree of phosphorylation of the Th2 transcription factor Stat6 was observed; however, concurrent inactivation of Stat1 and Stat6 in mice did not prevent BA after RRV infection. In contrast, depletion of macrophages or combined loss of Il13 and Stat1 reduced tissue infiltration by lymphocytes and myeloid cells, maintained epithelial integrity, and prevented duct obstruction. In concordance with our mouse model, humans at the time of BA diagnosis exhibited differential hepatic expression of Th2 genes and serum Th2 cytokines. These findings demonstrate compatibility between Th2 commitment and the pathogenesis of BA, and suggest that patient subgrouping in future clinical trials should account for differences in Th2 status.

Hepatocyte Growth Factor Suppresses Vascular Medial Hyperplasia and Matrix Accumulation in Advanced Pulmonary Hypertension of Rats

Background—Pulmonary hypertension (PH) is a progressive disease characterized by raised pulmonary vascular resistance, thought to be curable only through lung transplantation. Pathophysiologically, proliferation of pulmonary artery smooth muscle cells triggers pulmonary arterial stenosis and/or regurgitation, especially in advanced PH. Methods and Results—Using a rat model of advanced pulmonary vascular disease produced by injecting monocrotaline, we show that hepatocyte growth factor (HGF) targets pulmonary arterioles and blocks the progression of PH. In these rats, endogenous HGF production was dramatically downregulated during developing experimental PH, but c-Met/HGF receptor was abundant in the medial layers of pulmonary arterioles. HGF gene transfection 2 weeks after the monocrotaline injection resulted in milder medial hyperplasia in lung arterioles and inhibited overgrowth of pulmonary artery smooth muscle cells. Notably, exogenous HGF reduced lung expression levels of endothelin-1 and transforming growth factor-&bgr;, which are critically involved in PH-linked fibrogenic events. Overall, medial wall thickening of pulmonary arteries was almost completely prevented by HGF, and the total collagen deposition in the lung decreased; both effects contributed to the suppression of pulmonary artery hypertension. Conclusions—Our results suggest that the loss of endogenous HGF may be a feature of the pathogenesis of PH and that HGF supplementation may minimize pathological lung conditions, even advanced PH.

Gene expression signature for biliary atresia and a role for interleukin-8 in pathogenesis of experimental disease.

Biliary atresia (BA) is a progressive fibroinflammatory obstruction of extrahepatic bile ducts that presents as neonatal cholestasis. Due to the overlap in clinical, biochemical, and histological features with other causes of cholestasis, the diagnosis requires an intraoperative cholangiogram. Thus, we determined whether diseased livers express a gene expression signature unique to BA. Applying stringent statistical analysis to a genome‐wide liver expression platform of 64 infants with BA at the time of diagnosis, 14 age‐appropriate subjects with intrahepatic cholestasis as diseased controls and seven normal controls, we identified 15 genes uniquely expressed in BA with an accuracy of 92.3%. Among these genes, IL8 and LAMC2 were sufficient to classify subjects with BA distinctly from diseased controls with an area under the curve of 0.934 (95% confidence interval [CI]: 0.84‐1.03), sensitivity of 96.9%, and specificity of 85.7% using their combined first principal component. Direct measurement of interleukin (IL)8 protein in the serum, however, was not different between the two groups. To investigate whether the liver‐restricted increase in IL8 was relevant to disease pathogenesis, we inactivated the signaling of IL8 homologs by genetic targeting of the Cxcr2 receptor in a murine model of experimental BA. Disruption of Cxcr2 shortened the duration of cholestasis, decreased the incidence of bile duct obstruction, and improved survival above wild‐type neonatal mice. Conclusion: The hepatic expression of IL8 and LAMC2 has high sensitivity for BA at diagnosis and may serve as a biomarker of disease, with an important role for the IL8 signaling in experimental BA. (Hepatology 2014;60:211–223)

Integrative genomics identifies candidate microRNAs for pathogenesis of experimental biliary atresia

BackgroundBiliary atresia is a fibroinflammatory obstruction of extrahepatic bile duct that leads to end-stage liver disease in children. Despite advances in understanding the pathogenesis of biliary atresia, very little is known about the role of microRNAs (miRNAs) in onset and progression of the disease. In this study, we aimed to investigate the entire biliary transcriptome to identify miRNAs with potential role in the pathogenesis of bile duct obstruction.ResultsBy profiling the expression levels of miRNA in extrahepatic bile ducts and gallbladder (EHBDs) from a murine model of biliary atresia, we identified 14 miRNAs whose expression was suppressed at the times of duct obstruction and atresia (≥2 fold suppression, P < 0.05, FDR 5%). Next, we obtained 2,216 putative target genes of the 14 miRNAs using in silico target prediction algorithms. By integrating this result with a genome-wide gene expression analysis of the same tissue (≥2 fold increase, P < 0.05, FDR 5%), we identified 26 potential target genes with coordinate expression by the 14 miRNAs. Functional analysis of these target genes revealed a significant relevance of miR-30b/c, -133a/b, -195, -200a, -320 and −365 based on increases in expression of at least 3 target genes in the same tissue and 1st-to-3rd tier links with genes and gene-groups regulating organogenesis and immune response. These miRNAs showed higher expression in EHBDs above livers, a unique expression in cholangiocytes and the subepithelial compartment, and were downregulated in a cholangiocyte cell line after RRV infection.ConclusionsIntegrative genomics reveals functional relevance of miR-30b/c, -133a/b, -195, -200a, -320 and −365. The coordinate expression of miRNAs and target genes in a temporal-spatial fashion suggests a regulatory role of these miRNAs in pathogenesis of experimental biliary atresia.

Natural Killer Cells Promote Long-Term Hepatobiliary Inflammation in a Low-Dose Rotavirus Model of Experimental Biliary Atresia

Biliary atresia is a rapidly progressive obstructive cholangiopathy of infants. Mechanistic studies in the mouse model of Rhesus rotavirus (RRV)-induced biliary atresia have linked the importance of effector lymphocytes to the pathogenesis of extrahepatic bile duct (EHBD) injury and obstruction in experimental biliary atresia; however, studies of the progressive liver injury have been limited by early death of newborn mice. Here, we aimed to determine 1) if a lower inoculum of RRV induces obstruction of EHBDs while allowing for ongoing liver inflammation, and 2) if NK cells regulate intrahepatic injury. The administration of 0.25x106 fluorescence forming units of RRV induced an obstructive extrahepatic cholangiopathy, but allowed for restoration of the duct epithelium, increased survival, and the development of a progressive intrahepatic inflammatory injury with molecular and cellular signatures equivalent to the traditional infectious model. Investigating the mechanisms of liver injury, we found that NK cell depletion at the onset of jaundice decreased liver inflammation, suppressed the expression of fibrosis and inflammation/immunity genes, lowered plasma ALT and bilirubin and improved survival. Conclusions Lower inoculation of RRV-induced progressive liver injury and fibrosis via NK cells. These findings point to the potential use of NK cell-depleting strategies to block progression of liver disease in biliary atresia.

Circulating tricarboxylic acid cycle metabolite levels in citrin-deficient children with metabolic adaptation, with and without sodium pyruvate treatment

Citrin deficiency causes adult-onset type II citrullinemia (CTLN-2), which later manifests as severe liver steatosis and life-threatening encephalopathy. Long-standing energy deficit of the liver and brain may predispose ones to CTLN-2. Here, we compared the energy-driving tricarboxylic acid (TCA) cycle and fatty acid β-oxidation cycle between 22 citrin-deficient children (age, 3-13years) with normal liver functions and 37 healthy controls (age, 5-13years). TCA cycle analysis showed that basal plasma citrate and α-ketoglutarate levels were significantly higher in the affected than the control group (p<0.01). Conversely, basal plasma fumarate and malate levels were significantly lower than those for the control (p<0.001). The plasma level of 3-OH-butyrate derived from fatty acid β-oxidation was significantly higher in the affected group (p<0.01). Ten patients underwent sodium pyruvate therapy. However, this therapy did not correct or attenuate such deviations in both cycles. Sodium pyruvate therapy significantly increased fasting insulin secretion (p<0.01); the fasting sugar level remained unchanged. Our results suggest that citrin-deficient children show considerable deviations of TCA cycle metabolite profiles that are resistant to sodium pyruvate treatment. Thus, long-standing and considerable TCA cycle dysfunction might be a pivotal metabolic background of CTLN-2 development.