[show abstract][hide abstract] ABSTRACT: The fibrinogen genes FGA, FGB and FGG show coordinated expression in hepatocytes. Understanding the underlying transcriptional regulation may elucidate how their tissue-specific expression is maintained and explain the high variability in fibrinogen blood levels. DNA methylation of CpG-poor gene promoters is dynamic with low methylation correlating with tissue-specific gene expression but its direct effect on gene regulation as well as implications of non-promoter CpG methylation are not clear. Here we compared methylation of CpG sites throughout the fibrinogen gene cluster in human cells and mouse and zebrafish tissues. We observed low DNA methylation of the CpG-poor fibrinogen promoters and of additional regulatory elements (the liver enhancers CNC12 and PFE2) in fibrinogen-expressing samples. In a gene reporter assay, CpG-methylation in the FGA promoter reduced promoter activity, suggesting a repressive function for DNA methylation in the fibrinogen locus. In mouse and zebrafish livers we measured reductions in DNA methylation around fibrinogen genes during development that were preceded by increased fibrinogen expression and tri-methylation of Histone3 lysine4 (H3K4me3) in fibrinogen promoters. Our data support a model where changes in hepatic transcription factor expression and histone modification provide the switch for increased fibrinogen gene expression in the developing liver which is followed by reduction of CpG methylation.
PLoS ONE 01/2013; 8(8):e73089. · 3.73 Impact Factor
[show abstract][hide abstract] ABSTRACT: To demonstrate that adenosine triphosphate (ATP), which provides a valuable biomarker for kidney viability in the context of donation after cardiac death (DCD) transplantation, can be detected by means of (31)P magnetic resonance spectroscopy (MRS) if kidneys are perfused with oxygenated hypothermic pulsatile perfusion (O(2)+HPP).
Porcine kidney perfusion was carried out using a home made, MR-compatible HPP-machine. Consequently, kidney perfusion could be performed continuously during magnetic resonance imaging and magnetic resonance spectroscopy recording. (31)P MR spectroscopy consisted of 3-dimensional chemical shift imaging (CSI), which allowed for the detection of ATP level in line. (31)P CSI was performed at 3 tesla in 44 min with a nominal voxel size of 6.1 cc.
(31)P CSI enabled the detection of renal ATP when pO(2) was equal to 100 kPa. With pO(2) of 20 kPa, only phosphomonoester, inorganic phosphate and nicotinamide adenine dinucleotide could be found. Semi-quantitative analysis showed that ATP level was 1.3 mM in normal kidney perfused with pO(2) of 100 kPa.
This combined technology may constitute a new advance in DCD organ diagnostics prior to transplantation, as it allows direct assessment of ATP concentration, which provides a reliable indicator for organ bioenergetics and viability. In this study, kidneys presenting no warm ischemia were tested in order to establish values in normal organs. The test could be easily integrated into the clinical environment and would not generate any additional delay into the transplantation clinical workflow.
MAGMA Magnetic Resonance Materials in Physics Biology and Medicine 05/2012; 25(5):391-9. · 1.86 Impact Factor
[show abstract][hide abstract] ABSTRACT: Baboons receiving xenogeneic livers from wild type and transgenic pigs survive less than 10 days. One of the major issues is the early development of profound thrombocytopenia that results in fatal hemorrhage. Histological examination of xenotransplanted livers has shown baboon platelet activation, phagocytosis and sequestration within the sinusoids. In order to study the mechanisms of platelet consumption in liver xenotransplantation, we have developed an in vitro system to examine the interaction between pig endothelial cells with baboon platelets and to thereby identify molecular mechanisms and therapies.
Fresh pig hepatocytes, liver sinusoidal and aortic endothelial cells were isolated by collagenase digestion of livers and processing of aortae from GTKO and Gal+ MGH-miniature swine. These primary cell cultures were then tested for the differential ability to induce baboon or pig platelet aggregation. Phagocytosis was evaluated by direct observation of CFSE labeled-platelets, which are incubated with endothelial cells under confocal light microscopy. Aurintricarboxylic acid (GpIb antagonist blocking interactions with von Willebrand factor/vWF), eptifibatide (Gp IIb/IIIa antagonist), and anti-Mac-1 Ab (anti-α(M)β(2) integrin Ab) were tested for the ability to inhibit phagocytosis.
None of the pig cells induced aggregation or phagocytosis of porcine platelets. However, pig hepatocytes, liver sinusoidal and aortic endothelial cells (GTKO and Gal+) all induced moderate aggregation of baboon platelets. Importantly, pig liver sinusoidal endothelial cells efficiently phagocytosed baboon platelets, while pig aortic endothelial cells and hepatocytes had minimal effects on platelet numbers. Anti-MAC-1 Ab, aurintricarboxylic acid or eptifibatide, significantly decreased baboon platelet phagocytosis by pig liver endothelial cells (P<0.01).
Although pig hepatocytes and aortic endothelial cells directly caused aggregation of baboon platelets, only pig liver endothelial cells efficiently phagocytosed baboon platelets. Blocking vWF and integrin adhesion pathways prevented both aggregation and phagocytosis.
PLoS ONE 01/2012; 7(10):e47273. · 3.73 Impact Factor
[show abstract][hide abstract] ABSTRACT: Cytokine administration is a potential therapy for acute liver failure by reducing inflammatory responses and favour hepatocyte regeneration. The aim of this study was to evaluate the role of interleukin-1 receptor antagonist (IL-1ra) during liver regeneration and to study the effect of a recombinant human IL-1ra on liver regeneration.
We performed 70%-hepatectomy in wild type (WT) mice, IL-1ra knock-out (KO) mice and in WT mice treated by anakinra. We analyzed liver regeneration at regular intervals by measuring the blood levels of cytokines, the hepatocyte proliferation by bromodeoxyuridin (BrdU) incorporation, proliferating cell nuclear antigen (PCNA) and Cyclin D1 expression. The effect of anakinra on hepatocyte proliferation was also tested in vitro using human hepatocytes.
At 24h and at 48 h after hepatectomy, IL-1ra KO mice had significantly higher levels of pro-inflammatory cytokines (IL-6, IL-1β and MCP-1) and a reduced and delayed hepatocyte proliferation measured by BrdU incorporation, PCNA and Cyclin D1 protein levels, when compared to WT mice. IGFBP-1 and C/EBPβ expression was significantly decreased in IL-1ra KO compared to WT mice. WT mice treated with anakinra showed significantly decreased levels of IL-6 and significantly higher hepatocyte proliferation at 24h compared to untreated WT mice. In vitro, primary human hepatocytes treated with anakinra showed significantly higher proliferation at 24h compared to hepatocytes without treatment.
IL1ra modulates the early phase of liver regeneration by decreasing the inflammatory stress and accelerating the entry of hepatocytes in proliferation. IL1ra might be a therapeutic target to improve hepatocyte proliferation.
PLoS ONE 01/2011; 6(9):e25442. · 3.73 Impact Factor
[show abstract][hide abstract] ABSTRACT: Polyclonal rabbit anti-thymocyte globulin (rATG) is widely used in solid organ transplantation (SOT) as induction therapy or to treat corticosteroid-resistant rejection. In vivo, the effect of rATG on natural killer (NK) cells has not been studied. These cells are of particular relevance after SOT because classical immunosuppressive drugs do not inhibit or even can activate NK cells. A cohort of 20 recipients at low immunological risk, that had been receiving rATG as induction therapy, was analyzed for receptor repertoire, cytotoxicity and capacity of NK cells to secrete IFN-γ before kidney transplantation and at different time points thereafter. NK cells expressed fewer killer-cell immunoglobulin-like receptors (KIR), fewer activating receptors NKG2D, but more inhibitory receptor NKG2A compatible with an immature phenotype in the first 6 months post transplantation. Both cytotoxicity of NK cells and the secretion of IFN-γ were preserved over time after transplantation.
[show abstract][hide abstract] ABSTRACT: Statins act by reducing hepatic cholesterol synthesis, thus stimulating uptake of serum cholesterol. Statin therapy modulates a number of genes involved in hepatic cholesterol homeostasis. These have rarely been analyzed simultaneously in the same experimental setting, with virtually no studies of primary human hepatocytes. This study analyzed the efficacy of rosuvastatin in the coordinated regulation of a number of genes implicated in cholesterol metabolism in primary human hepatocytes. Expression of five cholesterol-related genes were significantly upregulated, notably the Niemann-Pick C1 like 1 protein, for whom functional studies have been essentially limited to the intestine. Two genes were significantly downregulated, including sterol recognition element binding protein-1 gene that is implicated in control of hepatic lipogenesis. The results show the coordinated regulation of several genes implicated in hepatic cholesterol homeostasis and suggest therapeutic targets that could complement that clinical action of statins.
Pharmacogenetics and Genomics 07/2010; 20(7):455-8. · 3.61 Impact Factor
[show abstract][hide abstract] ABSTRACT: Pancreatic cancer is associated with a poor prognosis, and surgical resection remains the only chance for curative therapy. In the absence of metastatic disease, which would preclude resection, assessment of vascular invasion is an important parameter for determining resectability of pancreatic cancer. A frequent error is to misdiagnose an involved major vessel. Obviously, surgical exploration with pathological examination remains the "gold standard" in terms of evaluation of resectability, especially from the point of view of vascular involvement. However, current imaging modalities have improved and allow detection of vascular invasion with more accuracy. A venous resection in pancreatic cancer is a feasible technique and relatively reliable. Nevertheless, a survival benefit is not achieved by curative resection in patients with pancreatic cancer and vascular invasion. Although the discovery of an arterial invasion during the operation might require an aggressive management, discovery before the operation should be considered as a contraindication. Detection of vascular invasion remains one of the most important challenges in pancreatic surgery. The aim of this article is to provide a complete review of the different imaging modalities in the detection of vascular invasion in pancreatic cancer.
World Journal of Gastroenterology 02/2010; 16(7):818-31. · 2.55 Impact Factor
[show abstract][hide abstract] ABSTRACT: The expression of interleukin 7 receptor alpha(high) (IL-7Ralpha(high)) discriminates between activated CD25(+)CD45RO(+)CD4(+) T cells [IL-7Ralpha(high) and forkhead box P3-negative (FoxP3(-))] and regulatory T cells (IL-7Ralpha(low) and FoxP3(+)). The IL-7Ralpha(high)CD25(+)CD45RO(+)CD4(+)FoxP3(-) T cell population has been shown to be expanded in the blood and tissues of patients after kidney transplantation and to contain alloreactive T cells (activated T cells). In the present study, we analyzed the distribution of IL-7Ralpha(high)CD25(+)CD45RO(+)CD4(+)FoxP3(-) T cells in the blood of 53 patients after liver transplantation. The IL-7Ralpha(high)CD25(+)CD45RO(+)CD4(+)FoxP3(-) T cell population was significantly expanded (P < 0.0001) in stable transplant recipients versus healthy donors. However, the magnitude of the expansion was significantly higher (P < 0.0001) in liver transplant recipients with no hepatitis C virus (HCV) infection in comparison with those with a preexisting HCV infection. Interestingly, effective suppression of HCV viremia after antiviral therapy was associated with an increase in the IL-7Ralpha(high)CD25(+)CD45RO(+)CD4(+)FoxP3(-) T cell population to levels comparable to those of liver transplant recipients not infected with HCV. The present results indicate that (1) the IL-7Ralpha(high)CD25(+)CD45RO(+)CD4(+)FoxP3(-) T cell population is expanded after liver transplantation, (2) it is a valuable immunological marker for monitoring activated and potential alloreactive CD4 T cells in liver transplantation, and (3) a preexisting HCV infection negatively influences the expansion of this population in liver transplant recipients.
[show abstract][hide abstract] ABSTRACT: Acute pancreatitis is a potentially lethal inflammatory disease with an increased incidence and a decreased mortality rate. The main etiologies are biliary stones and alcohol abuse. The therapeutic approach consists of the elimination of the cause, the hemodynamic and respiratory supports and the treatment of the complications. Moreover, severe acute pancreatitis requires a collaboration between surgeons, radiologists, gastroenterologists and intensive care physicians. The administration of prophylactic antibiotics and the early oral nutritional support are still controversial. In summary, the anticipation in diagnosis, etiology, classification of the severity and early reanimation are needed for an optimal treatment of this complex disease.
[show abstract][hide abstract] ABSTRACT: Multipotent mesenchymal stromal cells (MSC) are currently investigated clinically as cellular therapy for a variety of diseases. Differentiation of MSC toward endodermal lineages, including hepatocytes and their therapeutic effect on fibrosis has been described but remains controversial. Recent evidence attributed a fibrotic potential to MSC. As differentiation potential might be dependent of donor age, we studied MSC derived from adult and pediatric human bone marrow and their potential to differentiate into hepatocytes or myofibroblasts in vitro and in vivo. Following characterization, expanded adult and pediatric MSC were co-cultured with a human hepatoma cell line, Huh-7, in a hepatogenic differentiation medium containing Hepatocyte growth factor, Fibroblast growth factor 4 and oncostatin M. In vivo, MSC were transplanted into spleen or liver of NOD/SCID mice undergoing partial hepatectomy and retrorsine treatment. Expression of mesenchymal and hepatic markers was analyzed by RT-PCR, Western blot and immunohistochemistry. In vitro, adult and pediatric MSC expressed characteristic surface antigens of MSC. Expansion capacity of pediatric MSC was significantly higher when compared to adult MSC. In co-culture with Huh-7 cells in hepatogenic differentiation medium, albumin expression was more frequently detected in pediatric MSC (5/8 experiments) when compared to adult MSC (2/10 experiments). However, in such condition pediatric MSC expressed alpha smooth muscle more strongly than adult MSC. Stable engraftment in the liver was not achieved after intrasplenic injection of pediatric or adult MSC. After intrahepatic injection, MSC permanently remained in liver tissue, kept a mesenchymal morphology and expressed vimentin and alpha smooth muscle actin, but no hepatic markers. Further, MSC localization merges with collagen deposition in transplanted liver and no difference was observed using adult or pediatric MSC. In conclusion, when transplanted into an injured or regenerating liver, MSC differentiated into myofibroblasts with development of fibrous tissue, regardless of donor age. These results indicate that MSC in certain circumstances might be harmful due to their fibrogenic potential and this should be considered before potential use of MSC for cell therapy.
PLoS ONE 02/2009; 4(8):e6657. · 3.73 Impact Factor
[show abstract][hide abstract] ABSTRACT: Cytomegalovirus (CMV) infection is the most common viral complication after solid organ transplantation (SOT). Whilst current immunosuppression is known to impair antiviral-specific T-cell immunity in SOT, a potential role for natural killer (NK) cells not affected by immunosuppressive therapy remains to be determined. To address this, we compared the genotype of the NK immunoglobulin-like receptor (KIR) genes and their HLA cognate ligands to the rate of CMV infection in 196 kidney transplant recipients. We have shown that the absence of the HLA-C ligand for inhibitory KIR and the presence of activating KIR genes in the recipients were both associated with a lower rate of CMV infection after transplantation. In a cohort of 17 recipients with acute CMV infection, NK cells were phenotyped over a period of time after diagnosis by their expression profile of C-type lectin receptors and capacity to secrete IFN-gamma. The increased expression of the activating C-type lectin receptors NKG2C and NKG2D was paralleled by the decreased IFN-gamma secretion during the early phase of CMV infection. In conclusion, our findings suggest that KIR/HLA genotype and expression of NKG2C and NKG2D might play a significant role in regulating NK cell function and anti-CMV immunity after kidney transplantation.
American Journal of Transplantation 01/2009; 8(12):2674-83. · 6.19 Impact Factor
[show abstract][hide abstract] ABSTRACT: Phosphatase and tensin homolog (PTEN) is a regulator of phosphoinositide 3-kinase signaling and an important tumor suppressor mutated/deleted in human cancers. PTEN deletion in the liver leads to insulin resistance, steatosis, inflammation, and cancer. We recently demonstrated that unsaturated fatty acids trigger steatosis by down-regulating PTEN expression in hepatocytes via activation of a mammalian target of rapamycin (mTOR)/nuclear factor kappa B (NF-kappaB) complex, but the molecular mechanisms implicated in this process are still unknown. Here, we investigated potential genetic and epigenetic mechanisms activated by fatty acids leading to PTEN down-regulation. Our results indicate that unsaturated fatty acids down-regulate PTEN messenger RNA expression in hepatocytes through mechanisms unrelated to methylation of the PTEN promoter, histone deacetylase activities, or repression of the PTEN promoter activity. In contrast, unsaturated fatty acids up-regulate the expression of microRNA-21, which binds to PTEN messenger RNA 3'-untranslated region and induces its degradation. The promoter activity of microRNA-21 was increased by mTOR/NF-kappaB activation. Consistent with these data, microRNA-21 expression was increased in the livers of rats fed high-fat diets and in human liver biopsies of obese patients having diminished PTEN expression and steatosis. CONCLUSION: Unsaturated fatty acids inhibit PTEN expression in hepatocytes by up-regulating microRNA-21 synthesis via an mTOR/NF-kappaB-dependent mechanism. Aberrant up-regulation of microRNA-21 expression by excessive circulating levels of fatty acids exemplify a novel regulatory mechanism by which fatty acids affect PTEN expression and trigger liver disorders.
[show abstract][hide abstract] ABSTRACT: Previous studies have documented that the insulin-producing beta-cells of laboratory rodents are coupled by gap junction channels made solely of the connexin36 (Cx36) protein, and have shown that loss of this protein desynchronizes beta-cells, leading to secretory defects reminiscent of those observed in type 2 diabetes. Since human islets differ in several respects from those of laboratory rodents, we have now screened human pancreas, and islets isolated thereof, for expression of a variety of connexin genes, tested whether the cognate proteins form functional channels for islet cell exchanges, and assessed whether this expression changes with beta-cell function in islets of control and type 2 diabetics. Here, we show that (i) different connexin isoforms are differentially distributed in the exocrine and endocrine parts of the human pancreas; (ii) human islets express at the transcript level different connexin isoforms; (iii) the membrane of beta-cells harbors detectable levels of gap junctions made of Cx36; (iv) this protein is concentrated in lipid raft domains of the beta-cell membrane where it forms gap junctions; (v) Cx36 channels allow for the preferential exchange of cationic molecules between human beta-cells; (vi) the levels of Cx36 mRNA correlated with the expression of the insulin gene in the islets of both control and type 2 diabetics. The data show that Cx36 is a native protein of human pancreatic islets, which mediates the coupling of the insulin-producing beta-cells, and contributes to control beta-cell function by modulating gene expression.
Human Molecular Genetics 12/2008; 18(3):428-39. · 7.69 Impact Factor
[show abstract][hide abstract] ABSTRACT: Transplantation of in vitro generated islets or insulin-producing cells represents an attractive option to overcome organ shortage. The aim of this study was to isolate, expand, and characterize cells from human exocrine pancreas and analyze their potential to differentiate into beta cells.
Fibroblast-like cells growing out of human exocrine tissue were characterized by flow cytometry and by their capacity to differentiate into mesenchymal cell lineages. During cell expansion and after differentiation toward beta cells, expression of transcription factors of endocrine pancreatic progenitors was analyzed by reverse transcription polymerase chain reaction.
Cells emerged from 14/18 human pancreatic exocrine fractions and were expanded up to 40 population doublings. These cells displayed surface antigens similar to mesenchymal stem cells from bone marrow. A culture of these cells in adipogenic and chondrogenic differentiation media allowed differentiation into adipocyte- and chondrocyte-like cells. During expansion, cells expressed transcription factors implicated in islet development such as Isl1, Nkx2.2, Nkx6.1, nestin, Ngn3, Pdx1, and NeuroD. Activin A and hepatocyte growth factor induced an expression of insulin, glucagon, and glucokinase.
Proliferating cells with characteristics of mesenchymal stem cells and endocrine progenitors were isolated from exocrine tissue. Under specific conditions, these cells expressed little insulin. Human pancreatic exocrine tissue might thus be a source of endocrine cell progenitors.