Focal hyperplastic hepatocellular nodules in hepatic venous outflow obstruction: a clinicopathological study of four patients and 24 nodules

AIMS: In hepatic venous outflow obstruction (Budd-Chiari syndrome), focal hepatocellular nodules are occasionally discovered showing variable morphology. These could be interpreted either as neoplastic (adenoma), regenerative (large regenerative nodule) or reactive to abnormal vasculature (focal nodular hyperplasia). The aim of this study was to investigate their histogenesis and to determine their morphological characteristics in order to provide diagnostic criteria. MATERIAL AND METHODS: Twenty-four hepatocellular nodules were studied, which were found in three explanted livers and in one additional autopsied liver from four patients with Budd-Chiari syndrome. As controls, we employed three explanted livers without nodules from patients who also suffered from Budd-Chiari syndrome. We attempted to classify the nodules morphologically as either adenoma-like, large regenerative nodule or focal nodular hyperplasia-like, using criteria from the literature. RESULTS: Out of the four cases, we observed two nodules in each of two livers, five in the third one and up to 15 in the remaining one. The size of the nodules ranged from 4 to 25 mm. Eleven nodules could be categorized as large regenerative nodules (two of them with a central scar), seven as focal nodular hyperplasia-like and six as adenoma-like. Some large regenerative nodules showed proliferated arteries with muscular hyperplasia similar to that seen in focal nodular hyperplasia. In the individual livers we could find nodules of various categories. Patchy or diffuse monoacinar regeneration was seen in most cases (six out of seven cases) in the macroscopically non-nodular liver parenchyma. In addition, thrombotic obstruction of portal vein branches was present in all except one of the nodular cases, but in none of the controls. Thus, it appears that portal venous obstructions are frequently, but not invariably associated with the development of nodules. CONCLUSIONS: The hepatocellular nodules seen in livers from patients with Budd-Chiari syndrome share morphological characteristics with large regenerative nodules, focal nodular hyperplasia and hepatocellular adenomas. Their multiplicity, the existence of mixed lesions, the frequent hepatocellular regenerative background as well as the frequently associated portal venous obstructions suggest that these nodules are regenerative in nature and conditioned by an uneven blood perfusion throughout the liver. In their differential diagnosis, the clinicopathological context in which they occur is of paramount importance and should allow recognition that those resembling adenomas may not be true neoplasms.     

An intravital microscopic study of the hepatic microcirculation in cirrhotic mice models: relationship between fibrosis and angiogenesis

This intravital fluorescence microscopy (IVFM) study validates cirrhotic mice models and describes the different intrahepatic alterations and the role of angiogenesis in the liver during genesis of cirrhosis. Cirrhosis was induced by subcutaneous injection of carbon tetrachloride (CCl₄) and by common bile duct ligation (CBDL) in mice. Diameters of sinusoids, portal venules (PV), central venules (CV) and shunts were measured at different time points by IVFM. Thereafter, liver samples were taken for sirius red, CD31, Ki67, vascular endothelial growth factor (VEGF) and α‐smooth muscle actin (α‐SMA) evaluation by immunohistochemistry (IHC). In parallel with fibrogenesis, hepatic microcirculation was markedly disturbed in CCl₄ and CBDL mice with a significant decrease in sinusoidal diameter compared to control mice. In CCl₄ mice, CV were enlarged, with marked sinusoidal‐free spaces around CV. In contrast, PV were enlarged in CBDL mice and bile lakes were observed. In both mice models, intrahepatic shunts developed gradually after induction. During genesis of cirrhosis using CD31 IHC we observed a progressive increase in the number of blood vessels within the fibrotic septa area and a progressively increase in staining by Ki67, VEGF and α‐SMA of endothelial cells, hepatocytes and hepatic stellate cells respectively. In vivo study of the hepatic microcirculation demonstrated a totally disturbed intrahepatic architecture, with narrowing of sinusoids in both cirrhotic mice models. The diameters of CV and PV increased and large shunts, bypassing the sinusoids, were seen after both CCl₄ and CBDL induction. Thus present study shows that there is angiogenesis in the liver during cirrhogenesis, and this is probably due partially to an increased production of VEGF.     

Aberrant expressions of aquaporin-1 in association with capillarized sinusoidal endothelial cells in cirrhotic rat liver

Aquaporins (AQPs) are key regulators of water channels across the cell cytoplasm. Little is known about AQP localization and changes in the hepatic microvascular system. This study aimed to clarify the localization of AQP-1 in the microvessels in normal and cirrhotic rat liver. To establish a rat cirrhosis model, thioacetamide (TAA) was injected for 24 weeks. AQP-1 in liver specimens was examined by immunohistochemistry (IHC), Western blotting, and immunoelectron microscopy (IEM). IHC revealed that AQP-1 was localized in hepatic sinusoids, especially on the liver sinusoidal endothelial cells (LSECs), predominantly in zone 1 in control rats, whereas AQP-1 immunoreactivity was increased on LSECs in central portions of regenerative nodules in cirrhotic rats, and was expressed especially strongly on the outer side of the duplicated liver cell cords. IEM demonstrated that, in control livers, AQP-1 was mainly expressed on the plasma membrane of LSECs in zone 1. In cirrhotic livers, many immunogold particles showing the presence of AQP-1 were seen on the LSECs in central portions of regenerative nodules, and the number was significantly greater than that in zone 3 of control liver. Protein levels of AQP-1 examined by Western blot were almost the same in the cirrhotic liver and control liver. AQP-1 immunoreactivities were aberrantly expressed on LSECs in central portions of regenerative nodule (CPRN) of cirrhotic liver, which may be associated with capillarization of LSECs and remodeling in this region.     

Reparative egeneration of liver with experimentally induced cirrhosis

Summary Cirrhosis of the liver, accompanied by ascites, was induced in rabbits by subcutaneous administration of carbon tetrachloride, and one-half of the liver was subsequently removed. A marked reduction in the amount of connective tissue, with the structure of the liver approaching normal, was observed during regeneration of the cirrhotic liver. The weight of the liver was restored to normal.Animals with experimentally induced cirrhosis of the liver, and not subjected to partial resection, perished. At various stages of the regenerative process, biochemical analysis of liver tissue, blood, and bile were carried out. Some of the biochemical indices became normal, whereas the glycogen, fatty acid, and cholesterol content of the liver was not restored to the normal level even by the end of the month. After excision of one-half of the cirrhotic liver, regeneration of hepatic parenchyma is evidently greater than the connective tissue proliferation.(Presented by Active Member AMN SSSR, N. N. Zhukov-Berezhnikov) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 51, No. 1, pp. 74–79, January, 1961     

Analyzing the human liver vascular architecture by combining vascular corrosion casting and micro‐CT scanning: a feasibility study

Although a full understanding of the hepatic circulation is one of the keys to successfully perform liver surgery and to elucidate liver pathology, relatively little is known about the functional organization of the liver vasculature. Therefore, we materialized and visualized the human hepatic vasculature at different scales, and performed a morphological analysis by combining vascular corrosion casting with novel micro‐computer tomography (CT) and image analysis techniques. A human liver vascular corrosion cast was obtained by simultaneous resin injection in the hepatic artery (HA) and portal vein (PV). A high resolution (110 μm) micro‐CT scan of the total cast allowed gathering detailed macrovascular data. Subsequently, a mesocirculation sample (starting at generation 5; 88 × 68 × 80 mm³) and a microcirculation sample (terminal vessels including sinusoids; 2.0 × 1.5 × 1.7 mm³) were dissected and imaged at a 71‐μm and 2.6‐μm resolution, respectively. Segmentations and 3D reconstructions allowed quantifying the macro‐ and mesoscale branching topology, and geometrical features of HA, PV and hepatic venous trees up to 13 generations (radii ranging from 13.2 mm to 80 μm; lengths from 74.4 mm to 0.74 mm), as well as microvascular characteristics (mean sinusoidal radius of 6.63 μm). Combining corrosion casting and micro‐CT imaging allows quantifying the branching topology and geometrical features of hepatic trees using a multiscale approach from the macro‐ down to the microcirculation. This may lead to novel insights into liver circulation, such as internal blood flow distributions and anatomical consequences of pathologies (e.g. cirrhosis).     

CHOP‐mediated hepcidin suppression modulates hepatic iron load

The liver is the central regulator of iron metabolism and accordingly, chronic liver diseases often lead to systemic iron overload due to diminished expression of the iron‐regulatory hormone hepcidin. To study the largely unknown regulation of iron metabolism in the context of hepatic disease, we used two established models of chronic liver injury, ie repeated carbon tetrachloride (CCl₄) or thioacetamide (TAA) injections. To determine the impact of CCAAT/enhancer‐binding protein (C/EBP)‐homologous protein (CHOP) on hepcidin production, the effect of a single TAA injection was determined in wild‐type and CHOP knockout mice. Furthermore, CHOP and hepcidin expression was assessed in control subjects and patients with alcoholic liver disease. Both chronic injury models developed a distinct iron overload in macrophages. TAA‐, but not CCl₄‐ injected mice displayed additional iron accumulation in hepatocytes, resulting in a significant hepatic and systemic iron overload which was due to suppressed hepcidin levels. C/EBPα signalling, a known hepcidin inducer, was markedly inhibited in TAA mice, due to lower C/EBPα levels and overexpression of CHOP, a C/EBPα inhibitor. A single TAA injection resulted in a long‐lasting (> 6 days) suppression of hepcidin levels and CHOP knockouts (compared to wild‐types) displayed significantly attenuated hepcidin down‐regulation in response to acute TAA administration. CHOP mRNA levels increased 5‐fold in alcoholic liver disease patients versus controls (p < 0.005) and negatively correlated with hepcidin expression. Our results establish CHOP as an important regulator of hepatic hepcidin expression in chronic liver disease. The differences in iron metabolism between the two widely used fibrosis models likely reflect the differential regulation of hepcidin expression in human liver disease. Copyright © 2013 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Is rat liver affected by non-alcoholic steatosis more susceptible to the acute toxic effect of thioacetamide?

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic condition of the liver in the western world. There is only little evidence about altered sensitivity of steatotic liver to acute toxic injury. The aim of this project was to test whether hepatic steatosis sensitizes rat liver to acute toxic injury induced by thioacetamide (TAA). Male Sprague-Dawley rats were fed ad libitum a standard pelleted diet (ST-1, 10% energy fat) and high-fat gelled diet (HFGD, 71% energy fat) for 6 weeks and then TAA was applied intraperitoneally in one dose of 100 mg/kg. Animals were sacrificed in 24-, 48- and 72-h interval after TAA administration. We assessed the serum biochemistry, the hepatic reduced glutathione, thiobarbituric acid reactive substances, cytokine concentration, the respiration of isolated liver mitochondria and histopathological samples (H+E, Sudan III, bromodeoxyuridine [BrdU] incorporation). Activities of alanine aminotransferase, aspartate aminotransferase and alkaline phosphatase and concentration of serum bilirubin were significantly higher in HFGD groups after application of TAA, compared to ST-1. There were no differences in activities of respiratory complexes I and II. Serum tumour necrosis factor alpha at 24 and 48 h, liver tissue interleukin-6 at 72 h and transforming growth factor β1 at 24 and 48 h were elevated in TAA-administrated rats fed with HFGD, but not ST-1. TAA-induced centrilobular necrosis and subsequent regenerative response of the liver were higher in HFGD-fed rats in comparison with ST-1. Liver affected by NAFLD, compared to non-steatotic liver, is more sensitive to toxic effect of TAA.     

Transplanted hepatocytes engraft, survive, and proliferate in the liver of rats with carbon tetrachloride-induced cirrhosis

Repopulation of the cirrhotic liver with disease-resistant hepatocytes could offer novel therapies, as well as systems for biological studies. Establishing whether transplanted hepatocytes can engraft, survive, and proliferate in the cirrhotic liver is a critical demonstration. Dipeptidyl peptidase IV-deficient F344 rats were used to localize transplanted hepatocytes isolated from the liver of syngeneic normal F344 rats. Cirrhosis was induced by administration of carbon tetrachloride with phenobarbitone and these drugs were withdrawn prior to cell transplantation. Cirrhotic rats showed characteristic hepatic histology, as well as significant portosystemic shunting. When hepatocytes were transplanted via the spleen, cells were distributed immediately in periportal areas, fibrous septa, and regenerative nodules of the cirrhotic liver. Although some transplanted cells translocated into pulmonary capillaries, this was not deleterious. At 1 week, transplanted cells were fully integrated in the liver parenchyma, along with expression of glucose-6-phosphatase and glycogen as reporters of hepatic function. Transplanted cells proliferated in the liver of cirrhotic animals and survived indefinitely. At 1 year, transplanted hepatocytes formed large clusters containing several-fold more cells than normal control animals, which was in agreement with increased cell turnover in the cirrhotic rat liver. The findings indicate that the cirrhotic liver can be repopulated with functionally intact hepatocytes that are capable of proliferating. Liver repopulation using disease-resistant hepatocytes will be applicable in chronic conditions, such as viral hepatitis or Wilson's disease.     

Liver Perfusion in Sepsis,Septic Shock,and Multiorgan Failure

Sepsis causes significant alterations in the hepatic macro‐ and microcirculation. Diverging views exist on global hepatic blood flow during experimental sepsis because of the large variety in animal and sepsis models. Fluid‐resuscitated clinical sepsis is characterized by ongoing liver ischemia due to a defective oxygen extraction despite enhanced perfusion. The effects of vasoactive agents on the hepatosplanchnic circulation are variable, mostly anecdotal, and depend on baseline perfusion, time of drug administration, and use of concomitant medication. Microvascular blood flow disturbances are thought to play a pivotal role in the development of sepsis‐induced multiorgan failure. Redistribution of intrahepatic blood flow in concert with a complex interplay between sinusoidal endothelial cells, liver macrophages, and passing leukocytes lead to a decreased perfusion and blood flow velocity in the liver sinusoids. Activation and dysfunction of the endothelial cell barrier with subsequent invasion of neutrophils and formation of microthrombi further enhance liver tissue ischemia and damage. Substances that regulate (micro)vascular tone, such as nitric oxide, endothelin‐1, and carbon monoxide, are highly active during sepsis. Possible interactions between these mediators are not well understood, and their therapeutic manipulation produces equivocal or disappointing results. Whether and how standard resuscitation therapy influences the hepatic microvascular response to sepsis is unknown. Indirect evidence supports the concept that improving the microcirculation may prevent or ameliorate sepsis‐induced organ failure. Anat Rec, 291:714–720, 2008. © 2008 Wiley‐Liss, Inc.     

Hepatic stellate cells are activated around central scars of focal nodular hyperplasia of the liver--a potential mechanism of central scar formation

Focal nodular hyperplasia of the liver is typically accompanied by a central scar, but cases that lack the central scar are occasionally encountered. This study was performed to clarify the mechanism of the central scar formation in focal nodular hyperplasia. Immunohistochemical analysis was performed for liver sections of focal nodular hyperplasia with and without a central scar. For comparison, liver specimens of focal nodular hyperplasia-like nodules and nodular regenerative hyperplasia were used. Immunostaining showed that activated hepatic stellate cells, as determined by alpha-smooth muscle actin expression, were invariably observed in all cases of focal nodular hyperplasia with a central scar, whereas focal nodular hyperplasia without a central scar and nodular regenerative hyperplasia lacked hepatic stellate cell activation. Hepatic stellate cell activation in focal nodular hyperplasia with a central scar was accompanied by the expression of 8-hydroxy-2'-deoxyguanosine and inducible nitric oxide synthase in the liver. Expression of 8-hydroxy-2'-deoxyguanosine and inducible nitric oxide synthase was rarely seen in focal nodular hyperplasia without a central scar, focal nodular hyperplasia-like nodules, or nodular regenerative hyperplasia. Overexpression of vascular endothelial growth factor was also observed in focal nodular hyperplasia with a central scar. These results suggest that the central part of focal nodular hyperplasia suffers from hyperoxic conditions due to arterial hyperperfusion; and the resultant oxidative stress may activate hepatic stellate cells, leading to central scar formation. In addition, vascular endothelial growth factor may contribute to the proliferation of abnormal vessels as an angiogenic inducer.     

Transforming growth factors beta 1 and alpha in chronic liver disease. Effects of interferon alfa therapy

BACKGROUND. Cirrhosis is a diffuse process of hepatic fibrosis and regenerative nodule formation of unknown pathogenesis. Transforming growth factor (TGF) beta 1 induces the production of extracellular matrix proteins by liver cells and has been implicated in the pathogenesis of hepatic fibrosis in laboratory animals. TGF alpha is a hepatocyte mitogen that participates in liver regeneration. METHODS. Using Northern blot analysis, we studied the expression of TGF beta 1 messenger RNA (mRNA) in liver specimens from 42 patients with chronic hepatitis and cirrhosis and 12 subjects with either normal or fatty livers. The results were correlated with measurements of procollagen Type I mRNA in liver tissue, procollagen Type III peptide in serum, and the degree of histologic injury. We also investigated whether TGF alpha mRNA would be detectable in biopsy specimens of livers with proliferative activity. RESULTS. TGF beta 1 mRNA expression correlated closely with the expression of procollagen Type I mRNA (r = 0.94) and serum procollagen Type III peptide (r = 0.89) and with the histologic activity index (r = 0.73). All patients with increased fibrogenic activity (serum procollagen Type III peptide level, greater than 11.9 micrograms per liter) had increased levels of TGF beta 1 mRNA (2 to 14 times the levels in the control group or in patients with normal fibrogenic activity), and both TGF alpha and H3 histone (a marker of DNA synthesis) mRNAs were detectable in patients with regenerative nodules. Six of eight patients with hepatitis C treated with interferon alfa for one year had sustained clinical responses with normalization of serum procollagen Type III peptide and aminotransferase activity. All these patients had normal levels of TGF beta 1 mRNA in liver specimens obtained at the end of the year. CONCLUSIONS. TGF beta 1 may have an important role in the pathogenesis of fibrosis in patients with chronic liver disease, and TGF alpha expression may be associated with liver regeneration in these patients.     

肠源性内毒素血症对肝组织细胞间粘附分子-1表达的影响

目的:探讨肠源性内毒素血症对肝组织细胞间粘附分子-1(ICAM-1)表达的影响。方法:采用Western blot 的方法检测硫代乙酰胺(TAA)诱导的肠源性内毒素血症大鼠肝组织中ICAM-1表达的变化。结果:ICAM-1的分子量为95 kD,正常对照组与注射TAA 6 h组ICAM-1的表达很弱,而在注射TAA 12 h以后的表达有增强,且与血浆内毒素水平及反映肝损伤程度的ALT活性变化相一致。结论:肠源性内毒素血症可诱导肝组织中ICAM-1表达的上调,后者与肝损伤程度相一致。     

Sinusoid development and morphogenesis may be stimulated by VEGF‐Flk‐1 signaling during fetal mouse liver development

Early morphogenesis of hepatic sinusoids was histochemically and experimentally analyzed, and the importance of VEGF‐Flk‐1 signaling in the vascular development was examined during murine liver organogenesis. FITC‐gelatin injection experiments into young murine fetuses demonstrated that all primitive sinusoidal structures were confluent with portal and central veins, suggesting that hepatic vessel development may occur via angiogenesis. At 12.5–14.5 days of gestation, VEGF receptors designated Flk‐1, especially their mature form, were highly expressed in endothelial cells of primitive sinusoidal structures and highly phosphorylated on their tyrosine residues. At the same time, VEGF was also detected in hepatoblasts/hepatocytes, hemopoietic cells, and megakaryocytes of the whole liver parenchyma. Furthermore, the addition of VEGF to E12.5 liver cell cultures significantly induced the growth and branching morphogenesis of sinusoidal endothelial cells. Therefore, VEGF‐Flk‐1 signaling may play an important role in the growth and morphogenesis of primitive sinusoids during fetal liver development. Developmental Dynamics 239:386–397, 2010. © 2009 Wiley‐Liss, Inc.     

Iron-containing nodules of cirrhosis

In the absence of genetic hemochromatosis and systemic hemosiderosis, patients with cirrhosis can accumulate focal iron within regenerative or dysplastic hepatic nodules, commonly referred to as 'siderotic nodules'. Siderotic dysplastic nodules are premalignant lesions while siderotic regenerative nodules are a marker for severe viral or alcoholic cirrhosis. The relationship of hepatic iron deposition to hepatic cirrhosis and neoplasia has not been fully clarified. This article will review the current literature regarding selective iron accumulation in siderotic nodules in chronic liver disease, followed by a discussion of current MR imaging techniques for detection and characterization of these nodules.     

Adipose tissue derived stromal stem cell therapy in murine ConA‐derived hepatitis is dependent on myeloid‐lineage and CD4+ T‐cell suppression

Mesenchymal stromal stem cells (MSCs) are an attractive therapeutic model for regenerative medicine due to their pluripotency. MSCs are used as a treatment for several inflammatory diseases, including hepatitis. However, the detailed immunopathological impact of MSC treatment on liver disease, particularly for adipose tissue derived stromal stem cells (ADSCs), has not been described. Here, we investigated the immuno‐modulatory effect of ADSCs on hepatitis using an acute ConA C57BL/6 murine hepatitis model. i.v. administration of ADSCs simultaneously or 3 h post injection prevented and treated ConA‐induced hepatitis. Immunohistochemical analysis revealed higher numbers of CD11b⁺, Gr‐1⁺, and F4/80⁺ cells in the liver of ConA‐induced hepatitis mice was ameliorated after the administration of ADSCs. Hepatic expression of genes affected by ADSC administration indicated tissue regeneration‐related biological processes, affecting myeloid‐lineage immune‐mediating Gr‐1⁺ and CD11b⁺ cells. Pathway analysis of the genes expressed in ADSC‐treated hepatic inflammatory cells revealed the possible involvement of T cells and macrophages. TNF‐α and IFN‐γ expression was downregulated in hepatic CD4⁺ T cells isolated from hepatitis livers co‐cultured with ADSCs. Thus, the immunosuppressive effect of ADSCs in a C57BL/6 murine ConA hepatitis model was dependent primarily on the suppression of myeloid‐lineage cells and, in part, of CD4⁺ T cells.     

骨髓间充质干细胞移植修复二乙基亚硝胺诱导的肝纤维化

背景：研究表明间充质干细胞能够改善肝纤维化。 目的：观察间充质干细胞对二乙基亚硝胺诱导的大鼠慢性肝损伤模型中对纤维化的作用。 方法：20只雌性Wistar大鼠由二乙基亚硝胺诱导致慢性肝损伤模型后,随机等分为2组,间充质干细胞组(n=10)在第4,8,12,16周时尾静脉注射雄性大鼠来源的间充质干细胞(1×10⁹ L^-1),模型组注射等量的生理盐水。 结果与结论：慢性肝损伤20周后,Y染色体仅能在间充质干细胞组中检测出,说明间充质干细胞被成功移植并存活。MRI显示在间充质干细胞组中有大量的增生性结节。与模型组相比,间充质干细胞组中的结节数、纤维化评分、α-平滑肌肌动蛋白、胶原面积均明显增高(P < 0.05)。表明体循环中的间充质干细胞可以导致其植入肝脏组织,并且在由二乙基亚硝胺诱导的大鼠慢性肝损伤模型中促进了肝纤维化。     

Cerebrovascular MRI: a review of state‐of‐the‐art approaches,methods and techniques

Cerebrovascular imaging is of great interest in the understanding of neurological disease. MRI is a non‐invasive technology that can visualize and provide information on: (i) the structure of major blood vessels; (ii) the blood flow velocity in these vessels; and (iii) the microcirculation, including the assessment of brain perfusion. Although other medical imaging modalities can also interrogate the cerebrovascular system, MR provides a comprehensive assessment, as it can acquire many different structural and functional image contrasts whilst maintaining a high level of patient comfort and acceptance. The extent of examination is limited only by the practicalities of patient tolerance or clinical scheduling limitations. Currently, MRI methods can provide a range of metrics related to the cerebral vasculature, including: (i) major vessel anatomy via time‐of‐flight and contrast‐enhanced imaging; (ii) blood flow velocity via phase contrast imaging; (iii) major vessel anatomy and tissue perfusion via arterial spin labeling and dynamic bolus passage approaches; and (iv) venography via susceptibility‐based imaging. When designing an MRI protocol for patients with suspected cerebral vascular abnormalities, it is appropriate to have a complete understanding of when to use each of the available techniques in the ‘MR angiography toolkit’. In this review article, we: (i) overview the relevant anatomy, common pathologies and alternative imaging modalities; (ii) describe the physical principles and implementations of the above listed methods; (iii) provide guidance on the selection of acquisition parameters; and (iv) describe the existing and potential applications of MRI to the cerebral vasculature and diseases. The focus of this review is on obtaining an understanding through the application of advanced MRI methodology of both normal and abnormal blood flow in the cerebrovascular arteries, capillaries and veins. Copyright © 2015 John Wiley & Sons, Ltd.     

Inhibition of Vascular Endothelial Growth Factor Receptor Decreases Regenerative Angiogenesis in Axolotls

Angiogenesis is crucial for tissue growth and repair in mammals, and is chiefly regulated by vascular endothelial growth factor (VEGF) signaling. We evaluated the effect of chemical inhibition of VEGF receptor signaling in animals with superior regenerative ability, axolotl salamanders, to determine the impact on vascularization and regenerative outgrowth. Following tail amputation, treated animals (100 nM PTK787) and controls were examined microscopically and measured over the month‐long period of regeneration. Treatment with VEGFR inhibitor decreased regenerative angiogenesis; drug‐treated animals had lower vascular densities in the regenerating tail than untreated animals. This decrease in neovascularization, however, was not associated with a decrease in regenerative outgrowth or with morphological abnormalities in the regrown tail. Avascular but otherwise anatomically normal regenerative outgrowth over 1 mm beyond the amputation plane was observed. The results suggest that in this highly regenerative species, significant early tissue regeneration is possible in the absence of a well‐developed vasculature. This research sets the groundwork for establishing a system for the chemical manipulation of angiogenesis within the highly regenerative axolotl model, contributing to a better understanding of the role of the microvasculature within strongly proliferative yet well‐regulated environments. Anat Rec, 300:2273–2280, 2017. © 2017 Wiley Periodicals, Inc.     

Liver metallothionein expression in thioacetamide-intoxicated rats

Metallothioneins (MT), a group of ubiquitous low molecular weight proteins, implicated primarily in metal ion detoxification, are known to be expressed during hepatocellular proliferation after partial hepatectomy in rats. In the present study, we investigated the expression of MT in a rat model of liver injury and regeneration, induced by intraperitoneal administration of thioacetamide (TAA). The animals were killed at 0, 12, 24, 36, 48, 60, 72, 84, 96, 108 and 120 hours after TAA administration. The rate of tritiated thymidine incorporation into hepatic DNA, the enzymatic activity of thymidine kinase, and the assessment of the mitotic index in hepatocytes were used as indices of liver regeneration. Liver MTs were detected immunohistochemically. TAA administration caused severe hepatic injury, followed by regeneration. MT expression became prominent in hepatocytes as early as 12 hours post-TAA administration. At 24 and 36 hours post-TAA administration intense nuclear and cytoplasmic staining of hepatocytes was found in the vicinity of necrotic areas. The maximal nuclear and cytoplasmic MT expression coincides with the peak of hepatocyte proliferative capacity, occurring at 48 and 60 hours post-TAA administration. MT expression correlated positively with the Zn content of liver tissue, but negatively with serum one, at the time of maximum hepatocyte proliferative capacity. This study suggests that MT participates in hepatocyte replication after toxin-induced liver injury.     

Different hepatic vascular response to noradrenaline and histamine between guinea‐pig and rat

Aim: Hepatic xenotransplantation from guinea‐pig to rat has not been established. This failure is partly ascribed to differences in hepatic vascular characteristics between two species. However, the differences in hepatic vascular resistance distribution and responses to vasoconstrictors are not known. The present study was designed to determine basal levels of segmental vascular resistances and the responses to histamine and noradrenaline in isolated guinea‐pig and rat livers. Methods: The livers were haemoperfused (Hct 8.3%) via the portal vein at a constant flow. The sinusoidal pressure was measured by the double occlusion pressure, and was used to determine the pre‐ (R_pre) and post‐sinusoidal (R_post) resistances. Results: There was no significant difference in basal total hepatic vascular resistance (R_t) between two species, whereas R_pre in rat (69% of R_t) was significantly greater than that in guinea‐pig (61% of R_t). The responses to noradrenaline were similar; R_pre increased in a greater magnitude than R_post, and liver weight was reduced. However, the noradrenaline‐induced increase in R_t was greater in rats than in guinea‐pigs. In contrast, histamine increased predominantly R_post over R_pre, and increased liver weight in guinea‐pig, while it affected no haemodynamic variables in rat. Conclusion: There exist species differences in the hepatic vasculature between rat and guinea‐pig. Basal pre‐sinusoidal resistance in rat is greater than that in guinea‐pig. Although noradrenaline predominantly contracts pre‐sinusoidal vessels in both species, histamine causes predominant post‐sinusoidal vasoconstriction in guinea‐pig liver, while it has no vasoactive effects on rat liver.