Search PubMed⌕ Search

Biomedical subjects

E Wisse

Publications and source records attributed to E Wisse.

At least 37 records · Page 2Linked to original sources
PubMed1996

Centrolobular liver fibrosis in the hypercholesterolemic rabbit.

During a study on the development of atheromatous lesions in rabbits fed a diet with a low or high cholesterol supplement, we found a moderate to pronounced centrolobular liver fibrosis. This fibrosis developed in three stages. Early after supplementation of cholesterol, we observed increased immunoreactivity of collagen types I, III, and IV, and fibronectin, around central veins and in adjacent sinusoids. In the second stage, we observed further increase of collagen and fibronectin immunoreactivity, together with the appearance of alpha-smooth muscle actin (alpha-SM actin)-positive cells and anti-rabbit macrophage monoclonal antibody (RAM 11)-positive cells. In the third stage, we observed large numbers of alpha-SM actin-positive cells, together with heavy deposition of connective tissue proteins in pericentral sinusoids, in addition to focal atrophy of parenchymal cells. By transmission electron microscopy (TEM), fat-storing cells in the pericentral regions were shown to be enlarged, to lose their lipid-droplets, and to acquire dilated rough endoplasmic reticulum corresponding to an activated phenotype. Parenchymal cells were either normal or contained numerous small lipid-droplets. They sometimes were smaller and distorted. Northern hybridization performed on total RNA of whole liver showed an increased level of collagen alpha1(I), alpha1(III), and alpha1(IV) messenger RNA (mRNA) after 24 weeks of low dietary cholesterol supplementation. These data show enhanced expression of extracellular matrix proteins. We conclude that cholesterol overload induces pericentral liver fibrosis in rabbits. The diet clearly activates fat-storing cells to become fibrogenic effector cells. At present, we have no explanation why hypercholesterolemia induces phenotypic transition of fat-storing cells.

Actins↗
PubMed1996

The role of adhesion molecules in the recruitment of hepatic natural killer cells (pit cells) in rat liver.

Previous studies showed that blood large granular lymphocytes (LGL), which possess natural killer (NK) activity, develop within rat liver sinusoids into high-density (HD) and subsequently into low-density (LD) pit cells which show an increasing level and spectrum of tumor cytotoxicity. In this study, we investigated the role of adhesion molecules, such as CD2, CD11a, CD18, and CD54 in the recruitment of pit cells to the liver. Immunostaining for electron microscopy, and two color flow cytometry showed that most pit cells expressed CD2, CD11a, CD18, and CD54. After intravenous injections into rats with anti-CD2, anti-CD11a, and anti-CD18 antibodies, the number of pit cells per square millimeter in frozen sections of liver tissue decreased. Treatment of rats with zymosan increased the number of pit cells fivefold, whereas subsequent treatment with anti-adhesion-molecule antibodies resulted in approximately 60% lower number of pit cells. Anti-CD54, supposed to block CD54 expression on sinusoidal endothelial cells, also decreased the number of pit cells. The number of blood LGL was, however, not affected by these antibodies. These results indicate that blocking of CD2, CD11a, CD18, and CD54 antigens on blood LGL and/or liver endothelium decreased the number of pit cells in the liver. These adhesion molecules therefore play an important role in the recruitment of pit cells in the liver.

Animals↗
PubMed1996

Standardized mitotic counts in breast cancer. Evaluation of the method.

Twenty-one pathologists and technicians participated in a study evaluating the variation present in mitotic counts for prognostication of breast cancer. The participants counted the mitotic figures in 20 breast cancer samples from ten high power fields (mitotic activity index, MAI, giving the results in mitotic figures per 10 fields) and also made a correction for field size and area fraction of the neoplastic epithelium to get the standardized mitotic index (volume fraction corrected mitotic index, or M/VV index, giving the result in mitotic figures per square mm of neoplastic epithelium). The difference in variation between the two methods was not big, but the standardized mitotic index (SMI) showed consistently smaller variation among all participants and different subgroups. Experienced pathologists had the highest variation in mitotic counts, and specially trained technicians, the lowest. The efficiency of the mitotic counts in grading (the grading efficiency) was used to evaluate the mitotic counts. In groups without special training for mitotic counts the mean grading efficiency was lower (experienced and training pathologists both on average had the potential to grade 88% of the cases correctly) than in the group specially trained for the purpose (trained technicians had the potential to grade 95% of the cases correctly). Among the specially trained technicians, the grading efficiency was of the same magnitude as the grading efficiency achieved in determining the S-Phase fraction of cells from paraffin embedded breast cancers by flow cytometry in different laboratories. The results suggest that special training is helpful in making mitotic counts more reproducible, and that in trained hands, the mitotic counts give results comparable to more sophisticated methods of determining proliferative activity in breast cancer.

Breast Neoplasms↗
PubMed1996

Comparative atomic force and scanning electron microscopy: an investigation on fenestrated endothelial cells in vitro.

Rat liver sinusoidal endothelial cells (LEC) contain fenestrae, which are clustered in sieve plates. Fenestrae control the exchange of fluids, solutes and particles between the sinusoidal blood and the space of Disse, which at its back side is flanked by the microvillous surface of the parenchymal cells. The surface of LEC can optimally be imaged by by scanning electron microscopy (SEM), and SEM images can be used to study dynamic changes in fenestrae by comparing fixed specimens subjected to different experimental conditions. Unfortunately, the SEM allows only investigation of fixed, dried and coated specimens. Recently, the use of atomic force microscopy (AFM) was introduced for analysing the cell surface, independent of complicated preparations techniques. We used the AFM for the investigation of cultured LEC surfaces and the study of morphological changes of fenestrae. SEM served as a conventional reference. AFM images of LEC show structures that correlate well with SEM images. Dried-coated, dried-uncoated and wet-fixed LEC show a central bulging nucleus and flat fenestrated cellular processes. It was also possible to obtain height information which is not available in SEM. After treatment with ethanol or serotonin the diameters of fenestrae increased (+6%) and decreased (-15%), respectively. The same alterations of fenestrae could be distinguished by measuring AFM images of dried-coated, dried-uncoated and wet-fixed LEC. Comparison of dried-coated (SEM) and wet-fixed (AFM) fenestrae indicated a mean shrinkage of 20% in SEM preparations. In conclusion, high-resolution imaging with AFM of the cell surface of cultured LEC can be performed on dried-coated, dried-uncoated and wet-fixed LEC, which was hitherto only possible with fixed, dried and coated preparations in SEM and transmission electron microscopy (TEM).

Animals↗
PubMed1996

Microfilament-disrupting agent latrunculin A induces and increased number of fenestrae in rat liver sinusoidal endothelial cells: comparison with cytochalasin B.

This report describes the effect of the actin-disrupting marine toxin latrunculin A on the cytoskeleton and fenestrae of liver endothelial cells (LECs). Fluorescence microscopy and whole mount-transmission electron microscopic preparations of isolated, purified, and cultured LECs showed that latrunculin A, which sequesters actin monomers and depolymerizes actin filaments, caused profound changes in microfilament organization in LECs. Scanning electron microscopic preparations showed that latrunculin A almost doubles the number of fenestrae within 10 minutes, whereas the diameter is only slightly reduced. All new fenestrae possess the earlier described fenestrae-associated cytoskeleton ring. Cytochalasin B, which disrupts the network of actin filaments, principally by capping the fast growing end of actin filaments, produced comparable effects with regard to actin organization and the number and size of fenestrae. After 1 hour of treatment, an equal maximum number of fenestrae was observed for both agents. The effect of latrunculin A was obtained at concentrations about 100 times lower than cytochalasin B. Thus, two agents that alter the state of actin organization in LECs, albeit by different mechanisms, cause the doubling of the number of fenestrae within 10 to 30 minutes. This indicates that the state of assembly of the actin cytoskeleton is important in the numerical dynamics of LEC fenestrae and that the actin cytoskeleton of LECs is probably the main mechanical regulator for sieving between the sinusoidal blood and the parenchymal cells. Latrunculin A represents a new agent in the study of the de novo formation of fenestrae.

Actin Cytoskeleton↗
PubMed1996

Comparative scanning, transmission and atomic force microscopy of the microtubular cytoskeleton in fenestrated liver endothelial cells.

Endothelial fenestrae control the exchange of fluids, solutes and particles between the sinusoidal lumen and the microvillous surface of the parenchymal cells. Fenestrae have a critical dimension in the order of 150-200 nm, making it necessary to use microscopes with a resolution better than the light microscope. Comparative whole-mount preparations of isolated, purified and cultured rat liver sinusoidal endothelial cells (LEC) were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM). Examination of detergent-extracted LEC by SEM and TEM shows an integral cytoskeleton: sieve plates are delineated by a sieve plate-associated cytoskeleton ring and fenestrae by a fenestrae-associated cytoskeleton ring. By using microtubule altering agents we could demonstrate: (1) the architectural role of microtubules in arranging fenestrae, (2) the existence of a population of microtubules resistant against low temperature and colchicine, (3) the ability of LEC to shift the microtubule assembly-disassembly steady state under various conditions, (4) and the necessity of an intact microtubular cytoskeleton to support the increase in the number of fenestrae after cytochalasin B. Topographical examinations of AFM images revealed that sieve plates are delineated by elevated borders, probably projections of the underlying tubular cytoskeleton.

Animals↗
PubMed1995

Insulinlike growth factor-II/mannose 6-phosphate receptor is expressed on CCl4-exposed rat fat-storing cells and facilitates activation of latent transforming growth factor-beta in cocultures with sinusoidal endothelial cells.

Transforming growth factor beta (TGF-beta), a potent fibrogenic cytokine, is secreted in latent form. We examined which cell type in both normal and carbon tetrachloride (CCl4)-induced fibrotic rat liver bears surface type II IGF/mannose 6-phosphate (IGF-II/M6P) receptor, known to facilitate activation of TGF-beta. In addition, the role of the IGF-II/M6P receptor in activation of latent TGF-beta was investigated in a coculture system with sinusoidal endothelial cells. Northern hybridization analysis for IGF-II/M6P receptor messenger RNA (mRNA) was performed on total RNA of different isolated and purified liver cell types. In normal liver, cells expressed little IGF-II/M6P receptor mRNA. In fibrotic liver, we found significant expression only in fat-storing cells. The presence of IGF-II/M6P receptors was established by [125I]IGF-II binding assays on freshly isolated fat-storing cells from normal and CCl4-exposed rat livers. We found specific binding of [125I]IGF-II only on CCl4 exposed fat-storing cells. As determined by polyacrylamide gel electrophoresis after affinity labeling, the specific binding involved 220 kD type II IGF receptors. Scatchard analysis revealed the presence of 3,043 +/- 1,378 IGF-II/M6P high-affinity receptors/fat-storing cell, with a Kd of 387 = 165 pmol/L. With a mink lung epithelial cell (Mv1Lu) proliferation inhibition assay, inhibition of proliferation (a measure of active TGF-beta function) was determined using conditioned media of activated fat-storing cells, cocultures of fat-storing cells, and endothelial cells and pure endothelial cell cultures.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Experimental biliary fibrosis correlates with increased numbers of fat-storing and Kupffer cells, and portal endotoxemia.

In the present study, we have investigated the correlation between hepatic fibrosis in rats subjected to bile duct ligation, the numbers of Kupffer and fat-storing cells, and the level of endotoxin in both the portal and systemic circulation. The extent of hepatic fibrosis was measured by morphometry. Kupffer cells were identified by indirect immunoperoxidase staining using ED-2 anti-macrophage antibody. Fat-storing cells were stained with DE-B-5 anti-desmin antibody. Endotoxin levels were determined by the Limulus Lysate test. Following bile duct ligation, connective tissue septa rapidly developed in periportal areas. After 1 week, the volume density of connective tissue had increased from 0.6 +/- 0.1% in control animals to 3.8 +/- 1.1%. After 2 weeks, this volume increased to 19.9 +/- 1.3%, and after 3 weeks to 34.3% +/- 2.7%. The number of periportal fat-storing cells increased 2.8-fold during the first 2 weeks, whereas pericentral fat-storing cells increased only 1.7-fold. After 2 weeks, no further increase was observed. During the first week of bile duct ligation, the number of Kupffer cells increased nearly two-fold. Thereafter, no further increase was detected. In control rats, only two of ten rats showed low amounts of endotoxin in the portal blood. Portal endotoxemia increased with time after bile duct ligation. After 3 weeks, all rats were positive. The measured endotoxin levels were approximately 7 times higher than in control rats. We conclude that the development of fibrosis secondary to experimental bile duct ligation is accompanied by protal endotoxemia, and increases in the numbers of Kupffer and periportal fat-storing cells. We found a significant correlation between portal endotoxemia, the number of Kupffer and fat-storing cells, and the extent of fibrous septa, supporting the view that high endotoxemia levels coincide with Kupffer cell activation and fibrogenesis.

Adipocytes↗
PubMed1995

New observations on cytoskeleton and fenestrae in isolated rat liver sinusoidal endothelial cells.

Fenestrae control the exchange of fluids, dissolved compounds and small particles between the blood and the space of Disse, and are primarily limited at one side by parenchymal cells. We recently described a simple and rapid method for the isolation, purification and cultivation of rat liver sinusoidal endothelial cells. With regard to the purity and morphology of liver endothelial cells, a detailed microscopic study was performed. Purity and viability after selective adherence was 74 and 95%, respectively. Liver endothelial cell purity was further enhanced to about 95% during adherence and spreading on collagen after 8 h of culture. Liver endothelial cells isolated by this method provide a viable cell population, enabling the study of structure and function of these cells in vitro. We investigated the cytoskeleton associated with fenestrae and sieve plates of liver endothelial cells. Cultured cells were slightly fixed and treated with cytoskeleton extraction buffer containing 0.1% Triton. Whole mounts of extracted liver endothelial cells were prepared for scanning and transmission electron microscopy. Extracted liver endothelial cells show an integral, intricate cytoskeleton. Sieve plates and fenestrae are clearly delineated by cytoskeleton elements. Fenestrae are surrounded by a filamentous, fenestrae-associated cytoskeleton ring with an average filament thickness of 16 nm. Additionally, sieve plates are surrounded and delineated by microtubuli, which form a network together with additional branching cytoskeletal elements. Microtubuli are sometimes found delineating linear arrangements of fenestrae. In conclusion, liver endothelial cells possess a cytoskeleton, that defines and supports sieve plates and fenestrae. Fenestrae-associated cytoskeleton rings are involved in determining the size of fenestrae. The fenestrae-associated cytoskeleton therefore probably controls the important hepatic function of endothelial filtration.

Animals↗
PubMed1995

The role of Kupffer cells in the differentiation process of hepatic natural killer cells.

Pit cells, or hepatic natural killer (NK) cells, present in rat liver sinusoids, represent an organ-associated NK cell population, with a higher level of activation and a different morphology when compared with peripheral blood NK cells. These cells are the result of an influx of peripheral blood NK cells in the liver microenvironment, followed by an activation or differentiation process toward the highly activated phenotype. In this work we investigated the role of Kupffer cells in this differentiation process of NK cells in the liver sinusoids. In vivo elimination of Kupffer cells with the macrophage cytotoxic drug dichloromethylene diphosphonate induced a decrease in number of hepatic NK cells that paralleled that of Kupffer cells. This effect was further investigated in vitro. Kupffer cell-conditioned medium appeared to enhance the viability, tumor-cytotoxic activity, and adherence of hepatic NK cells to liver endothelial cells in vitro. We conclude therefore that Kupffer cells, present in the microenvironment of the liver sinusoids, play an essential role in the differentiation process of peripheral blood NK cells to the highly activated hepatic NK cell population.

Animals↗
PubMed1995

The number and distribution of hepatic natural killer cells (pit cells) in normal rat liver: an immunohistochemical study.

Pit cells are a unique population of cells in sinusoids and peripheral blood, which can be considered natural killer (NK) cells with large granular lymphocyte (LGL) morphology. The aim of this study was to investigate the use of the monoclonal antibody (MAb) 3.2.3 as a specific marker of rat pit cells to detect their number and distribution in the liver. The number of 3.2.3-positive cells was comparable to the number of LGL in liver low-density (LD) and high-density (HD) pit cell fractions and in blood lymphocytes (P > .05). Immunoelectron microscopy showed that nearly all LGL in hepatic LD and HD and in blood fractions were 3.2.3 positive. Using MAb 3.2.3 immunoperoxidase staining, the mean number of pit cells in liver frozen sections was determined to be 13.7 +/- 1.1/mm2. The number of pit cells was similar in the different liver lobes (P > .05). Reduced nicotinamide-adenine dinucleotide (NADH) oxidase histochemical staining, to visualize a portal to central vein gradient, combined with immunostaining was used to analyze the lobular distribution of pit cells. We found that 61.3% (17.1/mm2) of pit cells were in the periportal area and 38.7% (10.8/mm2) in the central area. We conclude that MAb 3.2.3 can be used as a specific marker of rat pit cells and therefore can be used to quantify rat pit cell number in various experimental models.

Animals↗
PubMed1995

Structure and dynamics of the fenestrae-associated cytoskeleton of rat liver sinusoidal endothelial cells.

This article describes the cytoskeleton associated with fenestrae and sieve plates of rat liver sinusoidal endothelial cells. Fenestrae control the exchange between the blood and parenchymal cells. We present evidence indicating that several agents that change the fenestrae and sieve plates also cause changes in the cytoskeleton. Cultured liver endothelial cells (LECs) were slightly fixed and treated with cytoskeleton extraction buffer. Detergent-extracted whole mounts of cultured cells were prepared for either scanning electron microscopy (SEM) or transmission electron microscopy (TEM). Extracted cells show an integral intricate cytoskeleton; sieve plates and fenestrae are delineated by cytoskeleton elements. Fenestrae are surrounded by a filamentous, fenestrae-associated cytoskeleton with a mean filament thickness of 16 nm. Sieve plates are surrounded and delineated by microtubuli, which form a network together with additional branching cytoskeletal elements. The addition of ethanol to cultured cells enlarged the diameter for these fenestrae-associated cytoskeleton rings by 5%, whereas serotonin treatment reduced the diameter by 20%. These observations indicate that the fenestrae-associated cytoskeleton probably changes the size of fenestrae after different treatments. After treatment with cytochalasin B the number of fenestrae increased. However, cytochalasin B did not change the structure of the fenestrae-associated cytoskeleton ring, but disperses the microtubuli. In conclusion, LECs have a cytoskeleton that defines and supports sieve plates and fenestrae. Fenestrae-associated cytoskeleton is a dynamic structure and plays a role in maintaining and regulating the size of fenestrae after different treatments. Therefore, the fenestrae-associated cytoskeleton controls the important hepatic function of endothelial filtration.

Animals↗
PubMed1994

Assessment of a method of isolation, purification, and cultivation of rat liver sinusoidal endothelial cells.

BACKGROUND: This paper describes a simple, low cost, and rapid method for the isolation, purification, and cultivation of rat liver sinusoidal endothelial cells (LEC). With regard to the purity, morphology, and responsiveness of the LEC, a detailed electron microscopy study was performed. In addition, we developed a method of automatic detection and analysis of the endothelial fenestrations using digitized scanning electron microscope images, allowing us to collect large sets of data. EXPERIMENTAL DESIGN: LEC were isolated by collagenase perfusion of the liver, isopycnic sedimentation in a two-step Percoll gradient, and selective adherence. The purification and cultivation of LEC was evaluated by light and electron microscopy. The addition of ethanol to LEC cultures showed responsiveness of LEC. RESULTS: Purity and viability of LEC after selective adherence was 73.7 +/- 5.8% and > or = 95%, respectively. LEC purity was further enhanced during adherence and spreading on collagen (type I, III). After 8 hours of culture, LEC monolayers were contaminated with less than 5% of other cells. After treatment with ethanol for 90 minutes, the diameters of LEC fenestrae increased approximately 10%. CONCLUSIONS: LEC isolated by this method provide a vital and responsive cell population enabling the study of structure and function of these cells in vitro. This method, in combination with a computer-assisted, on-line image analysis allows the acquisition of large numbers of measurements on these cells with high accuracy and with a minimum of bias.

Animals↗
PubMed1994

Effect of irradiation on hepatic natural killer cells.

The rat liver contains a population of natural killer cells consisting of two morphologically and functionally different subsets, a low-density and a high-density fraction. In this work we describe the influence of low-dose radiation on hepatic natural killer activity. The effect on the cytotoxicity against YAC-1 lymphoma and CC531 colon adenocarcinoma tumor cells was measured in chromium-51 assays, and morphological changes were analyzed by means of electron microscopy. The low-density natural killer fraction showed increased cytotoxicity against YAC-1 which was associated with an increased binding of natural killer cells to the YAC-1 tumor cells shortly after irradiation. These phenomena were paralleled by an increased number of multivesicular bodies and cytoplasmic granules with an electron-lucent halo. In contrast, the other hepatic natural killer cell fraction, the high-density natural killer cells, did not show increased cytotoxicity, binding or morphological alterations. The radiation-stimulated lysis of YAC-1 cells was also observed when in vivo irradiated cells were isolated and tested immediately for in vitro lysis of YAC-1 cells. Sixteen hours after in vitro or in vivo irradiation, the cytotoxicity of hepatic natural killer cells against YAC-1 was no longer enhanced. The cytolysis of and binding of hepatic natural killer cells to CC531 colon adenocarcinoma cells was not stimulated by in vitro irradiation. From these experiments, we conclude that low-dose radiation stimulates the cytotoxicity of hepatic low-density natural killer cells against YAC-1 lymphoma cells immediately after irradiation as the result of enhanced binding of the cells to the tumor cells, in addition to the synthesis of new cytotoxic granules.

Adenocarcinoma↗
PubMed1993

Origin and differentiation of hepatic natural killer cells (pit cells).

Liver sinusoids contain a population of large granular lymphocytes or natural killer cells, originally termed pit cells. After isolation and purification, these cells were separated into a low-density and a high-density fraction. The liver low-density fraction differs significantly in morphology and function from cells of the blood, whereas the liver high-density fraction shows intermediate properties. In this study we demonstrate that this morphological and functional heterogeneity is based on subsequent steps of differentiation of the large granular lymphocytes within the liver. When cell proliferation was suppressed by sublethal total body irradiation, the life span of the hepatic large granular lymphocytes could be determined: high-density and low-density populations were totally depleted within 1 and 2 wk after irradiation, respectively. By using intravenous asialo-GM1 anti-serum to deplete animals of asialo-GM1-positive cells, we found that the depletion of the asialo-GM1-positive cells preceded the depletion of asialo-GM1-negative hepatic low-density large granular lymphocytes by approximately 1 wk. Direct evidence that the asialo-GM1-positive high-density large granular lymphocytes are precursors of the low-density large granular lymphocytes was given by adoptive transfer experiments with fluorescent-labeled high-density cells. Three days after their injection, labeled large granular lymphocytes were found in the hepatic low-density fraction of the recipient rat, and these cells had developed morphological characteristics of low-density large granular lymphocytes. It is concluded therefore that marginating blood large granular lymphocytes differentiate through high-density large granular lymphocytes into the typical liver specific low-density large granular lymphocytes or pit cells.

Animals↗
PubMed1993

Identification of connective tissue gene transcripts in freshly isolated parenchymal, endothelial, Kupffer and fat-storing cells by northern hybridization analysis.

The aim of the present study was to identify the cell types that express collagen alpha 1(I), alpha 1(III) and alpha 1(IV), fibronectin and laminin B1 genes in normal rat liver. Parenchymal, sinusoidal endothelial, Kupffer and fat-storing (Ito) cells were isolated and purified. Total RNA of the freshly isolated cells was subjected to Northern hybridization analysis. We also compared the steady state levels of specific mRNAs in freshly isolated fat-storing cells to the levels in myofibroblast-like cells obtained from purified fat-storing cells cultured for two passages. The average purity of each cell preparation, and the percentage of contaminating cells, were determined by transmission electron microscopy and by examining the presence of vitamin A-autofluorescent cells. Fibronectin and collagen alpha 1(III) mRNAs were detected in total RNA of purified parenchymal cells. In poly(A)+ enriched RNA, small amounts of collagen alpha 1(I) mRNA were also present. In total RNA of freshly isolated fat-storing cells, collagen alpha 1(III), alpha 1(IV), and laminin B1 transcripts were found, whereas collagen alpha 1(I) and fibronectin mRNAs were not detected. Cultured fat-storing cells, however, did contain high levels of collagen alpha 1(I) and fibronectin mRNAs. The molecular size of the latter transcript was larger than the fibronectin transcript found in parenchymal cells and the whole liver. Endothelial cells contained small amounts of alpha 1(IV) mRNA. Kupffer cells did not contain the investigated transcripts. We conclude that normal parenchymal, fat-storing and endothelial cells each express a typical pattern of connective tissue molecules. When fat-storing cells are allowed to differentiate into myofibroblast-like cells, they express high levels of collagen alpha 1(I) and fibronectin mRNAs, in addition to collagen alpha 1(III) and alpha 1(IV), and laminin B1 chain mRNAs.

Adipocytes↗
PubMed1992

Localization and cellular source of the extracellular matrix protein tenascin in normal and fibrotic rat liver.

The distribution and the cellular source of the novel extracellular matrix glycoprotein tenascin were studied in normal and fibrotic rat liver. Cryostat sections of normal rat livers, livers of rats treated with intraperitoneal injections of CCl4 and 4-day-old and 8-day-old primary fat-storing cell cultures were stained for tenascin and desmin using an immunoperoxidase procedure or a double-label immunofluorescence technique. Fat-storing cell cultures were metabolically labeled with 3H-proline. Radiolabeled proteins were immunoprecipitated from the supernatant with antitenascin antiserum and subjected to polyacrylamide gel electrophoresis. In normal rat livers, tenascin was detected discontinuously along the sinusoids, whereas portal tracts were devoid of staining. In fibrotic rat livers, tenascin was preferentially expressed in areas of cell damage, in slender septa or at connective tissue-parenchymal interfaces. The middle region of broad septa was negative. Desmin-positive fat-storing cells accumulated in areas strongly immunoreactive for tenascin, and double-label immunofluorescence showed cells positive for both tenascin and desmin. In fat-storing cell cultures, both intracellular positivity for tenascin and staining of extracellular fibers were seen. Gel electrophoresis of immunoprecipitated proteins revealed two major and three minor bands with molecular weights consistent with tenascin. We conclude that tenascin is a component of the extracellular matrix of both normal and fibrotic rat livers. The strong expression of tenascin in areas of cell damage, in "early" septa or at septal-parenchymal interfaces, in contrast to its absence from the middle region of mature septa, suggests a role in early matrix organization. Fat-storing cells synthesize and secrete tenascin.

Animals↗