Kenjiro Wake

Perisinusoidal Stellate Cells (Fat-Storing Cells, Interstitial Cells, Lipocytes), Their Related Structure in and around the Liver Sinusoids, and Vitamin A-Storing Cells in Extrahepatic Organs

Publisher Summary This chapter discusses the history of the stellate cells. These cells are the integral elements of the wall of the sinusoids and that notion has introduced deep-rooted misconceptions in liver histology. The chapter discusses the morphological characteristics of stellate cells. The stellate cells are distributed only in the lobules of the liver and constitute 1.4% of parenchymal volume in the rat liver. They are stellate-shaped, are located in the space of Disse, and adhere to the sinusoidal wall. Their dendritic processes spread over the outer surface of the sinusoids and encircle the sinusoids or run longitudinally along them. Along the surface of these processes, a number of micropinocytotic vesicles or caveolae are observed. No basal lamina is discernible. The stellate cells are separated from the parenchymal cells by intercellular spaces of varying dimensions in which collagen bundles are often seen. The stellate cells in the liver of various mammals are morphologically classified into two types: in the first type, branching of the cytoplasmic processes is well developed many medium-sized lipid droplets are apparent; in the second type, cytoplasmic processes are not so conspicuous and one or two large lipid droplets are located in the vicinity of the nuclei.

Perisinusoidal stellate cells of the liver: important roles in retinol metabolism and fibrosis.

In mammals, liver perisinusoidal stellate cells play an important role as a main store of body retinol (vitamin A). This fat‐soluble vitamin is essential for vision, and regulates differentiation and growth of many cell types during embryonal development as well as in adult tissues. Thus, many cell types require a continuous supply of retinol. The storage of retinol (as retinyl esters) in stellate cells ascertains ample access of retinol to such cells also during periods with a low dietary intake. In lower vertebrates such as fish, vitamin A‐storing stellate cells are found not only in the hepatic lobule, but also in the connective tissues of organs like intestine, kidney, ovaries, testes, and gills. Extrahepatic vitamin A‐storing stellate cells are found in higher vertebrates when excessive doses of vitamin A are administered. It is not clear at present whether these cells also play a role in retinol metabolism under normal conditions. Stellate cells proliferate in a fibrotic liver, and they have been found to synthesize connective tissue compounds such as collagen. It was recently demonstrated that stellate cells are the principal cellular source of collagen and other extracellular substances in normal as well as fibrotic livers. Therefore, stellate cells, which seem to be a specialized type of pericyte, have a central role in the pathological changes observed during the development of liver fibrosis.—Blomhoff, R.; Wake, K. Perisinusoidal stellate cells of the liver: important roles in retinol metabolism and fibrosis. FASEB J. 5: 271–277; 1991.

Evidence of Hepatocyte Apoptosis in Rat Liver after the Administration of Carbon Tetrachloride

In acute liver injury induced by the injection of CCl4, cell death has been attributed to the necrosis of hepatocytes in the centrilobular area. In the present study, we re-examined the hepatic injury evoked by CCl4 in rats and explored the possibility that apoptosis may also contribute to its pathogenesis. Apoptotic hepatocytes were identified and quantified by light and electron microscopy, the in situ immunohistochemical labeling of nuclear DNA fragmentation, flow cytometry, and DNA gel electrophoresis. We found that a substantial number of hepatocytes underwent apoptosis. Apoptotic changes were also observed in ballooned hepatocytes. Apoptotic hepatocytes increased in number at 3 hours and peaked at 6 hours after the CCl4 injection. Apoptotic bodies were sequestrated in the adjacent hepatocytes and sinusoidal cells. Double staining of the cells with immunostaining for phagocytes and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling staining for labeling of DNA fragmentation showed that the majority of apoptotic hepatocytes were phagocytosed by Kupffer cells and macrophages. The results indicated that apoptosis occurs in the ballooned and injured hepatocytes of the centrilobular area. What occurs after CCl4 administration may be important in reducing inflammation, shortening the course of acute hepatic injury, and preventing the development of fibrosis.

Cell biology and kinetics of Kupffer cells in the liver.

Publisher Summary The study of Kupffer cells has developed rapidly and has been extended to problems concerning the origin, structure, and function of these cells in normal and pathological conditions This chapter provides an overview of the current morphological and biochemical data. Many of the major advances in Kupffer cells have resulted from the development of new methods, such as cell isolation, purification, and culture. Kupffer cells play a major role in the clearance of endotoxin from the blood, which induces the release of a number of mediators. Experimental virus infections provide the indications of the viral hepatitis development in human liver. The susceptibility of Kupffer cells to bacterial and viral infections is influenced by hormonal, immunological, nutritional, and genetic factors. The regulatory role of Kupffer cells in various hepatic disorders as well as in liver transplantation still requires further investigation. The chapter discusses the involvement of Kupffer cells and natural killer (NK) cells in the defense against tumor development and describes the way in which Kupffer cells coordinate their activities with liver-associated NK cells in tumor cell cytotoxicity. Since the descriptions of the isolation, purification, and culture of Kupffer cells from rat liver, the study of the function of these cells in vitro has made considerable progress.

24-hour rat liver preservation using UW solution and some simplified variants

The results of a series of 32 rat liver transplants are described to analyze the efficacy of components of UW solution. Rat livers were stored at 4°C in standard UW solution or one of three simplified variants for 24 hr prior to orthopic liver transplantation. In standard UW solution (solution A) the one-week survival rate was 3 of 8. Using solution B, which differs from solution A in the omission of hydroxyethyl starch and adenosine, the one-week survival rate was 2 of 8. Solution C, a further-simplified version of solution B with omission of allopurinol, Bactrim, and insulin, gave a one-week survival rate of 3 of 8. Solution D is identical to solution B except that the sodium and potassium concentrations are reversed. Using this solution, 5 of 8 rats survived more than one week. We conclude that the effectiveness of UW solution is maintained in a substantially simplified form, and that solution D, with the Na/K ratio reversed to give a high Na variant, may improve survival.

Distribution and morphological characteristics of the pit cells in the liver of the rat

SummaryPit cells, on which almost no further contributions have been presented since the first report by Wisse et al. (1976), are described in detail in the rat liver. These cells show several characteristic features: 1) “rod-cored vesicles”, a new type of vesicular inclusion observed first in our study; 2) electron-dense granules, which we consider to arise from multivesicular bodies by the accumulation of dense material; and 3) well-developed pseudopodia. Although these features clearly differentiate pit cells from conventional lymphocytes, these two cell types display similarities (i) in a number of ultrastructural features, (ii) in the pattern of their intralobular distribution, and (iii) in their presence in the spleen and peripheral blood.

The scavenger endothelial cell: a new player in homeostasis and immunity

To maintain homeostasis, the animal body is equipped with a powerful system to remove circulating waste. This review presents evidence that the scavenger endothelial cell (SEC) is responsible for the clearance of blood-borne waste macromolecules in vertebrates. SECs express pattern-recognition endocytosis receptors (mannose and scavenger receptors), and in mammals, the endocytic Fc gamma-receptor IIb2. This cell type has an endocytic machinery capable of super-efficient uptake and degradation of physiological and foreign waste material, including all major classes of biological macromolecules. In terrestrial vertebrates, most SECs line the wall of the liver sinusoid. In phylogenetically older vertebrates, SECs reside instead in heart, kidney, or gills. SECs, thus, by virtue of their efficient nonphagocytic elimination of physiological and microbial substances, play a critical role in the innate immunity of vertebrates. In major invertebrate phyla, including insects, the same function is carried out by nephrocytes. The concept of a dual-cell principle of waste clearance is introduced to emphasize that professional phagocytes (macrophages in vertebrates; hemocytes in invertebrates) eliminate larger particles (>0.5 μm) by phagocytosis, whereas soluble macromolecules and smaller particles are eliminated efficiently and preferentially by clathrin-mediated endocytosis in nonphagocytic SECs in vertebrates or nephrocytes in invertebrates. Including these cells as important players in immunology and physiology provides an additional basis for understanding host defense and tissue homeostasis.

Intralobular heterogeneity of perisinusoidal stellate cells in porcine liver

The aim of the present investigation was to elucidate the intralobular heterogeneity of the perisinusoidal stellate cells (fat-storing cells, lipocytes) in the porcine liver. Their three-dimensional structure, desmin immunoreactivity and vitamin-A storage were studied by use of the Golgi silver, immunocytochemical and gold chloride methods. In order to locate the stellate cells, the hepatic lobules were divided into 10 zones. The stellate cells were readily identified in Golgi preparations by their striking dendritic appearance with branching processes encompassing the sinusoids. The stellate cells in the centrolobular zones were conspicuously dendritic with longer processes in conspicuously dendritic with longer processes in comparison to those emitted by periportal elements. Such arborizations were studded with numerous thorn-like microprojections. Desmin immunoreaction in the periportal zones was stronger than that in the centrolobular zones. Vitamin-A storage in the stellate cells was well developed in zones 2–4, but reduced gradually toward the central region. The perisinusoidal etellate cells display marked heterogeneity in morphology and function based on their zonal location in the hepatic lobule.

MATURATION OF RAT DENDRITIC CELLS DURING INTRAHEPATIC TRANSLOCATION EVALUATED USING MONOCLONAL ANTIBODIES AND ELECTRON MICROSCOPY

Abstract Specific populations of hepatic sinusoidal cells were stained with monoclonal antibodies that recognize monocytes/macrophages (ED1), tissue macrophages (Kupffer cells) (ED2), MHC class II (Ia) antigen (MRC OX6), and dendritic cells/γ,δ T-cells (MRC OX62) and analyzed by light and electron microscopy. The majority of ED1+ and/or ED2+ cells were localized to the hepatic parenchyma, whereas OX6+ and/or OX62+ cells were more densely distributed within Glisson’s sheath than in the hepatic parenchyma. Double-immunoperoxidase staining of normal liver for ED1, ED2, and OX6 identified dendritic cells (DC) of two different phenotypes, ED1+ED2–OX6+ and ED1–ED2–OX6+. DC can be classified into three different types based on ultrastructural characteristics. The first type (type I) is characterized by one or more long cytoplasmic processes and a well-developed lysosomal system. The second type (type II) has an inconspicuous lysosomal system, abundant hyaloplasm, and characteristic short cytoplasmic processes. The third type (type I–II) has cytologic features intermediate between those of type I and type II DC. At the electron-microscopic level, these three cell types are found in the sinusoidal lumen, whereas the majority of type II DC are located in the space of Disse and Glisson’s sheath. Furthermore, some OX6-labeled elongated DC appeared to traverse the lumen of sinusoids through endothelial pores to enter the space of Disse. One hour after intravenous injection of latex particles (0.81 μm in diameter), numerous latex-laden dendritic cells (ED1+OX6+, type I and type I–II) were detected in the lumen of hepatic sinusoids, but not in the space of Disse or Glisson’s sheath. These findings suggest that normal rat liver contains resident dendritic cells which downregulate phagocytic activity and mature into potent accessory cells during migration from the portal vein toward the central vein. These DC then traverse the sinusoidal lumen to the hepatic lymph system via the space of Disse.

Modes of endocytosis of latex particles in sinusoidal endothelial and kupffer cells of normal and perfused rat liver

The endocytosis of latex particles (0.33, 0.46 and 0.80 micron in diameter) in the sinusoidal endothelial and Kupffer cells of the rat liver was studied electron microscopically. When the liver was perfused with serum-free oxygenated Krebs Ringer bicarbonate, latex particles of all three sizes were taken up by the endothelial cells. After a 10-min perfusion, particles were incorporated by the luminal cell surface of the perikarya or of the thick portion of the endothelial cells. A large patch of bristle coat was surrounding the ingested particle. The number of ingested particles in the endothelial cells, however, was much less than in the Kupffer cells. In in vivo experiments, no endocytosis of the latex particles was observed in the endothelial cells. In the Kupffer cells, particles were engulfed by the ruffled membranes or sank into the cytoplasm without a large patch of the bristle coat both in the perfusion system and in vivo. These observations show that at least 0.80 micron latex particles are taken up by the bristle-coated membranes in the sinusoidal endothelial cells of the perfused liver. The endocytic mechanism for latex particles in the endothelial cells is different from that of the Kupffer cells.