Lipid in the human gallbladder mucosa. A histochemical study by light and electron microscopy

Carcinoma in situ of the cystic duct

Cholelithiasis and cholesterolosis associated with carcinoma in situ of the cystic duct epithelium was observed in a male patient. Ultrastructurally, small acini-like lined a thickened, reduplicated basal lamina encompassing a pleiomorphic population of cells, including typical cholecystocytes, a poorly differentiated type, and cells containing modified mucous vesicles with heterogeneous fatty deposits. Even though the etiology of this apparent neoplastic epithelium and of its thickened basal lamina is unclear, it is hypothesized to be the result of an altered control of cell adhesion mechanisms, resulting from a repeated renewal of the typical epithelium abraded by the passage of the stones and the biliary sludge, associated with inflammatory stimuli that accompany cholecystolithiasis. Based on recent studies, it is suggested that investigations of molecular markers in extrahepatobiliary tract lesions and retrospective studies of these archival tissues could clarify the association of these neoplastic changes with other hepato-biliary lesions.

Intracellular liposomes and cholesterol deposits in chronic cholecystitis and biliary sludge

Ultrastructural study of a group of selected specimens of chronic cholecystitic gallbladders reveals cholecystocyte changes characterized by abraded and altered microvilli accompanied by mitochondrial damages in the apical regions as well as mucus accumulation with aggregated, angulated lysosomes and heterogeneous liposomes. These liposomes contain needle-like crystals, probably rich in cholesterol. Many fragments of cholecystocystes and damaged organelles or contents can be found in the biliary sludge. These data support previous reports suggesting that there is an association between cholecystitis and the presence of cholelithiasis, subsequent to the production of altered bile. The present data suggest that disintegrating, sloughed cholecystocyte contents also contribute to the bile sludge, a complex milieu enriched by lipids, cholesterol deposits, altered mucus due in part to changes in expression of apomucins. The instability of prolonged storage of such modified bile, caused and/or accompanied by other associated metabolic defects, including gallbladder sluggishness, would favor the nucleation and the enlargement of gallstones. Based on the aforementioned data, a comprehensive sequence for cholecystocyte ultrastructural alterations and pathologies is proposed, as a result of chronic cholecystitis.

Hepatic bile versus gallbladder bile: a comparison of protein and lipid concentration and composition in cholesterol gallstone patients

Many studies have demonstrated that gallbladder bile (but not hepatic bile) of animals or patients with cholesterol gallstones contains higher protein concentrations than does gallbladder bile of control patients without stones or with pigment stones. The underlying defect has not been elucidated. To establish whether there is net production or net absorption/degradation of protein by gallbladder epithelium for different classes of protein, paired samples of hepatic and gallbladder bile were obtained from fourteen patients with cholesterol gallstones during elective cholecystectomy. In these paired samples, lipid and protein composition were determined. To obtain the concentration ratio (CR) of protein and lipid, its concentration in the gallbladder was divided by the concentration determined in the paired hepatic bile sample. The CR of bile salts was used as a parameter for water absorption in the gallbladder. Of the biliary proteins that were determined only mucin, albumin, immunoglobulin (Ig) G, and aminopeptidase N appeared to increase in the gallbladder from another cause than water absorption. A strong correlation was found between mucin, albumin, and IgG. Haptoglobin, alpha1-acid glycoprotein, IgM, and IgA appeared to be absorbed by gallbladder epithelium in the majority of patients. In cholesterol gallstone patients, total protein concentration in gallbladder bile of cholesterol gallstone patients is increased when compared with hepatic bile. The increase in protein concentration cannot be explained for all bile samples solely by water absorption. In this study we show that the defect is largely caused by a selective increase in albumin, mucin, and IgG. All other proteins which were investigated are taken up by the gallbladder.

Biochemical and morphological correlations in human gallbladder with reference to membrane permeability

There is good evidence that gallbladder epithelium is permeable to a diverse range of molecules which move into the epithelial cell from the lumen or the basement membrane. Morphological investigations have shown both secretory mucous droplets, components of the endocytosis pathway together with evidence of a system allowing passage of molecules across the basement membrane. This indicates that the gallbladder epithelium may be influenced by molecules presented via the apical and basal membranes, complicating our understanding of gallbladder function, particularly in disease. Gallbladder disease increases the proteoglycan content of the basement membrane, but the implication of this in terms of permeability remains to be defined. Indeed, it remains unknown whether this precedes disease or is a manifestation of the disease process. The removal of water from hepatic bile by gallbladder involves two counter ion transport systems. Autoradiography shows that ion transport occurs into the lateral intracellular spaces but it remains unclear whether this leads to a hypertonic solution in these spaces causing an osmotically driven water absorption or if the process involves an osmotically linked isotonic secretion. These ion pumps are reversible, for water is absorbed during the interdigestive phase but fluid is secreted into the lumen during digestion or in the presence of disease. Appropriate neural stimulation can increase or decrease fluid absorption from the lumen while vasoactive intestinal peptide or secretin promote fluid secretion, probably mediated by prostaglandins leading to raised cyclic AMP acting at the cellular level. Immediate control may depend on intracellular Ca2+ which activates a calmodulin-protein kinase, phosphorylating the counter ion transporters to downregulate their activity. Failure of this regulatory process may explain the initial increase in bile concentrating potential seen in the development of gallstones although the mechanism of such failure remains unknown. More concentrated bile increases movement of biliary compounds into gallbladder epithelial cells which alter gallbladder function in a complex manner. Secondary bile acids are raised in gallstone disease and increase permeability of the gallbladder epithelium to molecules including cholesterol. This cholesterol absorbed from the lumen may have paramount importance to gallbladder function. Raised biliary cholesterol reduces gallbladder motility, possibly by increasing the amount of cholesterol in gallbladder muscle membranes and reducing contraction in response to cholecystokinin. However, increased secondary bile acids are also associated with an alteration in phospholipid acyl groups which may alter ion transport activity and/or cholesterol solubility within the micelle/vesicle. As the acyl groups show increased arachidonate levels the production of prostaglandins could be raised, although currently it is not known if this phospholipid arachidonate enters the epithelial cells. In addition, gallbladder inflammation is associated with raised phospholipase A2 activity, leading to formation of fatty acids and lysophospholipid which causes membrane damage. The fatty acids are likely to displace cholesterol from the micelle but may also act directly on the epithelium, possibly increasing prostaglandin production and thus stimulating mucin secretion. Increased mucin secretion is seen early in gallstone disease but the evidence presently available cannot determine if this is a causative factor.

Lipidosis induced in the dog gallbladder by a direct 5-lipoxygenase inhibitor

The direct 5-lipoxygenase inhibitor L-739,010 was administered at a dose of 60 mg/kg/day per os to beagle dogs for 15 days. Histopathological examination of gallbladders from treated dogs showed epithelial vacuolation and submucosal infiltration by foamy macrophages that were positive for lipids in Sudan Black-and/or Oil Red O-stained sections. Scanning electron microscopic examination of gallbladder mucosa showed thickening of epithelial folds and multifocal epithelial membrane disruptions. Transmission electron microscopy confirmed these findings and showed mucosal epithelial cell lipid droplet accumulation and submucosal infiltration of macrophages filled with lipid droplets, myelin figures, heterophagosomes, and cholesterol clefts. These changes resembled those reportedly seen in the human gallbladder with cholesterolosis and/or chronic cholecystitis.

Cholesterol absorption by the gall bladder

Model and real biles were used to investigate factors influencing cholesterol and dextran (70,000 molecular weight) absorption by the gall bladder. Cholesterol absorption was proportional to cholesterol concentration when real bile was used, but model biles showed maximal absorption at cholesterol saturation. Reduction of temperature reduced cholesterol absorption and serosal secretion, but had little effect on dextran absorption. This indicates differences in uptake where cholesterol undergoes passive diffusion but dextran is taken up by fluid-phase endocytosis. Model bile prepared with a single bile salt showed lowest cholesterol uptake from cholate bile, but there was no difference in serosal secretion. Dextran uptake was also lowest from cholate bile, although serosal secretion was highest. These results show that an increase in the biliary content of dihydroxy bile salts increases gall bladder permeability to both hydrophobic and hydrophilic molecules and may lead to the accumulation of lipids in the mucosa, as seen in cholesterolosis.

Xanthogranulomatous cholecystitis. Histopathological study and classification

Xanthogranulomatous cholecystitis (XC) is a chronic inflammatory lesion of the gallbladder histologically characterized by the presence of varying amounts of foamy histiocytes in the inflammatory infiltrate. In this study a review of 63 cases selected from 1207 surgically removed gallbladder is presented; the percentage found (5.2%) is slightly higher than that of previous reports showing that XC is less uncommon than generally believed. A detailed microscopic study is performed: the authors observed according to the histological features particularly the different patterns of distribution of the inflammatory infiltrate and postulate the existence of three subtypes of XC: multinodular, focal and diffuse XC. Finally, the main etiopathogenetic hypotheses are briefly discussed.

Characterization of lipid accumulation in the gallbladder mucosa of the ground squirrel fed a lithogenic diet

Richardson's ground squirrels (Spermophilus richardsonii) of both sexes were fed a 2 per cent cholesterol-enriched diet for intervals of 12, 18, and 24 h; 3, 5, and 7 days; and 2, 3, 10, and 20 weeks. It was shown that free (unesterified) cholesterol, phospholipid, and cholesterol ester accumulated in specific regions of the gallbladder mucosa during cholelithiasis. Electron microscopy revealed the presence of lipids inter- and intracellularly as early as 12 h after ingestion. By 7 days, lipids were seen in dilated endoplasmic reticulum, as well as in supranuclear and basal regions of epithelial cells. Histochemical localization revealed free cholesterol in dilated endoplasmic reticulum and residual bodies at the ultrastructural level. Neutral lipid was observed by light microscopy in the supranuclear and basal regions of the cells. In 10- and 20-week treated animals, lipid droplets were also seen in the lamina propria and macrophages. The lesion induced by cholesterol ingestion persisted throughout the experimental period, and while different from that in human tissue, it was similar to those observed in experimental canine cholesterosis.

Macrophages and mast cells in chronic cholecystitis and "normal" gall bladders

An attempt was made to quantify mast cells using toluidine blue and macrophages, with alpha-1-antitrypsin as a marker, from adjacent sections in the mucosa of two groups of gall bladders showing either minimal inflammatory change or established chronic cholecystitis. The results were expressed as cells/mm2 of mucosa. Alpha-1-antitrypsin showed both macrophages and mast cells, and therefore an estimate of macrophage numbers was obtained by subtraction. Mast cells comprised more than 60% of the alpha-1-antitrypsin positive cells. There were significantly (p greater than 0.001) more mast cells and macrophages in minimal inflammatory gall bladder mucosa than in established chronic cholecystitis.