Morphological alterations in epithelial cells of the mouse gallbladder 30 hours after treatment with lithogenic diet

Risk factors of biliary tract cancer in a large-scale population-based cohort study in Japan (JPHC study); with special focus on cholelithiasis, body mass index, and their effect modification

OBJECTIVES

We examined the association of potential risk factors with the incidence of biliary tract cancer in a large-scale population-based cohort study. Particular focus was placed on a history of cholelithiasis, body mass index (BMI), and their effect modification, and whether risk differs by cancer subsite, namely by gallbladder cancer and extrahepatic bile duct cancer.

DESIGN

We investigated 101,868 middle-aged and older Japanese subjects (48,681 men and 53,187 women) during 1,200,386 person-years of follow-up.

RESULTS

A total of 235 cases of biliary tract cancer (93 gallbladder cancer and 142 extrahepatic bile duct cancer) were newly diagnosed. Cholelithiasis was associated with an increased risk of biliary tract cancer [HR, 2.53; 95% CI, 1.56-4.12]. This association was similarly observed for both gallbladder [HR, 3.01; 95% CI, 1.56-6.19] and extrahepatic bile duct cancer [HR, 2.12; 95% CI, 1.08-4.18]. Body mass index was associated with an increased risk of extrahepatic bile duct cancer (P for trend = 0.03) and this effect was not modified by a history of cholelithiasis.

CONCLUSIONS

Cholelithiasis was confirmed to be associated with the risk of biliary tract cancer, both gallbladder and extrahepatic bile duct cancer. Obesity may increase the risk of extrahepatic bile duct cancer only, independent of cholelithiasis.

Ground squirrel model for cholelithiasis: role of epithelial glycoproteins

The cholesterol-fed Richardson's ground squirrel (Spermophilus richardsonii) has proven to be an effective animal model in which to study factors that influence cholesterol gallstone formation and associated alterations in the gallbladder epithelium. Ground squirrels of either sex, fed a 2% cholesterol-enriched diet, exhibit cholesterol monohydrate crystal precipitation within 24 hours and macroscopically visible cholesterol stones by 3 weeks. Data on bile chemistry, biliary cholesterol precipitation, and various mucosal alterations occurring prior to, during, and after stone formation were collected using sampling intervals from 6 hours to 20 weeks on the diet. The results indicate that mucin hypersecretion appears to be more closely related to the initiation of nucleation than does either bile calcium of pH. Mucus hypersecretion begins within 18 hours of diet initiation and continues throughout the 20 week experimental period. Apical excrescences became more common and were larger in size during the early stages of cholelithiasis. Administration of aspirin during the experimental period demonstrated an inhibition of mucin synthesis and release. Gallstones were not formed in these aspirin-treated animals. A lectin-binding panel for 10 epithelial glycoprotein-related sugars indicated the mucin secreted by the gallbladder epithelium of 7 day experimental animals differed from that of controls. The most obvious difference was the abolition of WGA binding in the experimental animals, suggesting an absence of sialic acid expression in the mucin during the lithogenic process. Ultrastructural histochemistry indicated that both sulphomucin and sialomucin were present in the secretory granules and within the surface mucus layer of both experimental and control animals. Experimental animals, however, exhibited a significant predominance for sulphomucin. This pattern varies from that typically seen in other regions of the gastrointestinal tract where sialomucins predominate during pathologic processes.

Ultrastructural aspects of human gallbladder epithelial cells in cholelithiasis: production of anionic mucus

The surface epithelium of 28 gallbladders removed during elective cholecystectomies and pathology collection was studied ultrastructurally. Focusing on 10 of the 28 cases that were diagnosed as cholecystitis, we found that the epithelium displayed numerous apical mucous granules and bulging apical apices. Mucous granule changes included 1) hyperproduction of secretory granules of neutral type containing an electron-dense proteinaceous spherule, similar to that described in other mucus-producing glands of the digestive system, and 2) production of anionic, osmiophilic secretory mucus. Other alterations of the surface epithelial cells included the production of bizarre surface appendages resembling primitive cilia without axoneme and epithelial excrescences.

Comparative morphology of the gallbladder and biliary tract in vertebrates: variation in structure, homology in function and gallstones

A review of investigations on the morphology of the gallbladder and biliary tract in fish, reptiles, amphibians, birds, and mammals was performed. Scanning electron microscopy, transmission electron microscopy, and light microscopy observations by the authors were also included. Variations in the presence or absence of a gallbladder, surface epithelium of the gallbladder, and differences in the morphology of the biliary tract in vertebrates were reported. Many differences were diet-related. Despite some dissimilarities observed, analogous functioning of the biliary system was accomplished by its various components, with the biliary ducts performing the function of the gallbladder when this organ was absent. In addition, the occurrence of peculiar parasitism and gallstones among some cases of vertebrates, including humans, was presented.

The histogenesis of adenocarcinoma of the gallbladder

A prospective study of 277 cholecystectomy specimens for evidence of isolated epithelial dysplasia of gallbladder mucosa is presented. In addition, 15 cases of primary adenocarcinoma of the gallbladder are retrospectively reviewed with particular reference to the presence of metaplasia and dysplasia adjacent to the infiltrating tumor, in order to establish the relationship between metaplasia, isolated epithelial dysplasia, and adenocarcinoma of the gallbladder. Only one case of isolated epithelial dysplasia was found in the 277 cholecystectomy specimens, and this arose within focal incomplete intestinal metaplasia. In the 15 cases of adenocarcinoma of the gallbladder, benign antral and/or incomplete intestinal metaplasia was found adjacent to the tumor in 11 cases. In 10 cases, dysplasia of this metaplastic epithelium was found in continuity with the tumor. The authors conclude that the most common pathway to adenocarcinoma is via dysplasia of metaplastic gallbladder epithelium.

Ultrastructural and histochemical study of the gallbladder epithelia of rainbow trout and tench

The simple, high columnar gallbladder epithelia of the rainbow trout (Salmo gairdneri, Rich.) and the tench (Tinca tinca, L.) are composed of light and dark cells. Within the dark cells two types must be distinguished: less hydrated, but normal epithelial cells and degenerating cells. The latter seem to be eliminated from the epithelium through phagocytosis by monocytes and macrophages, which possibly correspond with the 'basal regenerative cells' of earlier investigations. Since they are mainly found near the basement membrane, an hypothesis is put forth that they do not enter the gallbladder lumen, but migrate back into the subepithelial connective tissue after phagocytosis. Light and less hydrated dark cells are specialized for absorption of water and dissolved bile salts and for secretion of mucus, which mainly consists of acid glycoproteins. Interspecific differences are seen with regard to both functions. So, in the tench only single microvilli are developed apically, whereas a true brush border is seen in the rainbow trout. Thus, a higher absorptive rate can be assumed in the rainbow trout. Or, with respect to mucus secretion, in the rainbow trout the granular endoplasmic reticulum predominates, whereas in the tench the smooth endoplasmic reticulum, often associated with glycogen and even forming 'glycogen bodies', is better developed. In the rainbow trout fibrillar granules of highly condensed acid glycoproteins are seen to be secreted. In the tench only vesicles of flocculent content occur. Perhaps, these morphological and subsequent metabolic differences may be related to the various feeding habits of the predatory rainbow trout and the omnivorous tench. Seasonal variations as expected especially in the tench after winter rest could not be established.