Bile glycoprotein mucin in sludge occluding biliary stent

Endoscopic biliary stenting is a common treatment for the palliation of obstructive jaundice caused by inoperable malignant hepatobiliary tumors and benign strictures. The biliary stent, however, often becomes nonfunctional as a result of occlusion. In this study, we sought to confirm that bile glycoprotein mucin was a factor in stent occlusion and to investigate its possible role in biliary-stent blockage. The high-molecular-weight glycoprotein fraction was isolated from stent sludge with the use of gel filtration and a cesium chloride density gradient. This fraction was analyzed for amino-acid and carbohydrate compositions and was identified by means of immunoblotting with a specific monoclonal antibody against human gallbladder mucin. Furthermore, the distribution of bile glycoprotein mucin in stent sludge was immunologically demonstrated with fluorescent antibody, and the relationship between bile glycoprotein mucin and bacteria (demonstrated with DAPI stain) was observed. The high-molecular-weight glycoprotein extracts isolated from 11 patients' stent sludge showed strongly positive immunoreactivity with the monoclonal antibody against human gallbladder mucin. Immunofluorescence studies showed that very bright fluorescent signals of bile glycoprotein mucin often appeared on the surface of pigmented deposits, at the periphery of clumps of bacteria and along the inner wall of stents. In nonpigmented sludge, we noted fluorescent signals of bile glycoprotein mucin dispersed among clumps of bacteria. Bile glycoprotein mucin is a constituent of stent sludge. It may play a role in stent occlusion by affecting bacterial adherence to the stent surface or by promoting stent-sludge accumulation as one kind of cement among substances such as calcium bilirubinate and clumps of bacteria.