The pathological effect of Helicobacter pylori infection on liver tissues in mice

Helicobacter pylori infection is associated with chronic gastritis, peptic ulcer, gastric adenocarcinoma, and mucosa-associated lymphoid tissue lymphoma. Some reports also suggest that it causes extragastric disease, including hepatitis. In this study, the pathological changes in the liver and gall bladder in H. pylori -colonized C57BL/6 mice were investigated. Twenty mice were inoculated orally with H. pylori strain SS1, and ten controls were injected with phosphate-buffered saline. Gastric colonization with H. pylori was assessed at 2 months after inoculation. Mice were examined at 8 months by histopathology, culture for H. pylori , and PCR for specific H. pylori genes. All C57BL/6 mice infected with H. pylori for 8 months developed severe gastric mucosal inflammation. Three mice showed mild-to-moderate mutifocal hepatitis. The gall bladder mucosa of one H.  pylori -infected mouse showed thickening of the mucous membrane with mild submucosal lymphocytic infiltration. H. pylori was observed morphologically in four liver specimens and six gall bladders from infected mice by immunohistochemistry. Specific H. pylori genes were also detected in six liver samples from infected mice, six samples of bile, and two blood samples by nested PCR. Thus, H. pylori inoculated orally may reach the hepatobiliary system and cause inflammation as an independent aetiological factor. The pathway to the liver may be via the blood or the biliary system.