Gastritis-associated adenocarcinoma and intestinal metaplasia in a Syrian hamster naturally infected with Helicobacter species

Research-Relevant Conditions and Pathology of Laboratory Mice, Rats, Gerbils, Guinea Pigs, Hamsters, Naked Mole Rats, and Rabbits

Animals are valuable resources in biomedical research in investigations of biological processes, disease pathogenesis, therapeutic interventions, safety, toxicity, and carcinogenicity. Interpretation of data from animals requires knowledge not only of the processes or diseases (pathophysiology) under study but also recognition of spontaneous conditions and background lesions (pathology) that can influence or confound the study results. Species, strain/stock, sex, age, anatomy, physiology, spontaneous diseases (noninfectious and infectious), and neoplasia impact experimental results and interpretation as well as animal welfare. This review and the references selected aim to provide a pathology resource for researchers, pathologists, and veterinary personnel who strive to achieve research rigor and validity and must understand the spectrum of "normal" and expected conditions to accurately identify research-relevant experimental phenotypes as well as unusual illness, pathology, or other conditions that can compromise studies involving laboratory mice, rats, gerbils, guinea pigs, hamsters, naked mole rats, and rabbits.

Probiotics VSL#3 are effective in reversing non-alcoholic steatohepatitis in a mouse model

Background

Probiotic VSL#3 is used to treat ulcerative colitis. This study examines the effect of VSL#3 in non-alcoholic steatohepatitis (NASH) that has liver carcinogenic potential.

Methods

Western diet (WD)-fed wild-type (WT) mice that do not have hepatic inflammation with lymphocyte infiltration and carcinogenic potential were used for baseline comparison. Age-, sex-, and diet-matched bile acid (BA) receptor farnesoid X receptor (FXR) knockout (KO) mice, which developed severe NASH and had the potential for liver cancer development, were supplemented with and without VSL#3 for 7 months. All the mice were euthanized when they were 10 months old.

Results

Supplementation with VSL#3 completely abolished hepatic lymphocyte infiltration, reduced hepatic fat content, and improved insulin sensitivity in WD-fed FXR KO mice. In addition, VSL#3 normalized dysregulated BA homoeostasis by inhibiting the classical BA synthesis pathway, inducing the alternative BA pathway, and activating ileal G-protein coupled BA receptor 1 (GPBAR1)-regulated signaling. Moreover, VSL#3 reconstructed the gut microbiota by reducing Bacteroidaceae, Porphyromonadaceae, and Helicobacteraceae as well as increasing Lachnospiraceae. Further, VSL#3 enriched the abundance of Ruminococcus and Faecalibacterium, which generate butyrate, at the genus level. It also increased the copy number of the butyrate-producing genes bcoA and buk, suggesting their anti-inflammatory and metabolic effects.

Conclusions

VSL#3 is useful in reversing NASH that occurred due to dysregulated BA synthesis and dysbiosis, suggesting its potential in liver cancer prevention.

Western Diet-Induced Dysbiosis in Farnesoid X Receptor Knockout Mice Causes Persistent Hepatic Inflammation after Antibiotic Treatment

Patients who have liver cirrhosis and liver cancer also have reduced farnesoid X receptor (FXR). The current study analyzes the effect of diet through microbiota that affect hepatic inflammation in FXR knockout (KO) mice. Wild-type and FXR KO mice were on a control (CD) or Western diet (WD) for 10 months. In addition, both CD- and WD-fed FXR KO male mice, which had hepatic lymphocyte and neutrophil infiltration, were treated by vancomycin, polymyxin B, and Abx (ampicillin, neomycin, metronidazole, and vancomycin). Mice were subjected to morphological analysis as well as gut microbiota and bile acid profiling. Male WD-fed FXR KO mice had the most severe steatohepatitis. FXR KO also had reduced Firmicutes and increased Proteobacteria, which could be reversed by Abx. In addition, Abx eliminated hepatic neutrophils and lymphocytes in CD-fed, but not WD-fed, FXR KO mice. Proteobacteria and Bacteroidetes persisted in WD-fed FXR KO mice even after Abx treatment. Only polymyxin B could reduce hepatic lymphocytes in WD-fed FXR KO mice. The reduced hepatic inflammation by antibiotics was accompanied by decreased free and conjugated secondary bile acids as well as changes in gut microbiota. Our data revealed that Lactococcus, Lactobacillus, and Coprococcus protect the liver from inflammation.

Male Syrian Hamsters Experimentally Infected with Helicobacter spp. of the H. bilis Cluster Develop MALT-Associated Gastrointestinal Lymphomas

BACKGROUND

Aged hamsters naturally infected with novel Helicobacter spp. classified in the H. bilis cluster develop hepatobiliary lesions and typhlocolitis.

METHODS

To determine whether enterohepatic H. spp. contribute to disease, Helicobacter-free hamsters were experimentally infected with H. spp. after suppression of intestinal bacteria by tetracycline treatment of dams and pups. After antibiotic withdrawal, weanlings were gavaged with four H. bilis-like Helicobacter spp. isolated from hamsters or H. bilis ATCC 43879 isolated from human feces and compared to controls (n = 7 per group).

RESULTS

Helicobacter bilis 43879-dosed hamsters were necropsied at 33 weeks postinfection (WPI) due to the lack of detectable infection by fecal PCR; at necropsy, 5 of 7 were weakly PCR positive but lacked intestinal lesions. The remaining hamsters were maintained for ~95 WPI; chronic H. spp. infection in hamsters (6/7) was confirmed by PCR, bacterial culture, fluorescent in situ hybridization, and ELISA. Hamsters had mild-to-moderate typhlitis, and three of the male H. spp.-infected hamsters developed small intestinal lymphoma, in contrast to one control. Of the three lymphomas in H. spp.-infected hamsters, one was a focal ileal mucosa-associated lymphoid tissue (MALT) B-cell lymphoma, while the other two were multicentric small intestinal large B-cell lymphomas involving both the MALT and extra-MALT mucosal sites with lymphoepithelial lesions. The lymphoma in the control hamster was a diffuse small intestinal lymphoma with a mixed population of T and B cells.

CONCLUSIONS

Results suggest persistent H. spp. infection may augment risk for gastrointestinal MALT origin lymphomas. This model is consistent with H. pylori/heilmannii-associated MALT lymphoma in humans and could be further utilized to investigate the mechanisms of intestinal lymphoma development.

Pathology of the exotic companion mammal gastrointestinal system

A variety of disease agents can affect the gastrointestinal tract of the exotic companion mammal, some of which can pose zoonotic health concerns. Many conditions present with nonspecific clinical signs (lethargy, variable degrees of diarrhea, and for most sick rodents, presenting hunched with spiky fur), necessitating additional laboratory testing to reach a diagnosis. Primary tumors of the digestive tract are also presented as well as miscellaneous conditions ranging from toxins to trauma.

Infiltrative gastric adenocarcinoma in a chinchilla (Chinchilla lanigera)

A case of infiltrative gastric adenocarcinoma in a 5-year-old female chinchilla (Chinchilla lanigera) is described. The animal died after a 5-day period of lethargy and anorexia. Gross examination revealed increased gastric volume. The gastric wall was thickened and contained numerous firm, white nodules on the serosal surface. The lumen was obliterated by a firm mass and large amount of white, mucous secretion. Numerous white, irregular plaques and nodules were observed on the mesentery, visceral surface of the diaphragm, renal capsule, and uterine serosa (implantation metastases). Histopathological examination revealed an infiltrative gastric adenocarcinoma composed of neoplastic cells organized in a gland-like pattern interspersed with connective tissue. Neoplastic cells infiltrated the lamina propria, submucosa, and muscular layers, and were positive for cytokeratin. Detection of Helicobacter spp. in the gastric mucosa failed using Warthin-Starry and Steiner silver stains or immunohistochemistry, but a Helicobacter-specific nested polymerase chain reaction followed by sequencing was positive for Helicobacter pylori and showed more than 99% similarity to the 16S ribosomal RNA gene.

Gastric helicobacters in domestic animals and nonhuman primates and their significance for human health

Helicobacters other than Helicobacter pylori have been associated with gastritis, gastric ulcers, and gastric mucosa-associated lymphoid tissue lymphoma in humans. These very fastidious microorganisms with a typical large spiral-shaped morphology were provisionally designated "H. heilmannii," but in fact they comprise at least five different Helicobacter species, all of which are known to colonize the gastric mucosa of animals. H. suis, which has been isolated from the stomachs of pigs, is the most prevalent gastric non-H. pylori Helicobacter species in humans. Other gastric non-H. pylori helicobacters colonizing the human stomach are H. felis, H. salomonis, H. bizzozeronii, and the still-uncultivable "Candidatus Helicobacter heilmannii." These microorganisms are often detected in the stomachs of dogs and cats. "Candidatus Helicobacter bovis" is highly prevalent in the abomasums of cattle but has only occasionally been detected in the stomachs of humans. There are clear indications that gastric non-H. pylori Helicobacter infections in humans originate from animals, and it is likely that transmission to humans occurs through direct contact. Little is known about the virulence factors of these microorganisms. The recent successes with in vitro isolation of non-H. pylori helicobacters from domestic animals open new perspectives for studying these microorganisms and their interactions with the host.

Immunogenicity and pathogenicity of Helicobacter infections of veterinary animals

The initial discovery that the human stomach is commonly infected by the bacterium Helicobacter pylori subsequently resulted in the identification of a whole new family of pathogenic bacteria. In less than 25 years, the Helicobacter genus has grown from obscurity to number at least 38 different species with many more awaiting classifications. These bacteria, many of which are either direct or opportunistic pathogens, are present in virtually every mammalian species examined, and have also now been identified in a number of birds. The pathogenesis associated with these infections is predominantly the result of a chronic inflammatory response mounted by the host against the infection. This is typically a Th1-driven response which can result in a range of conditions from hepatitis, through gallstones to cancer. In some cases the inflammatory response to these infections is normally well managed by the host and disease only results when there is a breakdown or misbalance in the immunoregulatory process, which for example can result in inflammatory bowel disease in experimental models. Understanding the disease association and pathogenic mechanisms of the different Helicobacter infections is clearly of potential significance not only from an animal welfare point of view but also from the growing realisation of how commonly transmission of Helicobacter occurs between different mammals, including pathogenic zoonotic infections of humans.

Extragastric manifestations of Helicobacter pylori infection--other Helicobacter species

Recent studies have indicated a strong link between Helicobacter pylori and idiopathic thrombocytopenic purpura and iron deficiency anemia. Interesting results have also been obtained for ischemic heart disease, though most putative associations between H. pylori infection and extragastric disease remain speculative. With regard to other Helicobacter species, Helicobacter felis has been shown to play a role in gastric carcinogenesis in mouse models. An increased susceptibility to cholesterol gallstone formation has been described in animals fed a lithogenic diet and infected with Helicobacter bilis, or co-infected with Helicobacter hepaticus and Helicobacter rodentium. Finally, enterohepatic Helicobacter species have also been exploited to better understand inflammatory bowel disease.

Gastric adenocarcinoma and chronic gastritis in two related Persian cats

Two 12.5-year-old castrated male Persian cats from the same household, whose dams were littermates, presented simultaneously with gastric adenocarcinoma associated with proliferative and fibrosing gastritis. Intralesional adult Ollulanus tricuspis nematodes and rare surface-associated spiral-shaped bacteria were identified in one cat. No etiologic agents were identified in tissues from the second cat; however, gastric mucosa was examined following anthelmintic treatment. Clinical signs in each cat had commenced 2 months apart and included vomiting, hematemesis, intermittent melena, and weight loss. This is the first report of gastric adenocarcinoma occurring in housemate cats or cats of common descent. Carcinogenesis may have been influenced by shared undetermined genetic and environmental factors, possibly including Ollulanus tricuspis, spiral-shaped bacteria, or other etiologies for chronic gastritis that remain unidentified.