Down-regulation of a morphogen (sonic hedgehog) gradient in the gastric epithelium of Helicobacter pylori-infected Mongolian gerbils

Helicobacter pylori: present status and future prospects in Japan

The discovery of Helicobacter pylori has already changed the natural history of peptic ulcer disease, with most patients being cured at their first presentation. Similarly, the incidence of gastric cancer and other diseases related to H. pylori are likely to be greatly reduced in the near future. Isolation of the spiral intragastric bacterium H. pylori totally reversed the false dogma that the stomach was sterile, and it taught us that chronic infectious disease can still exist in modern society. Helicobacter pylori's unique location, persistence, and evasion of the immune system offer important insights into the pathophysiology of the gut. Also, the fact that it was overlooked for so long encourages us to think "outside the box" when investigating other diseases with obscure etiologies. We should consider such provocative scientific ideas as bridges to the future disease control.

The effect of Helicobacter felis and Helicobacter bizzozeronii on the gastric mucosa in Mongolian gerbils: a sequential pathological study

In contrast to Helicobacter(H.) pylori, little is known about the pathogenic mechanisms of gastric non-H. pylori Helicobacter species. Mongolian gerbils were inoculated intragastrically with H. felis or H. bizzozeronii and killed at different timepoints post-inoculation (p.i.), stomach tissue being taken for light and transmission electron microscopy (TEM) and polymerase chain reaction (PCR) analysis. Parietal cells (PCs), apoptosis, cell proliferation and nuclear factor-kappaB (NF-kappaB) activation were "visualized" immunohistochemically. Inflammation consisted of neutrophilic granulocytes, mainly in the antrum, and lymphocytic infiltrates around the limiting ridge and throughout the stomach mucosa and submucosa. From day 11 p.i. onwards, H. felis-inoculated animals showed moderate to severe loss of PCs extending from the limiting ridge into the fundus. Apoptotic cells, spiral bacteria, cell proliferation, and NF-kappaB activation were detected at the transition zone between affected and normal PCs. TEM revealed interaction of H. felis flagella with PCs and chief cells. Moreover, H. felis was seen in proximity to, and inside, necrotic cells. At 10 weeks p.i., some H. felis-infected gerbils showed complete loss of fundic glands, and mucous metaplasia of the epithelium. H. bizzozeronii, which made no flagellar contact with epithelial cells, was associated with only mild PC loss. The mechanism by which H. felis induces PC necrosis and apoptosis remains unclear. The observed flagellar contact and NF-kappaB activation may play an important role in H. felis-associated inflammation.

Helicobacter pylori infection stimulates intestinalization of endocrine cells in glandular stomach of Mongolian gerbils

Intestinal metaplasia has been investigated extensively as a possible premalignant condition for stomach cancer but its pathogenesis is still not fully understood. In the present study, we examined the relationship between endocrine and mucous cell marker expression periodically after Helicobacter pylori infection in the Mongolian gerbil model. The numbers of chromogranin A (CgA)-positive, gastrin-positive and gastric inhibitory polypeptide (GIP)-positive cells in H. pylori-infected groups was increased significantly compared with the non-infected case. However, CgA-positive and gastrin-positive cells then decreased from 50 through 100 experimental weeks after H. pylori infection, whereas GIP-positive cells increased. Coexistence of gastrin-positive and GIP-positive cells was detected in the same gastric and intestinal mixed phenotypic glandular-type glands. In conclusion, the endocrine cell phenotype is in line with that of the mucous counterpart in the glands of H. pylori-infected Mongolian gerbil stomach, supporting the concept that development of intestinal metaplasia is due to the abnormal differentiation of a stem cell.

Helicobacter pylori-infected animal models are extremely suitable for the investigation of gastric carcinogenesis

Although various animal models have been developed to clarify gastric carcinogenesis, apparent mechanism of gastric cancer was not clarified in recent years. Since the recognition of the pathogenicity of Helicobacter pylori (H pylori), several animal models with H pylori infection have been developed to confirm the association between H pylori and gastric cancer. Nonhuman primate and rodent models were suitable for this study. Japanese monkey model revealed atrophic gastritis and p53 mutation after long-term infection of H pylori. Mongolian gerbil model showed the development of gastric carcinoma with H pylori infection alone, as well as with combination of chemical carcinogens, such as N-methyl-N-nitrosourea and N-methyl-N-nitro-N'-nitrosoguanidine. The histopathological changes of these animal models after H pylori inoculation are closely similar to those in human beings with H pylori infection. Eradication therapy attenuated the development of gastric cancer in H pylori-infected Mongolian gerbil. Although several features of animal models differ from those seen in human beings, these experimental models provide a starting point for further studies to clarify the mechanism of gastric carcinogenesis as a result of H pylori infection and assist the planning of eradication therapy to prevent gastric carcinoma.

Helicobacter felis and Helicobacter bizzozeronii induce gastric parietal cell loss in Mongolian gerbils

Non-pylori helicobacter infections are associated with gastritis, gastric ulcers and MALT lymphomas in man. Approximately 50% of these are caused by helicobacters commonly found in dogs and cats, including Helicobacter felis, Helicobacter bizzozeronii and H. salomonis. In contrast to Helicobacter pylori, the virulence mechanisms of these species are unknown. In this study the virulence of H. felis, H. bizzozeronii and H. salomonis was investigated in Mongolian gerbils. Female SPF gerbils were inoculated intragastrically with H. felis, H. bizzozeronii or H. salomonis and sacrificed 3 weeks later. Fundus and antrum samples were taken for bacterial detection by PCR. A longitudinal strip covering all stomach regions was taken for histology. Gastric colonization, inflammation, apoptosis, loss of parietal cells and cell proliferation were assessed. Controls and H. salomonis inoculated gerbils were negative in PCR. H. felis and H. bizzozeronii inoculated animals were positive. H. felis inoculated animals showed loss of parietal cells extending from the limiting ridge into the fundus. A high cell proliferation rate was noticed in the mucosal area devoid of parietal cells. A dense band of apoptotic cells and large numbers of Helicobacter bacteria were seen at the transition zone between affected and normal parietal cells. In H. bizzozeronii infected gerbils, this was less pronounced. Focal apoptotic loss of gastric epithelial cells was spatially associated with the presence of bacteria especially in H. felis and to a lesser extent in H. bizzozeronii infected gerbils. This loss of cells may lead to intestinal metaplasia.