The expression of pepsinogen c mRNA in normal gastroduodenal mucosa and the gastric ulcer margin of the rat

Regeneration of gastric mucosa during ulcer healing follows pathways that correspond to the ontogenetic course of rat fundic glands

Gastric ulcers in humans are notoriously chronic and recurring lesions. Although the average individual who undergoes no treatments requires many years for healing, most studies on the healing process of the experimentally induced ulcers have mainly focused on the early stages. Natural history of the ulcer healing has not been completely revealed. We have undertaken long-term investigation up to the 150th day after the cryo-injury to shed light on the natural history of the ulcer healing process compared with developmental changes of postnatal fundic glands. By the 30th day, restitutive gastric glands were mostly seen to cover the ulcer lesions, where well-developed gland-type mucous cells, showing Griffonia simplicifolia agglutinin (GSA)-II labeling, appeared to occupy the basal portion. Most of the bromodeoxyuridine-labeled cells were superimposed on the GSA-II-positive cell zone, forming the proliferative zone. By the 150th day, the restitutive glands were complete, with all epithelial components and topology of the normal fundic glands. The process of the ulcer healing was quite compatible with the developmental changes of the postnatal fundic glands. These results imply that the regeneration of gastric epithelium during the ulcer healing follows pathways linked to the ontogenetic course of the fundic gland.

Parietal cell density during gastric ulcer healing in the rat

BACKGROUND

During the healing of gastric ulcers, extensive changes take place in the structure and proportion of the parietal cells in the ulcer margin. We aimed to determine whether these changes are influenced by compounds or by procedures that may promote or delay gastric ulcer healing.

METHODS

Acetic acid ulcers were produced in the rat gastric corpus; control rats were non-operated or sham-operated. All rats were provided with an osmotic minipump releasing 3H-thymidine for determination of the labelling index (LI). The rats were given omeprazole, gastrin or indomethacin, infected with Helicobacter pylori, or subjected to anterior vagotomy. They were killed after 1, 2, 6 or 13 days, and the ulcer margin and undamaged corpus wall were excised for histology. The proportion of parietal cells was calculated in relation to the total number, and the total volume, of the epithelial cells.

RESULTS

The parietal cells averaged 16%-21% of the number and 30%-32% of the volume of the epithelial cells in the unoperated control rats, but considerably less in the ulcer margin. This reduction was partially prevented by indomethacin. In the undamaged, dorsal epithelium the parietal cells increased to 23%-26% of the number, and 41%-47% of the volume, of the epithelial cells, both in the ulcer rats and in the sham-operated rats. The LI of the parietal cells was 6% in the undamaged epithelium of the 13-day ulcer rats, but close to 0% in all other groups examined.

CONCLUSION

Indomethacin prevents much of the loss of parietal cells in the ulcer margin. In the undamaged epithelium of the ulcer rats there is an increased proportion of parietal cells. The new parietal cells are not formed directly from dividing cells, but are probably recruited from existing precursor cells.

[An overview of acetic acid ulcer models and their utility for drug screening]

Since Takagi et al. reported an experimental chronic gastric ulcer model [acetic acid ulcers induced by submucosal injection of acetic acid (Type 1)], we further modified the methodology and subsequently devised three more models. The second model involves inducing ulcers by serosal application of an acetic acid solution (Type 2) and the third model achieves ulcer induction by intragastric application of an acetic acid solution (Type 3). The forth model was modification of the third model by giving the acetic acid solution and the same volume of air to make one ulcer in the stomach (Type 4). In general, animals accepted the procedures without problems and no undesirable effects were noticed. More importantly, this experimental animal model allows production of ulcers that highly resemble human ulcers in terms of both pathology and healing. Indeed, relapse is even endoscopically observed for 360 days after ulceration. The ulcers produced not only respond well to various anti-ulcer medications, such as antisecretory and mucosal protective drugs and growth factors, but also demonstrate appropriate responses to ulcerogenic agents such as NSAIDs. In addition, we have recently demonstrated that H. pylori infection resulted in delayed ulcer healing and recurrence of healed acetic acid ulcers induced in Mongolian gerbils. The present article gives a brief summary of the ulcer history before establishment of acetic acid ulcers and characteristic features of acetic acid ulcer, including both their merits and shortcomings.

Eosinophil infiltration and activation at the gastric ulcer margin in rats

BACKGROUND

Recruitment and activation of eosinophils have been studied intensely in asthma and other allergic diseases. Less is known about the infiltration and behaviour of eosinophils during gastric ulcer healing.

AIM

To examine the tissue infiltration and activation of eosinophils in the ulcer margin at different time points after ulcer induction (days 1-15).

METHODS

Eosinophil peroxidase (EPO) staining and transmission electron microscopy (TEM) were used to observe eosinophil infiltration and activation in rats with acetic-acid-induced ulcer in the oxyntic mucosa. The distribution of macrophages was evaluated by immunocytochemistry using the macrophage-specific antibodies ED1 and ED2.

RESULTS

There was a prominent increase in eosinophils around the ulcer margin at day 1 after ulcer induction, which peaked at day 5. TEM revealed characteristic signs of eosinophil activation, including cytolysis and piecemeal degranulation. Eosinophil cytolysis was the major form of activation, seen most frequently at day 5. A few scattered apoptotic eosinophils could also be observed. In normal controls and sham-operated rats, activated eosinophils were detected rarely. The distribution pattern of infiltrated eosinophils closely resembled that of macrophages at the ulcer margin. However, in the central part of the granulation tissue (at day 5) only macrophages could be found.

CONCLUSIONS

There is marked infiltration and signs of activation of eosinophils together with macrophages at the margin of newly formed ulcers.

Cholecystokinin-B/gastrin receptors enhance wound healing in the rat gastric mucosa

Although physiological functions of the CCK-B/gastrin receptor are well explored, little is known about its role during healing. Here, we evaluated the role of this receptor in the rat oxyntic mucosa following the introduction of a cryoulcer. In this model, we located and quantified CCK-B/gastrin receptors by reverse transcriptase PCR and receptor autoradiography. Rats with cryoulcers were treated with placebo, omeprazole, the CCK-B/gastrin receptor antagonist YF-476, omeprazole plus YF-476, gastrin-17, and gastrin 17 plus YF-476. During wound healing, CCK-B/gastrin receptors were specifically expressed and localized to the regenerative mucosal ulcer margin. This high expression was limited in time, and the pattern of expression of CCK-B/gastrin receptors correlated closely with the proliferative activity of the regenerative mucosa. Functionally, omeprazole and gastrin-17 caused profound hypergastrinemia, increased cell proliferation in the mucosal ulcer margin and accelerated the late ulcer healing phase. These effects were completely reversed by cotherapy with YF-476. These in vivo and vitro data suggest that CCK-B/gastrin receptors in regenerative rat gastric oxyntic mucosa enhance trophic effects during wound healing.

A rat model of chronic Helicobacter pylori infection. Studies of epithelial cell turnover and gastric ulcer healing

BACKGROUND

Our aim was to infect rats with Helicobacter pylori and to study the effects of the infection on the gastric mucosa in normal and in ulcer-operated rats.

METHODS

A mouse-adapted H. pylori (cagA-, VacA-) strain was inoculated into 23 rats. Another 20 uninfected rats served as controls. Two months later a gastric ulcer was induced in some rats. The animals were killed 3, 6, or 15 days after the ulcer operation. Tissues were taken for histology and for culture of H. pylori. Serum antibodies were determined.

RESULTS

All inoculated rats were infected by H. pylori after 2 months, mainly in the antrum. In these rats a mild to moderate chronic inflammation and a significantly increased frequency of apoptotic cells were observed in the antrum and in the ulcer margin, the ulcer healing was delayed, and the serum level of H. pylori-specific Ig was increased.

CONCLUSIONS

H. pylori infection in rats was successful and was accompanied by a mild to moderate mucosal inflammation. Gastric ulcer healing was delayed in infected rats, probably due to the inflammation and the increased apoptosis in epithelium.