Effect of anterior unilateral vagotomy on healing of kissing gastric ulcers induced in rats

Rapid and chronological expression of angiogenetic genes is a major mechanism involved in cell sheet transplantation in a rat gastric ulcer model

Introduction

Cell sheet technology has been applied in the treatment of patients with severe cardiac failure. Although the paracrine effect of cell sheets accelerating angiogenesis is thought to be the intrinsic mechanism for improvement of cardiac function, little is known about how a cell sheet would function in the abdomen.

Methods

We used acetic acid-induced gastric ulcer rat model to elucidate the mechanisms of myoblast sheet transplantation in the abdomen. Myoblast sheet was implanted onto the serosal side of the gastric ulcer and the effect of sheet transplantation was analyzed. The maximal diameter of the ulcer and the changes in the gene expression of various growth factors in transplanted site was analyzed. The progenitor marker CD34 was also examined by immunohistochemistry.

Results

Cell sheet transplantation accelerated the ulcer healing. qPCR showed that angiogenic growth factors were significantly upregulated around the ulcer in the transplantation group. In addition, at first, HIF-1a and SDF-1 continued to increase from 3 h after transplantation to 72 h, then VEGF increased significantly after 24 h with a slight delay. An immunohistochemical analysis showed a statistically significant increase in CD34 positivity in the tissue around the ulcer in the transplantation group.

Conclusion

Myoblast sheet secreted various growth factors and cytokines immediately after transplantation onto the serosal side of artificial ulcer in the abdomen. Autonomous secretion, resulting in the time-dependent and well-orchestrated gene expression of various growth factors, plays a crucial role in the cell sheet function. Cell sheet transplantation is expected to be useful to support angiogenesis of the ischemic area in the abdominal cavity.

Evaluation of the morphological changes of gastric mucosa induced by a low concentration of acetic acid using a rat model

Oral ingestion of concentrated acetic acid causes corrosive injury of the gastrointestinal tract. To assess the effects of a low concentration of acetic acid on gastric mucosa, we examined the gastric mucosal changes in rats at 1 and 3 days after the injection of 5% or 25% acetic acid into the gastric lumen. The area of the gastric ulcerative lesions in the 25% acetic acid group was significantly larger than that in the 5% acetic acid group. The lesion area was reduced significantly at 3 days after injection in the 5% acetic acid group, whereas no significant difference in lesion area was observed at 1 and 3 days in the 25% acetic acid group. Histologically, corrosive necrosis was limited to the mucosal layer in the 5% acetic acid group, whereas necrosis extended throughout the gastric wall in the 25% acetic acid group. At 3 days post-injection, the 25% acetic acid group showed widespread persistent inflammation, whereas the 5% acetic acid group showed widespread appearance of fibroblasts indicative of a healing process. These results indicate that a low concentration of acetic acid damages the gastric mucosa and that the degree of mucosal damage depends on the concentration of acetic acid.

Surface phospholipids in gastric injury and protection when a selective cyclooxygenase-2 inhibitor (Coxib) is used in combination with aspirin

BACKGROUND AND PURPOSE

Clinical studies demonstrate that aspirin consumption reverses the gastrointestinal (GI) benefits of coxibs, by an undefined mechanism.

EXPERIMENTAL APPROACH

Rodent models were employed to investigate the effects of combinations of celecoxib and aspirin on gastric ulcerogenesis, bleeding, surface hydrophobicity (by contact angle analysis) and ulcer healing. We also evaluated the effects of phosphatidylcholine (PC)-associated aspirin in these rodent models and confirmed its cyclooxygenase (COX)-inhibitory activity by measuring mucosal prostaglandin E(2) (PGE(2)) concentration. We present evidence that aspirin's ability to induce gastric injury and bleeding in rats, was exacerbated in the presence of a coxib and was dependent on its ability to reduce gastric surface hydrophobicity. In contrast, co-administration of phosphatidylcholine (PC)-associated aspirin and celecoxib induced little or no gastric injury/bleeding and maintained the stomach's hydrophobic properties. Interestingly, aspirin and aspirin/PC equally inhibited gastric mucosal PGE(2) concentration. Aspirin in combination with a coxib retarded the healing of experimentally induced gastric ulcers, whereas healing rates of rats treated with celecoxib in combination with aspirin/PC were comparable to controls.

CONCLUSIONS AND IMPLICATIONS

Aspirin's gastric toxicity in combination with a coxib can be dissociated from its ability to inhibit COX-1 and appears to be dependent, in part, on its ability to attenuate the stomach's surface hydrophobic barrier. This adverse drug interaction between aspirin and coxibs, which impacts the treatment of osteoarthritic and cardiac patients requiring cardiovascular prophylaxis, can be circumvented by the administration of phosphatidylcholine (PC)-associated aspirin, to maintain the stomach's hydrophobic properties.

An overview of acetic acid ulcer models--the history and state of the art of peptic ulcer research

Four types of experimental chronic ulcer models, named acetic acid ulcer models, have been developed to examine the healing process of peptic ulcers, screen anti-ulcer drugs, and better evaluate the adverse effects of various anti-inflammatory drugs on the gastrointestinal mucosa. The model easily and reliably produces round, deep ulcers in the stomach and duodenum, allowing acetic acid ulcer production in mice, rats, Mongolian gerbils, guinea pigs, cats, dogs, miniature pigs, and monkeys. These ulcer models highly resemble human ulcers in terms of both pathological features and healing process. The models have been established over the past 35 years and are now used throughout the world by basic and clinical scientists. One of the characteristic features of acetic acid ulcers in rats is the spontaneous relapse of healed ulcers >100 d after ulceration, an endoscopically confirmed phenomenon. Indomethacin significantly delays the healing of acetic acid ulcers, probably by reducing endogenous prostaglandins and inhibiting angiogenesis in ulcerated tissue. Helicobacter pylori significantly delays healing of acetic acid ulcers and causes relapse of healed ulcers at a high incidence in Mongolian gerbils. Anti-secretory drugs (e.g. omeprazole), prostaglandin analogs, mucosal defense agents (e.g. sucralfate), and various growth factors all significantly enhance healing of acetic acid ulcers. Gene therapy with epidermal growth factor and vascular endothelial growth factor applied to the base of acetic acid ulcers in rats is effective in enhancing ulcer healing. Since an inhibitor of nitric oxide syntase prevents ulcer healing, nitric oxide might be involved in the mechanism underlying ulcer healing. We conclude that acetic acid ulcer models are quite useful for various studies related to peptic ulcers.

Acetic Acid-Induced Gastro-duodenal Ulcers in Experimental Animals —Examples of Serendipity and Pseudoserendipity—

Our understanding of the function and etiology of various gastric diseases has exponentially expanded over the past 40 years. In particular, several animal models had been devised and used for screening of anti-ulcer drugs and elucidation of pathogenesis. This review describes how water-immersion stress ulcer model, Helicobacter pylori ulcer model, and acetic acid ulcer models were established in experimental animals. In recent years, genetically modified mice allowed rapid accumulation of very important findings. H(2)-receptor knockout mice revealed to exhibit Menetrier's disease-like gastric mucosal changes. Gastrin-transgenic mice infected with H. pylori revealed to develop gastric cancer. The hypothesis for the origin of parietal cells was provided.

Expression of functional neurokinin-1 receptors in regenerative glands during gastric wound healing in rodents

BACKGROUND & AIMS

Although functions of the neurokinin-1 receptor have been well explored in neurogenic inflammation and immunoinflammatory responses, little is known about neurokinin-1 receptors during gastric wound healing. The aim of this study was to assess whether neurokinin-1 receptors play a role in gastric wound healing.

METHODS

In vitro neurokinin-1 receptor autoradiography and immunohistochemistry were performed to identify, locate, and quantify neurokinin-1 receptors during wound healing in rodents with cryoulcers in the gastric corpus and antrum. Moreover, to assess the functionality of these receptors, the effect of the neurokinin-1 receptor antagonist NKP608 on gastric wound healing was quantified in vivo in wild-type and cyclooxygenase-2(-/-) mice.

RESULTS

Regenerative glands of the mucosal ulcer margin of rat cryoulcers of the gastric corpus showed strong expression of neurokinin-1 receptors in binding studies between days 3 and 22, with little expression on days 29-84. In addition, strong immunoreactivity for neurokinin-1 receptors was detected on the cell membrane of these regenerative glands. Expression of neurokinin-1 receptors in regenerative glands was confirmed in the rat antrum and the mouse gastric corpus. Moreover, in vivo functional tests during gastric ulcer healing showed that cell proliferation in the regenerative epithelia of the ulcer margin was significantly decreased by NKP608 compared with placebo; furthermore, gastric ulcer healing was significantly delayed by NKP608 both in wild-type and cyclooxygenase-2(-/-) mice.

CONCLUSIONS

This report shows the time-limited overexpression of neurokinin-1 receptors in the mucosal repair tissue of the corpus and antrum. Our in vitro and in vivo data suggest that neurokinin-1 receptors are involved in gastric wound healing.

[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.

Effect of temperature and mechanical strain on gastric epithelial cell line GSM06 wound restoration in vitro

BACKGROUND

The influence of the degree of cell differentiation and of physical stimulation on gastric mucosal wound healing is not completely understood.

METHODS

A gastric mucosal cell line, GSM06, derived from the gastric mucosal cells of transgenic mice harbouring the simian virus 40 large T antigen, was cultured at 33 degrees C to make a confluent cell sheet. Artificial wounds of constant size were created. Wound healing was monitored at different temperatures (33, 37 and 39 degrees C), which altered the degree of differentiation. Cell proliferation was detected by bromodeoxyuridine staining. Mechanical strain was applied to adherent GSM06 cells after wounding in order to increase their length by an average of 5 or 10% at 5 cycles/min for 60 h. Repair of the wound was monitored every 12 h.

RESULTS

Differentiated gastric epithelial cells showed a higher speed of migration. The number of proliferating cells around the wound was greatest at 33 degrees C and barely detectable at 39 degrees C. Under conditions of mechanical strain, the migration speed of differentiated cells (at 39 degrees C) slowed in a strain strength-dependent manner.

CONCLUSIONS

It is suggested that cell differentiation status and physical stimulants might play a role in gastric wound healing in vivo by modifying cellular migration.

Investigation on the mechanisms involved in the central protective effect of amylin on gastric ulcers in rats

1. The mechanisms involved in the protective effect of amylin (administered into the brain ventricle, i.c.v.) on gastric ulcers induced by the oral administration of ethanol 50% (EtOH, 2 ml/rat) or indomethacin (indomethacin, 20 mg kg(-1), at a dosing volume of 5 ml) were investigated in rats. 2. The possible involvement of endogenous nitric oxide (NO) in the beneficial effect of amylin against EtOH-induced ulcers was examined. The inhibitor of NO-synthesis, NG-nitro-L-arginine methyl ester (L-NAME, 70 mg kg(-1), s.c.) was injected 30 min before amylin (2.2 microg/rat, i.c.v.) followed by EtOH after a further 30 min. Rats were sacrificed 1 h after EtOH. L-NAME completely removed the protective effect of amylin. 3. The interaction between amylin and gastric nonprotein sulfhydryl groups was studied. The rats were treated with N-ethyl-maleimide (NEM, 25 mg kg(-1), s.c.) 30 min before amylin (2.2 microg/rat, i.c.v.) followed by EtOH 30 min after or by indomethacin 5 min after amylin. Rats were sacrificed 1 h or 6 h respectively after EtOH or indomethacin. NEM counteracted the protective effect of amylin against EtOH-induced ulcers but not against those provoked by indomethacin. 4. To determine whether amylin was able to promote ulcer healing, the peptide was injected 5 min after EtOH or 1 h after indomethacin. In the case of EtOH, the beneficial effect of amylin was lost whereas it was still effective on indomethacin-induced ulcers. 5. The results indicate that: the mechanisms involved in the antiulcer effects of amylin are different in these two types of gastric lesions probably because of the different etiopathology of various types of ulcers. Endogenous NO and nonprotein sulfhydryl groups are involved in the mucosal protective effects of amylin on EtOH and not on indomethacin-induced ulcers. Furthermore the effectiveness of amylin against indomethacin-induced lesions when administered after the ulcerogenic process has started suggests that amylin is involved not only in the protection but also in the healing mechanisms in this type of ulcer.

Effects of leminoprazole, omeprazole and sucralfate on indomethacin-induced delayed healing of kissing gastric ulcers in rats

We have examined whether or not repeated treatment with indomethacin delays the healing of kissing gastric ulcers induced in rats. The effects of leminoprazole, omeprazole and sucralfate on any delay in ulcer healing caused by indomethacin were also determined in relation to myeloperoxidase activity. Kissing gastric ulcers were induced by luminal application of an acetic acid solution. Indomethacin significantly delayed ulcer healing in a dose-dependent manner. Leminoprazole and omeprazole decreased the size and depth of ulcers, the healing of which was delayed by indomethacin, while sucralfate only decreased the ulcer depth. Histological studies showed that indomethacin inhibited tissue contraction and regeneration of the ulcerated mucosa. Leminoprazole and omeprazole prevented the inhibition of these parameters. The myeloperoxidase (MPO) activity of the ulcer portion in animals treated with indomethacin was markedly higher than in the control group. Both leminoprazole and omeprazole, but not sucralfate, significantly reduced MPO activity in contrast to the control value (in the presence of indomethacin). There was a significant relationship between the ulcerated area and myeloperoxidase activity. These results suggested that: (i) leminoprazole and omeprazole prevent the indomethacin-induced delay in ulcer healing by promoting tissue contraction and regeneration of the ulcerated mucosa; (ii) sucralfate prevents the indomethacin-induced delay in ulcer healing via the promotion of the formation of granulation tissue; and (iii) MPO activity will be useful to biochemically ensure the healing state of ulcers.

Changes in gastric function and healing of chronic gastric ulcers in aged rats

The present study was designed to determine the relationship between changes in gastric function caused by aging and the healing of gastric ulcers. Male Fischer-344 rats (young, 2 months; aged, 24-26 months) were used. Gastric ulcers were induced by luminal application of an acetic acid solution (60%, 0.2 ml, 45 sec). The basal and histamine-stimulated gastric acid secretions in aged animals were significantly lower than those in young animals. However, the serum gastrin levels were almost the same in the two groups. Gastric mucosal blood flow and mucosal cell proliferation were also decreased in aged animals. Gastric contractile activity induced by electrical vagal stimulation was almost the same in the two groups, while the gastric relaxative response was significantly reduced in aged animals. The development and healing rate of gastric ulcers in aged animals were almost the same as those in young animals. Histologically, regeneration of the ulcerated mucosa was significantly reduced and tissue contraction occurred in aged animals, as compared to in young animals. We concluded that aging had little or no influence on the development and healing rate of gastric ulcers in rats, but the quality of ulcer healing was quite different between young and aged animals, probably resulting from various gastric dysfunctions related to ulcer healing.

Acceleration of healing of gastric ulcers induced in rats by liquid diet: importance of tissue contraction

We examined the effect of a liquid diet or a combined diet of liquid plus cellulose on the healing of gastric ulcers induced in rats in comparison with that of solid chow. Ulcers were induced in the fundus of the stomach by luminal application of an acetic acid solution. The healing of ulcers could be divided into two phases based on the healing rate: early phase (days 1 to 10) and late phase (days 10 to 20). The liquid diet, but not the combined one, administered for 10 days significantly accelerated ulcer healing in both the early and late phases. The length of the ruptured muscularis mucosa decreased only in the liquid diet group in both phases. Regeneration of the ulcerated mucosa in the chow diet group was observed only in the late phase, it being markedly inhibited in the liquid diet group. The serum gastrin level significantly decreased in the liquid and combined diet groups in contrast to that in the chow group. The liquid and combined diets significantly reduced gastric mucosal DNA synthesis. We conclude that 1) the healing in this gastric ulcer model comprises two phases, and 2) tissue contraction is a major factor for the healing of gastric ulcers in the early phase, while both tissue contraction and regeneration of the ulcerated mucosa are involved in the healing in the late phase.