| Objective:Gastric mucosal defense-repair mechanisms include mucus-bicarbonate-phospholipids’barrier, gastric mucosal epithelial cells and tight junctions between cells, and gastric mucosal blood flow。 The integrity of the GMD-RM is necessary to maintain gastric mucosal function. Clinical findings that gastrointestinal ulcers, erosions and other inflammatory diseases in elder people have higher incidence and the conditions are more serious than in young people. Because of human specimens’collection is difficult, and cannot be controlled in many factors, therefore we can’t control the confounding factors in the experiment. And changes of GMD-RM with aging in rats have been studied a lot, so in our study we selected healthy adult Beagles, by observing the different age groups’normal antral mucosal, pyloric glands’and epithelial cells’histology, ultrastructure and the GMD-RM-related biological activity factors in order to discuss whether the GMD-RM’s function decline with aging, and investigate its preliminary mechanisms.Method:1, Selected 19 healthy adult Beagles, divided into three groups according to age:1.5-6 years old in the young group (n=8),6-9 years old in the junior elderly group (n=five), ≥9 years old in the senior elderly group (n=6). We measured the Beagles’weight and exsanguinated for routine blood test and biochemical test before they were given to intravenous anesthesia death. In ten minutes after death we took the stomach away from the body in order to take 3 pieces of antral mucosa:one for pathology, one for electron microscopic examination, frozen anther one immediately to do molecular biology detection. We observed the antral mucosal histology to find whether there is intestinal metaplasia, dysplasia, and semi-quantitative analysis of inflammatory index, measured the thickness of the lamina propria and calculated the percentage of mucus glands substantive through light microscope. We observed the antral mucosal epithelial cells’and pyloric glandular cells’ultrastructure, compared the changes of cell junctions with aging, calculated the ratio Am to Ac wih SigmaScan Pro 5 software under the electron microscopy. We detected some molecular biological activity factors, including MDA, MPO, LPO by TBA assay; NO by nitrate reductase; Survivin, PTEN, CGRP, VEGF, close junction protein ZO-1, COX-1, COX-2, Caspase-3, Caspase-9 and telomerase levels by Elisa assay.Results:(1) 19 Beagles’weight were in the 14～20Kg; both routine blood tests and biochemical tests were normal.(2) By qualitative analysis, no significant difference was found in the morphology of epithelial cells or pyloric glands or glandular cells. All specimens had no intestinal metaplasia or dysplasia, some of them had a small amount of inflammatory cells infiltration, the inflammation index of each group by semi-quantitative analysis had no significant difference (P= 0.977). However, interstitial hyperplasia was clearly seen in the lamina propria of senior elderly group, who also had a sparse arrangement of the pyloric glands. By quantitative analysis, the average thickness of the lamina propria and the proportion of antral mucous glands decreased with aging, also there were significant difference (P= 0.015, P= 0.002).(3) Under electron microscopy, by observing the ultrastructure of epithelial cells, the pyloric glandular cells and the junctions between epithelial cells. The results showed that there were no significant changes in the tight junctions of epithelial cells with aging, but the middle junctions and gap junctions have gradually loosened. There was a decreasing trend in organelles associated with mucus secretion with aging. Quantitative analysis showed there was a significant difference in the average ratio Am:Ac between all groups (P= 0.000).(4) Estimation of the content of MDA, LPO, MPO by TBA method in the gastric mucosa, the results showed that although MDA, MPO levels had an increasing trend, no significant difference was found between groups (P= 0.452, P= 0.094). In every two groups, MPO levels in senior elderly group were higher than the young group, and statistically significant (P= 0.044). LPO levels had an increasing trend and significant difference (P= 0.047).(5) Quantitative determination of the content of NO by nitrate reductase in the gastric mucosa, the levels tended to decrease with aging, but had no significant difference between groups (P= 0.200).(6) By Elisa method we found that during aging the gastric mucosal content of Survivin (P= 0.049) decreased significantly; PTEN (P= 0.015), caspase-9 (P= 0.002) levels increased significantly; while CGRP, VEGF, ZO-1, COX-1, COX-2, caspase-3, telomerase levels despite had a decreasing trend, but no significant difference. Comparison every two groups we found that the junior elderly group’s VEGF (P= 0.024), COX-1 (P= 0.033), COX-2 (P= 0.048) were significantly lower than the young group’s; caspase-3 (P= 0.026) in senior elderly group was significantly lower than the young group.Conclusion:In our study we find that the thickness of Beagles’antral mucosal, the tightness of middle junctions and gap junctions between epithelial cells, the density of pyloric glands and organelles associated with mucus secretion decreased with aging, indicating that the morphology of gastric antral mucosa and its functioning glands have deteriorated with aging. In the same time we find that the levels of MDA, LPO, MPO, which reflect the degree of lipid peroxidation and oxidative stress injury in gastric mucosa, had an increasing trend during aging. The levels of CGRP and NO, which related to the gastric mucosal blood flow’s regulation, decreased with aging; Survivin which plays an important role in anti-aging had a decreasing trend, while the others which can induce cells’apoptosis, such as PTEN, caspase-3, caspase-9, had decreasing trends during aging. VEGF, which reflects the regenerative capacity of GMBF, tended to decrease, COX-1 and COX-2, which regulate the GMBF indirectly, also had decreasing during aging. So we can draw the conclusion that gastric mucosa defense-repair mechanisms during aging is the result of a multifactorial interaction with multiple interlinks. |
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