Epithelial cell turnover and apoptosis.

The homeostasis of gastric epithelial cells is maintained by the balance between cell proliferation and apoptosis. Alterations of these physiological cellular events in chronic pathological conditions of the stomach. As far as the proliferative pattern is concerned, an increase in the total number of epithelial proliferating cells and an abnormal distribution of the latter are frequently observed in chronic gastritis, gastric atrophy, intestinal metaplasia, gastric dysplasia and gastric cancer. Conversely, apoptosis has been found to be impaired in intestinal metaplasia, gastric dysplasia and cancer. Helicobacter pylori infection is associated with changes in epithelial-cell turnover, though their significance in gastric carcinogenesis is still controversial. An increase in overall epithelial cell proliferation and the upward shift of replicating cells toward the superficial part of the gastric pits are patterns usually observed during Helicobacter pylori infection and these changes can be reversed by successful eradication of the infection. However, it seems that this reversibility will be lost during progression through the steps of gastric carcinogenesis, such as intestinal metaplasia, probably representing the phenotypic expression of the true initiating phase of the carcinogenetic process. The influence of Helicobacter pylori infection on gastric epithelial apoptosis in humans is still controversial, since different results having been obtained by different authors. It seems that cagA status influences the effect of Helicobacter pylori on epithelial apoptosis, so that a different cagA make-up of the studied groups could explain these conflicting results. However, further studies are needed to elucidate this issue in humans.