Injury, repair, inflammation and metaplasia in the stomach

Abstract The development of intestinal‐type gastric cancer is preceded by the emergence of metaplastic cell lineages in the gastric mucosa. In particular, intestinal metaplasia and spasmolytic polypeptide‐expressing metaplasia (SPEM) have been associated with the pathological progression to intestinal‐type gastric cancer. The development of SPEM represents a physiological response to damage that recruits reparative cells to sites of mucosal injury. Metaplastic cell lineages are characterized by mucus secretion, adding a protective barrier to the epithelium. Increasing evidence indicates that the influence of alarmins and cytokines is required to initiate the process of metaplasia development. In particular, IL‐33 derived from epithelial cells stimulates IL‐13 production by specialized innate immune cells to induce chief cell transdifferentiation into SPEM following the loss of parietal cells from the corpus of the stomach. While SPEM represents a physiological healing response to acute injury, persistent injury and chronic inflammation can perpetuate a recurring pattern of reprogramming and metaplasia that is a risk factor for gastric cancer development. The transdifferentiation of zymogen secreting cells into mucous cell metaplasia may represent both a general repair mechanism in response to mucosal injury in many epithelia as well as a common pre‐neoplastic pathway associated with chronic injury and inflammation. image