Immunoreactivity of infiltrating macrophages during gastric ulcer healing in rats

This study investigated a timeline of changes in the immunoreactivity of infiltrating macrophages during gastric ulcer healing. To this end, gastric tissue samples were obtained from an acetic acid-induced gastric ulcer model in rats on the 1st, 3rd, 7th, and 14th days of ulcer induction. Ulcerated gastric tissues were subjected to histologic and immunohistochemical evaluations for macrophage subtypes. The number of Iba-1+ macrophages in the gastric ulcer area significantly increased on day 3, reaching a maximum number on day 7, followed by a decrease on day 14. No Gal-3+ macrophages were seen in the gastric ulcer area until day 14. Interestingly, CD68 reacted with macrophages, (myo)fibroblast-like spindle-shaped cells, and endothelial cells in the gastric ulcer area. There was a significant increase in the α-SMA+ myofibroblasts and desmin+ microvessels on days 7 and 14. The increase in the number of Iba-1+ macrophages was followed by the appearance of α-SMA+ myofibroblasts and desmin+ blood vessels. These results suggest that (i) different macrophage subtypes are involved in gastric ulcer healing, (ii) Iba-1+ macrophages, observed in the early stages of gastric healing, participate in proinflammatory and regenerative activities, (iii) Gal-3+ macrophages, seen in the late stages of healing, contribute to proinflammatory response and tissue repair, and (iv) CD68 is not a macrophage-specific marker.