Intestinal macrophages contribute largely to maintain the intestinal homeostasis. Recent studies have revealed that the resident macrophages in the intestinal mucosa show M2 macrophage-like properties such as high production of IL-10 and expression of M2 macrophage markers. CD206 is one of the common M2 macrophage markers and a part of intestinal macrophages actually express CD206. However, the precise role of CD206 positive intestinal macrophages in the intestinal inflammation still remains unclear. In the present study, we investigated the role of CD206 positive intestinal macrophages in the acute colitis and wound healing after colonic epithelial damage.
To elucidate the role of CD206 positive intestinal macrophages, we used transgenic mice expressing human diphtheria toxin receptor (DTR) under the control of CD206 gene promoter. For ablation of CD206 positive macrophages, CD206-DTR transgenic mice were injected intraperitoneally with DT. The expression of IL-10 mRNA in the resident intestinal macrophages was decreased in those isolated from CD206 positive cell-depleted mice compared with WT mice. The acute colitis model was induced by treatment with 3% dextran sulfate sodium (DSS) in the drinking water for 7 days. There was no significant difference in the severity of acute colitis between WT and CD206-DTR mice. Next, we evaluated the repairing ability of CD206 positive intestinal macrophages on the colonic epithelial damage using CMT-93, a murine colonic epithelial cell line. The intestinal macrophages isolated from WT mice promoted the wound healing of CMT-93 after the scratch damage. We found that the CD206 positive cell-depleted intestinal macrophages did not affect the wound healing.
The present results suggest that CD206 positive intestinal macrophages play an important role in the wound healing following inflammatory damage to the intestinal mucosa such as inflammatory bowel disease.