• Naoki Kuroda, Masahiro Masuya, Isao Tawara, Junya Tsuboi, Misao Yoneda, Kenichiro Nishikawa, Yuki Kageyama, Kensuke Hachiya, Kohshi Ohishi, Hiroshi Miwa, Reiko Yamada, Yasuhiko Hamada, Kyosuke Tanaka, Takuma Kato, Yoshiyuki Takei, and Naoyuki Katayama.
• Department of Hematology and Oncology, Mie University Graduate School of Medicine, Tsu, Mie, 514-8507, Japan.
• Sci Rep. 2019 Jun 12; 9 (1): 8568.

AbstractIntestinal fibrosis is a serious complication in inflammatory bowel disease (IBD). Despite the remarkable success of recent anti-inflammatory therapies for IBD, incidence of intestinal fibrosis and need for bowel resection have not significantly changed. To clarify the contribution of haematopoietic-derived cells in intestinal fibrosis, we prepared bone marrow (BM) chimeric mice (chimeras), which were reconstituted with BM cells derived from enhanced green fluorescent protein (EGFP)-transgenic mice or CC chemokine receptor 2 (CCR2)-deficient mice. After 2 months of transplantation, BM chimeras were treated with azoxymethane/dextran sodium sulphate. During chronic inflammation, CCR2+ BM-derived monocyte and fibrocyte infiltration into the colon and CC chemokine ligand 2 production increased, leading to colon fibrosis in EGFP BM chimeras. In CCR2-deficient BM chimeras, monocyte and fibrocyte numbers in the colonic lamina propria significantly decreased, and colon fibrosis was attenuated. In colon tissue, mRNA expression of tissue inhibitor of metalloproteinase (TIMP)-1 but not of collagen I, transforming growth factor-β1 or matrix metalloproteinases was significantly different between the two chimeras. CCR2+ monocytes and fibrocytes showed high Timp1 mRNA expression. Our results suggest that infiltrating CCR2+ monocytes and their progenies, fibrocytes, promote colon fibrosis by inhibiting collagen degradation through TIMP-1 production.

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