Submucosal Fibrosis and Basic-Fibroblast Growth Factor-Positive Neutrophils Correlate with Colonic Stenosis in Cases of Ulcerative Colitis

Background and Aims: The frequency of benign stenosis in ulcerative colitis (UC) is low, reported as being 3.2–11.2%, with fibrosis in the submucosa or deeper pointed out as one of the causes. The aim of the present study was to assess stenosis in UC cases using immunostaining and to analyze differences between stenotic and nonstenotic cases, focusing on basic-fibroblast growth factor (b-FGF) expression and myofibroblasts. Methods: Totals of 9 stenotic and 17 nonstenotic UC cases were histopathologically examined and immunohistochemically stained for b-FGF, α-smooth muscle actin (α-SMA), CD34, CD68 and IL-6. To identify b-FGF-positive cells, double immunostaining for b-FGF and myeloperoxidase or CD68 was performed. Results: In addition to submucosal fibrosis, a significant increase of b-FGF-positive inflammatory cells and myofibroblasts was observed in stenotic portions. Most b-FGF-positive cells were also positive for myeloperoxidase, and a correlation between b-FGF-positive and total neutrophil counts was found. Conclusions: One of the major causes of stenosis in long-standing UC is fibrosis in the bowel wall, possibly induced by infiltrating inflammatory neutrophils producing b-FGF.