Inflammation driven by overexpression of the hypoglycosylated abnormal mucin 1 (MUC1) links inflammatory bowel disease and pancreatitis

Abstract

Objective: Pancreatitis occurs as an extraintestinal complication of inflammatory bowel disease (IBD), but the cause is poorly understood. Mucin 1 (MUC1) is overexpressed in an abnormal, hypoglycosylated form on the colonic epithelium in human IBD where it contributes to inflammation. MUC1 is also expressed on pancreatic ductal epithelia. We tested the possibility that in IBD, MUC1 expression on pancreatic ducts is also abnormal leading to inflammation and pancreatitis.

Methods: We used MUC1/interleukin-10 mice that develop IBD. We imaged abnormal MUC1 expression in these mice by adoptively transferring T cells from T cell receptor transgenic mice specific for abnormal MUC1. Cells were labeled with a novel perfluorocarbon tracer reagent and quantified and visualized in vivo using high-throughput F nuclear magnetic resonance spectroscopy and magnetic resonance imaging.

Results: MUC1-specific T cells migrated to the colon in mice with IBD and also to the pancreas. Immunohistochemistry confirmed increased expression on the pancreatic ducts of the abnormal MUC1 seen in the colon and the presence of cellular infiltrate.

Conclusions: Migration of MUC1-specific T cells to the colon and the pancreas in diseased mice suggests that pancreatitis is an extraintestinal site of IBD, characterized by proinflammatory abnormal expression of MUC1. Therapies directed against abnormal MUC1 have the potential of targeting the disease in both sites.

Figure 1. Inflammation and MUC1 expression in MUC1 Tg mice compared to MUC1⁺/IL10^-/- mice

Hematoxylin and eosin (H&E) stained mouse colon sections in (A) MUC1 Tg mice and (B) MUC1⁺/IL10^-/- mice. Scale bar, 50 μm. Immunofluorecence stained mouse colons in (C) MUC1 Tg mice and (D) MUC1⁺/IL10^-/- mice. Colon sections are stained with antibodies against MUC1 (green), nuclear stain (blue), and Phalloidin (red) for visualization of colonic tissue architecture.

Figure 2. MUC1-specific TCR-transgenic T cells (VFT cells) preferentially migrate to the colon and pancreas in MUC1⁺/IL10^-/- mice

(A) ¹⁹F NMR spectroscopy of the excised organs 72 hours after adoptive transfer of labeled VFT T cells into spleen, liver, pancreas, mesenteric lymph nodes, colon, kidney, lung, and thymus of MUC1 Tg mice, MUC1⁺/IL10^-/- mice, and IL10^-/- mice. Cell trafficking is normalized to the spleen (p<0.05, Wilcoxon rank sum test). (B) Cell trafficking to the colon is normalized to the spleen in individual mice. (C) Cell trafficking to the pancreas is normalized to the spleen in individual mice. (D and E) ¹H/¹⁹F MRI composite image through the abdomen of MUC1⁺/IL10^-/- mice 72 hours after adoptive transfer. ¹H image is rendered in grey scale and ¹⁹F image is rendered in pseudo-color. The border of the pancreas is delineated in green.

Figure 3. MUC1 expression in the pancreatic ducts of MUC1 Tg mice compared to MUC1⁺/IL10^-/- mice

Immunostaining (hematoxylin counterstained) of mouse pancreas in MUC1⁺/IL10^-/- mice (A) and MUC1 Tg mice (B) with anti-MUC1 antibody (3C6). Immunostaining (hematoxylin counterstained) of mouse pancreas in MUC1⁺/IL10^-/- mice (C) and MUC1 Tg mice (D) with anti-MUC1 antibody (4H5). Isotype control is negative for MUC1 staining (E). Scale bar, 50 μm.