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P004. SPARC enhances intestinal inflammation in dextran sodium sulphate-induced murine colitis

Y.‑L. Ng1, B. Klopcic2, F. Lyold2, W. Greene1, I. Lawrance2

1School of Veterinary and Biomedical Sciences, Murdoch University, Perth, Australia; 2Centre for Inflammatory Bowel diseases, School of Medicine and Pharmacology, Fremantle, Australia

Background: Secreted Protein Acidic and Rich in Cysteine (SPARC) is a matricellular protein expressed during tissue repair and regulates cell proliferation and migration. The aim was to determine if SPARC modifies intestinal inflammation.

Methods: Wild-type (WT) and SPARC-null (KO) 129/SvJ × C57/BL6 mice received 7 days of 3% dextran sodium sulphate (DSS) in the drinking water and were sacrificed on days 7, 14, 21 and 35. Inflammation was assessed endoscopically, clinically and histologically. Expression levels of IL1β, IL6, TNFα, MCP1, MIG, RANTES and TGFβ1 were assessed as was the cellular inflammatory infiltrate by the presence of CD3, CD4, CD25, FoxP3 by flow cytometry and CD11b, CD68 and Ly6G by immunofluorescence.

Results: Maximal histological inflammation was observed at day 7, but KO animals had lower endoscopic inflammatory scores at day 6 and each time point (days 6, 20 p < 0.05, day 34 p < 0.001), suffered less weight loss, diarrhoea, faecal blood and had lower spleen to body weight ratios at day 7 (p < 0.01) and 21 (p < 0.05) consistent with less colonic and systemic inflammation. In KO colons at day 7 there was less IL1β (p < 0.05) and MIG (p < 0.05) expression while IL6, TNFα levels were numerically lower but were not significant. RANTES was reduced at day 21 (p < 0.05). TGF β 1 levels were higher in KO colons that was significant at day 7 (p < 0.05). Flow cytometry identified a greater percentage of FoxP3 regulatory T cells in KO spleens (p < 0.01 days 14, 21 and 35) and in the draining lymph nodes (p < 0.05 day 14). KO colons also had less CD68+ macrophages at days 21 (p < 0.05) and 35 (p < 0.01) and were lower at days 7 and 14 but these differences were not significant. The number of CD11b+ cells and Ly6G+ neutrophils were significantly less in KO colons at day 35 (p < 0.05).

Conclusions: DSS induced less colonic and systemic inflammation in SPARC KO compared to WT mice and the inflammation appeared to resolve faster. This may be secondary to increased numbers of regulatory T cells and increased TGFβ1 levels which may inhibit effector cell activity, cytokine and chemokine expression and aid in the more rapid resolution of inflammation and restoration of the intestinal mucosa.