S1670 A Potential Role for Intestinal Alkaline Phosphatase in Colonic Inflammation

Abstract

Background: Colorectal cancer (CRC) is common and its incidence increases over time with the chronic intestinal inflammation observed in patients with Inflammatory Bowel Disease. Secreted Protein, Acidic and Rich in Cysteine (SPARC) has been show to affect tumour growth, cancer invasion and patient prognosis in numerous human cancers including bowel cancer. SPARC may also affect the colonic inflammatory response. Aim: To investigate SPARC's role on the development of colonic inflammation in the mouse. Methods: SPARC wild-type (WT) and knockout (KO) mice were treated with 3% dextran sodium sulphate (DSS) for 7 days. Intestinal inflammation was assessed on day 6, using the modified murine endoscopic score of colitis severity (MEICS), by high-resolution miniature video endoscopy. Mice were sacrificed and the colons assess histologically. In separate experiments, colons were harvested and total lymphocytes were isolated from the spleen, intra-epithelium (IE) and rest of colon (C) and were analysed for levels of CD4 and FoxP3 +ve cells by flow cytometry. Results: SPARC KO mice demonstrated less endoscopic colonic inflammation than WT mice (MEICS 4 vs 7; p=0.013) and less weight loss (KO 0.48% weight gain vs WT 6.2% weight loss p=0.074). Overall lymphocyte numbers isolated from spleen, IE and C fromKOwasmarkedly less than that isolated fromWTmice (0.77x108/ml vs 1.28x108/ml; 0.82x106/ml vs 16.8x106/ml and 4.4x106/ml vs 8.8x106/ml respectively). The percentage of CD4 +ve cells from spleen, IE and C were between 10-15% from both KO and WT mice. The percentage of FoxP3 +ve cells from spleen, IE and C from both KO and WT mice were 0.05% vs 1.85%, 1.2% vs 2.3%, 1.22% vs 1.75% respectively. Conclusion: SPARC affects the endoscopic colonic inflammatory response. Total lymphocyte counts are lower in inflamed SPARC KO colons and spleen consistent with a lower level of chronic inflammation. The percentage of FoxP3 +ve cells from the spleen and IE were lower in KO mice suggesting an impact of regulation of the immune response. The mechanistic impact of SPARC requires further elucidation.