Murine Colitis Is Inhibited in Mmp-9 Knockout Mice: the Addition of Igfbp-3 Overexpression Does Not Further Decrease Disease Severity
Raymond Baxter*1, Aviad Hoffman1, Ik-Yong Kim1, Abu Nasar1, Kumara H. Shantha1, Mark Foster1, Keith Hoffman1, Richard L. Whelan1
1Surgery, Columbia University Medical Center, New York, NY; 2Pathology, Columbia University Medical Center, New York, NY
Introduction: Matrix Metalloproteinase 9 (MMP-9) has been found to be upregulated in the setting of inflammatory bowel disease (IBD). In the absence of MMP-9 production the disease has been found to be significantly less severe. Levels of Insulin like Growth Factor Binding Protein 3 (IGFBP-3), a cell growth inhibitor that is cleaved by MMP-9, are significantly decreased during active episodes of IBD and return to normal during remission. Although unproven, IGFBP-3 may inhibit colitis. The goals of this study were to determine the severity of chemically induced colitis in wild type (WT), MMP-9 null (KO), and MMP9 null/IGFBP-3 transgenic(KO/TG) mice.
Methods: All mice used were CD1 Background: 10 WT, 10 KO, and 8 TG/KO. Colitis was induced with dextran sodium sulfate (DSS) supplemented drinking water given for 14 days after which the animals were sacrificed. On day of sacrifice body weight and occult blood in stool were assessed. The colons were resected and evaluated and paraffin blocks prepared after which slides were made and stained with H&E and scored by a pathologist according to an established method. Results are reported as mean±sd. Statistical analyses were done using Fischer’s exact test, student’s t-test, and student’s paired t-test. Significance is p<0.05.
Results: Fecal occult blood and colitis was noted in all mice. Histologic analysis by a blinded observer confirmed that severe colitis was found more frequently in WT mice than in either the TG/KO or KO groups (p=0.007 and 0.01 respectively). Specifically, 63% of the TG/KO and 60% of the KO mice had mild colitis based on the scoring system vs 0% of the WT animals. Although all animals lost weight, the least severe losses were noted in the TG/KO mice (13 ± 7 %) than in the KO mice (15 ±7%) or WT mice (21 ± 10%, vs TG/KO, p=0.058). There were no significant differences between the TG/KO and the KO groups for any of the parameters.
Conclusions: Less severe colitis and less weight loss were noted in both the TG/KO and the KO groups when compared to the WT mice. However, overexpression of IGFBP-3, in the absence of MMP-9, in this model, did not further attenuate the colitis. Although IGFBP-3 levels are influenced by IBD disease activity, IGFBP-3, in and of itself, may not inhibit colitis.
