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* = Presenting author

P038 Revised roles of matrix metalloproteinase/MMP-9 in inflammatory bowel diseases: from target to biomarker

M. de Bruyn*1, 2, C. Breynaert3, I. Arijs2, G. De Hertogh4, K. Geboes4, G. Thijs1, J. Hu5, J. Van Damme1, B. Arnold6, M. Ferrante7, S. Vermeire7, G. Van Assche7, J. Ceuppens3, G. Opdenakker1

1Rega Institute for Medical Research, KU Leuven, Department of Microbiology and Immunology, Leuven, Belgium, 2Translational Research Centre for Gastrointestinal Disorders (TARGID), KU Leuven, Department of Clinical and Experimental Medicine, Leuven, Belgium, 3Laboratory of Clinical Immunology, KU Leuven, Department of Microbiology and Immunology, Leuven, Belgium, 4Translational Cell and Tissue Research, KU Leuven, Department of Imaging and Pathology, Leuven, Belgium, 5Key Laboratory of Modern Chinese Medicines, China Pharmaceutical University, Ministry of Education, Nanjing, China, 6German Cancer Research Centre (DKFZ), Department of Molecular Immunology, Heidelberg, Germany, 7University Hospitals Leuven, KU Leuven, Department of Gastroenterology, Leuven, Belgium

Background

MMP-9 is elevated in blood and intestinal tissue of IBD patients and is suggested by knockout (KO) mouse and inhibitor studies as a key causal factor. MMP-9 antagonists are presently evaluated in clinical trials for IBD. Our aim was to reinvestigate the role of MMP-9 in acute and chronic intestinal inflammation.

Methods

MMP-9 KO mice were backcrossed for 13 generations into C57BL/6J mice and bred under identical environmental conditions for >15 years in our animal facility. In 8–10-week-old MMP-9 KO mice and their WT littermates, acute colitis was induced by oral administration of 3% dextran sodium sulphate (DSS) for 7 days, followed by 2 days of regular water. Chronic colitis was induced by 3 cycles of 1 week 1.75%–2.0% DSS each followed by a recovery phase of 2 weeks. Intestinal inflammation and fibrosis were assessed by macroscopic parameters, histopathology analysis, and tissue collagen levels. In colonic tissue, MMP-9 levels were determined by zymography analysis, and gene expression differences were assessed with RNA sequencing (Illumina HiSeq2500, fold change [FC] > 2, 10% false discovery rate [FDR]). Pharmacological inhibition of MMP-9 was tested by administration of 2 peptide inhibitors (CPU1 and CPU2) to acute DSS-treated C57BL/6J mice via daily intraperitoneal injections (250 µg) and via implanted osmotic pumps (30 mg/kg/day). The inhibitory effect was evaluated by clinical, histopathological, and qRT-polymerase chain reaction (PCR) analyses.

Results

In contrast to previously reported phenotypes, clinical and histopathological parameters were not attenuated in MMP-9 KO mice after acute DSS administration compared with WT littermates. Zymography analysis confirmed absence of MMP-9 in our KO mice and showed increased MMP-9 levels after DSS in WT mice only. Similar expression of host genes in WT and MMP-9 KO control mice was observed, with exception of Mmp9 (FC = 3.8), Rims4 (FC = -6.0), and Slpi (FC = 2.5). After induction of colitis, 11 genes involved in antimicrobial response were differentially expressed between WT and MMP-9 KO mice. Development of fibrosis was not altered in chronic DSS-treated MMP-9 KO mice, although less goblet cell loss was observed compared with WT mice. Pharmacological inhibition of MMP-9 with CPU1 and CPU2 did not improve parameters of intestinal inflammation. On the contrary, increased Mmp3, Mmp8, and Mmp9 expression was observed in DSS-treated mice that received CPU2 compared with saline.

Conclusion

Against prevailing evidences, we demonstrate that MMP-9 deletion or inhibition does not lead to clinical and histopathological attenuation of DSS-induced colitis. Whereas MMP-9 remains an excellent inflammatory marker in IBD, ongoing clinical trials with MMP-9 inhibition as a therapeutic option for IBD need to be carefully followed.