title: Diffusion-weighted magnetic resonance imaging reversal by gene knockdown of matrix metalloproteinase-9 activities in live animal brains.
abstract: The involvement of matrix metalloproteinase-9 (MMP-9) activities in the development of abnormal water diffusion in the brain after cardiac arrest is not fully understood. We used magnetic resonance imaging to determine the correlation between MMP-9 activity and the mechanism of abnormal water diffusion after global cerebral ischemia (GCI)-induced brain damage in C57black6 mice. We induced GCI in mice by occluding both carotid arteries for 60 min, then allowing reperfusion. We labeled a short DNA that targets mmp-9 mRNA activity [phosphorothioate-modified oligodeoxynucleotide (sODN)-mmp9] or a control probe without intracellular target (sODN-Ran) with iron-based MR contrast agent [superparamagnetic iron oxide nanoparticle (SPION)-mmp9 or SPION-Ran] or fluorescein isothiocyanate (FITC)-sODN-mmp9 or FITC-sODN-Ran; we then delivered these probes by intracerebroventricular infusion or intraperitoneal injection within 3 h of reperfusion. At low dose (120 pmol/kg) the SPION-mmp9 probe was retained at significant levels in the striatum and cortex of living brains 10 h after GCI. Probe retention was validated by similar elevation of mmp-9 mRNA and antigens in postmortem samples taken from regions that exhibited GCI-induced hyperintensity in diffusion-weighted imaging, and a significant reduction in apparent diffusion coefficient (rADC, p = 0.0006, n = 12). At a higher dose (120 nmol/kg), the FITC-sODN-mmp9 probe revealed significant knockdown of MMP-9 activity, per zymography, and a reversal of striatal rADC (p = 0.004, n = 6). These observations were not duplicated in the control group. We conclude that expression of mmp-9 mRNA is associated with abnormal ADC after GCI.
authors.affiliation: Laboratory for Transcript Targeting, Imaging and Repair, A. A. Martinos Center for Biomedical Imaging, Department of Radiology, and Department of Pediatrics, Massachusetts General Hospital, Charlestown, Massachusetts 02129, USA.
authors.forename: Christina H
authors.initials: CH
authors.lastname: Liu
authors.forename: Zerong
authors.initials: Z
authors.lastname: You
authors.forename: Charng-Ming
authors.initials: CM
authors.lastname: Liu
authors.forename: Young R
authors.initials: YR
authors.lastname: Kim
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Whalen
authors.forename: Bruce R
authors.initials: BR
authors.lastname: Rosen
authors.forename: Philip K
authors.initials: PK
authors.lastname: Liu
mesh_terms: D000818:Animals; D001921:Brain / Q000201:enzymology*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D055785:Gene Knockdown Techniques / Q000379:methods*; D008297:Male; D020780:Matrix Metalloproteinase 9 / Q000096:biosynthesis* / Q000235:genetics*; D051379:Mice; D008810:Mice, Inbred C57BL
chemical_list: D020780:Matrix Metalloproteinase 9