Therapeutic application of gene silencing MMP‐9 in a middle cerebral artery occlusion‐induced focal ischemia rat model

Abstract

RNA interference appears to have a great potential not only as an in vitro target validation, but also as a novel therapeutic strategy based on the highly specific and efficient silencing of a target gene. We hypothesize that MMP‐9 siRNA can be effective as an MMP‐9 protein inhibitor in a rat focal ischemia model. Male Sprague‐Dawley rats (156) were subjected to 2 h of middle cerebral artery occlusion (by using the suture insertion method)followed by 24 h of reperfusion. In the treatment group, 5 μl MMP‐9 siRNA was administrated by intracerebroventricular injection within 60 min after 2 h of focal ischemia. The siRNA transfection was demonstrated by fluorescence conjugated siRNA. Treatment with MMP‐9 siRNA produced a significant reduction in the cerebral infarction volume, brain water content, mortality rate and accompanying neurological deficits. The following were recorded: Evan's blue and IgG extravasation were reduced; the expression of MMP‐9 mRNA and protein were significantly silenced; and Immunohistochemistry and Western blot analysis revealed that the expression of MMP‐9 and VEGF were reduced while occludin and collagen‐ IV were up‐regulated in brain tissues. Our findings provide evidence that a liposomal formulation of siRNA might be used in vivo to silence the MMP‐9 gene and could potentially serve as an important therapeutic alternative in patients with cerebral ischemia.