Does poly-L-lysine coating of the middle cerebral artery occlusion suture improve infarct consistency in a murine model?

Background and Purpose: Rodent models of stroke that employ an intraluminal suture to cause focal cerebral ischemia are associated with some variability of resultant infarct volumes, thus requiring increased numbers of animals to determine significant differences between experimental groups. A recent modification of the occluding suture by coating with poly-L-lysine has been shown to create more uniform infarct volumes in rats. Methods: To evaluate the utility of this modification in murine models of both transient and permanent focal cerebral ischemia, male C57B16J mice were subjected to reversible middle cerebral artery occlusion (MCAo) for 45 minutes (n=42), or to permanent MCAo (n=25), with an intraluminal monofilament suture. Three types of sutures were used: untreated, partially coated, and completely coated with poly-L-lysine. Relative changes in regional cerebral blood flow, severity of neurological deficits, and infarct volumes were measured 24 hours after the ischemic injury. Results: Animals subjected to 45 minutes of temporary occlusion with completely coated poly-L-lysine sutures had infarct volumes of 13.8%±5% compared with infarct volumes of 7.2%±4% in those subjected to partially coated sutures and 22.4%±6% in the group occluded with untreated sutures (P=ns). Use of completely coated sutures resulted in significantly less reperfusion following suture removal. Control animals undergoing permanent occlusion with untreated sutures had infarct volumes of 17%±7% compared with 14.1%±5% using completely coated sutures and 6.5%±3% in animals with partially coated sutures (P=ns). There were no significant differences in cerebral blood flow between the experimental groups undergoing permanent MCAo. Conclusions: Poly-L-lysine coating of intraluminal sutures does not increase the consistency of infarct volumes in a murine model of temporary/permanent MCAo. These findings are in marked contrast to findings in rats.