Therapeutic Evaluation Of R-tPA On Super Time Window Intravenous Thrombolysis To The Rats Of Acute Cerebral Infarction

BackgroundStroke is the most common disease cause of death worldwide, is also the first cause of adult disability. Acute ischemic stroke account for1/3～1/4of all stroke. Therefore, treat acute ischemic stroke actively is the most important issues we faced. Thrombolysis treatment in time is the only effective mean for acute ischemic stroke therapy at present, which can recanalization cerebrovascular and restore hemoperfusion of local tissues to reduce infract volume and improve nerve function defect.Alteplase (R-tPA) is the only FDA-approved drug for treatment of acute ischemic stroke. The perfectly valid and safe time of r-tPA for intravenous is before4.5hours after acute ischemic stroke. But, how about the validness and safety of thrombolysis after4.5hours? There is still controversial. Recently, a large number of studies reported that the cerebral ischemia penumbra could be found by the mismatch of DWI sequence and PWI sequence. They found that can still benefit from intravenous thrombolysis with r-tPA between3to9hours after acute ischemic stroke, the time is so-called super time window. But the mechanism and the degree it benefits from super time window intravenous thrombolysis remains unsolved.ObjectiveIn this study, we explore the effect and mechanism of extending the time window of r-tPA intravenous thrombolysis therapyby observing cerebral infarction area, microvessel density, and changes of adherence factors expression (ICAM-1and VCAM-1) using thrombus middle cerebral artery occlusion rat model made by SD rats.Methods1. Animal models:Two hundred andsixteen healthy adult male SD rats were randomly divided into control group, stroke group, rtPA4.5h group and rtPA6h group. RtPA4.5h group and rtPA6h group were injected r-tPA at4.5h and6h after cerebral infarction respectively. Stroke group, rtPA4.5h group and rtPA6h group were divided into three subgroups,and the brain of each subgroup were drawn from the animals on the1st day,3r dday and7th day after cerebral infarction respectively. The control group rat had the same operation method with only saline injected, and the brain were drawn in the corresponding time points.2. TTC staining:The cerebral infarction volume was observed by TTC staining. The infract part was white and others was red. The cerebral infarction was calculated by image analysis software.3.Immunohistochemistry(PV):The microvessel around ischemic core were observed on different time points (1,3,7d) of each group by using CD34antibody. The microvessel density was calculated then.4. Real-time PCR:Detect the expression quantity of ICAM-1,VCAM-1mRNA expression of tissues around cerebral infracts on different time points(1,3,7d).Results1. Compared to stroke group, the cerebral infarction volume was obviously reduced in rtPA4.5h group or rtPA6h group on each time point (1,3,7d)(P<0.0/).The cerebral infarction volume of rtPA6h group was larger than that in rtPA4.5h group on each point(P<0.05). There was no infarction zone found in stroke group.2. The microvessel density(MVD)was higher in rtPA4.5h group and rtPA6h group compared with stroke group on the3th day(P<0.05), and apparently higher on the7th day(P<0.01). The MVD of rtPA4.5h group and rtPA6h group increased with time extended, and the increasing was obvious on the7th day than on the3th day(P<0.05).There was no statistical differences of MVD between the rtPA4.5h group and rtPA6h groupon1,3,7d(P>0.05). The microvessel density had no significant change in control group and stroke group.3. The ICAM-1or VCAM-1mRNA expression after stroke started to elevate (P<0.01) at the1st day after thrombolysis,attained peak at the3rd day(P<0.01), and remained significantly elvated at the7th day (P<0.05) compared with control group. Compared to stroke group, The ICAM-1or VCAM-1mRNA expression was apparently lower in rtPA4.5h group and rtPA6h group on each time point(P<0.05). As the thrombolysis time extended, the ICAM-1, VCAM-1mRNA expression increased, There was statistical differences between the rtPA4.5h group and rtPA6h group on each time point(P<0.05).ConclusionThe thrombolysis of r-tPA super time window can reduce the area of infarct volume and increase the microvessel density around cerebral infarct as well as inhibit the expression of immune adherent factors. It offers a reliable theoretical basis to the thrombolytic therapy of super time window for stroke.