Protection of cerebral microvasculature after moderate hypothermia following experimental focal cerebral ischemia in mice.

Clinical studies have shown that the treatment of ischemic stroke with hypothermia is promising. In this animal study, we investigated the fate of the microvasculature following focal cerebral ischemia in mice with and without hypothermia. Focal cerebral ischemia was induced by occlusion of the middle cerebral artery (MCAO) (3 h) with an intraluminal filament technique. Eight mice received normothermia (36.5 degrees C, NT) and eight received hypothermia (32-34 degrees C, HT) treatment during 24 h of reperfusion. Another six mice represented the sham group. Analysis of the hypothermic group in comparison to the normothermic group revealed a significantly reduced infarct volume (NT: 63.56+/-4.62 mm3 SEM, HT: 38.09+/-4.83 mm3 SEM; P<0.01) and showed considerably ameliorated neurological deficits (Garcia-score) after 24 h (P<0.01). In addition, the degradation of the microvascular basal lamina antigen collagen type IV after normothermia was strongly reduced (P<0.05) compared to sham. Hypothermia diminished this effect so that collagen type IV was not significantly reduced compared to sham. Moreover the hemoglobin extravasation was strongly reduced under hypothermic treatment compared to the normothermic group (P<0.01). In the hypothermia group the urokinase plasminogen-activator (uPA) activity (P=0.01) was significantly decreased compared to the normothermia group. Also MMP-9 was significantly reduced (P<0.05) during hypothermic treatment. In conclusion, for the first time we show in mice that hypothermia preserves the microvascular wall structures after ischemia. We have demonstrated that hypothermia protects the basal lamina, reduces the infarct volume and hemorrhage, and reduces proteolytic enzymes. These protective effects in an additional animal model of ischemia and reperfusion strongly recommend hypothermia as a potential beneficial treatment for stroke.

Vascular integrin immunoreactivity is selectively lost on capillaries during rat focal cerebral ischemia and reperfusion.

The alpha1-integrin cell adhesion molecules, the principal endothelial receptors for basal lamina (BL) components disappear during transient ischemia. The current study investigated the localization of integrins, the time dependency and vessel size selectivity in the normal rat brain before and after 3 h of cerebral ischemia (I3) and reperfusion (R). Additionally we looked for a correlation to the amount of extravasation and hemorrhage. In the normal brain, there was a clear immunoreactivity for the alpha1, alpha6, and beta1 integrins on the endothelial perivascular cells. After I3 followed by variable reperfusion intervals of 0, 9, and 24 h (R0, R9 and R24; respectively), the number of vessels and staining intensity indicating immunoreactivity in the ischemic area were compared with the contralateral side. The number of the beta1-immunoreactive capillaries was steadily decreasing with the reperfusion time: -12+/-5%, -15+/-7% and -43+/-8% at I3R0, I3R9 and I3R24 (all p<0.05). The beta1-staining intensity decreased homogeneously to -21% at I3R24 (p<0.05). Vascular staining for alpha1 was affected similarly. Interestingly, the alpha6-positive arterioles/venules were also reduced by -21% at I3R24 (p<0.05) in a diameter-selective way on vessels with diameters larger than 15 mum. The correlated break-down of the blood-brain-barrier was demonstrated by the significant rise of the extravasation of BSA from the perfusion solution as well as the increased hemorrhage after MCAO/R (hemoglobin: 103+/-4% versus 330+/-17%; BSA 101+/-3% versus 132+/-9% in I0R0 and I3R24, respectively). The prominent capillary vulnerability contributes significantly to the impairment of the microvascular integrity and after ischemia and reperfusion.