A new approach to reduce the number of animals used in experimental focal cerebral ischemia models

Numerical and length densities of microvessels in the human brain: Correlation with preferential orientation of microvessels in the cerebral cortex, subcortical grey matter and white matter, pons and cerebellum

To provide basic data on the local differences in density of microvessels between various parts of the human brain, including representative grey and white matter structures of the cerebral hemispheres, the brain stem and the cerebellum, we quantified the numerical density N_V and the length density L_V of microvessels in two human brains. We aimed to correlate the density of microvessels with previously published data on their preferential orientation (anisotropy). Microvessels were identified using immunohistochemistry for laminin in 32 samples harvested from the following brain regions of two adult individuals: the cortex of the telencephalon supplied by the anterior, middle, and posterior cerebral artery; the basal ganglia (putamen and globus pallidus); the thalamus; the subcortical white matter of the telencephalon; the internal capsule; the pons; the cerebellar cortex; and the cerebellar white matter. N_V was calculated from the number of vascular branching points and their valence, which were assessed using the optical disector in 20-μm-thick sections. L_V was estimated using counting frames applied to routine sections with randomized cutting planes. After correction for shrinkage, N_V in the cerebral cortex was 1311±326mm^-3 (mean±SD) and L_V was 255±119mm^-2. Similarly, in subcortical grey matter (which included the basal ganglia and thalamus), N_V was 1350±445mm^-3 and L_V was 328±117mm^-2. The vascular networks of cortical and subcortical grey matter were comparable. Their densities were greater than in the white matter, with N_V=222±147mm^-3 and L_V=160±96mm^-2. N_V was moderately correlated with L_V. In parts of brain with greater N_V, blood vessels lacked a preferential orientation. Our data were in agreement with other studies on microvessel density focused on specific brain regions, but showed a greater variability, thus mapping the basic differences among various parts of brain. To facilitate the planning of other studies on brain vascularity and to support the development of computational models of human brain circulation based on real microvascular morphology; stereological data in form of continuous variables are made available as supplements.

Contrasting roles of immune cells in tissue injury and repair in stroke: The dark and bright side of immunity in the brain

Despite considerable efforts in research and clinical studies, stroke is still one of the leading causes of death and disability worldwide. Originally, stroke was considered a vascular thrombotic disease without significant immune involvement. However, over the last few decades it has become increasingly obvious that the immune responses can significantly contribute to both tissue injury and protection following stroke. Recently, much research has been focused on the immune system's role in stroke pathology and trying to elucidate the mechanism used by immune cells in tissue injury and protection. Since the discovery of tissue plasminogen activator therapy in 1996, there have been no new treatments for stroke. For this reason, research into understanding how the immune system contributes to stroke pathology may lead to better therapies or enhance the efficacy of current treatments. Here, we discuss the contrasting roles of immune cells to stroke pathology while emphasizing myeloid cells and T cells. We propose that focusing future research on balancing the beneficial-versus-detrimental roles of immunity may lead to the discovery of better and novel stroke therapies.

Protective effect of oxysophoridine on cerebral ischemia/reperfusion injury in mice

Oxysophoridine, a new alkaloid extracted from Sophora alopecuroides L., has been shown to have a protective effect against ischemic brain damage. In this study, a focal cerebral ischemia/reperfusion injury model was established using middle cerebral artery occlusion in mice. Both 62.5, 125, and 250 mg/kg oxysophoridine, via intraperitoneal injection, and 6 mg/kg nimodipine, via intragastric administration, were administered daily for 7 days before modeling. After 24 hours of reperfusion, mice were tested for neurological deficit, cerebral infarct size was assessed and brain tissue was collected. Results showed that oxysophoridine at 125, 250 mg/kg and 6 mg/kg nimodipine could reduce neurological deficit scores, cerebral infarct size and brain water content in mice. These results provided evidence that oxysophoridine plays a protective role in cerebral ischemia/reperfusion injury. In addition, oxysophoridine at 62.5, 125, and 250 mg/kg and 6 mg/kg nimodipine increased adenosine-triphosphate content, and decreased malondialdehyde and nitric oxide content. These compounds enhanced the activities of glutathione-peroxidase, superoxide dismutase, catalase, and lactate dehydrogenase, and decreased the activity of nitric oxide synthase. Protein and mRNA expression levels of N-methyl-D-aspartate receptor subunit NR1 were markedly inhibited in the presence of 250 mg/kg oxysophoridine and 6 mg/kg nimodipine. Our experimental findings indicated that oxysophoridine has a neuroprotective effect against cerebral ischemia/reperfusion injury in mice, and that the effect may be due to its ability to inhibit oxidative stress and expression of the N-methyl-D-aspartate receptor subunit NR1.

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.

rt-PA causes a dose-dependent increase in the extravasation of cellular and non-cellular blood elements after focal cerebral ischemia

While recombinant tissue plasminogen activator (rt-PA) is successfully used for thrombolysis in human stroke, it may increase the risk of hemorrhagic complications. We describe the effects of different doses of rt-PA (saline, 0.9, 9, or 18 mg rt-PA/kg body weight) on the extravasation of blood components following experimental cerebral ischemia (3 h, 24 h reperfusion, suture model) in rats. The damage to the blood-brain barrier and the hemoglobin extravasation were quantified by Western blotting and immunohistochemistry. Both were significantly elevated in the ischemic cortex and basal ganglia. As rt-PA doses rose, the hemoglobin content as well as the damage to the blood-brain barrier in the ischemic side also rose significantly (p<0.001). This correlated significantly with the rising MMP-9 (matrix metalloproteinase) after increasing doses of rt-PA. Despite various benefits, rt-PA is responsible for a dose-dependent increase of edema and hemorrhage after cerebral ischemia. Clinicians should consider using the lowest effective dose of rt-PA in stroke patients.

Doxycycline inhibits MMPs via modulation of plasminogen activators in focal cerebral ischemia

Tetracyclines inhibit matrix metalloproteinases (MMPs) and reduce infarction volume following cerebral ischemia. In this thesis an involvement of urokinase could be proven. Cerebral ischemia in rats was induced for 3 h followed by 24 h reperfusion (suture model). Each 6 animals received orally either doxycycline or water. Doxycycline treatment began 10 days before ischemia. MMP-2 and MMP-9 were substantially decreased. The possibility of involvement of the endogenous MMP inhibitors in the MMP inhibiting mechanisms was excluded. The plasminogen activator uPA was significantly decreased by doxycycline indicating an MMP inhibiting mechanism including the plasminogen/plasmin system. In the doxycycline group, this resulted in a decreased damage to the cerebral microvessels and less loss of the basal lamina antigen collagen type IV. Hemoglobin extravasation was also significantly reduced. Our results suggest that doxycycline may have a potential use as an anti-ischemic compound since it provides microvascular protection by inhibiting the plasminogen system.