Microvascular Basal Lamina Injury after Experimental Focal Cerebral Ischemia and Reperfusion in the Rat

Abstract

To define the location and extent of microvascular damage of the basal lamina after cerebral ischemia and reperfusion in rats, the authors subjected animals (n = 16) to 3 hours of focal cerebral ischemia and 24 hours of reperfusion using the suture middle cerebral artery occlusion model; sham-operated animals served as controls (n = 6). The Western blot technique was used to define the collagen type IV protein content in various brain regions, whereas immunohistochemistry identified microvascular basal lamina loss (anticollagen type IV staining). The extent of damage was quantified by automatic morphometric video-imaging analysis. Statistical analysis was based on the Mann-Whitney test and the paired Student's t-test. The ischemic hemisphere showed a reduction of the collagen type IV protein content after ischemia and reperfusion in the Western blot (reduction compared with the nonischemic side: total hemisphere, 33% +/- 6%; basal ganglia, 25% +/- 7%; cortex 49% +/- 4%; P < 0.01) [corrected]. There was also a decrease in the number of cerebral microvessels between the ischemic and nonischemic hemispheres (20% +/- 2%), cortical (8% +/- 3%), and basal ganglia areas (31% +/- 3%) (P < 0.001). Besides a reduction of the vessel number, there was also a loss in basal lamina antigen-positive stained area in ischemic areas (hemisphere, 16% +/- 3%; cortex, 14% +/- 3%; basal ganglia, 21% +/- 4%; P < 0.01) [corrected]. Cortical areas had a less pronounced basal lamina loss than basal ganglia (P < 0.05). For the first time, microvascular basal lamina damage, indicated by collagen type IV loss, is proven in rats by biochemical and morphometric analysis. These changes are comparable with those found in nonhuman primates. The authors report novel data regarding microvascular ischemic changes in the cortex. These data provide a basis for future experiments to determine the mechanisms of ischemic microvascular damage and to devise new therapeutic strategies.

Responses of Endothelial Cell and Astrocyte Matrix-Integrin Receptors to Ischemia Mimic Those Observed in the Neurovascular Unit

“…23,24 This is accompanied by alterations in the vascular basal lamina matrix. 13,26,35 Because these events coincide with increased cerebrovascular permeability, 36 loss of endothelial and astrocyte adhesion to the microvascular basal lamina may be an early pivotal event that contributes to loss of the microvascular permeability barrier. In the neurovascular unit, the proximity of astrocyte end-feet to the abluminal surface of the endothelium suggests roles in integrin signaling by the matrix in both cell compartments that support their maintenance of the permeability barrier.…”

Hemorrhagic Transformation after Ischemic Stroke in Animals and Humans

“…40 Within 10 minutes of reperfusion, there is evidence of basal lamina degradation and BBB disruption. 41,42 In humans, early opening of the BBB has been documented within 2 to 6 hours (median 3.8 hours) of stroke onset. 21,43 The early disruption of the BBB in stroke may not be uniform over time.…”

“…166 In ischemic stroke, collagen type IV is reduced in the basal lamina within the first 1 to 24 hours, thus it may contribute to coagulationrelated HT. 12,42 Antiplatelet agents also increase the risk of HT in patients. 8,50,144,[167][168][169] Antiplatelet use before tPA treatment or antiplatelet use within the first 24 hours of tPA treatment increases the risk of tPA-related HT.…”

Cerebral Microvessel Responses to Focal Ischemia

“…Exclusively in the brain, microvascular endothelial cells and astrocytes contribute to the primary permeability barrier and the vascular ECM, which protect the brain parenchyma from edema and hemorrhage (Risau and Wolburg, 1990). The secondary barrier involves integrin receptor cell-associated matrix adhesion (Hamann et al, 1995;Haring et al, 1996a;Wagner et al, 1997;Tagaya et al, 2001;Hamann et al, 2002).…”