In vivo optical imaging of ischemic blood-brain barrier disruption

The blood-brain barrier (BBB) disruption following cerebral ischemia (stroke) contributes to the development of life-threatening brain edema. Recent studies suggested that the ischemic BBB disruption is not uniform throughout the affected brain region. The aim of this study was to establish in vivo optical imaging methods to assess the size selectivity and spatial distribution of the BBB disruption after a focal cerebral ischemia. The BBB permeability was assessed in mice subjected to a 60-min middle cerebral artery occlusion and 24 h of reperfusion using in vivo time domain near-infrared optical imaging after contrast enhancement with two tracers of different molecular size, Cy5.5 (1 kDa) and Cy5.5 conjugated with bovine serum albumin (BSA) (67 kDa). Volumetric reconstruction of contrast-enhanced brain areas in vivo and ex vivo indicated that the BSA-Cy5.5-enhancement is identical to the volume of infarct determined by TTC staining, whereas the volume of enhancement with Cy5.5 was 40% greater. The volume differential between areas of BBB disruption for small and large-size molecules could be useful for determining the size of peri-infarct tissues (penumbra) that can respond to neuroprotective therapies.