Longitudinal monitoring of blood perfusion and brain tissue damage in photothrombotic ischemic stroke rat model

Abstract

The brain experiences alterations including cerebral ischemia and tissue damage after focal ischemic stroke. A thorough understanding of the spatiotemporal dynamics of blood perfusion and tissue damage is of great importance in stroke research. In chronic rat photothrombotic (PT) stroke model, a parallel study of both vascular and cellular responses to regional ischemia was performed with optical coherence tomography (OCT) in a label-free and depth-resolved manner. OCT revealed that vessels of different types and depth presented various spatial and temporal dynamics. In the ischemic core area, the distal middle cerebral arteries (dMCAs) were blocked gradually with laser irradiation and a spontaneous recanalization was observed at Day 5. In the chronic recovery period, the blocked small pial microvessels presented an apparent neovascularization progressing from the peripheral into the core area, with the final blood flow volume exceeding the baseline before PT. While the cortical capillary perfusion of the core area totally disappeared at Day 3 after PT and never recovered in the core area till the end of observation. The results demonstrated that blood reperfusion mainly occurred in the dMCAs vessels and pial microvessels of the superficial layer, but not in capillaries located deep in the cortex. The response of the cellular scattering and tissue damage showed a high spatial and temporal correlation with the capillary perfusion. On the whole, ischemic area and lesion area from attenuation coefficient are not exactly the same but complentary, with great help in understanding stroke mechanism comprehensively.