Real-time in-vivo imaging of blood flow in a photothrombotic cortical mouse microinfarction model

Micro-ischemic strokes, or microinfarcts, are small blood clots that obstruct cerebral blood flow to the brain. They are commonly observed in patients with dementia and have been linked to cognitive decline. However, the precise mechanisms underlying this association remain largely unknown. To advance our understanding of micro-strokes, it is imperative to observe real-time blood flow changes during the formation of microinfarcts. In this study, we successfully achieved in vivo real-time imaging of red blood cell (RBC) and dextran flow in a microinfarction model using a video-rate intravital confocal microscope. A cortical microinfarct was induced by photo-thrombosis in the cortex of a mouse following the intravenous injection of Rose Bengal, accompanied by a 5-second exposure to 7mW, 561nm light through a cranial window. Real-time imaging of blood flow allowed us to capture dynamic changes in RBC flow, along with changes in vessel diameter and cortical tissue volume after inducing the microinfarction. Initially, the obstruction resulted in reduced blood flow in the surrounding vessels and micro-vessels with minimal change in cortical volume. However, subsequent observations revealed an increase in cerebral volume, vessel thickness, and blood flow. These changes slightly decreased again afterward. Despite these fluctuations, no angiogenesis was observed. Further in-depth analysis of these complex microvascular changes from the acute stages of microinfarction to subsequent recovery could provide valuable insights into the pathophysiology of micro-ischemic strokes and offer clues for the development of novel therapeutic strategies.