Sensory Stimulation-Induced Astrocytic Calcium Signaling in Electrically Silent Ischemic Penumbra

From static to dynamic: live observation of the support system after ischemic stroke by two photon-excited fluorescence laser-scanning microscopy

Ischemic stroke is one of the most common causes of mortality and disability worldwide. However, treatment efficacy and the progress of research remain unsatisfactory. As the critical support system and essential components in neurovascular units, glial cells and blood vessels (including the blood-brain barrier) together maintain an optimal microenvironment for neuronal function. They provide nutrients, regulate neuronal excitability, and prevent harmful substances from entering brain tissue. The highly dynamic networks of this support system play an essential role in ischemic stroke through processes including brain homeostasis, supporting neuronal function, and reacting to injuries. However, most studies have focused on postmortem animals, which inevitably lack critical information about the dynamic changes that occur after ischemic stroke. Therefore, a high-precision technique for research in living animals is urgently needed. Two-photon fluorescence laser-scanning microscopy is a powerful imaging technique that can facilitate live imaging at high spatiotemporal resolutions. Two-photon fluorescence laser-scanning microscopy can provide images of the whole-cortex vascular 3D structure, information on multicellular component interactions, and provide images of structure and function in the cranial window. This technique shifts the existing research paradigm from static to dynamic, from flat to stereoscopic, and from single-cell function to multicellular intercommunication, thus providing direct and reliable evidence to identify the pathophysiological mechanisms following ischemic stroke in an intact brain. In this review, we discuss exciting findings from research on the support system after ischemic stroke using two-photon fluorescence laser-scanning microscopy, highlighting the importance of dynamic observations of cellular behavior and interactions in the networks of the brain's support systems. We show the excellent application prospects and advantages of two-photon fluorescence laser-scanning microscopy and predict future research developments and directions in the study of ischemic stroke.

Low-Frequency Vibrations Enhance Thrombolytic Therapy and Improve Stroke Outcomes

Background and Purpose- We aim to determine the potential impact on stroke thrombolysis of drip-and-ship helicopter flights and specifically of their low-frequency vibrations (LFVs). Methods- Mice with a middle cerebral artery autologous thromboembolic occlusion were randomized to receive rtPA (recombinant tissue-type plasminogen activator; or saline) 90 minutes later in 3 different settings: (1) a motion platform simulator that reproduced the LFV signature of the helicopter, (2) a standardized actual helicopter flight, and (3) a ground control. Results- Mice assigned to the LFV simulation while receiving tPA had smaller infarctions (31.6 versus 54.9 mm3; P=0.007) and increased favorable neurological outcomes (86% versus 28%; P=0.0001) when compared with ground controls. Surprisingly, mice receiving tPA in the helicopter did not exhibit smaller infarctions (47.8 versus 54.9 mm3; P=0.58) nor improved neurological outcomes (37% versus 28%; P=0.71). This could be due to a causative effect of the 20- to 30-Hz band, which was inadvertently attenuated during actual flights. Mice using saline showed no differences between the LFV simulator and controls with respect to infarct size (80.9 versus 95.3; P=0.81) or neurological outcomes (25% versus 11%; P=0.24), ruling out an effect of LFV alone. There were no differences in blood-brain barrier permeability between LFV simulator or helicopter, compared with controls (2.45-3.02 versus 4.82 mm3; P=0.14). Conclusions- Vibration in the low-frequency range (0.5-120 Hz) is synergistic with rtPA, significantly improving the effectiveness of thrombolysis without impairing blood-brain barrier permeability. Our findings reveal LFV as a novel, safe, and simple-to-deliver intervention that could improve the outcomes of patients. Visual Overview- An online visual overview is available for this article.