Abstract
Ischemic stroke causes cellular alterations in the “neurovascular unit” (NVU) comprising neurons, glia, and the vasculature, and affects the blood-brain barrier (BBB) with adjacent extracellular matrix (ECM). Limited data are available for the zone between the NVU and ECM that has not yet considered for neuroprotective approaches. This study describes ischemia-induced alterations for two main components of the neurovascular matrix adhesion zone (NMZ), i.e., collagen IV as basement membrane constituent and fibronectin as crucial part of the ECM, in conjunction with traditional NVU elements. For spatio-temporal characterization of these structures, multiple immunofluorescence labeling was applied to tissues affected by focal cerebral ischemia using a filament-based model in mice (4, 24, and 72 h of ischemia), a thromboembolic model in rats (24 h of ischemia), a coagulation-based model in sheep (2 weeks of ischemia), and human autoptic stroke tissue (3 weeks of ischemia). An increased fibronectin immunofluorescence signal demarcated ischemia-affected areas in mice, along with an increased collagen IV signal and BBB impairment indicated by serum albumin extravasation. Quantifications revealed a region-specific pattern with highest collagen IV and fibronectin intensities in most severely affected neocortical areas, followed by a gradual decline toward the border zone and non-affected regions. Comparing 4 and 24 h of ischemia, the subcortical fibronectin signal increased significantly over time, whereas neocortical areas displayed only a gradual increase. Qualitative analyses confirmed increased fibronectin and collagen IV signals in ischemic areas from all tissues and time points investigated. While the increased collagen IV signal was restricted to vessels, fibronectin appeared diffusely arranged in the parenchyma with focal accumulations associated to the vasculature. Integrin α5 appeared enriched in the vicinity of fibronectin and vascular elements, while most of the non-vascular NVU elements showed complementary staining patterns referring to fibronectin. This spatio-temporal characterization of ischemia-related alterations of collagen IV and fibronectin in various stroke models and human autoptic tissue shows that ischemic consequences are not limited to traditional NVU components and the ECM, but also involve the NMZ. Future research should explore more components and the pathophysiological properties of the NMZ as a possible target for novel neuroprotective approaches.
Highlights
Despite enormous efforts concerning a more detailed understanding of pathophysiological mechanisms, ischemic stroke often leads to long-term disability and is still ranging among the three most common causes of death worldwide (Benjamin et al, 2018; Campbell et al, 2019)
Twenty-four hours of focal cerebral ischemia in mice resulted in a critical affection of the blood-brain barrier (BBB) integrity as visualized by an extravasation of serum albumin into the parenchyma in ischemic areas, whereas no albumin extravasation was visible in non-affected areas
Concerning fibronectin as part of the extracellular matrix (ECM), an increased immunosignal was routinely observed in ischemia-affected areas (Figures 1A',A''') with both a strongly vessel-associated pattern and a diffuse appearance in close vicinity to the vasculature not necessarily overlapping with cellular structures (Figures 1A''',B''')
Summary
Despite enormous efforts concerning a more detailed understanding of pathophysiological mechanisms, ischemic stroke often leads to long-term disability and is still ranging among the three most common causes of death worldwide (Benjamin et al, 2018; Campbell et al, 2019). More than 10 years ago, a group of regionally and functionally associated cells were termed as the “neurovascular unit” (NVU) in order to learn more than their roles and interplay during stroke evolution. In the setting of stroke, endothelial cells are believed to have a pivotal role in BBB integrity as the leakage of blood-sourced substances was found via a transendothelial route together with morphological features like an endothelial swelling (Krueger et al, 2013, 2015, 2019). Abnormalities within the NVU with a consecutive impairment of the BBB integrity are known to increase the risk for secondary hemorrhage associated with recanalizing therapies, and critically impact the patients’ outcome (Yang and Rosenberg, 2011)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
