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Development of tissue damage, inflammation and resolution following stroke: an immunohistochemical and quantitative
1Department of Cellular and Biochemistry, SmithKline Beecham Pharmaceuticals, King of Prussia, PA 19406.
Abstract:
Development and resolution of the lesion produced by occlusion of the middle cerebral artery (MCAO) was studied through quantitative planimetry and histologic/immunohistochemical techniques. MCAO, performed in spontaneously hypertensive rats (SHR), initially (1-3 days) produced large, consistent cerebral cortical infarctions and an increase in ipsilateral hemispheric size (i.e., swelling) quantitated by planimetry on 2,3,5-triphenyltetrazolium chloride (TTC)-stained gross tissue sections. These initial changes correlated well with changes identified from 2 h to 3 days using hematoxylin and eosin stained histologic tissue sections and immunohistochemical techniques including: the progressive development of a cortical area of pan necrosis, infiltration of neutrophils into infarcted tissues, and activation of astroglia. During the initial 2 days following MCAO, glial fibrillary acidic protein immunoreactive cells increased in number and became larger and more intensely fluorescent medial to the cortical infarct. At 5 to 15 days, both the infarct and the ipsilateral hemisphere decreased in size. These changes correlated with the presence of abundant macrophages, and cavitation of the lesion along its medial border. Also during this period, a loose connective tissue matrix formed along the superficial aspect of the infarct. This connective tissue contained fibroblasts, extracellular matrix immunoreactive for laminin and collagen, capillary buds indicating neovascularization, and abundant macrophages. By the final timepoint (30 days), necrotic tissue could no longer be detected in either gross or histologic tissue sections, the inflammatory infiltrate had resolved, and the connective tissue was removed.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Middle cerebral artery occlusion (MCAO) in rats causes brain infarction and swelling, followed by lesion resolution and tissue repair over 30 days. This study tracks the development and healing of stroke-induced damage.
Area of Science:
- Neuroscience
- Pathology
- Histology
Background:
- Middle cerebral artery occlusion (MCAO) is a common model for studying ischemic stroke.
- Understanding the temporal dynamics of lesion development and resolution is crucial for therapeutic development.
Purpose of the Study:
- To quantitatively assess the development and resolution of cerebral lesions after MCAO in spontaneously hypertensive rats (SHR).
- To correlate gross morphological changes with detailed histological and immunohistochemical findings.
Main Methods:
- Quantitative planimetry on TTC-stained sections to measure infarct and hemisphere size.
- Histological analysis using hematoxylin and eosin staining.
- Immunohistochemical techniques to identify inflammatory cells (neutrophils) and glial markers (GFAP).
Main Results:
- MCAO induced cortical infarction and swelling within 1-3 days, characterized by necrosis, neutrophil infiltration, and astroglia activation.
- Between 5-15 days, infarcts resolved, accompanied by macrophage infiltration, cavitation, and connective tissue formation with neovascularization.
- By 30 days, necrotic tissue was resolved, inflammation subsided, and the connective tissue matrix was removed.
Conclusions:
- The study provides a detailed timeline of ischemic lesion development and resolution following MCAO.
- It highlights the dynamic interplay of inflammation, tissue degradation, and repair processes in the infarcted brain.
- Findings contribute to understanding stroke pathophysiology and potential therapeutic targets.