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Angiogenesis in the Outer Membrane of Chronic Subdural Hematomas through Thrombin-Cleaved Osteopontin and the
Koji Osuka1, Yusuke Ohmichi2, Mika Ohmichi2
1Department of Neurological Surgery, Aichi Medical University, 1-1 Yazakokarimata, Nagakute 480-1195, Japan.
Insights
The N-terminal half of Osteopontin (OPN) in chronic subdural hematoma (CSDH) fluid promotes new blood vessel growth. This extracellular matrix protein plays a key role in CSDH development through integrin signaling.
Area of Science:
- Neuroscience
- Cell Biology
- Biochemistry
Background:
- Chronic subdural hematoma (CSDH) is characterized by inflammation and angiogenesis.
- The outer membrane of CSDH, rich in inflammatory cells, is crucial for its development.
- Osteopontin (OPN), an extracellular matrix protein, is cleaved by thrombin, with its N-terminal half mediating integrin signaling.
Purpose of the Study:
- To investigate the expression of the N-terminal half of OPN in CSDH fluid.
- To examine the expression of integrins α9 and β1 and downstream angiogenic signaling components in the CSDH outer membrane.
- To determine if CSDH fluid activates focal adhesion kinase (FAK) in endothelial cells.
Main Methods:
- ELISA was used to measure N-terminal OPN concentrations in CSDH fluid.
- Western blot and immunohistochemistry analyzed the expression of integrins (α9, β1), vinculin, talin-1, FAK, paxillin, α-actin, Src, and β-actin.
- In vitro experiments assessed FAK activation in endothelial cells treated with CSDH fluid.
Main Results:
- N-terminal OPN levels were significantly higher in CSDH fluid than in serum.
- Integrins α9 and β1, FAK, and paxillin were detected in endothelial cells of the CSDH outer membrane vessels.
- CSDH fluid induced significant phosphorylation of FAK in cultured endothelial cells.
Conclusions:
- The N-terminal half of OPN in CSDH fluid promotes endothelial cell neovascularization via integrins α9 and β1.
- This OPN fragment is a critical component of the extracellular matrix that drives CSDH progression.
Background:
A chronic subdural hematoma (CSDH) is considered to be an inflammatory and angiogenic disease. The CSDH outer membrane, which contains inflammatory cells, plays an important role in CSDH development. Osteopontin (OPN) is an extracellular matrix protein that is cleaved by thrombin, generating the N-terminal half of OPN, which is prominently involved in integrin signal transduction. We explored the expression of the N-terminal half of OPN in CSDH fluid and the expression of integrins α9 and β1 and the downstream components of the angiogenic signaling pathways in the outer membrane of CSDHs.
Methods:
Twenty samples of CSDH fluid and eight samples of CSDH outer membrane were collected from patients suffering from CSDHs. The concentrations of the N-terminal half of OPN in CSDH fluid samples were measured using ELISA kits. The expression levels of integrins α9 and β1, vinculin, talin-1, focal adhesion kinase (FAK), paxillin, α-actin, Src and β-actin were examined by Western blot analysis. The expression levels of integrins α9 and β1, FAK and paxillin were also examined by immunohistochemistry. We investigated whether CSDH fluid could activate FAK in cultured endothelial cells in vitro.
Results:
The concentration of the N-terminal half of OPN in CSDH fluid was significantly higher than that in the serum. Western blot analysis confirmed the presence of these molecules. In addition, integrins α9 and β1, FAK and paxillin were localized in the endothelial cells of vessels within the CSDH outer membrane. FAK was significantly phosphorylated immediately after treatment with CSDH fluid.
Conclusion:
Our data suggest that the N-terminal half of OPN in CSDH fluid promotes neovascularization in endothelial cells through integrins α9 and β1. The N-terminal half of OPN, which is part of the extracellular matrix, plays a critical role in the promotion of CSDHs.
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