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Collagen type III deficiency in patients with rupture of intracranial saccular aneurysms
1Department of Neurosurgery, Aarhus Kommunehospital, Denmark.
Insights
A collagen type III deficiency in middle cerebral arteries of aneurysm patients increases vascular extensibility, potentially contributing to aneurysm rupture. This was not observed in brachial arteries.
Area of Science:
- Vascular Biology
- Biomedical Engineering
- Biochemistry
Background:
- Intracranial saccular aneurysms are associated with arterial wall abnormalities.
- The role of specific collagen types in cerebral artery biomechanics and aneurysm formation requires further investigation.
Purpose of the Study:
- To investigate the biomechanical properties and collagen composition of middle cerebral arteries (MCA) and brachial arteries in patients with ruptured intracranial saccular aneurysms compared to controls.
- To determine if collagen type III deficiency is linked to altered arterial mechanics in aneurysm patients.
Main Methods:
- Post-mortem arterial samples (MCA and brachial) from 14 aneurysm patients and 14 controls.
- Biomechanical testing of arterial specimens under constant deformation rate.
- Collagen type I and III quantification using SDS-PAGE of cyanogen bromide peptides.
Main Results:
- A deficiency in collagen type III was found in MCA specimens of 6 out of 14 aneurysm patients.
- This collagen deficiency did not alter mechanical strength but significantly increased MCA extensibility at relevant blood pressures.
- No biomechanical differences were observed in the brachial arteries of aneurysm patients compared to controls, despite similar collagen type III deficiency.
Conclusions:
- Collagen type III deficiency in MCA may lead to increased vascular extensibility, compromising arterial integrity.
- This altered biomechanical property, combined with hemodynamic stress, could be a key factor in the pathogenesis of saccular aneurysms.
- The findings highlight potential structural vulnerabilities in cerebral arteries of patients susceptible to aneurysms.
Abstract:
Samples of the middle cerebral artery (MCA) and the brachial artery were obtained post mortem from 14 patients who died following rupture of intracranial saccular aneurysms and from a control group of 14 age- and sex-matched patients who died of causes unrelated to aneurysm rupture. The biomechanical properties of ring-shaped arterial specimens were investigated by loading the specimens at a constant deformation rate until rupture. The relative amounts of collagen type I and type III were determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) studies of cyanogen bromide peptides of collagen prepared from the arterial samples. A deficiency of collagen type III was demonstrated in specimens of the MCA in six of 14 patients with a ruptured intracranial saccular aneurysm. This deficiency was not accompanied by alterations in the mechanical arterial strength but resulted in a significant increase in the extensibility at stress values corresponding to blood pressures between 100 and 200 mm Hg. No difference was found between aneurysm patients and the control group in regard to the biomechanical properties of the brachial artery, despite the presence of a significant deficiency of collagen type III. The increase in vascular extensibility of the MCA may represent alterations in the fibrous structure and functional integrity of the cerebral arteries of aneurysm patients with collagen type III deficiency. Together with aggravating hemodynamic stresses, this deficiency may be an important factor in the pathogenesis of saccular aneurysms.