Collagen cross-linkage, elastolytic and collagenolytic activities in cerebral aneurysms: a preliminary investigation

The pathogenesis of aneurysms formation and rupture is not clearly understood and is undoubtedly a multifactorial event. It is generally accepted that the aneurysm arises from an interaction between structural weakness of arterial wall and hemodynamic factors. Previous studies suggested the possible role of collagenolytic and elastolytic activities in aneurysm development, leading to extracellular matrix alteration. The content of collagen 3-hydroxypiridinium cross-links and elastase and collagenase activities were measured in 12 samples of intracranial aneurysms and in control specimens obtained from temporal superficial arteries and from autoptic samples of Willis Circle. Collagen content is significantly lower in aneurysm than in autoptic control samples (p < 0.01). The total amount of cross-links is significantly lower in ruptured aneurysms than in unruptured and autoptic controls (p < 0.01). Collagenase and elastase activities are significantly increased in ruptured cerebral aneurysms versus unruptured aneurysms (p < 0.01). Linear regression shows that an inverse relationship exists between cross-links content and both elastolytic (p = 0.0032) and collagenolytic (p < 0.001) activities in aneurysmal samples. Multiple regression shows that collagenase has a more important statistic impact (p = 0.027) than elastase (p = 0.08). The results of the study supports the hypothesis that an imbalance of protease-antiprotease homeostasis with elevated collagenolytic and elastolytic activities may represent the predisposing condition leading to aneurysms rupture through collagen depauperation and reduced cross-linkage of collagen fibres.