Robertson Anne M, Duan Xinjie, Aziz Khaled M, Hill Michael R, Watkins Simon C, Cebral Juan R
Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, PA, USA,
Ann Biomed Eng. 2015 Jul;43(7):1502-15. doi: 10.1007/s10439-015-1252-4. Epub 2015 Jan 30.
Intracranial aneurysms are pathological enlargements of brain arteries that are believed to arise from progressive wall degeneration and remodeling. Earlier work using classical histological approaches identified variability in cerebral aneurysm mural content, ranging from layered walls with intact endothelium and aligned smooth muscle cells, to thin, hypocellular walls. Here, we take advantage of recent advances in multiphoton microscopy, to provide novel results for collagen fiber architecture in 15 human aneurysm domes without staining or fixation as well as in 12 control cerebral arteries. For all aneurysm samples, the elastic lamina was absent and the abluminal collagen fibers had similar diameters to control arteries. In contrast, the collagen fibers on the luminal side showed great variability in both diameter and architecture ranging from dense fiber layers to sparse fiber constructs suggestive of ineffective remodeling efforts. The mechanical integrity of eight aneurysm samples was assessed using uniaxial experiments, revealing two sub-classes (i) vulnerable unruptured aneurysms (low failure stress and failure pressure), and (ii) strong unruptured aneurysms (high failure stress and failure pressure). These results suggest a need to refine the end-point of risk assessment studies that currently do not distinguish risk levels among unruptured aneurysms. We propose that a measure of wall integrity that identifies this vulnerable wall subpopulation will be useful for interpreting future biological and structural data.
颅内动脉瘤是脑动脉的病理性扩张，据信是由血管壁的渐进性退变和重塑引起的。早期使用经典组织学方法的研究发现，脑动脉瘤壁成分存在差异，从具有完整内皮和排列整齐的平滑肌细胞的分层壁，到薄的、细胞成分少的壁。在这里，我们利用多光子显微镜的最新进展，在不进行染色或固定的情况下，对15个人类动脉瘤瘤顶以及12条对照脑动脉的胶原纤维结构提供了新的结果。对于所有动脉瘤样本，弹性膜缺失，瘤外壁胶原纤维直径与对照动脉相似。相比之下，瘤内壁胶原纤维在直径和结构上表现出很大的变异性，从致密的纤维层到稀疏的纤维结构，提示重塑效果不佳。使用单轴实验评估了8个动脉瘤样本的机械完整性，发现了两个亚类：（i）易破裂的未破裂动脉瘤（低破坏应力和破坏压力），以及（ii）坚固的未破裂动脉瘤（高破坏应力和破坏压力）。这些结果表明，有必要完善目前未区分未破裂动脉瘤风险水平的风险评估研究的终点。我们建议，一种能够识别这种易损壁亚群的壁完整性测量方法，将有助于解释未来的生物学和结构数据。
