Cheheltani Rabee, Pichamuthu Joseph E, Rao Jayashree, Weinbaum Justin S, Kiani Mohammad F, Vorp David A, Pleshko Nancy
Department of Mechanical Engineering, Temple University, Philadelphia, PA, USA.
Department of Radiology, University of Pennsylvania, Philadelphia, PA, USA.
Cardiovasc Eng Technol. 2017 Mar;8(1):70-80. doi: 10.1007/s13239-016-0289-3. Epub 2016 Dec 19.
Abdominal aortic aneurysm (AAA) is a degenerative disease of the aorta characterized by severe disruption of the structural integrity of the aortic wall and its major molecular constituents. From the early stages of disease, elastin in the aorta becomes highly degraded and is replaced by collagen. Questions persist as to the contribution of collagen content, quality and maturity to the potential for rupture. Here, using our recently developed Fourier transform infrared imaging spectroscopy (FT-IRIS) method, we quantified collagen content and maturity in the wall of AAA tissues in pairs of specimens with different wall stresses. CT scans of AAAs from 12 patients were used to create finite element models to estimate stress in different regions of tissue. Each patient underwent elective repair of the AAA, and two segments of the AAA tissues from anatomic regions more proximal or distal with different wall stresses were evaluated by histology and FT-IRIS after excision. For each patient, collagen content was generally greater in the tissue location with lower wall stress, which corresponded to the more distal anatomic regions. The wall stress/collagen ratio was greater in the higher stress region compared to the lower stress region (1.01 ± 1.09 vs. 0.55 ± 0.084, p = 0.02). The higher stress region also corresponded to the location with reduced intraluminal thrombus thickness. Further, collagen maturity tended to decrease with increased collagen content (p = 0.068, R = 0.38). Together, these results suggest that an increase in less mature collagen content in AAA patients does not effectively compensate for the loss of elastin in the aortic wall, and results in a reduced capability to endure wall stresses.
腹主动脉瘤（AAA）是一种主动脉退行性疾病，其特征是主动脉壁及其主要分子成分的结构完整性严重破坏。从疾病早期开始，主动脉中的弹性蛋白就会高度降解并被胶原蛋白取代。关于胶原蛋白的含量、质量和成熟度对破裂可能性的影响，问题依然存在。在此，我们使用最近开发的傅里叶变换红外成像光谱（FT-IRIS）方法，对具有不同壁应力的成对标本中AAA组织壁中的胶原蛋白含量和成熟度进行了量化。利用12例患者的AAA的CT扫描创建有限元模型，以估计组织不同区域的应力。每位患者均接受了AAA的择期修复，切除后通过组织学和FT-IRIS对来自解剖区域更近端或远端且具有不同壁应力的两段AAA组织进行评估。对于每位患者，胶原蛋白含量通常在壁应力较低的组织位置更高，该位置对应于更远端的解剖区域。与低应力区域相比，高应力区域的壁应力/胶原蛋白比值更大（1.01±1.09对0.55±0.084，p = 0.02）。高应力区域也对应于腔内血栓厚度减小的位置。此外，胶原蛋白成熟度倾向于随着胶原蛋白含量的增加而降低（p = 0.068，R = 0.38）。总之，这些结果表明，AAA患者中不太成熟的胶原蛋白含量增加并不能有效补偿主动脉壁中弹性蛋白的损失，并且导致承受壁应力的能力降低。
