Department of Biomechanics, University of Nebraska Omaha, Omaha, NE, USA.
Department of Biomechanics, University of Nebraska Omaha, Omaha, NE, USA.
Acta Biomater. 2024 Nov;189:413-426. doi: 10.1016/j.actbio.2024.10.010. Epub 2024 Oct 11.
Aortic dissection is a life-threatening condition caused by layer separation. Despite extensive research, the relationship between the aortic wall's structural integrity and dissection risk remains unclear. Glycosaminoglycan (GAG) accumulation and elastin loss are suspected to play significant roles. We investigated how age-related changes in aortic structure affect dissection susceptibility. Peeling tests were performed on longitudinal and circumferential thoracic (TA) and abdominal aortic (AA) strips from 35 donors aged 13-76 years (mean 38 ± 15 years, 34 % female). GAG, elastin, collagen, and smooth muscle cell (SMC) contents were assessed using bidirectional histology. Young TAs resisted longitudinal peeling better than circumferential, with delamination strengths of 65.4 mN/mm and 44.2 mN/mm, respectively. Delamination strength decreased with age in both directions, more rapidly longitudinally, equalizing at ∼20-25 mN/mm in older TAs. Delamination strength in AAs was 22 % higher than in TAs. No sex differences were observed. GAG density increased, while elastin density decreased by 2.5 % and 4 % per decade, respectively. Collagen density did not change with age, while SMC density decreased circumferentially. GAGs partially mediated the reduction in longitudinal delamination strength due to aging, while circumferential strength reduction was not mediated by changes in either GAG or elastin densities. This study explains why aortic dissections are more common in TAs, especially in older individuals, and why they typically propagate spirally. TAs exhibit lower delamination strength compared to AAs and experience strength reduction with age, a phenomenon linked to increased GAG accumulation and elastin loss. These findings enhance our understanding of the pathophysiological mechanisms behind aortic dissection. STATEMENT OF SIGNIFICANCE: This work explores the age-dependent relationships between delamination strength in human aortas and wall structural content. We investigated 35 human aortas from donors aged 13 to 76 years, providing new insights into the biomechanical and histological factors that influence aortic dissection risk. Our findings elucidate how variations in elastin, glycosaminoglycan, collagen, and smooth muscle cell densities impact the structural integrity of the aorta, contributing significantly to the understanding of aortic dissection mechanisms.
主动脉夹层是一种由层分离引起的危及生命的疾病。尽管进行了广泛的研究，但主动脉壁结构完整性与夹层风险之间的关系仍不清楚。糖胺聚糖（GAG）积累和弹性蛋白丢失被怀疑起重要作用。我们研究了主动脉结构随年龄变化如何影响夹层易感性。对 35 名年龄在 13-76 岁（平均 38 ± 15 岁，34%为女性）的供体的胸主动脉（TA）和腹主动脉（AA）的纵向和环向条带进行了剥离测试。使用双向组织学评估 GAG、弹性蛋白、胶原蛋白和平滑肌细胞（SMC）含量。年轻的 TA 在纵向方向上比环向方向更能抵抗剥离，分层强度分别为 65.4 mN/mm 和 44.2 mN/mm。在两个方向上，分层强度随年龄的增加而降低，在较老的 TA 中，纵向降低更快，平衡在约 20-25 mN/mm。AA 的分层强度比 TA 高 22%。未观察到性别差异。GAG 密度增加，而弹性蛋白密度每十年分别降低 2.5%和 4%。胶原蛋白密度不随年龄变化，而 SMC 密度环向降低。GAG 部分介导了由于老化导致的纵向分层强度降低，而环向强度降低不受 GAG 或弹性蛋白密度变化的影响。这项研究解释了为什么主动脉夹层在 TA 中更常见，尤其是在老年人中，以及为什么它们通常呈螺旋状扩展。TA 与 AA 相比，分层强度较低，且随年龄增长强度降低，这一现象与 GAG 积累和弹性蛋白丢失有关。这些发现提高了我们对主动脉夹层背后的病理生理机制的理解。
