Embryological Divergence and Molecular Mechanisms in Thoracic and Abdominal Aortic Aneurysms: Bridging Developmental Biology and Clinical Insights

Aortic aneurysms are complex, predominantly asymptomatic vascular diseases with distinct incidence patterns depending on anatomical localisation. The incidence of thoracic aortic aneurysms (TAAs) has moderately increased, whereas that of abdominal aortic aneurysms has declined, primarily due to public health measures. Undiagnosed or poorly managed aneurysms are at significant risk of progression to acute aortic syndrome, with high associated mortality. The embryological origins of the aorta may have a substantial impact on its structural, cellular, and functional heterogeneity. Specifically, smooth-muscle cells (SMCs) in the thoracic aorta are derived from cardiac neural crest and mesodermal cells, whereas abdominal aortic SMCs originate from the paraxial and splanchnic mesoderm. To explore these developmental and regional distinctions, we conducted a narrative review based on targeted literature retrieval and expert curation, highlighting how these distinctions might potentially influence susceptibility to aneurysms and their clinical presentation. Histological differences, such as the number of lamellar units and the presence or absence of vasa vasorum, could further explain regional vulnerability. Molecular mechanisms underlying aneurysm formation include inflammation, oxidative stress, extracellular matrix degradation, phenotypic switching, and dysregulated signalling pathways, notably transforming growth factor-beta (TGF-β) and angiotensin II. Genetic mutations significantly contribute to TAAs, with genes involved in the elastin–contractile unit and TGF-β signalling pathways playing pivotal roles. However, the complex interplay between genetic susceptibility and risk factors explains why some patients develop aneurysms while others do not. Clinical management strategies have evolved, emphasising early risk stratification, surveillance, and timely surgical intervention, guided increasingly by genetic profiling and segment-specific molecular understanding. Advances in genomic technologies, biomarker identification, and computational modelling promise to enhance individualised care. Bridging developmental biology, molecular genetics, and clinical practice is crucial for improving outcomes in patients with aortic aneurysms, thereby reinforcing a multidisciplinary approach to patient-centred cardiovascular medicine.