I. Biological Background and Research Significance

Thoracic Aortic Aneurysm and Dissection (TAAD) is a group of life-threatening vascular diseases with abrupt onset and extremely poor prognosis. Genetic factors and disorders of molecular regulatory networks are its core pathogenic mechanisms. As a candidate pathogenic factor, TAAD2 is mainly expressed in vascular smooth muscle cells, fibroblasts, and endothelial cells. The chromosomal region where its encoding gene is located is closely associated with susceptibility in TAAD families. Early studies have shown that TAAD2 may affect the integrity of the aortic wall by participating in extracellular matrix (ECM) remodeling, maintaining the contractile phenotype of smooth muscle cells, and regulating inflammatory signals. However, its specific functions, mechanisms of action, and clinical value still require in-depth exploration, which is expected to provide new directions for the early diagnosis and targeted therapy of TAAD.

II. Molecular Structure and Expression Characteristics

Molecular Structure and Conserved Domains: TAAD2 contains an N-terminal calmodulin-binding domain (responds to calcium signals and participates in the transmission of smooth muscle contraction) and a C-terminal serine/threonine kinase-like domain (interacts with MLCK and other molecules to indirectly regulate cytoskeletal phosphorylation). The middle region has post-translational modification sites, and its function is dynamically regulated. TAAD2 is highly conserved in mammals, with more than 85% homology in functional domains between humans and rodents, providing a reliable basis for research using animal models.

Expression Patterns: In normal aorta, TAAD2 is mainly localized in medial smooth muscle cells (co-localized in the cytoplasm and cell membrane), with low expression in adventitial fibroblasts and almost no expression in endothelial cells. During embryonic development, its expression increases with aortic differentiation and remains stable after birth, suggesting its involvement in aortic maturation. In pathological conditions, TAAD2 expression in the dissection tissues of TAAD patients decreases by 40%-60%, and its subcellular localization shifts from the cell membrane to diffuse distribution in the cytoplasm. In abdominal aortic aneurysms, the phosphorylation level of TAAD2 is significantly elevated, but its regulatory mechanisms (such as epigenetic modification and miRNA action) remain unclear and require further verification.

III. Functions in Aortic Wall Homeostasis Regulation

ECM Remodeling: TAAD2 interacts with MMPs (e.g., MMP2, MMP9) and TIMPs to inhibit MMP2 activity and promote TIMP1 secretion, thereby reducing the degradation of collagen and elastin. Meanwhile, it binds to TβRI to inhibit its activation, negatively regulating the TGF-β/Smad pathway, balancing ECM synthesis and degradation, and preventing aortic wall weakness.

Smooth Muscle Cell Phenotype: TAAD2 maintains the contractile phenotype. After knockdown, the expression of contractile-related proteins (α-actin, MYH11) decreases, and cells switch to a synthetic phenotype. It may interact with MRTF-A to promote its nuclear translocation, enhancing SRF-mediated transcription of contractile genes. The calmodulin-binding domain may affect MRTF-A transport by regulating calcium ion concentration.

Inflammation and Oxidative Stress: TAAD2 inhibits the NF-κB pathway (binds to IKK to prevent IκBα phosphorylation) to reduce the release of pro-inflammatory factors (IL-6, TNF-α). It also enhances the expression of antioxidant enzymes such as SOD1 and GPx, reducing ROS and MDA levels, and its protective effect depends on the activation of the endogenous antioxidant system.

IV. Pathological Association with TAAD

Genetic Variants: There are pathogenic SNPs in the TAAD2 gene. A missense mutation reduces its ability to bind calmodulin, weakens the inhibition of MMP2, and accelerates the phenotypic switching of smooth muscle cells. Carriers of this mutation have faster aortic dilation and a 2.3-fold higher incidence of dissection, making it an important risk factor.

Dynamic Changes: TAAD2 expression decreases progressively with disease progression (20% reduction in asymptomatic aneurysms, over 50% reduction in acute dissection), showing a negative correlation with aortic dilation and inflammatory infiltration, and may serve as a marker of disease progression. Serum levels of soluble TAAD2 fragments increase significantly during acute dissection, with higher diagnostic sensitivity and specificity than D-dimers, and are expected to become an early identification indicator.

V. Summary and Outlook

TAAD2 regulates aortic wall homeostasis through multiple pathways, and its structural conservation, abnormal expression, and genetic variants provide key clues for TAAD research. Currently, it is necessary to clarify the functional regulatory mechanisms of its post-translational modifications, its role differences in different types of TAAD, and the effects of targeted intervention strategies (e.g., gene editing, small molecule agonists) in animal models. In the future, combining multi-omics analysis and gene-edited models is expected to reveal the core mechanisms of TAAD2, providing new targets and theoretical support for the precise prevention and treatment of TAAD.

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