The Role of Matrix Metalloproteinases in Thoracic Aortic Disease: Are They Indicators for the Pathogenesis of Dissections?

Matrix metalloproteinases and their tissue inhibitors as indicators of aortic aneurysm and dissection development in extracellular matrix remodeling

Aneurysms and dissections represent some of the most serious cardiovascular diseases. The prevailing theory posits that mechanical overloading of the vessel wall is the underlying cause. Inspired by Barkhordarian et al, the authors present matrix metalloproteinases (MMPs) and their inhibitors in immunohistological analyses as contributing factors in the pathophysiology of aortic aneurysms (AA). Data analysis of MMP-1, MMP-9, tissue inhibitors of metalloproteinases (TIMPs), including TIMP-1 and TIMP-2 expression reveals a varied distribution between the adventitia and media and a non-uniform expression of the investigated markers. These elements, as key components of the extracellular matrix (ECM), indicate that the formation of AA is not solely driven by endoluminal pressure loading of the aortic wall. Instead, degenerative processes within ECM elements contribute significantly. Importantly, AA do not necessarily imply dissection. Tissue destruction, allowing blood flow entry, arises from reduced oxygen supply to the media, primarily due to incomplete capillarization or neocapillarization.

Targeting the S100A9/P38 MAPK/HSPB1 axis as a novel approach for aortic dissection therapy

INTRODUCTION

Aortic dissection (AD) is caused by inflammatory responses and extracellular matrix (ECM) degradation processes, in which S100A9, a proinflammatory protein, may play a role. This study explored the role S100A9/P38 MAPK/HSPB1 signaling axis in AD pathogenesis and the therapeutic potential of targeting this pathway.

METHODS

S100A9 expression in the aortic tissues of patients with AD/healthy controls were analyzed using bioinformatics, ELISA, qPCR, western blotting, and immunohistochemistry. In an AD mouse model induced by β-aminopropionitrile and angiotensin II (Ang-II), S100A9 expression was inhibited using specific inhibitors to assess its relationship with AD, and proteomics were performed to explore the pathways related to S100A9 expression. Human aortic vascular smooth muscle cells (HVSMC) were treated with Ang-II, S100A9 knockdown, P38 MAPK inhibitors, and HSPB1 knockdown, and experimental methods were used to assess changes in inflammatory cytokines, ECM remodeling, cell proliferation, and apoptosis. Rescue experiments validated the role of the S100A9/P38 MAPK/HSPB1 axis.

RESULTS

S100A9 was significantly upregulated in patients with AD, while levels of inflammatory cytokines and matrix metalloproteinases (MMPs) were elevated. S100a9 inhibition reduced the incidence of AD, improved survival, and stabilized the aortic structure in mice, with reduced collagen deposition and SMC apoptosis in vitro. S100A9 knockdown reduces Ang-II-induced HVSMC proliferation, apoptosis resistance, and ECM degradation. Mechanistic studies revealed that the S100A9/P38 MAPK/HSPB1 axis regulates inflammatory cytokine and MMPs release.

CONCLUSION

S100A9 regulates inflammation and ECM degradation through the P38 MAPK/HSPB1 axis, influencing HVSMC proliferation and apoptosis and promoting AD development. This pathway may be a promising therapeutic target for AD treatment.

Circulating Matrix Metalloproteinases for Prediction of Aortic Dilatation in Children with Bicuspid Aortic Valve: A Single-Center, Observational Study

Circulating biomarkers have been proposed for early identification of aortic dilatation progression associated with bicuspid aortic valve (BAV), but matrix metalloproteinases (MMPs) are distinguished as signatures of increased extracellular matrix degradation, a landmark of aneurysm formation. The current study aims to identify the role of MMP-1, MMP-2, MMP-9, and the MMP inhibitor, TIMP-1, in identifying aortic dilation in children with BAV. We conducted a study on 73 children divided into two study groups, depending on the presence of aortic dilatation (group 1-43 BAV controls and group 2-30 children with BAV and aortic dilatation). Each patient underwent a cardiac ultrasound and, in each case, serum MMP-1, MMP-2, MMP-9, and TIMP-1 were quantified using xMAP technology. Comparison of the MMPs between the two study groups revealed significantly higher values only in the case of TIMP-1, among BAV controls. Moreover, the same TIMP-1 inversely correlated with aortic annulus absolute size and z score, as well as with ascending aorta z score. No particular correlation between the aortic phenotype and the presence of aortic dilatation was found. Future longitudinal research starting at pediatric ages could show the significance of MMPs screening in BAV individuals as predictors of aortic aneurysm formation.