An abdominal aortic aneurysm (AAA) specimen shows replacement of the medial layer with atherosclerotic plaque, loss of smooth muscle cells, and fragmentation of elastic laminae. The key protease that destroys the extracellular matrix of the aortic wall in AAA is:

• A Elastase released from eosinophil granules
• B Thrombin activating plasminogen to plasmin
• C Matrix metalloproteinases (MMP-2, MMP-9) secreted by macrophages and smooth muscle cells ✓
• D Cathepsin D released from apoptotic endothelial cells

Explanation

AAA pathogenesis involves macrophage and VSMC production of MMP-2 (gelatinase A) and MMP-9 (gelatinase B), which degrade elastin and collagen in the media, leading to progressive weakening and dilation. The ratio of MMP activity to tissue inhibitors of metalloproteinases (TIMPs) favours matrix destruction. Smoking and male sex are risk factors partly because they upregulate MMP expression.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.