CTSS and aneurysm: CTSS is involved in the pathogenesis of cardiovascular diseases via its effect on extracellular matrix protein degradation, protein transport, and cell signaling.[28] CTSS can be secreted into the extracellular matrix via lysosomes, increasing collagen and elastin degradation, promoting vascular smooth muscle migration, and ultimately causing atherosclerosis.[29] Apoptosis of the medial smooth muscle cells of the arterial wall is an important marker of AAA, with an increase in apoptosis during aneurysm formation.