Stent-graft compliance modulates regional mechanical and structural remodeling of the aorta

Endovascular aortic stent-grafts often introduce a compliance mismatch with the native aorta, potentially leading to adverse remodeling. This study assessed how stent-graft compliance affects structural, mechanical, and morphometric adaptation in a porcine model by comparing a conventional stiff polyethylene terephthalate stent-graft (CS-SG) to a compliant nanofibrillar stent-graft (NF-SG). Four months after implantation, aortas were harvested and systematically analyzed. Morphometric assessment of aortic rings, planar biaxial mechanical testing, and quantification of elastin, collagen, and smooth muscle cell (SMC) densities were performed. Remodeling with the CS-SG was primarily localized to regions under stent contact and included increased collagen accumulation (∼25-30 % vs. ∼15 % in the inner media), elastin compaction, significant loss of SMCs (∼10-15 % vs. ∼20-25 % in inner media), and thick neointima formation. These changes were associated with increased aortic stiffness (0.47 MPa vs. 0.37 MPa) and loss of non-linearity, especially in distal stented segments, while remote regions exhibited minimal alterations. In contrast, NF-SG implantation was associated with fewer localized structural and mechanical changes, including preserved SMC density, reduced collagen accumulation, reduced neointima formation, and maintained compliance at stented and adjacent regions. Overall, these findings suggest that compliant stent-grafts may mitigate localized adverse remodeling at stent-tissue interfaces compared to conventional stiff devices. These results highlight the potential importance of compliance-matching in stent-graft design, although broader effects across the aorta were limited within the four-month observation period. Future studies in diseased and aged models with extended follow-up are warranted. STATEMENT OF SIGNIFICANCE: This study quantifies morphological, mechanical, and structural changes in the porcine aorta four months after implantation of either a stiff or a compliant stent-graft. Aortic remodeling was highly localized, occurring primarily in the stented and distal segments, with minimal changes in regions remote from the stent-graft. Our results demonstrate that compliant stent-grafts better preserve aortic structure, smooth muscle cell density, and mechanical function compared to stiff devices, which induce pronounced pathological changes in areas directly exposed to stent contact. These findings underscore the clinical importance of designing more compliant stent-grafts to mitigate adverse vascular remodeling and improve long-term outcomes after endovascular aortic repair.