A single glycosaminoglycan-linked residual-straincoefficient explains regional opening angle changes afterdepletion in the porcine thoracic aorta

Residual stresses in arteries are commonly revealed by the opening of a ring after a radial cut. Glycosaminoglycans (GAGs) contribute to this response, but fixed-charge-density (FCD)-driven Donnan swelling alone does not fully explain the opening-angle reduction measured after enzymatic GAG depletion. We therefore tested whether the transmural FCD profile defines a removable preferred-stretch field superposed on a structural field retained after GAG depletion. A reduced analytical-computational axisymmetric closure framework was applied to regional-average measurements from the ascending aorta, arch, and descending porcine thoracic aorta. Each control state was fitted using its measured circumferential opening angle, geometry, material properties, and through-wall FCD profile. GAG depletion was represented by removing the FCD-linked preferred-stretch component. One coefficient governing this removable component was selected jointly from the three measured regional post-depletion angles. A one-layer wall was the primary parsimonious model; a two-layer wall tested anatomical robustness. The one-layer model fitted a shared coefficient of -1.4226 x 10-3 (mEq/L)-1 and predicted depleted angles of 82.639{degrees}, 44.032{degrees}, and 19.979{degrees}, compared with measured values of 85{degrees}, 41{degrees}, and 18{degrees} (three-region RMSE 2.50{degrees}). The two-layer model fitted -1.51746 x 10-3 (mEq/L)-1 and predicted 82.972{degrees}, 44.273{degrees}, and 18.534{degrees} (RMSE 2.24{degrees}). Thus, layer differentiation improved aggregate fit only modestly. These findings support a parsimonious mechanism in which GAG depletion removes an FCD-shaped circumferential preferred-stretch component while most residual-stress architecture remains in a structural field retained after depletion. Donnan swelling remains mechanically relevant, but it is insufficient alone to explain the measured regional response. Statement of SignificanceGlycosaminoglycans are charged extracellular-matrix constituents that influence arterial residual stresses through osmotic effects and interactions with the fibrous matrix. We tested whether the through-wall FCD pattern also plays a role in the development of residual stresses and can be modeled as a removable circumferential preferred-stretch component. One coefficient linking that pattern to the GAG depletion response explained the post-depletion opening angles of the ascending aorta, arch, and descending aorta within 3.3{degrees} using a one-layer model. A two-layer model improved aggregate error only modestly. The result provides a compact mechanistic link between extracellular-matrix composition and residual opening without requiring a separately fitted GAG effect in each region.