A reduced glycosaminoglycan-linked residual-strain model captures regional opening angle changes after depletion in the porcine thoracic aorta

Abstract

Residual stresses in arteries are commonly revealed by the spring 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 regional mean depletion responses are consistent with a removable preferred stretch field shaped by the transmural FCD profile and superposed on a structural field retained after 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}). These results show that the three regional mean depletion responses can be represented by one common FCD-linked removable preferred-stretch contribution. Because the model uses regional averages and fitted region-specific control structural fields, it does not establish specimen-level predictive validity or uniquely identify the underlying GAG-mediated mechanism. Donnan swelling remains mechanically relevant, but it is insufficient alone to explain the measured regional response.