The Effects of Glycosaminoglycans on Corneal Mechanical Response

This study investigates the role of glycosaminoglycans (GAGs) in regulating corneal biomechanics through a series of ex vivo mechanical experiments, including dynamic shear tests, uniaxial and biaxial tensile tests, and transmission electron microscopy (TEM). The findings reveal that corneal collagen crosslinking (CXL) significantly enhances the mechanical properties of the porcine corneal stroma by increasing tensile tangent modulus, shear modulus, and interfibrillar compaction. TEM analysis highlights the depth-dependent ultrastructure of the corneal stroma, with larger collagen fibrils in the anterior region compared to the posterior. It demonstrates that CXL compacts the collagen-proteoglycan matrix without altering fibril diameter. Uniaxial tests show that enzymatic GAG depletion reduces the stiffening effects of CXL, emphasizing GAGs' role in maintaining corneal strength and resilience. Planar biaxial testing reveals non-linear stress-strain relationships, isotropic behavior under equibiaxial loading, and significant stiffening due to CXL and preconditioning effects. The results also underscore the importance of displacement rates in influencing mechanical response. Additionally, enzymatic digestion confirms the critical role of GAGs in viscoelastic shear properties, with depletion causing substantial reductions in shear modulus and disrupting collagen fibril organization. This comprehensive assessment highlights the complex interplay between corneal ultrastructure and biomechanics, demonstrating the significance of GAGs and collagen crosslinking in maintaining corneal integrity. The findings provide a foundation for future in vivo studies and contribute to developing advanced therapeutic strategies for corneal disorders.