Swelling Induced Hardening and Degradation Induced Slow-Expansion Hydrogel for a Modified Cervical Spinal Cord Compression Animal Model.

This study presents the development of a polyurethane hydrogel (PUG) for use in a chronic cervical spinal cord compression animal model, leveraging microphase separation and dynamic covalent bonds to achieve swelling induced hardening and degradation-induced slow expansion. PUG-SS and PUG-SS-60% were synthesized with varying disulfide bond concentrations, offering controllable degradation rates and mechanical properties. The hydrogels demonstrated significant swelling-induced hardening and maintained compression above the cervical spinal cord's intrinsic modulus. MRI and histopathological analyses confirmed effective and sustained spinal cord compression, with PUG-SS-60% showing prolonged effects. Behavioral tests, including the BBB locomotor scale, von Frey pain test, and catwalk gait analysis, indicated quicker motor function recovery with PUG-SS and sustained compression with PUG-SS-60%. In vitro cytotoxicity assays showed no significant hydrogel-induced cell death. This study underscores the potential of PUG-SS-60% for providing controlled, sustained compression in chronic spinal cord compression models, paving the way for advanced nonsurgical treatment strategies and improved understanding of degenerative cervical myelopathy (DCM) pathology.