A preliminary feasibility study of a tough hydrogel as a nucleus pulposus substitute for degenerative disc disease.

INTRODUCTION: Degenerative disc disease is characterized by low back pain caused by degeneration of the intervertebral discs. Hydrogels, with favorable biocompatibility and characteristics resembling the nucleus pulposus, have received attention as potential replacement materials. In this study, we developed a tough hydrogel with enhanced mechanical performance and conducted an initial assessment of its feasibility as a nucleus pulposus substitute. METHODS: The hydrogel was fabricated by incorporating 2-hydroxyethyl methacrylate-treated silk fibers into the core of a polyvinyl alcohol hydrogel. In vitro experiments, including cytotoxicity, cell adhesion and short-term proliferation tests, and mechanical assessments such as swelling, static compression, tensile testing, and dynamic mechanical analysis, were performed. Pilot in vivo studies involved implanting the hydrogel into porcine intervertebral discs, with a 21-day observation period. RESULTS AND DISCUSSION: The in vitro results demonstrated no acute cytotoxicity and showed that the hydrogel supports cell adhesion and short-term proliferation, while mechanical testing indicated favorable elastic and viscoelastic properties comparable to those of the native nucleus pulposus. Histological analyses at 21 days indicated that the hydrogel remained within the nucleus pulposus space. These findings suggest that the developed hydrogel exhibits promising biocompatibility and mechanical characteristics; however, further studies are required to fully establish its suitability as a nucleus pulposus replacement for degenerative disc disease.