Semi‐synthetic degradable notochordal cell‐derived matrix hydrogel for use in degenerated intervertebral discs: Initial in vitro characterization

Abstract

Low back pain is the leading cause of disability worldwide, but current therapeutic interventions are palliative or surgical in nature. Loss of notochordal cells (NCs) and degradation of the healthy matrix in the nucleus pulposus (NP), the central tissue of intervertebral discs (IVDs), has been associated with onset of degenerative disc changes. Recently, we established a protocol for decellularization of notochordal cell derived matrix (NCM) and found that it can provide regenerative cues to nucleus pulposus cells of the IVD. Here, we combined the biologically regenerative properties of decellularized NCM with the mechanical tunability of a poly(ethylene glycol) hydrogel to additionally address biomechanics in the degenerate IVD. We further introduced a hydrolysable PEG‐diurethane crosslinker for slow degradation of the gels in vivo. The resulting hydrogels were tunable over a broad range of stiffness's (0.2 to 4.5 kPa), matching that of NC‐rich and ‐poor NP tissues, respectively. Gels formed within 30 min, giving ample time for handling, and remained shear‐thinning post‐polymerization. Gels also slowly released dNCM over 28 days as measured by GAG effusion. Viability of encapsulated bone marrow stromal cells after extrusion through a needle remained high. Although encapsulated NCs stayed viable over two weeks, their metabolic activity decreased, and their phenotype was lost in physiological medium conditions in vitro. Overall, the obtained gels hold promise for application in degenerated IVDs but require further tuning for combined use with NCs.

Hydrogel-Based Strategies for Intervertebral Disc Regeneration: Advances, Challenges and Clinical Prospects

“…Polymer was designed to mimic slow degradation under physiological conditions to promote a slow replacement of hydrogel with newly deposited matrix within the IVD, as NP matrix turnover takes months to years. [26,33] Alternatively, natural hydrogels are usually derived from animal and plant extracts. According to Yan et al and Ying et al, commonly used natural hydrogels include gelatin, collagen, fibrin, hyaluronate, alginate, agarose, and chitosan [12,26].…”

Getting to the Core: Exploring the Embryonic Development from Notochord to Nucleus Pulposus

“…Studies indicate that NCM enhances ECM production, cell proliferation, and the expression of NPC markers [ 11 , 149 ]. While challenges in optimizing decellularization methods persist, decellularized NCM could potentially be used as a cell-free therapeutic agent or as a carrier [ 150 , 151 ] for cell-based therapies to support NP tissue repair [ 60 ].…”

Recent advances in the repair of degenerative intervertebral disc for preclinical applications

“…At the same time, TMC3 has properties such as high adhesion strength, slow degradation, and excellent cytocompatibility, but extrusion occurs under high stress and cyclic loading, requiring further optimization of TMC ( Long et al, 2018 ). Schmitz et al reported that PEG combined decellularisation of notochordal cell derived matrix (DNCM) showed excellent biocompatibility, but further biomechanical adjustments are required ( Schmitz et al, 2023 ). Regarding the progress of research on PVA hydrogel as an NP replacement material, Leone et al found that PVA with PVP molar ratio of 1:1 has excellent biomechanical characteristics which is a promising NP replacement material ( Leone et al, 2019 ).…”