The Effect of Genipin Matrix Augmentation on the Retention of Glycosaminoglycans in the Intervertebral Disc—A Pilot Study

Abstract

The degradation of intervertebral disc proteoglycans, including the loss or shortening of their hydrophilic glycosaminoglycan chains, causes a loss of disc hydration, leading to an increase in solid matrix stresses. This illustrates one aspect of the complex multifactorial relationship between tissue degradation and the resulting mechanical dysfunction. Genipin matrix augmentation has previously been evaluated with regard to its ability to improve mechanical properties of the disc, increasing joint stability and permeability. The study aim was to evaluate the ability of genipin augmentation to increase retention of glycosaminoglycans in disc specimens subjected to free swelling. Three different models were utilized: whole bovine caudal discs, partial annulus specimens from bovine, and human thoracic discs. Total glycosaminoglycan release to a surrounding bath was quantified using a modified dimethyl-methylene blue assay. Genipin solution injections reduced glycosaminoglycan loss by 44.0% in intact bovine discs compared to buffer-only controls (p = 0.027), by 75.8% in partial bovine annulus specimens (p = 0.0004), and by 51.9% in human annulus specimens (p = 0.017). The combination of increased permeability and glycosaminoglycans retention may produce beneficial effects on nutritional flow, diurnal irrigation, and reduction of matrix solid phase stress. Combining these effects with the ability to improve joint stability and augment tissue mechanical properties suggests this nano-scale device may be capable of arresting ongoing degeneration.