Can UVA-light-activated riboflavin-induced collagen crosslinking be transferred from ophthalmology to spine surgery? A feasibility study on bovine intervertebral disc

Abstract

Background Collagen cross-links contribute to the mechanical resilience of the intervertebral disc (IVD). UVA-light-activated riboflavin-induced collagen crosslinking (UVA-CXL) is a well-established and effective ophthalmological intervention that increases the mechanical rigidity of the collagen-rich corneal matrix in Keratoconus. This study explores the feasibility, safety and efficacy of translating this intervention in reinforcing the IVD. Methods Annulus fibrosus (AF) cells were isolated from bovine IVDs and treated with different combinations of riboflavin (RF) concentrations (0.05–8 mM) and UVA light intensities (0.3–4 mW/cm2). Metabolic activity (resazurin assay), cell viability (TUNEL assay), and gene expression of apoptosis regulators C-FOS and PT5 were assessed immediately and 24 hours after treatment. Biomechanical effects of UVA-CXL on IVDs were measured by indentation analysis of changes in the instantaneous modulus and by peel-force delamination strength analysis of the AF prior and after treatment. Results Different intensities of UVA did not impair the metabolic activity of AF cells. However, RF affected metabolic activity (p < 0.001). PT53 expression was similar in all RF conditions tested while C-FOS expression decreased 24 hours after treatment. Twenty-four hours after treatment, no apoptotic cells were observed in any condition tested. Biomechanical characterizations showed a significant increase in the annular peel strength of the UVA-CXL group, when compared to controls of UVA and RF alone (p < 0.05). UVA-CXL treated IVDs showed up to 152% higher (p < 0.001) instantaneous modulus values compared to the untreated control. Conclusion This is the first study on UVA-CXL treatment of IVD. It induced significantly increased delamination strength and instantaneous modulus indentation values in intact IVD samples in a structure–function relationship. RF concentrations and UVA intensities utilized in ophthalmological clinical protocols were well tolerated by the AF cells. Our findings suggest that UVA-CXL may be a promising tool to reinforce the IVD matrix.

The Use of Collagen-Based Materials in Bone Tissue Engineering

“…R-UV-CXL has also been studied in the fields of wound healing [ 91 ], skin repair [ 92 ], cardiac valves [ 93 ], and vascular regeneration [ 94 ]. A study by Vasilikos et al on the R-UV-CXL treatment of intervertebral disc (IVD) matrices suggested that this treatment may be a promising tool to reinforce the IVD matrix [ 95 ]. In addition, some other photocrosslinking techniques have also been proposed.…”

Exogenous Crosslinking of Tendons as a Strategy for Mechanical Augmentation and Repair: A Narrative Review

“…Vasilikos et al at Ulm University in Germany have investigated the photochemical crosslinking of intervertebral disc (IVD) employing the system UV-A radiation/riboflavin, at an irradiance of 3 mW/cm 2 . They have shown 29 that the photocrosslinking of IVD led to reduced annular delamination, increase of the peel strength, and a significant increase of Young’s modulus. In another study, 30 the subject was the shoulder’s glenohumeral joint capsule; its laxity is one of the main lesions leading to shoulder instability.…”