Effect of collagen cross-linking on quantitative MRI parameters of articular cartilage

Objective To investigate the sensitivity of quantitative magnetic resonance imaging (MRI) parameters to increase of collagen cross-linking in articular cartilage, a factor possibly contributing to the aging-related development of osteoarthritis (OA). The issue has not been widely studied although collagen cross-links may significantly affect the evaluation of cartilage imaging outcome. Design Osteochondral samples (n = 14) were prepared from seven bovine patellae. To induce cross-linking, seven samples were incubated in threose while the other seven served as non-treated controls. The specimens were scanned at 9.4 T for T₁, T_1Gd (dGEMRIC), T₂, adiabatic and continuous wave (CW) T_1ρ, adiabatic T_2ρ and T_1sat relaxation times. Specimens from adjacent tissue were identically treated and used for reference to determine biomechanical properties, collagen, proteoglycan and cross-link contents, fixed charge density (FCD), collagen fibril anisotropy and water concentration of cartilage. Results In the threose-treated sample group, cross-links (pentosidine, lysyl pyridinoline (LP)), FCD and equilibrium modulus were significantly (P < 0.05) higher as compared to the non-treated group. Threose treatment resulted in significantly greater T_1Gd relaxation time constant (+26%, P < 0.05), although proteoglycan content was not altered. Adiabatic and CW-T_1ρ were also significantly increased (+16%, +28%, P < 0.05) while pre-contrast T₁ was significantly decreased (−10%, P < 0.05) in the threose group. T₂, T_2ρ and T_1sat did not change significantly. Conclusion Threose treatment induced collagen cross-linking and changes in the properties of articular cartilage, which were detected by T₁, T_1Gd and T_1ρ relaxation time constants. Cross-linking should be considered especially when interpreting the outcome of contrast-enhanced MRI in aging populations.