Changes of the end plate cartilage are associated with intervertebral disc degeneration: A quantitative magnetic resonance imaging study in rhesus monkeys and humans

BACKGROUND: The end plate plays an important role in intervertebral disc degeneration progression. The aim of the study was to examine the compositional and structural changes of the end plate with age and to investigate the correlation between end plate and disc degeneration by T1ρ and T2 map magnetic resonance imaging. METHODS: There were 12 young monkeys (6-7 years old), 20 aged monkeys (14-17 years old) and 12 human participants (30-50 years old) in this study. T1ρ or T2 map values of the nucleus pulposus and end plate cartilage were analyzed according to Pfirrmann grades and age. Afterwards, micro computed tomography and histological analysis were used to confirm the end plate changes in monkeys. Pearson’s correlation was performed to investigate the relationship between end plate and disc degeneration. RESULTS: In monkeys, T1ρ (r=-0.794, P<0.001) and T2 map values (r=-0.8, P<0.001) of the nucleus pulposus were negatively associated with Pfirrmann grades. Moreover, the T2 map was more suitable than T1ρ for the evaluation of end plate degeneration. Age was an important influence factor of end plate and disc degeneration, which was confirmed by microcomputed tomography, Safranin O/fast green staining, and collagen II staining. The T2 map value of lower end plate degeneration positively correlated with that of the intervertebral discs in monkeys (R(2)=0.3133, P<0.001) and humans (R(2)=0.2092, P<0.001). CONCLUSION: This study suggests that the compositional and structural changes of the end plate can be quantitatively evaluated by T2 map. Furthermore, cartilage end plate degeneration is associated with disc degeneration during ageing. THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE: A better understanding of how the cartilage end plate affects disc degeneration is needed, which may propose a new clinical application using T2 map to evaluate end plate degeneration.