Exploring the correlation between magnetic resonance diffusion tensor imaging (DTI) parameters and aquaporin expression and biochemical composition content in degenerative intervertebral disc nucleus pulposus tissue: a clinical experimental study

Abstract

Abstract Objective This study investigates the correlation between magnetic resonance diffusion tensor imaging (DTI) parameters and biochemical composition in degenerative intervertebral disc nucleus pulposus tissue, offering a potential reference for the clinical diagnosis and efficacy evaluation of intervertebral disc degeneration. Methods Human lumbar intervertebral disc nucleus pulposus tissue samples were collected via full endoscopic minimally invasive surgery. DTI was employed to quantitatively measure fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values in the degenerative nucleus pulposus, examining the relationship between Pfirrmann grading and these DTI parameters. Western blotting was used to detect the expression levels of aquaporin 1 (AQP1) and aquaporin 3 (AQP3) in the degenerative tissue. The glycosaminoglycan (GAG) content was quantified using the dimethylmethylene blue (DMMB) colorimetric assay, and collagen content was assessed with the Sircol soluble collagen assay kit. The relationship between Pfirrmann grading and biochemical composition was also analyzed. Finally, correlation analysis was performed between the FA and ADC values from the human nucleus pulposus tissue and their GAG and collagen contents. Results A total of 39 patients (19 males, 20 females) with lumbar disc herniation (LDH), averaging 54.41 years of age, were included. As the degree of Pfirrmann degeneration increased, FA values rose, while ADC values continuously declined. Concurrently, as degeneration progressed, expression of AQP1 and AQP3 proteins decreased, GAG content significantly diminished, and collagen content increased. FA values exhibited a moderate negative correlation with GAG content (r = -0.5974, P < 0.0001) and a strong positive correlation with collagen content (r = 0.8694, P < 0.0001). ADC values showed a moderate positive correlation with GAG content (r = 0.6873, P < 0.0001) and a strong negative correlation with collagen content (r = -0.8502, P < 0.0001). Conclusion The FA and ADC values derived from magnetic resonance DTI, along with the protein expression levels of AQPs, can reflect the severity of intervertebral disc degeneration to a certain extent. Additionally, the content of glycosaminoglycans and collagen in the nucleus pulposus of the intervertebral disc correlates with the FA and ADC values of the DTI parameters. Therefore, magnetic resonance DTI quantitative imaging provides a means to assess the biochemical composition changes within the intervertebral discs, offering valuable insights for the clinical diagnosis and evaluation of therapeutic efficacy in intervertebral disc degenerative diseases. Trial registration Chinese Clinical Trial Registry, ChiCTR2000041151, Registered on 19 December, 2020, https://www.chictr.org.cn/showproj.html?proj=206119 .

Keywords

• Intervertebral disc degeneration (IDD)
• Diffusion tensor imaging (DTI)
• Aquaporins
• Glycosaminoglycan content
• Collagen content