Abstract
BackgroundSmall animal models that can mimic degenerative disc disease (DDD) are commonly used to examine DDD progression. However, assessments such as histological studies and macroscopic measurements do not allow for longitudinal studies because they can only be completed after the animal is sacrificed. Dynamic contrast-enhanced MRI (DCE-MRI) may provide a reliable, non-invasive in vivo method for detecting the progression.MethodsThe present study investigated the progression of changes in lumbar discs and the effect of endplate conditions on diffusion into the lumbar discs of aging sand rats after intravenous administration of gadolinium-containing contrast medium through the tail vein. Contrast enhancement was measured in the lumbar intervertebral discs on each image. The results were compared with those from conventional histological characterizations.ResultsT2-weighted images revealed that with aging, the shape of L3–L4, L4–L5, L5–L6, and L6–S1 nucleus pulposus (NP) became irregular, while the mean areas, signal intensities, and T2 values of the NP were significantly decreased. Each of the observed disc changes demonstrated a progressive increase in phase during 2-min scout scans. Post-contrast MRI showed impaired endplate nutritional diffusion to the disc with aging, enhancement was significantly greater in young animals than in old animals. Endplate calcification or sclerosis was histologically confirmed; histologic score was correlated with the age. We found the histological score of the endplate negatively corresponded to the DCE-MRI results.ConclusionsDCE-MRI studies offer a non-invasive in vivo method for investigating the progress of diffusion into the discs and the functional conditions of the endplate. We conclude that quantitative DCE-MRI can identify the severity of disc degeneration and efficiently reflect the progression of vertebral endplate changes in the aging sand rat lumbar spine via the NP contrast enhancement patterns.
Highlights
Small animal models that can mimic degenerative disc disease (DDD) are commonly used to examine DDD progression
Intervertebral disc degeneration (IDD) is one of the most common causes of low back pain, and the vertebral endplate plays an important role in disc degeneration
Area and signal intensity values of nucleus pulposus (NP) T2-weighted images Representative serial MRI scans of the lumbar spine of one sand rat are shown in Fig. 1, consisting of T2-weighted, sagittal plane images of the L3–L4, L4–L5, L5–L6, and L6– S1 discs (Fig. 1a, b)
Summary
Small animal models that can mimic degenerative disc disease (DDD) are commonly used to examine DDD progression. Assessments such as histological studies and macroscopic measurements do not allow for longitudinal studies because they can only be completed after the animal is sacrificed. Intervertebral disc degeneration (IDD) is one of the most common causes of low back pain, and the vertebral endplate plays an important role in disc degeneration. Recent research results have shown that nutrient diffusion through the vertebral endplate into the disc depends on fluid flow. Calcification or sclerosis of Histological studies and macroscopic assessments remain the “gold standard” for evaluating IDD progression using animal experiments. Improvement is necessary, as most animal experiments can only be
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