Comparative study of three needle injection of ethanol methods for establishing intervertebral disc degeneration models in rat

English Keywords:Intervertebral disc degeneration  Percutaneous injection of anhydrous ethanol  Rat  Disc height index

English Abstract:

  【Abstract】 Objectives: To compare the differences in three rat intervertebral disc degeneration(IDD) models constructed by needle injections of ethanol into the nucleus pulposus, annulus fibrosus, and endplate, respectively. Methods: 45 6-week-old Sprague-Dawley rats were randomly divided into three groups using a random number table method, with 15 rats in each group. Three different needle injection of ethanol methods including nucleus pulposus injection(nucleus pulposus injection group), annulus fibrosus injection(annulus fibrosus injection group), and endplate injection(endplate injection group) were used to construct IDD models at the Co6/7 intervertebral disc in rats. At 1, 2, 3, and 4 weeks post-modeling, 3 rats from each group were randomly selected using a random number table for X-ray examination to measure and calculate the disc height index(DHI) of the Co6/7 in rats. Subsequently, rats were euthanized under excessive anesthesia, and the Co6/7 intervertebral disc along with adjacent vertebral bodies were harvested for hematoxylin-eosin(HE) staining to observe degeneration, and the degeneration degree was histologically scored. Results: One rat in each of the nucleus pulposus injection group and annulus fibrosus injection group died unexpectedly due to anesthesia； In the endplate injection group, two rats died due to postoperative infection. At 1, 2, 3, and 4 weeks after modeling, 3 rats were selected from each group of the remaining rats, and a total of 36 rats were included in the result analysis. The remaining rats were sacrificed by excessive anesthesia. One week after modeling, the Co6/7 DHI in each group was lower than that before modeling(Nucleus pulposus injection group: 0.117±0.002 vs 0.134±0.005; Annulus fibrosus injection group: 0.126±0.005 vs 0.133±0.005; Endplate injection group: 0.127±0.002 vs 0.130±0.007, all P<0.05), which gradually decreased over time. After modeling in each group, the annulus fibrosus broke, the arrangement of fibers gradually became disordered, the matrix and cells of the nucleus pulposus were gradually lost or even completely disappeared, the intervertebral discs gradually collapsed, and the intervertebral spaces gradually narrowed. The degeneration rate and degree of the nucleus pulposus injection group were faster and higher than those of the other two groups. Four weeks after modeling, the DHI of the nucleus pulposus injection group was 0.090±0.008, which was lower than that of the annulus fibrosus injection group(0.106±0.007, P<0.05) and endplate injection group(0.109±0.000, P<0.05); The histological score of the nucleus pulposus injection group was 10.00±0.82, which was higher than that of the annulus fibrosus injection group(9.00±1.41, P<0.05) and endplate injection group(8.75±0.96, P<0.05). Conclusions: The three needle injection of ethanol methods have their own unique characteristics for constructing IDD models. Nucleus pulposus injection induces the fastest and most severe degeneration, endplate injection leads to slower degeneration but is more in line with natural degeneration processes, and annulus fibrosus injection falls between the other two methods in terms of degeneration characteristics.