Establishment of a rat caudal disc degeneration model by percutaneous fine-needle aspiration of the fibrous ring

Objective To compare the effect of different size needle gauges to the degenerative response in rat caudal discs. Methods A total of 40 Sprague Dawley (SD) rats, level 5/6, 7/8 and 9/10 interverbral discs of rat caudal spine were punctured with 18 or 21 or 25-gauge needles respectively. Radiographs and magnetic resonance imaging (MRI) were obtained at 1, 2, 4 and 6 weeks postsurgery. At each time point, ten rats from each group were sacrificed for histological analysis. Real-time fluorescent quantitative polymerase chain reaction (qPCR) was used to examine mRNA expression level. Results Significant differences were identified in the disc height index (DHI %) and MRI grade between 18 G and normal group, MRI grade, histological score between 21 G and normal group at 2, 4, and 6 weeks postsurgery. Significant differences were also identified in the histological score and mRNA expression levels between 18 G and normal group, alcian blue stain and hypoxia inducible factor-1α (HIF-1α) mRNA expression level between 21G and normal group at all time point postsurgery. Significant differences existed in DHI%, type Ⅱ collagen and aggrecan mRNA expression levels between 21 G and normal group, all type mRNA expression levels between 25 G and normal group at 4, 6 weeks. There were significant differences in MRI grade and histological score between 25 G and normal group at 6 weeks. Significant differences existed in almost all parameters compared between 18 G and 25 G at all time point. There were significant differences in DHI%, MRI grade, histological score and HIF-1α mRNA expression levels between 18 G and 21 G at 4, 6 weeks. There were significant differences in type Ⅱ collagen and aggrecan mRNA expression levels between 18 G and 21 G at all time point. Significant differences exist in DHI% and HIF-1α mRNA expression level between 21 G and 25 G at 6 weeks. Compared with the 25 G group, the DHI% and Pfirrmann scores and the pathological score of each time at 2, 4 and 6 weeks after operation in 18 G group have significant difference (P<0.05). Conclusions The middle size needle (21G) is better to induce disc degeneration. The 2-week time point may be the better time frame to further experimental treatments. Key words: Spinal puncture/MT/AE; Intervertebral disk degeneration/ET; Disease models, animal; Rats