Development and application of a new mold for rat tail disc degeneration

English Keywords:Intervertebral disc degeneration  Modeling  Acupuncture  Rat

English Abstract:

  【Abstract】 Objectives: To invent a modeling instrument for simple, minimally invasive, stable and controllable model of rat intervertebral disc degeneration. Methods: A new type of molding instrument for rat caudal intervertebral disc was designed, which was composed of C-ring and spiral needle tube. Twenty 3-month-old male SD rats were divided into the control group(n=10) and the acupuncture group(n=10). The c-type sleeve ring of the modeling instrument was placed on the tails of rats, and a 21G needle was used for spiral puncture, then the model puncture instrument was used to perform transverse puncture(10mm) and semi-transverse puncture(5mm) on the Co6/7 and Co8/9 intervertebral discs in the experimental group. There was no treatment of caudal vertebra in control group. Before and 4 weeks after modeling, the X-ray and MRI were performed for both groups. The disc height was measured on the X-ray and the percentage of the target disc height index(DHI) was calculated. The Pfirrmann score was used to evaluate the disc degeneration scores on the MRI T2 image. Then the rats were killed, and the sections of the target intervertebral disc were taken and stained with safranine O to observe the degeneration of the intervertebral disc. After injecting contrast agent(iohexol) into the non-acupuncture caudal disc segment, the nucleus pulposus tissue was developed under X-ray and aspirated by needle. Results: No rats died under anesthesia, and no postoperative complication such as infection was found. Iohexol was injected into the intervertebral discs of rats, and the contrast and development were good. A certain amount of nucleus pulposus tissue could be extracted by needle. 4 weeks after modeling, the rate of DHI of Co6/7 and Co8/9 in the acupuncture group was 0.65±0.07 and 0.73±0.09, respectively. The Pfirrmann regression scores were 4.3±0.82 and 3.5±0.71 points, respectively. The results were 0.98±0.02 and 0.97±0.02, 1.1±0.32 and 1.1±0.32 points, in the control group, respectively. There were significant differences in the comparison of the same segments between the two groups(P<0.05). There were significant differences in the comparison of the two segments in the acupuncture group(P<0.05), and no significant difference in the comparison between the two segments in the control group(P>0.05). In the acupuncture group, Co6/7 nucleus disappeared, the boundary between the nucleus and the annulus fibrosus was unclear, and the endplate became ossified. The nucleus pulposus and fibrous structure on the side of Co8/9 puncture were disordered, the nucleus pulposus and annulus fibrosus on the other side were relatively intact. In the control group, Co6/7 and Co8/9 nucleus pulposus, annulus fibrosus and endplate had complete shape and clear structure. Conclusions: The model of caudal intervertebral disc degeneration can be successfully established by instrument-setting puncture, and the severity of degeneration aggravated as the puncture depth increased. The molding device can also be used to extract the nucleus pulposus by intradermal injection of contrast agents or drugs.