Disc Degeneration Model Induced By Needle Puncture In The Rat Tail And The Safe Injection Volume

Background. Lower back pain is a common health problem that affects millions of people worldwide.Degenerative disc disease is strongly associated with back pain.The treatment of degenerative disc disease includes conservation and surgery, however, the treatment outcomes are not satisfactory. Recent advances in molecular biology and biomaterials have enabled the development of degenerative disc biotherapies such as protein treatment, cell therapy, gene therapy and tissue engineering. With so many novel potential therapies to be tested, there is a need for simpler and quicker animal models that could be used to screen them effectively.Moreover, direct injection via a syringe is considered the best method for transferring biological material, cells, or genetic material into discs. But the injection volume may also induce intervertebral disc degeneration.In this study, a simple disc degeneration model was induced by percutaneous annulus needle puncture through rat tail vertebral discs, and the effects of injection volume on rat tail disc degeneration were also assessed.Part I:A Simple Disc Degeneration Model Induced by Percutaneous Needle Puncture in the Rat TailObjective. To develop a simple animal model of disc degeneration.Methods. Two consecutive rat tails vertebral discs, proximal and distal to the eighth coccygeal vertebra, were randomized for injury and control. The disc selected for injury was punctured percutaneously using a 20-gauge needle with either full penetration or half penetration. The discs were harvested 1,2. and 4 weeks later. Measurements included disc height on molybdenum target digital radiographs, biochemistry (water content, glycosaminoglycans, and hydroxyproline), and histology.Results. Needle punctures with full or half penetration caused significant disc space narrowing and progressive histologic changes of degeneration as early as 1 and 2 weeks after injury, respectively. Significant decrease in glycosaminoglycan content was observed at 4 weeks in the half-penetration puncture discs and at 2 and 4 weeks in discs punctured penetratively. Penetrative puncture resulted in a faster decrease in disc height (P2W< 0.05; P4W< 0.01), lower glycosaminoglycan content (P2W< 0.05), and higher grades of histologic degeneration (P1w<0.05; P2.4w<0.01). The water and hydroxyproline content of the discs did not change appreciably.Conclusion. Tail disc percutaneous needle puncture is a simple method for inducing disc degeneration and the rate of degeneration is positively related to the depth of needle puncture. This model still has some limitations that should be taken into consideration when results of disc regeneration research in this model are interpreted and extrapolated to human. Part?:The Effect of Injection Volume on Disc Degeneration in a Rat Tail ModelObjective. To evaluate the effect of injection volume on disc degeneration in a rat tail disc model.Methods.180 Sprague Dawley rats were randomized into 5 groups and injected with 0(control),1.0,2.0,2.5, or 3.0?l of PBS solution. Discs were harvested at weeks 1,2, and 4 after injection and were evaluated using radiography, histology, and biochemistry (glycosaminoglycan, hydroxyproline, and water content).Results. No significant differences in radiography, biochemistry, or histology were observed at any of the 3 sampling times between 1.0,2.0?l groups and the control.2.5 and 3.0?l groups exhibited significant decrease in radiographic disc height index and water content since week 2. The glycosaminoglycan content of 2.5?l group decreased significantly by week 4 and that of 3.0?l group decreased at weeks 2 and 4. Significant hydroxyproline content decrease was only observed for 3.0?l group during week 4. Significantly higher histologic score was observed in 3.0ul group since week 1 and 2.5?l group since week 2. The three parameters of 3.0?l group indicated more severe disc degeneration than those of 2.5?l group, particularly during week 4.Conclusion. When the volume of PBS injected into the rat tail-disc exceeded a threshold, it rapidly exhibited degenerative changes according to radiographic, biochemical, and histologic analysis. The degenerative changes were dose-dependent and increased as the dose increased. Moreover, the safe injection volume for the treatment of degenerative disc disease in this model is less than 2.0?l.