Basic Study on Retardation of Disc Degeneration (Long Term Follow-up Experimental Animal Models with reinserted nucleus pulposus)

【目的】通过两种动物模型的长期随访研究，探讨退变椎间盘中髓核（Nucleus pulposus，NP）的存在是否在延缓椎间盘进一步退变中发挥重要作用，并在体外研究NP与纤维环（anulus fibrossus，AF）之间的生化影响。[材料与方法]本研究由2个实验组成。实验研究-1：在40只Wistar大鼠的第5 ~ 8尾骨间建立椎间盘突出症动物模型，并从尾骨5/6和6/7处吸出髓核（PN）。PN后，将新的NP插入尾骨5/6。（尾骨6/7作为Asham对照，7/8作为对照，8/9作为供体椎间盘）。再插入后2、4、10和16周，对每个椎间盘的标本进行组织病理学研究，了解结构完整性和凋亡细胞的出现。实验研究-2：在20只日本白色家兔中诱导椎间盘突出的动物模型。PN后两周，将L2/3和L3/4的NP重新插入L415和L5/6。在2，4，8和16周后，从每个椎间盘标本进行了组织学研究和II型胶原进行了测试，利用共聚焦激光扫描显微镜（CLSM）。[结果] PN后AF和终板的退行性改变随着时间的推移逐渐进行，大圆形的脊索细胞数量减少，取而代之的是小细长的成纤维细胞样细胞。在髓核复位的椎间盘中，AF内层周围可见凋亡细胞，而非髓核复位的椎间盘中凋亡细胞较少。在AF的nonreinserted光盘的II型胶原蛋白的荧光强度高的内层和低的外层，与轻微的变化，在一个reinserted光盘。

[Purpose] The purpose of these consecutive studies is to discuss whether an existence of the nucleus pulposus (NP) in degenerated discs plays an important role of decelerating further disc degeneration or not, using two animal models with the reinserted nucleus pulposus at the long term follow-up, and investigate biochemical influences between NP and the anulus fibrosus (AF) in vitro.[Materials and Methods] The study was composed of 2 experiments. Experimental study -1 : An animal model of disc herniation was induced in 40 Wistar rats between 5th and 8th Coccyx and NP from Coccyx 5/6 and 6/7 was aspirated (PN). After PN, afresh NP was inserted into Coccyx 5/6. (Coccyx 6/7 served as asham control, 7/8 as a control, and 8/9 as a donor disc). Two, 4, 10 and 16 weeks after reinsertion, specimens from each disc were studied histopathologically regarding the structural integrity and an emergence of apoptosis cells. Experimental study-2 : An animal model of disc herniation was induced in 20 Japanese white rabbits. Two weeks alter PN, NP from L2/3 and L3/4 was reinserted into L415 and L5/6. In 2, 4, 8, and 16 weeks after reinsertion, specimens from each disc were studied histologically and type II collagen was tested utilizing aconfocal laser scanning microscopy (CLSM).[Results] Degenerative changes of AF and an end plate gradually progressed with time after PN.Large round cells identified as notochord cells were decreased in number and replaced by small elongated fibroblast-like cells. Chondrocyte-like cells were also occasionally found in the reversed AF.These degenerative changes were less evident in reinserted discs of NP.Apoptosis cells around the inner layer of AF were noted in the discs with reinserted pulposus and very less observed in nonreinserted disc. A fluorescent intensity of Type II collagen in AF of a nonreinserted disc was high n the inner layer and low in the outer, compared with slight changes in a reinserted disc.