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

【目的】这些连续研究的目的是通过对两种动物模型进行长期随访，重新植入髓核，探讨椎间盘退变中髓核（NP）的存在是否对椎间盘进一步退变起到重要的减速作用，并在体外研究NP与纤维环（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：用40只Wistar大鼠第5 ~ 8尾骨建立椎间盘突出动物模型，从尾骨5/6、6/7抽取NP （PN）。PN后，将新的NP插入尾骨5/6。（尾骨6/7作为对照，7/8作为对照，8/9作为供椎间盘）。重新插入后2周、4周、10周和16周，对每个椎间盘标本进行组织病理学研究，观察其结构完整性和凋亡细胞的出现。实验研究二：用20只日本大白兔建立椎间盘突出动物模型。两周改变PN，将L2/3和L3/4中的NP重新插入L415和L5/6中。在重新插入后2、4、8和16周，对每个椎间盘标本进行组织学研究，并利用共聚焦激光扫描显微镜（CLSM）检测II型胶原蛋白。【结果】假手术后AF及终板的退行性改变随时间的推移而逐渐加重。被鉴定为脊索细胞的大圆形细胞数量减少，取而代之的是细长的小成纤维细胞样细胞。软骨细胞样细胞也偶有出现在逆转的af中。这些退行性改变在NP重新插入的椎间盘中不太明显。椎间盘复位组AF内层周围有凋亡细胞，未复位组AF内层周围凋亡细胞较少。非复位椎间盘AF的II型胶原荧光强度在内层高，在外层低，与复位椎间盘的轻微变化相比。

[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.