Detection of apoptosis and matrical degeneration within the intervertebral discs of rats due to passive cigarette smoking

Although low-back pain is considered to be associated with cigarette smoking, the influence of cigarette smoking on the intervertebral discs (IVD) has not been confirmed. We established a rat model of passive cigarette smoking-induced IVD degeneration, and investigated the cytohistological changes in the IVD and the accompanying changes in gene expression. IVD from rats exposed to 8 weeks of passive cigarette smoking were stained with Elastica van Gieson, and exhibited marked destruction of the supportive structure of the reticular matrix in the nucleus pulposus (NP). Positive signals on safranin O, alcian blue, type II collagen and aggrecan staining were decreased in the destroyed structure. Safranin O and type II collagen signals were also decreased in the cartilage end-plate (CEP) after 4- and 8-weeks of cigarette smoking. In the CEP, the potential for apoptosis was increased significantly, as demonstrated by staining for single-strand DNA. However, there were no signs of apoptosis in the NP or annulus fibrosus cells. Based on these findings, we hypothesized that passive cigarette smoking-induced stress stimuli first affect the CEP through blood flow due to the histological proximity, thereby stimulating chondrocyte apoptosis and reduction of the extracellular matrix (ECM). This leads to reduction of the ECM in the NP, destroying the NP matrix, which can then progress to IVD degeneration.尽管目前临床普遍认为腰痛与吸烟相关，但吸烟对椎间盘（intervertebral discs, IVD）的具体影响尚未得到明确证实。本研究构建了被动吸烟诱导的椎间盘退变大鼠模型，对椎间盘的细胞组织学变化及伴随的基因表达改变进行了探究。对暴露于被动吸烟8周的大鼠椎间盘行弹力范吉森（Elastica van Gieson）染色后可见，髓核（nucleus pulposus, NP）内网状基质的支撑结构出现显著破坏；番红O、阿尔辛蓝、II型胶原及聚集蛋白聚糖染色的阳性信号在该破坏区域中均显著减弱。被动吸烟4周及8周后，软骨终板（cartilage end-plate, CEP）内的番红O与II型胶原信号同样出现降低。通过单链DNA染色检测证实，软骨终板内的细胞凋亡潜能显著升高，但髓核与纤维环细胞未观察到凋亡迹象。基于上述实验结果，本研究提出假说：被动吸烟产生的应激刺激首先通过血流动力学作用，影响解剖位置邻近的软骨终板，进而诱导软骨细胞凋亡及细胞外基质（extracellular matrix, ECM）合成减少；这一过程将导致髓核内细胞外基质含量下降，破坏髓核基质结构，最终进展为椎间盘退变。