老化大鼠坐骨神经Fas与FasL的表达及纤维结构变化

The expression of Fas and FasL and the structural changes of nerve fibers in saiatic nerve of the aged rats

为了观察老化对神经纤维组成和结构的影响以及对凋亡相关因子Fas及其配体FasL表达的影响,随机取3月龄(成年组)和24月龄(老年组)正常SD大鼠各16只进行以下实验:采用透射电镜(TEM)观察坐骨神经的超微结构变化;苏木精-伊红(HE)染色计数轴突数与Schwann细胞数的比例;免疫组织化学染色检测大鼠坐骨神经老化时Fas和FasL的表达变化。结果显示:透射电镜下可见老年大鼠坐骨神经轴突直径增加,轴突周围间隙扩大,多数髓鞘分离,部分板层结构排列紊乱、破坏甚至呈气球样变。老年组的轴突数与Schwann细胞数的比例较成年组变大(P<0.01)。两组动物坐骨神经的髓鞘与轴突均可见Fas和FasL免疫组化阳性染色,但老年组大鼠的Fas和Fasl表达量明显增多(P<0.05)。以上结果提示老化大鼠坐骨神经神经纤维的形态结构发生很大的变化,可能与凋亡相关基因产物Fas及其配体FasL的表达增加有关。

To investigate the effect of ageing on the composition and structural changes of nerve fibers and to observe the expression change of apoptosis-associated factors （Fas and FasL）, 16 adult rats （3 months） and 16 aged rat （24 months） were used for following aims： transmission electronmicroscopy （TEM） was used to observe the uhrastructural changes of sciatic nerve; conventional hematoxylin-eosin （HE） staining was used to calculate the ratio of axon number to Schwann cell number; immunohistochemistry was used to detect the expression changes of Fas and FasL. The TEM experhnent showed that there were obvious differences in the ultrastructure of myelin sheath and axon in aged rats over adult rats, i. e, increased diameter of axons, increased gaps betwecm axon and myelin, separated compact layer, destructed myelin sheath and the appearance of ballooning like changes therein. HE staining showed that the ratio of axon number to Schwann cell number became larger in aged group （P 〈 0.01 ）. Immunohistochemistry showed that both aged and adult rats showed Fas and FasL inmmnoreactivity. But the expression level was higher in aged group than in young group （P 〈 0.05）. These results suggest that the morphology and structure of nerve fibers in sciatic nerve undergoes essential changes with ageing, which might involves the increased expression of Fas and FasL as a potential mechanism.