大鼠坐骨神经髓鞘相关蛋白随年龄的变化

Change of myelin-associated protein expressions in rat sciatic nerves with age

目的：研究大鼠坐骨神经髓鞘相关蛋白随年龄的变化及与髓鞘板层数之间的相互关系.方法：SD大鼠分别于饲养1周、1月、3月、9月、15月和21月后取坐骨神经,利用透射电镜观察计数髓鞘板层；采用免疫印迹检测髓鞘相关蛋白—髓鞘碱性蛋白（MBP）、髓鞘相关糖蛋白（MAG）和P0蛋白（P0）的表达变化,并分析与板层数之间的相关性；采用荧光免疫组织化学显色观察MBP的表达变化.结果：透射电镜观察显示,大鼠坐骨神经髓鞘板层数从1周到15月逐渐增加,直到21月无显著变化.免疫印迹显示,MBP的表达随年龄增长而增加,21月时达到高峰,与髓鞘板层数呈正性直线相关；MAG在出生后1周表达最高,而P0在1月时达峰值,后皆随年龄增加而下降,MAG与髓鞘板层数呈负性直线相关,而P0与髓鞘板层数之间呈非直线相关.荧光免疫组织化学显色显示,随着年龄增长,MBP在大鼠坐骨神经的髓鞘表达的荧光强度逐渐增强.结论：大鼠坐骨神经髓鞘相关蛋白随年龄改变呈现不同的表达模式,并与髓鞘板层数之间存在一定相关性.

Objective： To investigate the chang~ of myelin-associated proteins in myelin of rat sciatic nerves with age, as well as the relationships between the protein expressions and morphology changes. Methods： Sparague-Dawley （SD） rats were randomly divided into 6 distinct age groups： 1-week, 1-, 3-, 9-, 15- and 21-month age groups. The number of myelin sheath lamellae of the sciatic nerve was counted with electron micrographs. Western blotting was performed to examine the changes of protein expression levels of myelin-associated proteins in rat sciatic nerves, such as myelin basic protein （MBP）, myelin associated glycoprotein （MAG） and myelin protein zero （P0）. And fluorescent immunohistochemistry was performed to observe the change of MBP in the sciatic nerve. The relationships between myelin sheath lamellae and the expression of myelin-associated proteins were analyzed. Results： The number of myelin sheath lamellae gradually increased from 1 week through 15 months of age,and then remained nearly unchanged until 21 months of age. MBP protein level was increased with age and peaked at 21 months. MAG and P0 levels peaked at 1 week and 1 month respectively, and then both of them were decreased gradually during the maturation and aging process. The protein expressions of MBP and MAG were positively and negatively correlated with the number of myelin sheath lamellae, while the protein expression of P0 protein was not linearly correlated with the number of myelin sheath lamellae. Conclusion： Myelin-associated proteins display different age-related patterns, suggesting that these proteins might perform distinct actions on the formation, maturation, degeneration and regeneration of rat sciatic nerve myelin sheath.