Differentiation of oligodentrocyte progenitor cell from aged rat brain

髓鞘是中枢神经系统中少突胶质细胞的质膜的多层的、缠绕的延伸。这种特殊的结构表现出低电容，因此作为轴突绝缘体，促进通过跳跃式传导传递神经冲动。最近的数据表明，在衰老过程中，皮质神经仍然保留，而白色物质的显着损失确实发生。尤其是正常健康老年人的白色物质中发生髓鞘分解。目前还不清楚神经系统的年龄相关改变是由于一个独特的老化过程或已知的退行性和/或脱髓鞘疾病的影响的总和。为阐明衰老过程中形态学的变化，我们用电镜观察了有髓神经纤维结旁区的完整结构，表明衰老大鼠脑中存在异常的结旁环。在32月龄大鼠中观察到形态学异常，特别是结旁区连续终末环之间缺乏专门的紧密连接。Western blot分析显示年轻成人和/或老年成人髓鞘之间MBP和N钙粘蛋白表达水平的主要差异。老年轴突萎缩和纤维丢失的机制尚不清楚。然而，我们的研究结果表明，年龄相关的髓鞘丢失可能是异常的基础，包括结旁区的分子组织。

The myelin sheath is a multilamllar, spirally wrapping extension of the plasma membrane of oligodendrocytes in the central nervous system. This specialized structure exhibits a low capacitance and as a result serves as an axonal insulator that facilitates transmission of nerve impulses by saltatory conduction. Recent data have provided that during aging, the cortical nervous remain preserved, while a significant loss of white matter does occur. Especially, myelin breakdown occurs in the white matter of normal healthy aged adult. It is also unclear whether age-related alterations of the nervous system are due to a unique aging process or to a summation of the effects of known degenerative and/or demyelinating diseases. To elucidate the variety of morphological feature with aging, using a electron microscpy, we have demonstrated the complete structure in the paranodal regions of the myelinated fibers, indicating the abnormal paranodal loops in aging rat brain. The morphological abnormalities, especially the lack of specialized tight junctions between successive terminal loops in the paranodal regions are seen in 32-month old rats. Western blot analysis revealed the major difference in the level of MBP and N cadherin expression between the young adult and/or aged adult myelin sheaths. The mechanisms underlying axonal atrophy and fiber loss with old age are unknown. However, our findings suggest the age-related loss of myeline may underlie the abonormalities including the molecular organization of paranodal region.