Differentiation of oligodentrocyte progenitor cell from aged rat brain

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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.