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Abstract:
Chronic plaques in central nervous system tissue fixed by in situ perfusion for electron microscopy were examined for evidence of remyelination in 2 patients with multiple sclerosis (MS). Fibers with abnormal central myelin sheaths of several types were found at the margins of most of the plaques studied. The most common of these were: (1) the presence of bare stretches of axon between contiguous internodes, (2) the presence of thin paranodes, (3) internodes which changed markedly in thickness along their length due to premature termination of superficial or deep myelin lamellae that ended as hypertrophic lateral loops, and (4) abnormally thin internodes which were of uniform thickness along their length, which were shorter than normal, and which terminated in the form of normal nodal complexes. The finding of internodes of the last type at the edges of many plaques indicates that remyelination by oligodendrocytes can occur in the adult human CNS and that it is common in some cases of MS, although limited in its extent.
Insights
Remyelination by oligodendrocytes occurs in the adult central nervous system (CNS) and is common in multiple sclerosis (MS) plaques. This study found evidence of remyelination at the edges of chronic plaques in MS patients.
Area of Science:
- Neuroscience
- Pathology
- Cell Biology
Background:
- Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS).
- Demyelination and remyelination are key pathological processes in MS.
- Understanding remyelination is crucial for developing therapeutic strategies.
Purpose of the Study:
- To investigate evidence of remyelination in chronic plaques of multiple sclerosis (MS) lesions.
- To characterize the morphological features of abnormal myelin sheaths at the plaque margins.
Main Methods:
- Electron microscopy examination of central nervous system (CNS) tissue.
- In situ perfusion fixation of tissue from two multiple sclerosis patients.
- Analysis of myelin sheath morphology in chronic plaques.
Main Results:
- Abnormal central myelin sheaths were observed at the margins of most MS plaques.
- Common findings included bare axon segments, thin paranodes, and variable internode thickness.
- Abnormally thin, uniformly thick internodes with normal nodal complexes were frequently found at plaque edges.
Conclusions:
- The presence of specific remyelinated internode types indicates oligodendrocyte-mediated remyelination in the adult human CNS.
- Remyelination is a common, albeit limited, process in some cases of multiple sclerosis.
- These findings support the potential for endogenous repair mechanisms in MS.