Cortical Remyelination Is Heterogeneous in Multiple Sclerosis

Area of Science:

• Neuroscience
• Pathology
• Immunology

Background:

• Cortical lesions (CLs) are key in multiple sclerosis (MS) pathology, correlating with disability.
• Remyelination, the repair of myelin sheaths, is a critical process in MS.
• Understanding remyelination in gray matter (GM) versus white matter (WM) is crucial for MS treatment.

Purpose of the Study:

• To quantify and compare remyelination extent in CLs and white matter lesions (WMLs).
• To investigate oligodendrocyte (OGD) maturation and its role in remyelination.
• To explore the clinical relevance of remyelination in MS, particularly in primary progressive MS (PPMS).

Main Methods:

• Immunohistochemical staining of brain tissue from 21 chronic MS patients.
• Staining for myelin proteolipid protein and Olig2 (an OGD marker).
• Scoring of normal-appearing GM/WM, de/remyelination, and OGD precursor cell (OPC) and OGD cell counts.

Main Results:

• Remyelination was significantly more extensive in CLs compared to WMLs.
• A trend suggested more GM remyelination in PPMS patients versus relapse-onset MS patients.
• Higher OPC counts were observed in both remyelinated and non-remyelinated CLs compared to WMLs.

Conclusions:

• Gray matter exhibits more extensive remyelination than white matter in MS brains.
• Remyelination in MS is not significantly limited by oligodendrocyte precursor cell recruitment in the gray matter.
• These findings offer new insights into the mechanisms of remyelination failure in MS.