Strijbis EM, Kooi EJ, van der Valk P, Geurts JJ.
Cortical Remyelination Is Heterogeneous in Multiple Sclerosis. J Neuropathol Exp Neurol. 2017. doi: 10.1093/jnen/nlx023. [Epub ahead of print]
Cortical lesions (CLs...Lesions on the outer part of the brain) are an important component of multiple sclerosis (MS) pathology; they correlate better with physical disability and cognitive impairment than white matter lesions (WMLs). Because remyelination can be extensive in CLs, we quantified remyelination in gray matter (GM) and white matter (WM), addressing oligodendrocyte (OGD) maturation state and clinical relevance of remyelination.
Brain tissue samples from 21 chronic MS patients were immunohistochemically stained for myelin proteolipid protein, Olig2, which is strongly expressed in OGD precursor cells (OPCs), but weakly expressed in mature OGDs and other OGD markers. Sections were scored for the presence of normal-appearing WM and GM, de- and remyelination, and OPC and OGD cell counts.
Remyelination was significantly more extensive in CLs than in WMLs with a trend toward more GM remyelination in primary progressive MS (PPMS) vs relapse-onset MS patients (Trend means no real difference, but should have done more samples to get an answer one way or another). More OPCs were found in remyelinated and non-remyelinated CLs vs remyelinated WMLs and non-remyelinated WMLs. Thus, there is more remyelination in the GM than in the WM in MS patient brains, with a trend (no difference but trying to make it sound interesting) toward more remyelination in those with PPMS. There does not seem to be a significant OPC recruitment failure in the GM, which casts new light on the process of remyelination failure.
The reason for demyelination is suggested to be a failure to remyelinate. This has been suggested to be due to loss of oligodendrocyte precursors. So this study says that there is remyelination in the grey matter and these is no real failure to remyelinate grey matter as there are still plenty of precursors cells about. Yet there are grey matter lesions.
However it is known that they remyelinate better, and this was said many years ago.
Hopefully this will protect the cortical nerves from damage, maintaining cognition.
And before that:
Extensive cortical remyelination in patients with chronic multiple sclerosis.Albert M, Antel J, Brück W, Stadelmann C.
Brain Pathol. 2007 Apr;17(2):129-38.