Co-ordinated production and loss of factors are needed for remyelination

Zhao C, Ma D, Zawadzka M, Fancy SP, Elis-Williams L, Bouvier G, Stockley JH, de Castro GM, Wang B, Jacobs S, Casaccia P, Franklin RJ. Sox2 Sustains Recruitment of Oligodendrocyte Progenitor Cells following CNS Demyelination and Primes Them for Differentiation during Remyelination. J Neurosci. 2015 19; 35:11482-99. 

The Sox family of transcription factors have been widely studied in the context of oligodendrocyte development. Here we show that the expression of Sox2 occurs in oligodendrocyte progenitor cells (OPCs) in rodent models during myelination and in activated adult OPCs responding to demyelination, and is also detected in multiple sclerosis lesions. In normal adult white matter of both mice and rats, it is neither expressed by adult OPCs nor by oligodendrocytes (although it is expressed by a subpopulation of adult astrocytes). Overexpression of Sox2 in rat OPCs in vitro maintains the cells in a proliferative state and inhibits differentiation, while Sox2 knockout results in decreased OPC proliferation and survival, suggesting that Sox2 contributes to the expansion of OPCs during the recruitment phase of remyelination. Loss of function in cultured mouse OPCs also results in an impaired ability to undergo normal differentiation in response to differentiation signals, suggesting that Sox2 expression in activated OPCs also primes these cells to eventually undergo differentiation. In vivo studies on remyelination following experimental toxin-induced demyelination in mice with inducible loss of Sox2 revealed impaired remyelination, which was largely due to a profound attenuation of OPC recruitment and likely also due to impaired differentiation. Our results reveal a key role of Sox2 expression in OPCs responding to demyelination, enabling them to effectively contribute to remyelination.
SIGNIFICANCE STATEMENT: Understanding the mechanisms of CNS remyelination is central to developing effective means by which this process can be therapeutically enhanced in chronic demyelinating diseases such as multiple sclerosis. In this study, we describe the role of Sox2, a transcription factor widely implicated in stem cell biology, in CNS myelination and remyelination. We show how Sox2 is expressed in oligodendrocyte progenitor cells (OPCs) preparing to undergo differentiation, allowing them to undergo proliferation and priming them for subsequent differentiation. Although Sox2 is unlikely to be a direct therapeutic target, these data nevertheless provide more information on how OPC differentiation is controlled and therefore enriches our understanding of this important CNS regenerative process.

SRY (sex determining region Y)-box 2, also known as SOX2, is a transcription factor that is essential for maintaining self-renewal, or pluripotency, of undifferentiated embryonic stem cells. Sox2 has a critical role in maintenance of embryonic and neural stem cells. For repair to occur after demyelination you have to clear up the debris from the damage then the oligoprecursor cells  have to migrate into the areas of damage and you may need to proliferate and then the precursor cells have to differentiate into mature oligodendrocytes and become myelin forming cells. This is co-ordinated and things are turned on an off in the process. This shows that Sox2 is important in in the repopulation of demyelinated areas and gets them ready for  becoming oligodendrocytes, but this needs to be switched off before cells begin remyelinating. This shows that it may not always be a simple case of switch-on things to get effective remyelination.

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  • Sounds like a trip to the dentist for a filling, remove damaged area first then once good material is left add the filling.

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