Inhibition of oligodendrocyte precursor cell differentiation by myelin-associated proteins

Abstract

<jats:sec> <jats:title>Object</jats:title> <jats:p>Promoting repair of central nervous system (CNS) white matter represents an important approach to easing the course of a number of tragic neurological diseases. For this purpose, strategies are currently being evaluated for transplanting cells capable of generating new oligodendrocytes into areas of demyelination and/or enhancing the potential of endogenous stem/precursor cells to give rise to new oligodendrocytes. Emerging evidence, however, indicates that increasing the presence of cells capable of forming new myelin sheaths is not sufficient to promote repair because of unknown inhibitors that accumulate in lesions as a consequence of myelin degeneration and impair the generation of new oligodendrocytes. The aim of the present study was to characterize the nature of the inhibitory molecules present in myelin.</jats:p></jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>Differentiation of primary rat oligodendrocyte precursor cells (OPCs) in the presence of CNS and peripheral nervous system myelin was assessed by immunocytochemical methods. The authors further characterized the nature of the inhibitors by submitting myelin membrane preparations to biochemical precipitation and digestion. Finally, OPCs were grown on purified Nogo-A, oligodendrocyte myelin glycoprotein, and myelin-associated glycoprotein, the most prominent inhibitors of axon regeneration.</jats:p></jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>Myelin membrane preparations induced a differentiation block in OPCs that was associated with down-regulation of expression of the transcription factor Nkx2.2. The inhibitory activity in myelin was restricted to the CNS and was predominantly associated with white matter. Furthermore, the results demonstrate that myelin proteins that are distinct from the most prominent inhibitors of axon outgrowth are specific inhibitors of OPC differentiation.</jats:p></jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>The inhibitory effect of unknown myelin-associated proteins should be considered in future treatment strategies aimed at enhancing CNS repair.</jats:p></jats:sec>

Nogo-A antibodies enhance axonal repair and remyelination in neuro-inflammatory and demyelinating pathology

“…Therefore, the neutralization of Nogo-A by antibodies can potentially be exploited to enhance remyelination. The involvement of Nogo-A and its receptors during myelin formation is supported by several other developmental in vitro and in vivo studies [92][93][94].…”

Inhibition of CNS Remyelination by the Presence of Semaphorin 3A

“…OPCs were seeded onto PLL-or Sema3A-coated 8-well chamber slides (2 ϫ 10 4 cells/well). Following differentiation (48 h), cells were stained with O4 (1:100; Calbiochem;) or A2B5 antibodies (1:100; Millipore Corporation; Cy3-conjugated secondary antibody 1:100 dilution, Jackson ImmunoResearch) (Syed et al, 2008;Baer et al, 2009). To assess OPC differentiation the percentage of O4 ϩ cells to Ͼ100 4Ј,6-diamidino-2-phenylindole dihydrochloridestained nuclei per experiment for each condition in randomly selected…”

“…For this purpose we used a well established assay (Robinson and Miller, 1999;Baer et al, 2009) in which the expression of O4 was assessed on primary OPCs cultured on substrates prepared from various molecules as summarized in Table 1 and by Syed et al (2008). Of the molecules tested only the presence of Sema3A resulted in a reduction of differentiating O4-positive OPCs ( Fig.…”

“…So far a number of OPC differentiation inhibitors have been indentified in MS lesions (Wang et al, 1998;Charles et al, 2002;John et al, 2002;Back et al, 2005;Fancy et al, 2009;Nakahara et al, 2009). Adding to the group of inhibitors, we were recently able to show that unknown proteins in myelin debris (myelin-associated inhibitors) that accumulate as a consequence of demyelination also inhibit remyelination by inhibiting OPC differentiation (Kotter et al, 2006;Syed et al, 2008;Baer et al, 2009).…”

Engineering Biomaterials to Influence Oligodendroglial Growth, Maturation, and Myelin Production

“…Advances in oligodendrocyte growth and maturation, and, most importantly, myelination, can proceed with a host of different strategies, as described above. These may continue to rely upon soluble factors, but recent work indicates that topographical cues [Lee et al, 2013], physical properties of the ECM [Leipzig and Shoichet, 2009], cell-cell communication [Kirby et al, 2006;Syed et al, 2008], and chemical presentation [Willerth et al, 2008] are just as vital to influencing oligodendrocyte fate. Pursuing such factors in the context of a relevant 3D environment will greatly advance the field and provide unique insights to clinical regeneration strategies to spinal cord regeneration at the cellular and tissue level, ultimately resulting in better behavioral function.…”