Tissue-type plasminogen activator exerts EGF-like chemokinetic effects on oligodendrocytes in white matter (re)myelination.

The ability of oligodendrocyte progenitor cells (OPCs) to give raise to myelin forming cells during developmental myelination, normal adult physiology and post-lesion remyelination in white matter depends on factors which govern their proliferation, migration and differentiation. Tissue plasminogen activator (tPA) is a serine protease expressed in the central nervous system (CNS), where it regulates cell fate. In particular, tPA has been reported to protect oligodendrocytes from apoptosis and to facilitate the migration of neurons. Here, we investigated whether tPA can also participate in the migration of OPCs during CNS development and during remyelination after focal white matter lesion. OPC migration was estimated by immunohistological analysis in spinal cord and corpus callosum during development in mice embryos (E13 to P0) and after white matter lesion induced by the stereotactic injection of lysolecithin in adult mice (1 to 21 days post injection). Migration was compared in these conditions between wild type and tPA knock-out animals. The action of tPA was further investigated in an in vitro chemokinesis assay. OPC migration along vessels is delayed in tPA knock-out mice during development and during remyelination. tPA enhances OPC migration via an effect dependent on the activation of epidermal growth factor receptor. Endogenous tPA facilitates the migration of OPCs during development and during remyelination after white matter lesion by the virtue of its epidermal growth factor-like domain.