An Extract of Chinpi, the Dried Peel of the Citrus Fruit Unshiu, Enhances Axonal Remyelination via Promoting the Proliferation of Oligodendrocyte Progenitor Cells.

The aging-induced decrease in axonal myelination/remyelination is due to impaired recruitment and differentiation of oligodendrocyte progenitor cells (OPCs). Our previous studies have shown that a monoclonal antibody to DEAD (Asp-Glu-Ala-Asp) box polypeptide 54 (Ddx54), a member of the DEAD box family of RNA helicases, (1) specifically labels oligodendrocyte lineages, (2) binds to mRNA and protein isoforms of myelin basic proteins (MBP), and (3) regulates migration of OPCs from ventricular zone to corpus callosum in mice. It has also been demonstrated that specific loss of a 21.5 kDa MBP isoform (MBP21.5) reflects demyelination status, and oral administration of an extract of Chinpi, citrus unshiu peel, reversed the aging-induced demyelination. Here, we report that Chinpi treatment induced a specific increase in the MBP21.5, led to the reappearance of Ddx54-expressing cells in ventricular-subventricular zone and corpus callosum of aged mice, and promoted remyelination. Treatment of in vitro OPC cultures with Chinpi constituents, hesperidin plus narirutin, led to an increase in 5-bromo-2'-deoxyuridine incorporation in Ddx54-expressing OPCs, but not in NG2- or Olig2-expressing cell populations. The present study suggests that Ddx54 plays crucial role in remyelination. Furthermore, Chinpi and Chinpi-containing herbal medicines may be a therapeutic option for the aging-induced demyelination diseases.