title: PDGF is required for remyelination-promoting IgM stimulation of oligodendrocyte progenitor cell proliferation.
abstract: BACKGROUND
  Promotion of remyelination is a major goal in treating demyelinating diseases such as multiple sclerosis (MS). The recombinant human monoclonal IgM, rHIgM22, targets myelin and oligodendrocytes (OLs) and promotes remyelination in animal models of MS. It is unclear whether rHIgM22-mediated stimulation of lesion repair is due to promotion of oligodendrocyte progenitor cell (OPC) proliferation and survival, OPC differentiation into myelinating OLs or protection of mature OLs. It is also unknown whether astrocytes or microglia play a functional role in IgM-mediated lesion repair.
  
  
  METHODS
  We assessed the effect of rHIgM22 on cell proliferation in mixed CNS glial and OPC cultures by tritiated-thymidine uptake and by double-label immunocytochemistry using the proliferation marker, Ki-67. Antibody-mediated signaling events, OPC differentiation and OPC survival were investigated and quantified by Western blots.
  
  
  RESULTS
  rHIgM22 stimulates OPC proliferation in mixed glial cultures but not in purified OPCs. There is no proliferative response in astrocytes or microglia. rHIgM22 activates PDGFαR in OPCs in mixed glial cultures. Blocking PDGFR-kinase inhibits rHIgM22-mediated OPC proliferation in mixed glia. We confirm in isolated OPCs that rHIgM22-mediated anti-apoptotic signaling and inhibition of OPC differentiation requires PDGF and FGF-2. We observed no IgM-mediated effect in mature OLs in the absence of PDGF and FGF-2.
  
  
  CONCLUSIONS
  Stimulation of OPC proliferation by rHIgM22 depends on co-stimulatory astrocytic and/or microglial factors. We demonstrate that rHIgM22-mediated activation of PDGFαR is required for stimulation of OPC proliferation. We propose that rHIgM22 lowers the PDGF threshold required for OPC proliferation and protection, which can result in remyelination of CNS lesions.
authors: Departments of Neurology and Immunology, Mayo Clinic College of Medicine, Rochester, Minnesota, United States of America.
authors: Jens O
authors: JO
authors: Watzlawik
authors: Arthur E
authors: AE
authors: Warrington
authors: Moses
authors: M
authors: Rodriguez
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D015153:Blotting, Western; D001973:Bromodeoxyuridine; D049109:Cell Proliferation / Q000187:drug effects*; D006801:Humans; D007075:Immunoglobulin M / Q000378:metabolism* / Q000494:pharmacology; D007150:Immunohistochemistry / Q000379:methods; D008856:Microscopy, Fluorescence; D009103:Multiple Sclerosis / Q000188:drug therapy*; D009186:Myelin Sheath / Q000187:drug effects / Q000502:physiology; D009836:Oligodendroglia / Q000166:cytology*; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013234:Stem Cells / Q000378:metabolism / Q000502:physiology*; D013936:Thymidine
chemical_list: D007075:Immunoglobulin M; D010982:Platelet-Derived Growth Factor; D001973:Bromodeoxyuridine; D013936:Thymidine
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