Platelet-derived growth factor-? receptor-positive oligodendroglia are frequent in multiple sclerosis lesions

Platelet-derived growth factor (PDGF) ligand is a potent glial cell mitogen. When its cognate receptor (PDGF-alphaR) is expressed on oligodendroglial lineage cells, such cells are considered capable of division, and the receptor thus serves as a phenotypic marker for oligodendrocyte precursor cells. Here we identify using immunohistochemistry a considerably enlarged, PDGF-alphaR-expressing oligodendrocyte cell population within multiple sclerosis (MS) white matter lesions compared to control brains. Numerous PDGF-alphaR-positive oligodendroglia also colabel heavily with the nuclear cell proliferation marker antibody Ki-67. Our finding of large numbers of proliferating oligodendroglia in MS brains expressing up-regulated PDGF-alphaR suggests that these progenitor-like cells represent an important source of regenerating cells for the healing MS lesion.