Figure 2.

Inhibition of oligodendrocyte (OL) differentiation and promotion of astrocyte differentiation of adult oligodendrocyte precursor cells (OPCs) by BMP2 and 4. Adult OPCs expressed BMPR Ia (Aa), Ib (Ab), and II (Ac). Although they were slightly downregulated, all three BMPRs were persistently expressed in immature O1+ and more mature MBP+ OLs after Dif3d and Dif5d, respectively (Ad). Treatment with BMP2, 4, or both decreased the number of O1+ OLs, with concurrent increases in the number of GFAP+ astrocytes (Ba–Bd). The number of MBP+ OLs was also decreased (Be–Bh). Quantification of cells immunostained for GFAP, O1, or MBP showed a dose-dependent increase in the number of GFAP+ astrocytes and decrease of O1+ or MBP+ OLs differentiated from adult OPCs by BMP2, 4, or both, respectively (C). Data represent the mean ± SD (n = 4; one and two stars represent p < .05 and 0.01, respectively). Western blot experiments confirmed the dose-dependent activation of pSmad1/5/8, ID4, the intracellular downstream target of BMP signaling with the increasing and decreasing expression of GFAP and MBP, respectively, by BMP2, 4, or both (D). Scale bar = 20 μm (Aa–Ac) and 25 μm (Ba–Bh). Abbreviations: BMP, bone morphogenetic protein; BMPR, bone morphogenetic protein receptor; DAPI, 4,6-diamidino-2-phenylindole; Dif3d, differentiation for 3 days; Dif5d, differentiation for 5 days; GFAP, glial fibrillary acidic protein; MBP, myelin basic protein; Undif, undifferentiated.