Fig. 1.

Differentiation of rat oligodendrocytes in a primary culture. Cell nuclei are stained with Hoechst 33258 (blue). a Neural stem cells, clearly discernible due to the expression of A₂B₅ marker (red), which are already oligodendroglia-biased (Olig-1 marker, green). b Oligodendroglial progenitors characterized by either nuclear (arrows) or cytosolic presence of transcription factor Olig-2 (green) after 24 h of in vitro culture. c Dividing OPCs expressing NG2 (red) and Ki67 (green) markers, indicating proliferating cells. d Visualization of PDGF-AA receptor (PDGFαR, green) characteristic for OPCs. e Immature NG2-positive cells (green), which are characterized by branched cell processes (polydendrocytes). f Immature oligodendrocytes recognized by their typical marker O4 (red), which are still able to divide, as indicated by Ki67 staining (green). g After 48 h of in vitro culturing, differentiating O4⁺ (red) oligodendrocytes express the GalC antigen (green). h The next step of oligodendrocyte (GalC⁺, red) differentiation associated with the expression of myelin components (MBP⁺, green). i Maturating cells recognized by their two most characteristic markers: CNP (red) and GalC (green). j Vanishing O4 presence (red) is replaced by GalC (green) expression in multibranched cells with long cellular extensions. k Cells with complex morphology, characterized by the presence of GalC (red) and MBP (green). l Mature oligodendroroglia expressing major myelin proteins: PLP (red) and MBP (green). m Magnification of double-labeled differentiated (PLP-red, MBP-green) myelinating oligodendrocyte on day 5 of in vitro culture