The differentiation of OPCs on collagen microspheres. (A) Differentiated oligodendrocyte progenitor cells (OPCs) in cell culture plates are labeled with anti-MBP antibody. Scale bar: 200 μm. (B-D) Differentiated OPCs grown on collagen microspheres are labeled with anti-myelin basic protein (MBP) antibody. Scale bar: 200 μm. (E) and (F) The morphology of differentiated OPCs on a collagen microsphere. Scale bar: 50 μm.