Co-culture of DRGs and OPCs carried by collagen microspheres. (A) Co-culture of dorsal root ganglions (DRGs) with oligodendrocyte progenitor cells (OPCs) in cell culture plate. Scale bar: 200 μm. (B) and (C) Magnified images shows the oligodendrocytes (OLs) wrap DRG neurites. Scale bar: 50 μm. (D-F) Co-culture of DRGs and OPCs carried by collagen microspheres. Scale bar: 200 μm. (D) Bright field image shows that collagen microspheres attach to the cell culture plate. The arrows point at the collagen microspheres. (E) and (F) OPCs on collagen microspheres differentiated into OLs. The processes of OLs wrapped the neurites of DRGs. (G-I) Magnified images for the microsphere indicated by blue arrow in (D) show the irregular shape of the collagen microsphere and the neurites of DRGs were wrapped by OLs. Scale bar: 100 μm.