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. Author manuscript; available in PMC: 2010 Mar 22.
Published in final edited form as: Exp Neurol. 2009 Feb 21;217(1):184–196. doi: 10.1016/j.expneurol.2009.02.006

Fig. 8.

Fig. 8

Comparison of DRG neurite outgrowth on the OPCs or mature oligodendrocytes at 3 days in vitro. (A–C) Representative photomicrographs show DRG neurites (NF+, green) growing into the OPC (A2B5+, red) monolayer in thick bundles (A) or scattered fibers (B). Note that these neurites grew in close proximity to the OPCs and contacted directly on the surface of the OPCs (B, C, open arrows). At higher magnification (C), the growing neurites were found to contact directly on the surface of the OPCs (open arrow). (D–F) Although DRG neurite bundles (NF+, green) penetrated into the mature oligodendrocyte monolayer (MBP+, red), they were thin and grew for a shorter distance. Notably, an acellular space (asterisk) between growing neurites and mature oligodendrocytes was observed. Interestingly, the presence of only a few oligodendrocytes (E, arrowhead) at the border effectively blocked the growth of DRG neurites. At higher magnification (F), the lack of growth cone-like structures at the tip of neurites, the creation of an acellular space surrounding the neurite fascicle (asterisks), and the lack of direct contact between the growing neurites and mature oligodendrocytes are clearly seen. Cultures in A, C, D and F were counterstained with Hoechst 33342, a fluorescent nuclear dye. Dashed lines in B and E indicate the seeding border of OPCs and oligodendrocytes, respectively. Measurements of fascicle length (G) and area (H) showed that DRG neurites grew significantly farther into the OPC monolayer (p = 0.011) and occupied more area (p = 0.043) compared to that of the oligodendrocytes. (I) Although the number of fascicles that penetrated into the cell monolayer between the two cell types was similar (left panel), significantly fewer oligodendrocytes contacted the growing neurites compared to that of the OPCs (right panel, **, p<0.001). (J) Less space was found between OPCs and growing neurites either at the midpoint (left panel) or the tip of the fascicles (right panel) compared to the mature oligodendrocytes (**, p<0.001). Scale bars, A, D: 400 µm; B, E: 100 µm, C, F: 50 µm.