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. 2012 Aug 23;75(4):633–647. doi: 10.1016/j.neuron.2012.06.021

Figure 6.

Figure 6

Myelin Clearance Is Slow in Injured c-Jun Mutant Nerves

(A) Unlike WT nerves, mutant nerves (cKO) are not translucent 4 weeks postcut, indicating lipid retention. Bar: 2 mm.

(B) Lipid persistence in mutant nerves shown by quantification of osmium stained area in transverse sections of sciatic nerve 4 weeks post cut (no regeneration). Error bars: ± SEM; p < 0.001, n = 4.

(C) Electron micrograph showing lipid droplets in denervated Schwann cells of mutant nerves 4 weeks post cut. Bar: 2 μm.

(D) Electron micrograph showing relative preservation of intact myelin sheaths in mutants 3 days postcut, 3 mm from cut site. Right, counts of intact sheaths in tibial nerves of WT and mutants 3 days after cut. Error bars: ± SEM; p < 0.05, n = 5. Bar: 20 μm.

(E) Myelin sheath counts in tibial nerves following axotomy in vivo and in nerve segments in vitro, as indicated. Note that sheath preservation in the mutant does not depend on blood-born macrophages. Error bars: ± SEM; p < 0.05, n = 4.

(F) Normal myelin breakdown fails in mutant Schwann cells, shown by persistence of myelin debris in mutant cells in phase-contrast micrographs of cultures from p8 WT and mutant nerves and maintained 6 days in vitro. Bar: 50 μm.

(G) Immunolabeling of mutant Schwann cells (green; S100 antibodies), bloated with myelin debris (red; MBP antibodies) (arrows indicate two cells). Bar: 50 μm.

(H) Counts of cells containing the myelin proteins MPZ and MBP at different times after plating cells from WT and mutant p8 nerves show delay in myelin protein clearance by mutant Schwann cells. 0 = 3 hr after plating. Differences between cKO and WT were significant at all time points. Error bars: ±SEM; p < 0.001, (two way ANOVA), n = 5.

(I) Electron micrograph shows the persistence in mutant nerves of large, foamy macrophages (example arrowed). Bar: 5 μm.

(J) Lipid droplet counts in macrophages in tibial nerve sections 28 days postcut (no regeneration), show a strong delay in lipid clearance by macrophages in the mutant. Error bars: ±SEM; p < 0.05, n = 4.

See also Figures S3 and S5.