Figure 6.

miR-155 deletion reduces intraspinal macrophage activation/accumulation in mice subjected to a peripheral conditioning lesion and spinal cord dorsal column crush injury. miR-155 KO spinal cord epicenters have reduced density of Iba1+ macrophages/microglia. Top, Overview of Iba1 immunoreactivity in horizontal sections of WT and miR-155 KO dorsal columns. A, A′, WT and miR-155 KO spinal cords had similar Iba1+ cell densities in rostral dorsal columns. Rostral is to the left; dashed line delineates injury epicenter. B, B′, graphs, miR-155 KO spinal cords had reduced Iba1+ macrophage/microglial density in the injury epicenter. C, C′, GFP+ axons and endbulbs localized near inflammatory Iba1+ cells. Note the more rostral location of activated macrophages that colocalize with regrowing axon tips in KO spinal cord. D, D′, Confocal images showing detail of Iba1+ cells and GFP+ axons at the rostral-most front of growing axons. E, In miR-155 KO mice, Iba1 density was significantly reduced compared with WT mice from 200 μm rostral to 400 μm caudal to injury epicenter. F, Compared with WT mice, Iba1+ cell density in the KO epicenter was reduced by 46% (quantified between 200 μm and −200 μm). *p < 0.05 versus WT control. R-C, Rostral–caudal axis; R-L, right–left (horizontal axis). Scale bars: top, alternating gray and white bars, each 400 μm; inset panels, 50 μm.