Multilayered retinal microglial response to optic nervetransection in rats

[摘要] Purpose: Microglia normally exist in several layers across theretinal thickness. When retinal ganglion cells undergo apoptosis afterlesion to their axons, microglial cells proliferate and promptly clearthe debris. We have previously reported on the phagocytic responsefollowing optic nerve axotomy. Here, we present how microglial cells ofdeeper retinal layers are affected by transection of the optic nerve.Methods: Normal and reactive microglia in the retina of adult ratswhose optic nerves had been lesioned were labeled by using antibodiesOX42 and ED1. Analysis of the time course (between 1 and 180 dayspost-axotomy) of appearance and distribution of microglial cells in theretinal layers was performed.Results: In normal retinas, microglia were found in the ganglioncell layer (GCL), the superficial inner nuclear layer (INL) and theouter plexiform layer (OPL). Increases in numbers of microglia occurredmaximally in the GCL at day 12 post-axotomy. Increases were alsodetected in the superficial INL. The proliferation of these phagocyticcells led to their highest numbers in the more central eccentricities inthe two most superficial layers. Microglia in the OPL remainedundisturbed. Microglial normal histology is restored over a period of 6months as dying ganglion cells disappear.Conclusions: Histological characteristics of normal rat retinalmicroglia are uniform across different retinal eccentricities for eachof the three laminae where they exist. Retinal microglia of variouslayers respond to optic nerve damage. Their increase in numbers andmorphological transformation follow retinal ganglion cell death. Theirmorphology, density, and layered distribution slowly return to normal,confirming that retinal ganglion cells, or their densities, do not playany role in dictating microglial distribution within the differentretinal layers.

[学科分类] 生物化学/生物物理