Abstract
Purpose :
Proliferation of microglia cells is deemed as a hallmark of ongoing neurodegenerative diseases and microglia activation has been analyzed in many animal models of different eye diseases. The cone-dominant ground squirrel retina is a unique rodent model potentially useful for studying retinal degenerative diseases. Here, we investigated the morphology, populations and distribution of microglia cells in the ground squirrel retina to lay a foundation for future works on retinal diseases in this animal model.
Methods :
Six adult mix-gender age-matched ground squirrels were used. Retinal whole mount tissues and vibratome sections were immunostained with anti Iba-1 for detecting microglia cell populations. A computer algorithm was developed for microglia quantification, which enabled the estimation of microglia cells in the inner and outer plexiform layers and the evaluation the area of the retina occupied by Iba-1+ microglia in the nerve fiber-ganglion cell layer.
Results :
1) There are three major layers of microglia soma located in the OPL, IPL, and GCL, similar to what have been reported for the mouse retina. 2) In the OPL, the density of microglia is significantly different between the superior and inferior retina which are separated by the visual streak. Microglia distribution in the superior retina is extremely sparse. In contrast, dendrites of microglia tile the inferior retina, similar to what has been observed in the mouse retina. 3) In the IPL, there is not a significant difference in the distribution of microglia across the whole retina. Notably, some microglia cells extend long processes across the IPL and reach the GCL. 4) In the GCL, microglia soma located right beneath the IPL and often had bushy processes traverse through the ganglion cell soma and terminate in the NFL with enlarged varicosities.
Conclusions :
The morphology, populations and distribution of microglia cells in ground squirrel is different from other rodents such as mouse and rat, which may be attributed to its unique photoreceptor composition and optic nerve organization. These findings would provide a foundation for future studies on the pre-inflammatory and inflammatory responses in eye disease models in the cone-dominant ground squirrels.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.