Retinal Astrocyte Morphology and Physiology in Naïve and Diseased Mice

Abstract

In biological systems, structure and function are inextricably linked. In the retina, study of astrocyte function has been hampered by a lack of technology for rapid and complete visualization of their single-cell structure. Most existing strategies are limited in their ability to resolve membranous structures, and the ones which can are very low throughput and have a high technical barrier to entry. This work details the development of a mouse model for stochastic labeling of astrocytes for full membranous morphology which can be visualized using immunohistochemistry. Over 3,500 individual astrocytes were imaged in both naïve animals and those in early diabetic disease. This work shows that astrocytes have recurring morphological motifs which are predictive of the neuronal and vascular architecture of the inner retina, and the frequency of those motifs changes with injury and disease- likely indicative of altered neuroglial communication. Additionally, astrocyte labeling in this model reveals a distinct subpopulation in the inner plexiform layer which was not previously known. This population bears the same neuronal associated motifs as its counterparts in the nerve fiber layer. Moreover, electrophysiological responses to light and voltage step show that mouse retinal astrocytes interact with Müller glia in a light-evoked potassium circuit. Responses to voltage step also show that both macroglia are rectifying cells, unlike many astrocytes found in other regions of the central nervous system, and the rectification pattern is dependent on prior stimulation. The responses of both astrocytes in the nerve fiber layer and the inner plexiform layer are similar, suggesting conserved physiology.