No abstract

The post-injury responses of retinal ganglion cells elicit a number of glial reactions which have not been completely understood. The bilateral pattern of non-neuronal retinal cell proliferation was examined in association with the differential fates of unilaterally injured adult retinal ganglion cells by means of bromodeoxyuridine (BrdU) immunocytochemistry. Lateralization of the glioproliferative events was studied by analysing both the experimental and the uninjured contralateral as well as matched retinas of sham-operated animals. Control adult rat retina included very few BrdU-positive cells within the nerve fibre and ganglion cell layers; however, experimental retinas of degenerating groups exhibited statistically significantly higher densities of newborn cells in most layers. Clusters of labelled cells were found in the inner plexiform layer related to OX-42 staining, indicating their microglial nature. Indeed, double-labelling experiments, after short-term unilateral optic nerve crushing, identified proliferating retinal glial cells in vivo. Both types of glia, astroglial and microglial cells, exhibited BrdU-positive labelling in injured as well as uninjured experimental rat retinas. Moreover, microglial proliferating cells were also identified in explanted retinal pieces after 2 days in culture. Affected and contralateral retinas responded similarly to the unilateral experimental manipulations applied with respect to BrdU labelling. The acute glial responses observed suggest that bilateral glial proliferation might represent a common response related to degeneration events in both retinas, i.e. ipsi- and contralateral to the experimental injury.

Primary cilia are required for several signaling pathways, but their function in cellular morphogenesis is poorly understood. Here we show that emergence of an hexagonal cellular pattern during development of the corneal endothelium (CE), a monolayer of neural crest-derived cells that maintains corneal transparency, depends on a precise temporal control of assembly of primary cilia that subsequently disassemble in adult corneal endothelial cells (CECs). However, cilia reassembly occurs rapidly in response to an in vivo mechanical injury and precedes basal body polarization and cellular elongation in mature CECs neighboring the wound. In contrast, CE from hypomorphic IFT88 mutants (Tg737 orpk ) or following in vivo lentiviral-mediated IFT88 knockdown display dysfunctional cilia and show disorganized patterning, mislocalization of junctional markers, and accumulation of cytoplasmic acetylated tubulin. Our results indicate an active role of cilia in orchestrating coordinated morphogenesis of CECs during development and repair and define the murine CE as a powerful in vivo system to study ciliary-based cellular dynamics. intraflagellar transport | eye development | ciliary length | microtubules

The activity and survival of retinal photoreceptors depend on support functions performed by the retinal pigment epithelium (RPE) and on oxygen and nutrients delivered by blood vessels in the underlying choroid. By combining single-cell and bulk RNA sequencing, we categorized mouse RPE/choroid cell types and characterized the tissue-specific transcriptomic features of choroidal endothelial cells. We found that choroidal endothelium adjacent to the RPE expresses high levels of Indian Hedgehog and identified its downstream target as stromal GLI1+ mesenchymal stem cell–like cells. In vivo genetic impairment of Hedgehog signaling induced significant loss of choroidal mast cells, as well as an altered inflammatory response and exacerbated visual function defects after retinal damage. Our studies reveal the cellular and molecular landscape of adult RPE/choroid and uncover a Hedgehog-regulated choroidal immunomodulatory signaling circuit. These results open new avenues for the study and treatment of retinal vascular diseases and choroid-related inflammatory blinding disorders.