Abstract
Purpose :
Previously we reported that the retinal environment imparts significant control over the phenotype and function of mononuclear cells. However, the origin and function of any particular phenotype of mononuclear cell in either retinal homeostasis or injury response are matters of active investigations. To determine the control exerted by resident mononuclear cells or other retinal cells in recruiting and retaining mononuclear cells, we analyzed the retinal expression of chemokines and cytokines associated with mononuclear cell function in mice that had been depleted of mononuclear cells and allowed to recover with or without injury to the retina.
Methods :
CD11c-DTR/GFP mice (GFP and diphtheria toxin receptor under control of a transgenic CD11c promoter), CX3CR1-YFP-CreER mice, (CX3CR1+ cells express yellow fluorescent protein and are depletable by tamoxifen, TAM), and F1 crosses were used. Fluorescence activated cell sorting (FACS) was used to analyze mononuclear cell populations in the retina. Gene expression analysis was done by quantitative RT-PCR on mRNA prepared from whole retinas or pools of phenotypically defined mononuclear cells sorted from the retina by FACS. Retinal injury was induced by optic nerve crush (ONC).
Results :
Expression analysis from whole retinas of various F1 mice groups (untreated, TAM depleted only, ONC only, and TAM depleted plus ONC) was performed. Some genes (IL-34, CXCL12, and CXCL13) were unchanged between any groups suggesting they were not made by any retinal mononuclear cell or not involved in recruitment or injury responses. CSF-1 was upregulated in ONC only mice suggesting it is made by non-mononuclear retinal cell(s) in response to injury. Other genes (CCL2, CCL3, CCL5, CXCL10) appeared to be made by mononuclear cells that were recruited to, or only became activated within the retina, in response to injury. CCL4, CCL21, and CXCL1 expression was lower in TAM only mice compared to controls suggesting that they are constitutively expressed by resident mononuclear cells, but only CCL4 was increased upon ONC stimulation.
Conclusions :
These results have allowed us to categorize the retinal cellular origin of certain chemokines and cytokines associated with mononuclear cells, and to determine if those factors are important in retaining and/or recruiting those cells to the retina.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.