Abstract
Purpose :
The signals by which inflammatory cells are recruited to the eye and activated in human uveitis remain poorly defined. To identify these, we profiled 31 cytokines in aqueous fluid and blood. To identify the cellular source of these cytokines, we also profiled aqueous immune cells using single cell RNA sequencing.
Methods :
Using the Luminex platform, we measured 31 cytokines in 46 aqueous humor samples (n=20 control, n=26 uveitis). For 20 uveitis patients, we also measured cytokines in the peripheral blood. Using the 10x Genomics platform, we performed single cell RNA sequencing on aqueous immune cells from uveitis patients (n=23). We assessed for statistical significance using appropriate parametric/non-parametric tests.
Results :
Twenty-three cytokines measured in the aqueous were increased in uveitis compared to controls (Mann Whitney test p-value < 0.05, n=20-26). In paired measurements of plasma and aqueous from uveitis patients, 21 cytokines were different in plasma vs. aqueous (Wilcoxon matched-pairs signed rank test p-value < 0.05, n=20 pairs). These included CXCL10, CCL2, CXCL8, CCL3, CCL14, CXCL9, IL6, and TNF, which were greater in the aqueous than in plasma. Of these, CXCL10 and CCL2 were enriched in aqueous vs. plasma in all 20 patients, suggesting these chemokines may be a conserved signal that recruits inflammatory cells to the eye in uveitis. In contrast, CXCL8 and IL6 were enriched in the aqueous (aqueous > plasma) for 15 of 20 patients, whereas they were enriched in the plasma (plasma > aqueous) for the remaining 5. Thus, some ocular inflammatory signatures may be broadly shared by many uveitis patients, whereas others may be patient-specific. We next analyzed gene expression of these cytokines by aqueous immune cells. Of the cytokines that were greater in aqueous than plasma in uveitis, CCL2, CXCL10, and CXCL8 were specifically expressed by macrophages, suggesting that macrophages play a central role in recruiting inflammatory cells in human uveitis.
Conclusions :
These data suggest that ocular macrophages may be critical for recruiting inflammatory cells to the eye in human uveitis by robustly expressing chemokines such that local ocular levels exceed those in the systemic circulation. Some of these may be broadly relevant in most uveitis patients whereas others may be patient-specific. Further studies in a larger cohort of patients are necessary to validate these findings.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.