Differential analysis of aqueous humor cytokine levels in patients with macular edema secondary to diabetic retinopathy or retinal vein occlusion

AIM: To evaluate the difference and the correlation between the concentrations of cytokines in the aqueous humor of eyes with macular edema secondary to diabetic retinopathy (DR) or retinal vein occlusion (RVO). METHODS: This is a retrospective case control study. The aqueous humor samples were collected during intravitreal injection of anti-vascular endothelial growth factor (VEGF) for patients diagnosed with macular edema secondary to DR (DME) or RVO (RVO-ME) at Xijing Hospital from August 2021 to July 2022. Meanwhile, aqueous humor samples during vitrectomy from patients with idiopathic macular hole (IMH) were also collected and served as controls. The aqueous humor concentrations of VEGF, platelet-derived factor (PDGF), interleukin (IL)-6, IL-8, IL-18, tumor necrosis factor-α (TNF-α) and monocyte chemoattractant protein 1 (MCP-1) were measured with Human Premixed Multi-Analyte Kit (Luminex). The difference of the aqueous cytokines and the correlation between the two diseases were analyzed. RESULTS: A total of 40 eyes of 38 patients were enrolled in the study, including 13 eyes of 11 DME patients (DME group), 16 eyes of 16 RVO-ME patients (RVO-ME group) and 11 eyes of 11 IMH patients (control group). The VEGF, PDGF, IL-6, IL-8, and MCP-1 levels of the aqueous humor were higher in both DME and RVO-ME groups compared with the control group (all P<0.05), the levels of TNF-α was higher in the DME group than in the control group (P<0.05). The VEGF, IL-6, MCP-1, and TNF-α levels in the aqueous humor were significantly higher in the DR group than those in the RVO group (all P<0.05). Correlation analyses revealed that there were complex positive correlations between IL-6, IL-8, IL-18, MCP-1, and TNF-α levels in the aqueous humor of eyes with two diseases. CONCLUSION: Although ischemic and inflammatory factors are similarly involved in the pathogenesis of DME and RVO-ME, the roles of these factors are more significant or more likely to be activated in DR patients, suggesting different treatment strategies should be considered for the two diseases.