Vitreous from patients with proliferative diabetic retinopathy induced changes in neutrophil activation markers

Diabetic retinopathy (DR), a microangiopathic complication of diabetes mellitus, is a leading cause of vision loss in working-age adults and older individuals. While the etiology of DR is not fully understood, it is strongly linked to systemic and local inflammation. Systemic immune-inflammation indices, such as the platelet-to-lymphocyte ratio, neutrophil-to-lymphocyte ratio, and monocyte-to-lymphocyte ratio, are useful predictors of diabetes mellitus-related diseases and inflammatory complications. In addition to systemic markers, local inflammatory molecules and immune cells, particularly neutrophils and their associated inflammatory mechanisms, play crucial roles in DR pathogenesis. Cumulative evidence indicates a concentration of inflammatory mediators in the vitreous humor, making its analysis a valuable tool for investigating retinal complications. This study aimed to identify differential cytokine expression in the vitreous humor of patients with diabetic macular edema (DME) and proliferative diabetic retinopathy (PDR) and to determine the impact of these vitreous samples on neutrophil activation.

Vitreous samples were collected during vitrectomy from patients with DME (n = 8), patients with PDR (n = 15), and surrogate controls (n = 8; rhegmatogenous retinal detachment, n = 5; macular hole, n = 3). Undiluted vitreous samples from the central vitreous cavity were analyzed individually via an angiogenic cytokine protein array at a concentration of 250 mg/ml of vitreous proteins. Cytokine levels were normalized to those of surrogate controls, and fold changes were calculated. For in vitro neutrophil stimulation, peripheral blood was incubated with diluted vitreous from different conditions, and neutrophil activation markers (CD15, CD11b, and CD66b) were assessed via flow cytometry.

The study revealed increased neutrophil-to-lymphocyte ratio and monocyte-to-lymphocyte ratio values in patients with PDR and DME compared with controls (p < 0.05). Compared with those from controls, the vitreous from patients with PDR presented a twofold increase in the expression of the inflammatory cytokines CCL2, CXCL5, and angiogenin. Notably, compared with the control vitreous humor, the PDR vitreous humor significantly downregulated the neutrophil activation markers CD11b and CD15 (p < 0.05), while CD66b expression remained unchanged (p > 0.05). The DME vitreous did not significantly change any of the analyzed neutrophil activation markers.

This study highlights the importance of inflammation and its components in the pathophysiology and progression of DR and suggests that CCL2, CXCL5, and angiogenin are potential therapeutic targets for PDR. Our results also suggest that vitreous fluid from patients with PDR contains immunosuppressive or exhaustion-inducing factors that may alter neutrophil function and inflammation in DR.