Differential association of elevated inflammatory cytokines with postoperative fibrous proliferation and neovascularization after unsuccessful vitrectomy in eyes with proliferative diabetic retinopathy

BACKGROUND Pars plana vitrectomy is the only treatment for advanced proliferative diabetic retinopathy (PDR). However, vitrectomy is not always successful despite current progress in vitreoretinal surgical techniques. The aim of our study was to investigate whether the vitreal concentrations of MCP-1, IL-6, IL-8, and VEGF are elevated after unsuccessful vitrectomy in patients with PDR and to investigate whether the altered levels of these cytokines are associated with the cause for the reoperation. PATIENTS AND METHODS Vitreous samples were collected from 263 eyes of 233 patients: PDR (n=129 eyes), proliferative vitreoretinopathy (PVR; n=24 eyes) and nondiabetic controls (n=110 eyes) prior to vitrectomy. Vitreous samples were also collected from 14 eyes of 14 patients with PDR before vitrectomy and from the same 14 eyes before a second vitrectomy for reoperation. The levels of MCP-1, IL-6, IL-8, and VEGF were measured by flow cytometry using a cytometric bead array (CBA) assay. RESULTS The mean concentrations of vitreal MCP-1, IL-6, IL-8, and VEGF were significantly higher in patients with PDR and PVR (P<0.01). There were significantly high correlations among the concentrations of MCP-1, IL-6, and IL-8, whereas the correlation of VEGF with the other 3 cytokines was lower. Among the 14 patients who required reoperation, the mean vitreal concentrations of MCP-1, IL-6, and IL-8 were higher than that at the time of the initial vitrectomy (P<0.01). At the time of the reoperation vitrectomy, the mean vitreous level of MCP-1, IL-6, and IL-8 in eyes with fibrous proliferation was higher than in those without fibrous proliferation (P<0.05). In contrast, VEGF in eyes with neovascular glaucoma (NVG) or anterior hyaloidal fibrovascular proliferation (AHFVP) was higher than in the eyes without NVG and AHFVP (P<0.05). CONCLUSION The elevated levels of MCP-1, IL-6, and IL-8 may be the cause of the postoperative fibrous proliferation. In contrast, VEGF may be the cause of the neovascularization after unsuccessful vitrectomy in the eyes of PDR patients.