Effect of intravitreal ranibizumab on fibrovascular membranes in patients with proliferative diabetic retinopathy

? AIM: To assess the effects of intravitreal ranibizumab (IVR) on angiogenesis and glial activity of the fibrovascular membrane (FVM) in patients with proliferative diabetic retinopathy (PDR).? METHODS: Forty-two eyes from 42 patients with PDR requiring vitrectomy were included and divided into two groups: control group (n=16) did not receive IVR, while IVR group (n=26) underwent IVR 5d before vitrectomy. FVM specimens were collected by the same surgeon during the interventions. Histopathological morphology was examined by hematoxylin-eosin (H-E) staining and cell densities in the FVM was assessed. Microvessels were outlined by immunohistochemical staining of CD31 and microvessel density (MVD) assessed as an index of FVM angiogenesis. Dual-color immunofluorescence staining, and confocal microscopy was used to detect co-localization and relative expression levels of glial fibrillary acidic protein (GFAP) and alpha-smooth muscle actin (alpha-SMA) as markers of glial-mesenchymal transition (GMT). The GMT index (GI; ratio of relative GFAP/alpha-SMA expression) was used to semi-quantify the degree of GMT or glial activity of FVMs.? RESULTS: H-E staining showed similar vascularization in both groups, with microvessels and scattered stromal cells in the matrix. Infiltrated cell densities did not differ significantly between the two groups (P>0.05). The MVD of the IVR group (130.62 +/- 15.46/mm2) was significantly lower than that of the controls (142.25 +/- 19.16/mm2, P<0.05). In both groups, all sections were strongly immunostained for GFAP and alpha-SMA. The Pearson's correlation coefficients (PCC) of intensity of automated pixel count of two markers indicated GFAP and alpha-SMA co-stained well and GMT participated in the remolding of FVMs in PDR. The mean relative GFAP expression in the IVR group was significantly lower, whereas that of alpha-SMA was significantly higher than in controls (P<0.05). GI in the IVR group (1.10 +/- 0.10) was significantly lower than in the controls (1.21 +/- 0.12, P<0.05).? CONCLUSION: IVR can reduce angiogenesis, glial activity of FVM and promote glial-fibrotic transformation by reducing MVD and promoting GMT but does not decrease the cell density in patients with PDR.