Differential distribution of fibrovascular proliferative membranes in 25-gauge vitrectomy for proliferative diabetic retinopathy.

AIM: To analyze the distribution of fibrovascular proliferative membranes (FVPMs) in proliferative diabetic retinopathy (PDR) patients that treated with pars plana vitrectomy (PPV), and to evaluate the outcomes separately. METHODS: This was a retrospective and cross-sectional study. Consecutive 25-gauge (25-G) PPV cases operated for PDR from May 2018 to April 2020. According to the FVPMs images outlined after operations, subjects were assigned into three groups: arcade type group, juxtapapillary type group, and central type group. All patients were followed up for over one year. General characteristics, operation-related variables, postoperative parameters and complications were recorded. RESULTS: Among 103 eyes recruited, the FVPMs distribution of nasotemporal and inferiosuperioral was significantly different (both P<0.01), with 95 (92.23%) FVPMs located in the nasal quadrants, and 74 (71.84%) in the inferior. The eyes with a central FVPM required the longest operation time, with silicon oil used in most patients, generally combined with tractional retinal detachment (RD) and rhegmatogenous RD, the worst postoperative best-corrected visual acuity (BCVA) and the highest rates of recurrent RD (all P<0.05). FVPM type, age of onset diabetes mellitus, preoperative BCVA, and combined with tractional RD and rhegmatogenous RD were significantly associated with BCVA improvement (all P<0.05). Compared with the central type group, the arcade type group had higher rates of BCVA improvement. CONCLUSION: FVPMs are more commonly found in the nasal and inferior mid-peripheral retina in addition to the area of arcade vessels. Performing 25-G PPV for treating PDR eyes with central FVPM have relatively worse prognosis.

Injectable in situ cross-linking hyaluronan hydrogel for easier removal of posterior vitreous cortex in vitrectomy.

PURPOSE: Removing transparent vitreous tissues, such as a residual vitreous cortex (VC) or proliferative membrane, without damaging the retina is often problematic in vitrectomy. We examined the feasibility of an injectable in situ cross-linking hyaluronan hydrogel (XL-HA) for vitrectomy. STUDY DESIGN: Experiments using ex vivo and in vivo animal models. METHODS: HA-dibenzocyclooctyne and HA-azidoethylamine solutions were mixed to form XL-HA, which then gradually formed a hydrogel. We tested the function of XL-HA in ex vivo porcine eyes. We then examined the performance of XL-HA in in vivo rabbit models of posterior vitreous detachment, posterior VC removal, and proliferative vitreoretinopathy. RESULTS: The ex vivo study showed that XL-HA rapidly embedded triamcinolone acetonide, mimicking VC attached to the retina, and became hard enough to be pinched with tweezers within 3 minutes, allowing us to remove only the triamcinolone acetonide without impairing the internal limiting membrane. In the in vivo rabbit models, XL-HA injection improved posterior vitreous detachment, and the thin and fragile posterior VC or fibrous proliferative membrane was readily peeled off without any damage to the underlying retina as compared with untreated controls. A short-term intraocular biocompatibility test demonstrated that the intraocular pressure remained normal with XL-HA injected into the eye. In addition, transmission electron microscopy showed no obvious abnormalities in the cornea or in the inner and outer retina. CONCLUSION: The results indicate that XL-HA is a potential adjunctive device to help make vitrectomy safe, effective, and successful.

The Novel Pathogenesis of Retinopathy Mediated by Multiple RTK Signals is Uncovered in Newly Developed Mouse Model.

Pericyte desorption from retinal blood vessels and subsequent vascular abnormalities are the pathogenesis of diabetic retinopathy (DR). Although the involvement of abnormal signals including platelet-derived growth factor receptor-ß (PDGFRß) and vascular endothelial growth factor-A (VEGF-A) have been hypothesized in DR, the mechanisms that underlie this processes are largely unknown. Here, novel retinopathy mouse model (N-PRß-KO) was developed with conditional Pdgfrb gene deletion by Nestin promoter-driven Cre recombinase (Nestin-Cre) that consistently reproduced through early non-proliferative to late proliferative DR pathologies. Depletion of Nestin-Cre-sensitive PDGFRß+NG2+αSMA- pericytes suppressed pericyte-coverages and induced severe vascular lesion and hemorrhage. Nestin-Cre-insensitive PDGFRß+NG2+αSMA+ pericytes detached from the vascular wall, and subsequently changed into myofibroblasts in proliferative membrane to cause retinal traction. PDGFRα+ astrogliosis was seen in degenerated retina. Expressions of placental growth factor (PlGF), VEGF-A and PDGF-BB were significantly increased in the retina of N-PRß-KO. PDGF-BB may contribute to the pericyte-fibroblast transition and glial scar formation. Since VEGFR1 signal blockade significantly ameliorated the vascular phenotype in N-PRß-KO mice, the augmented VEGFR1 signal by PlGF and VEGF-A was indicated to mediate vascular lesions. In addition to PDGF-BB, PlGF and VEGF-A with their intracellular signals may be the relevant therapeutic targets to protect eyes from DR.