Analysis Of Vitreous Microparticles In Proliferative Vitreoretinopathy

Purpose To determine whether microparticles(MPs)were present in the vitreous fluid of patients with proliferative vitreoretinopathy(PVR)and evaluate their correlations with the disease.Methods The vitreous samples were collected from patients who underwent vitrectomy at the Opthalmology Department of Tianjin Medical University General Hospital from July 2016 to November 2018.Undiluted vitreous fluid samples were obtained from 27 patients as control(28 eyes),29 patients with rhegmatogenous retinal detachment(30 eyes)and 28 patients with ocular trauma(28 eyes).In our study,MPs were separated from cells and isolated from cells by differential centrifugation.Transmission electron microscope(TEM)was used to validate the morphological characteristics of vitreous MPs.Nanoparticle tracking analysis(NTA)was used to measure the size distribution and concentrations of MPs in vitreous fluid.Standardized flow cytometry methods were used to analyze the following MPs: phosphatidylserine-expressing MPs,photoreceptor cell derived MPs,microglial derived MPs,and macrophage derived MPs.Results MPs had clearly defined and relatively intact bilayer membrane structure under TEM.NTA showed that vitreous MPs had a diameter between 100 nm to 500 nm.Photoreceptor,microglial,macrophage derived MPs and express phosphatidylserine MPs were present in the vitreous fluid,and their levels were significantly increased in patients with ocular trauma that developed PVR in comparison with the control group(P=0.0008,0.0013,0.0005,0.0162).In patients with rhegmatogenous retinal detachment,the photoreceptor and microglial derived MPs were much higher in those with severe PVR(grade C and grade D)(P=0.0083,0.0303).Conclusion Our study demonstrated the presence of high amounts of photoreceptor cells,microglial cells and macrophages-derived MPs in vitreous fluid of patients with PVR.These MPs had a diameter of 100 to 500 nm and had relatively intact membrane but no apparent granules.In patients with rhegmatogenous retinal detachment that developed PVR,photoreceptor derived MPs in the vitreous were higher than the control group,suggesting photoreceptor derived MPs might contribute to the disease progression.The levels of vitreous MPs derived from various cells were all increased in patients with ocular trauma that developed PVR compared with the control group,suggesting that MPs in vitreous fluid may contribute to disease progression.