Level And Significance Of Vitreous Microparticles Shedding In Proliferative Diabetic Retinopathy

Purpose This study intended to investigate the morphology and size of vitreous shedding microparticles(MPs)in patients with proliferative diabetic retinopathy(PDR);detecting respectively the levels of endothelial cell-derived MPs(EMPs),platelet-derived MPs(PMPs),retinal photoreceptor cell-derived MPs(RMPs),and Phosphatidylserine-expressing MPs(PS-MPs)shedding in the vitreous body fluid samples of PDR patients;analyzing the relationship between level of different MPs and clinical characteristics of PDR,as to discuss the role of MPs in PDR pathogenesis,and to provide evidences for research about clinical intervention.Methods The enrolled patients were hospitalized in ophthalmology department in Tianjin Medical University General Hospital from January to December in 2018,who had undergone vitrectomy.A total of 74 eyes were divided into 2 groups,the study group enrolled 54 eyes diagnosed with PDR,of which 17 eyes had intravitreal injection history of anti-vascular endothelial growth factor(VEGF)agents,and the control group totally enrolled 20 eyes,including the idiopathic macular hole(6 eyes),idiopathic epiretinal membrane(6 eyes),vitreousmacular tractional syndrome(2 eyes)and dislocation of lens(6 eyes).Vitreous microparticle samples were prepared by the methods of density gradient centrifugation and ultracentrifugation,observed under the transmission electron microscope for morphological identification.The size and diameter range of MPs were analyzed by nanoparticle tracking technique.Flow cytometry method was used to detect the level of EMPs,PMPs,RMPs and PS-MPs shedding in vitreous body fluid samples,to compare the differences between the study and control group.The correlation was analyzed between the level of MPs and clinical characteristcs including diabetes duration,blood glucose,and visual acuity of PDR patients.Furthermore,the level of MPs between different stage of PDR,with or without preoperative intravitreal injection,PDR with intravitreal injection and control group,with or without vitreous hemorraghe were compared respectively.Results MPs observed under the electron microscope had various shapes,of which mostly showed typical round or oval vesicle-like,with complete double-layer membrane structure,with size from 100 nm to 1000 nm.Nanosight showed thatvitreous MPs were distributed in 119 nm,229nm,327 nm,536nm,and 691 nm size ranges.Using flow cytometry,the detection method of MPs shedding in human vitreous fluid samples was successfully established.In PDR group,level of EMPs(3915.69±4841.12)and PMPs(3881.61±5970.95)were higher than control group(525.7±532.36)(P <0.001),(750.0±1590.88)(P =0.001).Level of RMPs in PDR group(4797.84 ± 5106.12)was lower than control group(7429.30 ± 6965.74)(P=0.018).Correlation analysis showed that PS-MPs level was significantly correlated with diabetes duration(r=0.271,P =0.048)and preoperative visual acuity(r=0.338,P=0.017).With the progression of PDR,level of MPs trended to increase,with PMPs from 2563.51 ±4332.54 to 5952.91±7554.69(P =0.041),RMPs from 3610.16±3804.07 to 6664.21±6320.88(P =0.031),EMPs from 3850.80±5097.23 to 4017.65±4529.67(P =0.903),PS-MPs from 1324.80±2906.79 to 2813.23±5285.65(P=0.188).Additionally,PDR subgroup with preoperative intravitreal injection showed lower level of EMPs(1902.69 ± 2266.01)than the others(4840.57 ± 5424.83)(P=0.007),but higher than control group(525.74±532.36)(P =0.025).PDR subgroup without vitreous hemorraghe showed higher level of PMPs(8249.20±8748.14)than the others(2633.73±4286.75)(P =0.030).Conclusions(1)There were vitreous EMPs,PMPs,RMPs and PS-MPs shedding in PDR,with complete doubled layer membranes.(2)The levels of EMPs and PMPs in PDR were higher,which possibly resulted from retinal microvessels damage.(3)PS-MPs level had positive correlation with diabetes duration and preoperative visual acuity,which reflected the severity of PDR.(4)All types of the detected MPs were increased as the progression of PDR,of which increasing PMPs and RMPs had significances,suggesting with the damaged retinal vessels and tissue became worse,more cells were stimulated and released more MPs.(5)PDR patients with preoperative anti-VEGF showed a certain treatment effect by decreasing EMPs level,but cannot rapidly and completely repaired the lesions.(6)Vitreous hemorraghe in PDR possibly resulted from the role of PMPs.