Effects Of Apelin-13 On Retinal Microglial Cells In A Rat Model Of Oxygen-induced Retinopathy Of Prematurity

Part one The study on the morphology of the retina of the OIR rat model.Objective:To establish the OIR rat model and observe the morphological and ultrastructural changes of the retina of the OIR rat model,and provide a theoretical basis for the study of the pathogenesis of ROP.Methods:Evans rats on the 7^th day after birth were divided into normal control group and OIR group.The rats in OIR group were placed in closed plexiglass container,and inhalated humidified 100%oxygen at the rate of 0.75liters/minute.They were placed in the normal environment after 5 days of treatment,and then retinas were harvested on the 12^th,14^th and 17^st day of birth.The morphological changes of the retina were observed under optical microscope,and the ultrastructure changes were observed under electron microscope.the morphology and distribution of blood vessels were highlighted by ADP immunochemistry.Results:The retinal layers in the normal control group had no or very few vascular endothelial cells breaking through the retinal membrane.The retinal vessels were basically mature,well distributed,and the branch vessels can be seen.The mitochondria were slender.The changes in OIR include:The structure of the retinal ganglion cells was disorganized;the gap between cells widened;the vacuoles were visible;the number of nuclei in the inner and outer layers decreased;and the outer mitochondria became shorter.A large number of vascular endothelial cells penetrated the inner membrane of the retina and formed a lumen.The large retinal vessels grew further outward,forming a dense,disorganized network.Conclusions:Hypoxia induced changes in morphology,vascular morphology and distribution of the rat retina.Part two Apelin-13 inhibits the activation and proliferation of microglia cells in the retina of the OIR rat modelObjective:To explore the effects of Apelin-13 on retinal microglial cells in rat models of oxygen-induced retinopathy of prematurity.Methods:The rats were divided into three groups,the normal control group,the OIR+vehicle group and the OIR+Apelin group.Rats in the OIR+vehicle group and the OIR+Apelin group received single intravitreal injections of vehicle or Apelin-13 on postnatal day 7.The morphology and cell number of microglia cells were detected by immunohistochemistry.The mRNA and protein expression of CD11b and IBA-1 were detected by RT-qPCR and Western-blot.Results:A large number of amoeboid microglia appeared in the OIR group.While the normal control group and OIR+Apelin group had more branching microglia.And the mRNA and protein expression of CD11b and IBA-1 were lower than that of the OIR+vehicle group.There was no significant difference between the normal control group and the OIR+Apelin group.Conclusions:Apelin-13 vitreous injection with appropriate concentration can reduce retinal microglial cells in the OIR rat model,and reduce the mRNA and protein expression of CD11b and IBA-1 in the retina of the OIR model rats.Part three Apelin-13 protects OIR model rat blood-retina barrierObjective:To study the effects of Apelin-13 on retinal vascular permeability,the mRNA and protein expression of TNF-αand iNOS in the OIR rat model.Methods:The rats were divided into three groups,the normal control group,the OIR+vehicle group and the OIR+Apelin group.Rats in the OIR+vehicle group and the OIR+Apelin group received single intravitreal injections of vehicle or Apelin-13 on postnatal day 7.The permeability of retinal vessels was detected by Evans blue staining,and the mRNA and protein expression of TNF-αand iNOS were detected by RT-qPCR and Western-blot,respectively.Results:Compared with the normal control group,the permeability of retinal vessels was increased,and the mRNA and protein expression of TNF-αand iNOS were up-regulated in OIR+vehicle group.Compared with OIR+vehicle group,the mRNA and protein expression of TNF-αand iNOS were decreased in OIR+Apelin group.Conclusions:Intravitreal delivery of Apelin-13 protected BRB integrity against vascular leakage and decreased the mRNA and protein expression of TNF-αand iNOS in the OIR model rats.