Effect Of Laser Photocoagulation On Cytokines In Diabetic Retinopathy

Chapter 1 VEGF,NGF and Chemerin expressions after subthreshold micropulse yellow laser(577 nm)therapy in early stage diabetic ratsAim:To investigate VEGF,NGF and Chemerin expressions after subthreshold micropulse yellow laser(577 nm)therapy in early stage diabetic rats.Methods:A total of 40 Brown Norway rats were treated with streptozocin(65mg·kg-1).20 diabetic BN rats' right eyes were received subthreshold micropulse yellow laser(577 nm)therapy after two weeks.The threshold energy was determined for each right eye by creating a threshold burn to make a visible "test burn" with continuous wave laser energy for 0.2s at a diameter of 200?m at peripheral retinal.Subsequently,subthreshold micropulse yellow laser(577-nm)treatment was performed in the micropulse mode using the 5%duty cycle micropulse mode at 400%of threshold energy for 0.2s at a diameter of 200?m,which delivered at 4x4 model.The left eyes were used as control group.At 3,7,14,28 days after laser therapy,5 BN rats were randomly to perform RT-PCR and Weston-blot.The expressions of mRNA and protein of VEGF?NGF and Chemerin were analyzed.Results:The expression of VEGF mRNA and protein increased in control group at 3,7,14 and 28 days(P<0.05).Comparing to the control group,VEGF mRNA and protein decreased in the subthreshold micropulse yellow laser(577 nm)group(all P<0.05).The expression of NGF mRNA and protein decreased in the control group at 3,7,14 and 28 days(P<0.05),however the difference was not statistically significant between 3 days and 7 days(P>0.05).Comparing to the control group,NGF mRNA and protein increased in the subthreshold micropulse yellow laser(577 nm)group(all P<0.05),with maximum expression at 14 days.The expression of Chemerin mRNA and protein increased at 3,7,14 and 28 days in the control group(P<0.05).Comparing to the control group,Chemerin mRNA and protein decreased in the subthreshold micropulse yellow laser(577 nm)group(all P<0.05).Conclusion Subthreshold micropulse yellow laser(577 nm)can suppress VEGF,Chemerin expression and up-regulate NGF expression in early stage diabetic rats.Chapter 2 Comparative Study of Conventional Laser Photocoagulation and Subthreshold Micropulse Laser Photocoagulation on Vitreous Levels of VEGF,IL-33 and NO in the Eyes with PDRAim To compare the vitreous levels of vascular endothelial growth factor,VEGF),interleukin-33(IL-33)and nitric oxide(NO)in proliferative diabetic retinopathy(PDR)eyes after conventional laser photocoagulation and subthreshold micropulse laser photocoagulation.Metnods This is an interventional case-control study.The clinical data of 39 patients of PDR and 11 patients of idiopathic macular pucker(IMP)were analyzed.15 eyes with PDR were treated with conventional laser photocoagulation.13 eyes with PDR were treated with subthreshold micropulse laser.11 eyes with PDR without any laser therapy.11 eyes from 11 patients with IMP were as control group.Three days after the two kinds of laser procedure,all vitreous samples obtained during vitrectomy.Central fovea thickness(CFT)were measured in optical coherence tomography in PDR eyes after vitrectomy.Levels of VEGF,IL-33,NO were determined using enzyme-linked immune sorbent assay(ELISA)kits.The correlations of levels of VEGF,IL-33,NO and the CFT were analyzed.Results PDR without laser photocoagulation had the highest VEGF levels;the difference was significant compared with conventional laser photocoagulation group(P=0.005),subthreshold micropulse laser group(P=0.018)and IMP group(P<0.001).There was no significant difference of VEGF levels between conventional laser photocoagulation group and subthreshold micropulse laser group(P=0.69).Conventional laser photocoagulation group had the highest IL-33 levels;the difference was significant compared with subthreshold micropulse laser group(P=0.001),in PDR without any laser therapy group(P<0.001),in IMP group(P<0.001).There was no statistically significant difference of IL-33 levels between subthreshold micropulse laser group and PDR without any laser therapy group(P=0.30).IMP group had the lowest NO levels(P<0.001 vs.conventional laser photocoagulation group,subthreshold micropulse laser group and PDR without any laser therapy group).There was no statistically difference of NO levels between conventional laser photocoagulation group and subthreshold micropulse laser group(P=0.23).In PDR without any laser therapy group,central fovea thickness was positively correlated with NO levels(r=0.67,P=0.025).Conclusions Both conventional laser photocoagulation and subthreshold micropulse laser photocoagulation can decrease vitreous VEGF levels after three days and subthreshold micropulse laser photocoagulation induce led to less inflammatory reaction.