Applying Optical Coherence Tomography To Evaluate Retinal Pathology Of Adoptively Transferred Uveitis In Mice

Objective In this study, we used Spectralis optical coherence tomography(OCT)(Heidelberg) to dynamically monitor in vivo the retinal changes of experimental autoimmune uveitis(EAU) in mice induced by T cell adoptively transfer. The sensitivity of OCT was evaluated by comparing OCT scores with clinical and pathological assessment and ERG evaluation, and the retinal thickness(RT) was also obtained by OCT.Method 1. Induction of adoptively transferred EAU model: To induce adoptively transferred EAU model, the IRBP1-20 specific T cells were injected intraperitoneally into na?ve C57BL/6 mice. 2. Clinical observation:From the 9th day after transfer,we used indirect ophthalmoscope with +90D lens to observe the fundus of eyes and record clinical scores every 3 days. The disease was divided into 6 phases including onset phase,early phase, pre-peak phase,peak phase,resolution phase and late phase. Clinical scores were assessed using Xu criteria. 3. Histopathological observation: The eyeballs were collected on day 9, 22 and 60 after transfer. The histopathological of retina were examined by hematoxylin and eosin staining and assessed using Caspi criteria. 4. Retinal function detection: To evaluate retinal function, dark-adapted ERG was recorded on day 12, 26, and 60 after transfer. 5. OCT examination: Since the 9th day after transfer, we used Spectralis OCT to examine the retina. RT was measured at the area about 1 disc from the disc edge on 9、11、16、21、25、30、35、40、50 and 60 days post-transfer.OCT score was recorded from 0-4.0.Result 1. Adoptively transferred EAU model was successfully induced. 2. At the onset of EAU,optic disc showed slight swelling with edges not clearly delineated,and retina was also slightly swelling;At the early phase of EAU,isolated small lesions appeared on the retina;At pre-peak phase of EAU,retinal linear lesions could be found,diffuse infiltrates might present on the optic disc and retinal vascular segments were surrounded by a few whitish infiltrates;At the peak phase of EAU,vitreous were seriously cloudy;At the resolution phase of EAU,retinal infiltration,disc inflammation and vascular whitish infiltration were faded;At the late phase of EAU,the fundus showed grey atrophic retina. 3. Histological examination revealed slight infiltration of inflammation cells and relatively normal retinal structure at the onset of EAU;Massive infiltration and disordered retinal structure appeared at pre-peak of EAU. And in the resolution phase of EAU, the inflammatory cells resolved and retina was astrophic and thinned. 4. During the disease course, OCT score were 0.35±0.24,1.4±0.52,2.8±0.42 and 3.6±0.52 on 9d, 16 d, 21 d and 26 d after transfer respectively, which were corresponding to onset phase,early phase, pre-peak phase and peak phase respectively.On 30 d post-transfer,in the resolution phase of EAU,the inflammatory cells in vitreous reduced obviously and OCT score was2.5±0.53.Inflammatory cells in vitreous disappeared and retina was atrophic in late phase of EAU,with OCT score of 0.5±0.53 on 60 d.OCT scores were well correlated with clinical scores in EAU(r=0.9579,P<0.0001). 5. With development of the disease,the RT increased gradually due to the edema of the retina.At the peak of the disease,the RT was about 1.5 times of baseline because of severe inflammation.The RT started to decrease after the peak phase.In the late phase of EAU, the RT was below the baseline because of retinal atrophy, especially the loss of photoreceptor cells. 6. ERG was normal on 7d post-transfer. EAU development led to a detectable reduction about 15% in dark a- and b-wave amplitudes on 12 d post immunization. At the peak of disease,ERG amplitudes decreased by more than 50%.In the late phase of EAU,the inflammation was faded but ERG could not fully recover.Conclusion 1. OCT examination is a highly sensitive and reliable technology that can be used to monitor the development of EAU. OCT evaluation is consistent with clinical and histological assessment. 2. OCT scoring criteria is a simple and easy method in monitoring disease dynamically. 3. The grading systems of OCT, clinical and histopathological evaluation focus mainly on retinal inflammation, which can’t reflect the final atrophy of the retina. Therefore, RT is an important parameter for semi-quantitative evaluation.