Multimodal imaging and functional analysis of the chick NMDA retinal damage model.

OBJECTIVES: The chick is rapidly becoming a standardized preclinical model in vision research to study mechanisms of ocular disease. We seek to comprehensively evaluate the N-methyl-D-aspartate (NMDA) model of excitotoxic retinal damage using multimodal imaging, functional, and histologic approaches in NMDA-damaged, vehicle-treated, and undamaged chicks. METHODS: Chicks were either left undamaged in both eyes or were injected with NMDA in the left eye and saline (vehicle) in the right eye. TUNEL assay was performed on chicks to assess levels of retinal cell death one day post-injection of NMDA or saline and on age-matched untreated chicks. Spectral domain optical coherence tomography (SD-OCT) was performed weekly on chicks and age-matched controls day 1 (D1) up to D28 post-injection. Light adapted electroretinograms (ERG) were performed alongside SD-OCT measurements on post-injection chicks along with age-matched untreated controls. RESULTS: Untreated and vehicle-treated eyes had no TUNEL positive cells while NMDA-treated eyes accumulated large numbers of TUNEL positive cells in the Inner Nuclear Layer (INL), but not other layers, at D1 post injection. Significant inner retina swelling or edema was found on SD-OCT imaging at D1 post-injection which resolved at subsequent timepoints. Both the INL and the inner plexiform layer significantly thinned by one-week post-injection and did not recover for the duration of the measurements. On ERG, NMDA-treated eyes had significantly reduced amplitudes of all parameters at D1 with all metrics improving over time. The b-wave, oscillatory potentials, and ON/OFF bipolar responses were the most affected with at least 70% reduction immediately after damage compared to the fellow eye control. CONCLUSION: This study establishes a normative baseline on the retinal health and gross functional ability as well as intraocular pressures of undamaged, vehicle-treated, and NMDA-damaged chicks to provide a standard for comparing therapeutic treatment studies in this important animal model.

Genetic Variants in Host Protein Disulfide Isomerase 2 (PDIA2) are Associated with Susceptibility to Chlamydia Trachomatis Infection.

OBJECTIVES: Objective: Host genetics can influence susceptibility to Chlamydia trachomatis infection. This study examined two genetic variants in human protein disulfide isomerase A2 (PDIA2), a member of a family of protein chaperones that participate in the chlamydial life cycle. Methods: A total of 278 male and female subjects, positive or negative for C. trachomatis infection, were genotyped for PDIA2 polymorphisms (rs400037 and rs419949) using real-time PCR and pyrosequencing. Results: There was a significant odds ratio of 8.21 (95% CI: 1.77-38.16) for rs400037 and 9.89 (95% CI: 1.19-82.10) for rs419949, for the AA genotypes. Conclusion: This indicates that individuals with the PDIA2 AA genotypes have significantly increased susceptibility to C. trachomatis infection as compared to the other PDIA2 genotypes (GG, GA). This correlation may be explained by an interactive role of host protein disulfide isomerases in the attachment and entry of C. trachomatis into cells.

Oral Selumetinib Does Not Negatively Impact Photoreceptor Survival in Murine Experimental Retinal Detachment.

Purpose: Mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) signaling is neuroprotective in some retinal damage models but its role in neuronal survival during retinal detachment (RD) is unclear. In addition, serous RDs are a prevalent side effect of MEK inhibitors (MEKi), blocking MAPK/ERK signaling for treatment of certain cancers. We tested the hypothesis that MEKi treatment in experimental RD would increase photoreceptor death. Methods: The MEKi selumetinib was delivered daily to C57BL/6 mice at a clinically relevant dose (10 mg/mL) starting 1 day prior to creating RD with subretinal hyaluronic acid injection. Photoreceptor TUNEL and outer nuclear layer (ONL) thickness were analyzed. Phospho-ERK1/2 (pERK) distribution, glial fibrillary acidic protein (GFAP) accumulation, and Iba-1 (microglia/macrophages) were evaluated with immunofluorescence. Results: pERK accumulated in the Müller glia in detached retinas, but this was effectively blocked by selumetinib. Selumetinib did not induce serous RDs at day 1 and did not increase TUNEL positive photoreceptors or further decrease ONL thickness compared to controls. Retinal gliosis was not altered, but selumetinib did block the increase in intraretinal microglia/macrophage Iba-1 fluorescence intensity and acquisition of amoeboid morphology. Conclusions: MAPK/ERK is neuroprotective in some retinal damage models; in RD, selumetinib blocked Müller pERK accumulation and changed the retinal microglia/macrophage phenotype but did not alter photoreceptor survival. This is consistent with the relatively good visual acuity seen in patients developing transient retinal detachments on MEK inhibitor therapy. Compensation by other neuroprotective pathways in the retina during retinal detachment may occur in the presence of MEK inhibition.