Longitudinal Photoreceptor Phenotype Observation and Therapeutic Evaluation of a Carbonic Anhydrase Inhibitor in a X-Linked Retinoschisis Mouse Model

Abstract

PurposeTo study the long-term photoreceptor changes and to evaluate the effects of topical application of a carbonic anhydrase inhibitor (CAI) in a mouse model of X-linked retinoschisis (XLRS).MethodsConventional electroretinograms (ERGs) and dark-adapted 10-Hz flicker ERGs were recorded in control and Rs1−/Y mice generated with CRISPR/Cas9. ON-pathway blocker 2-amino-4-phosphobutyric acid (APB) was injected intravitreally. Morphology was evaluated with histology and optical coherence tomography (OCT). Mice were treated with a CAI inhibitor brinzolamide eye drops (10 mg/ml) three times a day for 3 months. OCT and ERG findings at 1, 4, and 10 months were analyzed.ResultsNegative ERGs and retinal cavities were evident in Rs1−/Y mice. Both a-wave and b-wave amplitudes decreased with age when compared with age-matched controls. The APB-isolated a-wave (a′) amplitudes of Rs1−/Y mice were reduced in all age groups. In dark-adapted 10-Hz flicker ERG, the amplitude-intensity curve of Rs1−/Y mice shifted down. The thickness of ONL and IS/OS decreased in Rs1−/Y mice. CAI reduced the splitting retinal cavities but didn't affect the ERG.ConclusionsIn addition to post receptoral impairments, photoreceptor cells underwent progressive dysfunction since early age in Rs1−/Y mice. Long-term CAI treatment improved the shrinkage of the splitting retinal cavity, while no functional improvement was observed.

Retinal Proteomic Alterations and Combined Transcriptomic-Proteomic Analysis in the Early Stages of Progression of a Mouse Model of X-Linked Retinoschisis

“…At P15, the cell numbers in the ONL of RS1-KO retinas were comparable to those in the wild type (WT), whereas a marked decrease was observed at P56. This was consistent with our previous study, which showed that the thickness of the ONL and OS+IS in RS1-KO retinas declined during a long-term observation [ 24 , 25 ].…”

“…By comparison, at P56, the DEPs were mostly enriched in visual functions, such as visual perception, visual phototransduction, and photoreceptor cell differentiation. Specifically, the differentially expressed proteins, including Cntf, Fgf2, and Slc4a7, were enriched in retinal cell programmed cell death, which is consistent with the decline of ONL and OS+IS thickness in the progress of XLRS [ 24 , 25 ].…”

“…Moreover, the transcriptomic and proteomic data revealed decreased levels of proteins in photoreceptors, including Rdh12, Reep6, Rom1, Opn1mw, and Arr3. Our previous report also revealed that the thickness of OS and IS in XLRS mice and patients decreased with age, and reduction in a-wave amplitude correlated well with the decline in ONL and OS+IS thickness [ 24 , 25 ]. Based on these findings, we infer that photoreceptor cells underwent progressive dysfunction from the early stages.…”

“…XLRS and age-matched litter-mate WT mice were generated in our laboratory. Construction and verification of the XLRS mouse model were detailed in our previous work [ 25 ] To evaluate the morphology of RS1-KO retinas in the early postnatal periods, we performed hematoxylin–eosin (HE) staining. In Figure 1 a, large cavities within the INL were observed at P15, which became collapsed and shrunken by P56.…”

“…In this period, the outer nuclear layer (ONL) undergoes a slow progressive loss of photoreceptors. Additionally, our previous study also indicates that the thickness of the OS and the IS in RS1-KO mice decreases with age [ 24 , 25 ].…”