In retinitis pigmentosa (RP), one of many possible genetic mutations causes rod degeneration, followed by cone secondary death leading to blindness. Accumulating evidence indicates that rod death triggers multiple, non-cell-autonomous processes, which include oxidative stress and inflammation/immune responses, all contributing to cone demise. Inflammation relies on local microglia and recruitment of immune cells, reaching the retina through breakdowns of the inner blood retinal barrier (iBRB). Leakage in the inner retina vasculature suggests similarly altered outer BRB, formed by junctions between retinal pigment epithelium (RPE) cells, which are crucial for retinal homeostasis, immune response, and privilege. We investigated the RPE structural integrity in three models of RP (rd9, rd10, and Tvrm4 mice) by immunostaining for zonula occludens-1 (ZO-1), an essential regulatory component of tight junctions. Quantitative image analysis demonstrated discontinuities in ZO-1 profiles in all mutants, despite different degrees of photoreceptor loss. ZO-1 interruption zones corresponded to leakage of in vivo administered, fluorescent dextran through the choroid-RPE interface, demonstrating barrier dysfunction. Dexamethasone, administered to rd10 mice for rescuing cones, also rescued RPE structure. Thus, previously undetected, stereotyped abnormalities occur in the RPE of RP mice; pharmacological targeting of inflammation supports a feedback loop leading to simultaneous protection of cones and the RPE.

Brain plasticity is a well-established concept designating the ability of central nervous system (CNS) neurons to rearrange as a result of learning, when adapting to changeable environmental conditions or else while reacting to injurious factors. As a part of the CNS, the retina has been repeatedly probed for its possible ability to respond plastically to a variably altered environment or to pathological insults. However, numerous studies support the conclusion that the retina, outside the developmental stage, is endowed with only limited plasticity, exhibiting, instead, a remarkable ability to maintain a stable architectural and functional organization. Reviewed here are representative examples of hippocampal and cortical paradigms of plasticity and of retinal structural rearrangements found in organization and circuitry following altered developmental conditions or occurrence of genetic diseases leading to neuronal degeneration. The variable rate of plastic changes found in mammalian retinal neurons in different circumstances is discussed, focusing on structural plasticity. The likely adaptive value of maintaining a low level of plasticity in an organ subserving a sensory modality that is dominant for the human species and that requires elevated fidelity is discussed.

In a recent study, we obtained two novel cortisone-derived molecules: 1,9β,17,21- tetrahydroxy-4-methyl-19-nor-9β-pregna-1,3,5(10)-trien-11,20-dione(SCA)and 1,9β,17,20β,21-pentahydroxy-4-methyl-19-nor-9β-pregna-1,3,5(10)-trien-11-one(SCB). These compounds showed a dual activity combining potent anti-inflammatory and antioxidant properties, suggesting their potential as therapeutic agents for conditions characterized by inflammation and oxidative stress, such as severe ocular disorders. In this study, in vitro experiments using human ARPE-19 and mouse 661 W cell lines, which model the retinal pigment epithelium and retinal photoreceptors respectively, revealed that pretreatment with SCA and SCB under oxidative stress with H₂O₂ preserved cell viability, reduced intracellular ROS levels, maintained tight junction integrity and Trans Epithelial Electrical Resistance (TEER). Moreover, both compounds enhanced mitochondrial respiration, thereby improving cellular bioenergetics. These results indicate that SCA and SCB could provide an effective alternative to traditional corticosteroids in treating complications in which oxidative stress and inflammation are combined, including diseases such as age-related macular degeneration (AMD) and retinitis pigmentosa (RP). Preclinical studies on animal models and trials on human ocular diseases are necessary to validate these findings in vivo and explore their therapeutic potential.