Oksana Kutsyr

Pannexins are large channels involved in purinergic signaling within the nervous system. However, their role in human disease and their therapeutic potential remain poorly understood, particularly for Pannexin-2 (Panx2). The aim of this study was to investigate whether Panx2 is associated with retinal neurodegenerative diseases. Using immunohistochemistry and flow cytometry, we analyzed Panx2 expression in the retina of the P23H mouse model of retinitis pigmentosa and in control C57BL/6J mice. We observed that healthy retinas contained a small population of Panx2-positive cells. In contrast, the Panx2 positive population was increased in the retinas of P23H retina, particulary at advanced stages of the disease. Panx2 was found to co-occur with the purinergic receptors P2X7R but not with P2X4R. This result was further supported by the reanalysis of RNA-seq data from GEO functional genomics data repository, which indicated an increased Panx2 mRNA expression in P23H mice at intermediate stages of the disease, compared with control animals. Together, these findings suggest that Panx2 expression is altered during retinal degeneration in the P23H model and may be associated with purinergic signaling pathways involved in disease progression. These results raise interesting questions for further investigation regarding the role of Panx2 in retinal degeneration. Graphical Abstract Schematic representation of the study design, highlighting the key findings using the P23H mouse model of retinitis pigmentosa

Central areolar choroidal dystrophy (CACD) is a progressive macular dystrophy without treatment. Although PRPH2 mutations are the most common cause of disease, the mechanisms driving their phenotypic variability remain poorly understood. Here, a comprehensive characterization of the pathophysiological consequences of p.Arg195Leu mutation in PRPH2 was carried out in a mouse model (Prph2 ^KI/WT ). For evaluating the retinal degeneration, this study combines the analysis of electroretinographic responses together with a complete study of bulk RNA-seq transcriptomics and the key cellular and molecular pathways using confocal imaging, flow-cytometry and western blotting. Results from this work demonstrate that ageing and sex influence retinal degeneration. In young mutant mice, retinal functional impairment and structural disorganization of photoreceptor outer segments were accompanied by a reduced expression of Prph2 and Rom1 genes, together with the activation of the immune system and complement pathways. Middle-age stages represent a critical transition point where the increase of cell death and epithelial barrier dysfunction mark the beginning of retinal degeneration. These pathological events become evident at 9 months of age, where visual pathways-related genes were deregulated. Functional, cellular and molecular alterations observed in the mutant mice do not affect males and females equally. From the earliest stages of the disease, females exhibited greater and sustained inflammatory activation, mainly promoted by complement system upregulation and increased CD11b immunoreactivity, and potentially mediated by IL-6/STAT3/ERK signaling. Moreover, females had greater functional decline and photoreceptor loss. Together, these results could explain the high inter- and intrafamilial variability observed in CACD patients carrying the same mutation. Our findings identify inflammatory biomarkers accompanied by visual function loss, prior to evident retinal degeneration, and demonstrate that age and sex critically shape disease onset and severity. These insights underscore the necessity of incorporating sex-specific biology and early anti-inflammatory treatment into the development of targeted therapies for PRPH2-related dystrophies.

Age-related macular degeneration (AMD) represents one of the therapeutic challenges of aging eye diseases. Our investigation reveals the stimulator of interferon genes (STING) pathway as an orchestrator of immune-mediated retinal degeneration, exhibiting biphasic, stage-dependent functionality—providing cytoprotection in healthy tissue but driving pathogenic inflammation during early AMD progression. Through immunohistochemical analysis of human eyes, we demonstrate stage-dependent cytoplasmic STING upregulation with parallel IFN-β activation. Using patient-derived induced pluripotent stem cells-retinal pigment epithelium (iPSC-RPE) from AMD siblings, we discovered polarized cytokine secretion: apical IFN-β triggers photoreceptor apoptosis in human retinal organoids, while basal IL-17A compromises choroidal neovascularization. The Cryba1 conditional knockout (cKO) AMD-like mouse model confirms STING-driven IL-17A expression, while Il17a knock-in mice substantiate vascular alterations. STING activation establishes a pathogenic feed-forward loop between interferons and IL-17A. Single-cell transcriptomics following AAV2-mediated IFN-β overexpression reveals metabolic and phototransduction dysregulation. Both pharmacological STING inhibition with SN-011 and genetic approaches demonstrate therapeutic rescue. Cryba1 / Sting double heterozygous (dhet) mice maintain homeostatic gene expression preserving retinal architecture and function. These findings establish STING as the master regulator simultaneously controlling multiple AMD pathologies through spatially organized inflammation, transforming from protective surveillance to pathogenic driver, and identifying a unified therapeutic target with demonstrated functional rescue across multiple experimental paradigms.

Ischemia is the main cause of cell death in retinal diseases such as vascular occlusions, diabetic retinopathy, glaucoma, or retinopathy of prematurity. Although excitotoxicity is considered the primary mechanism of cell death during an ischemic event, antagonists of glutamatergic receptors have been unsuccessful in clinical trials with patients suffering ischemia or stroke. Our main purpose was to analyze if the transient receptor potential channel 7 (TRPM7) could contribute to retinal dysfunction in retinal pathologies associated with ischemia. By using an experimental model of acute retinal ischemia, we analyzed the changes in retinal function by electroretinography and the changes in retinal morphology by optical coherence tomography (OCT) and OCT-angiography (OCTA). Immunohistochemistry was performed to assess the pattern of TRPM7 and its expression level in the retina. Our results show that ischemia elicited a decrease in retinal responsiveness to light stimuli along with reactive gliosis and a significant increase in the expression of TRPM7 in Müller cells. TRPM7 could emerge as a new drug target to be explored in retinal pathologies associated with ischemia.

Central areolar choroidal dystrophy is an inherited disorder characterized by progressive choriocapillaris atrophy and retinal degeneration and is usually associated with mutations in the PRPH2 gene. We aimed to generate and characterize a mouse model with the p.Arg195Leu mutation previously described in patients. Heterozygous (Prph2^WT/KI) and homozygous (Prph2^KI/KI) mice were generated using the CRISPR/Cas9 system to introduce the p.Arg195Leu mutation. Retinal function was assessed by electroretinography and optomotor tests at 1, 3, 6, 9, 12, and 20 months of age. The structural integrity of the retinas was evaluated at the same ages using optical coherence tomography. Immunofluorescence and transmission electron microscopy images of the retina were also analyzed. Genetic sequencing confirmed that both Prph2^WT/KI and Prph2^KI/KI mice presented the p.Arg195Leu mutation. A progressive loss of retinal function was found in both mutant groups, with significantly reduced visual acuity from 3 months of age in Prph2^KI/KI mice and from 6 months of age in Prph2^WT/KI mice. Decreased amplitudes in the electroretinography responses were observed from 1 month of age in Prph2^KI/KI mice and from 6 months of age in Prph2^WT/KI mice. Morphological analysis of the retinas correlated with functional findings, showing a progressive decrease in retinal thickness of mutant mice, with earlier and more severe changes in the homozygous mutant mice. We corroborated the alteration of the outer segment structure, and we found changes in the synaptic connectivity in the outer plexiform layer as well as gliosis and signs of microglial activation. The new Prph2^WT/KI and Prph2^KI/KI murine models show a pattern of retinal degeneration similar to that described in human patients with central areolar choroidal dystrophy and appear to be good models to study the mechanisms involved in the onset and progression of the disease, as well as to test the efficacy of new therapeutic strategies.

Purpose Central areolar choroidal dystrophy is an inherited disorder characterized by progressive choriocapillaris atrophy and retinal degeneration, usually associated with mutations in the PRPH2 gene. We aimed to generate and characterize a mouse model with the p.Arg195Leu mutation previously described in patients.Methods Heterozygous (Prph2^WT/KI) and homozygous (Prph2^KI/KI) mice have been generated using the CRISPR/Cas9 system to introduce the Arg195Leu mutation. Retinal function was assessed by electroretinography and optomotor test at 1, 3, 6, 9, 12, and 20 months of age. The structural integrity of the retinas was evaluated at the same ages using optical coherence tomography. Immunofluorescence and transmission electron microscope images of the retina were also analyzed.Results Genetic sequencing confirmed that both Prph2^WT/KI and Prph2^KI/KI mice presented the p.Arg195Leu mutation. A progressive loss of retinal function was found in both mutant groups, with significantly reduced visual acuity from 3 months of age in Prph2^KI/KI and from 6 months of age in Prph2^WT/KI mice. Decreased amplitudes in the electroretinography responses were observed from 1 month of age in Prph2^KI/KI and from 6 months of age in Prph2^WT/KI. Morphological analysis of the retinas correlated with functional findings, showing a progressive decrease in retinal thickness of mutant mice, with earlier and more severe changes in the homozygous mutant mice. We corroborated the alteration of the outer segment structure, and we found changes in the synaptic connectivity in the outer plexiform layer as well as gliosis and signs of microglial activation.Conclusions The new Prph2^WT/KI and Prph2^KI/KI murine models show a pattern of retinal degeneration similar to that described in human patients with CACD and appear as good models to study the mechanisms involved in the onset and the progression of the disease, as well as to test the efficacy of new therapeutic strategies.

Summary: Purpose: We aimed to generate and phenotype a mouse model of FHONDA (Foveal Hypoplasia, Optic Nerve Decussation Defects, and Anterior Segment Dysgenesis), a rare disease associated with mutations in SLC38A8 that causes severe visual alterations similar to albinism without affecting pigmentation. Methods: The FHONDA mouse model was generated with CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats)/Cas9 technology using an RNA guide targeting the Scl38a8 murine locus. The resulting mice were backcrossed to C57BL/6J. Melanin content was measured using spectrophotometry. Retinal cell architecture was analyzed through light and electron microscopy. Retinal projections to the brain were evaluated with anterograde labelling in embryos and adults. Visual function was assessed by electroretinography (ERG) and the optomotor test (OT). Results: From numerous Slc38a8 mouse mutant alleles generated, we selected one that encodes a truncated protein (p.196Pro*, equivalent to p.199Pro* in the human protein) closely resembling a mutant allele described in patients (p.200Gln*). Slc38a8 mutant mice exhibit wild-type eye and coat pigmentation with comparable melanin contents. Subcellular abnormalities were observed in retinal pigment epithelium cells of Slc38a8 mutant mice. Anterograde labelling experiments of retinal projections in embryos and adults showed a reduction of ipsilateral fibers. Functional visual analyses revealed a decreased ERG response in scotopic conditions and a reduction of visual acuity in mutant mice measured by OT. Conclusions: Slc38a8 mutant mice recapitulate the phenotype of FHONDA patients concerning their normal pigmentation and their abnormal visual system, as observed in all types of albinism. These mice will be helpful in better understanding the pathophysiology of this genetic condition.

The purinergic receptor P2X7 (P2X7R) is implicated in all neurodegenerative diseases of the central nervous system. It is also involved in the retinal degeneration associated with glaucoma, age-related macular degeneration, and diabetic retinopathy, and its overexpression in the retina is evident in these disorders. Retinitis pigmentosa is a progressive degenerative disease that ultimately leads to blindness. Here, we investigated the expression of P2X7R during disease progression in the rd10 mouse model of RP. As the purinergic receptor P2X4 is widely co-expressed with P2X7R, we also studied its expression in the retina of rd10 mice. The expression of P2X7R and P2X4R was examined by immunohistochemistry, flow cytometry, and western blotting. In addition, we analyzed retinal functionality by electroretinographic recordings of visual responses and optomotor tests and retinal morphology. We found that the expression of P2X7R and P2X4R increased in rd10 mice concomitant with disease progression, but with different cellular localization. Our findings suggest that P2X7R and P2X4R might play an important role in RP progression, which should be further analyzed for the pharmacological treatment of inherited retinal dystrophies.

Inherited retinal dystrophies (IRDs) are a large group of genetically and clinically heterogeneous diseases characterized by the progressive degeneration of the retina, ultimately leading to loss of visual function. Oxidative stress and inflammation play fundamental roles in the physiopathology of these diseases. Photoreceptor cell death induces an inflammatory state in the retina. The activation of several molecular pathways triggers different cellular responses to injury, including the activation of microglia to eliminate debris and recruit inflammatory cells from circulation. Therapeutical options for IRDs are currently limited, although a small number of patients have been successfully treated by gene therapy. Many other therapeutic strategies are being pursued to mitigate the deleterious effects of IRDs associated with oxidative metabolism and/or inflammation, including inhibiting reactive oxygen species’ accumulation and inflammatory responses, and blocking autophagy. Several compounds are being tested in clinical trials, generating great expectations for their implementation. The present review discusses the main death mechanisms that occur in IRDs and the latest therapies that are under investigation.

Significance: The retina is considered a window to the brain, and retinal degenerative diseases involve the same mechanisms as those of other neurodegenerative disorders. Neuronal degeneration is a complex process involving environmental stress, which can affect vulnerable neurons. High-fat diet–induced metabolic alterations may influence retinal homeostasis and exacerbate retinal degenerative diseases. This study provides evidence that short-term high-fat feeding promotes glucose intolerance, gut microbiome dysbiosis, retinal oxidative stress, and inflammation and accelerates the pathologic processes in retinal disease.