Early remodeling of müller cells in the rd/rd mouse model of retinal dystrophy

We studied the anatomical remodeling and gliosis of retinal Müller cells in the rd/rd mouse model of photoreceptor degeneration. A computational calculation of glutamine synthetase immunoreactivity was developed so we could specifically quantify changes in Müller cell anatomy between control mice (C57Bl/6) and the dystrophic strain. We found no change in the number of Müller cell somata between mice strains, indicating no cell proliferation as a function of development and degeneration. The retinal area occupied by the total Müller cell body (soma and processes) was significantly less in the rd/rd mouse retina compared with control mice. When only the outer retina was considered, we found rd/rd Müller cell processes were dramatically reduced during the cone phase of photoreceptor degeneration. However, at older ages an increase in Müller cell processes was seen. Conversely, glial fibrillary acidic protein (GFAP) expression showed a significant increase during cone degeneration followed by a reduction in older ages. Müller cell electrophysiology, particularly K⁺ currents and membrane potential, was similar between rd/rd and control Müller cells during cone degeneration. Together, these results show that glial remodeling in the rd/rd retina follows separate phases—an initial conservative glial response involving the loss of Müller cells processes, hyperexpression of GFAP, and preservation of normal electrophysiology followed by an active growth of Müller cell processes, glial seal formation, and attenuation of GFAP expression after complete photoreceptor loss. J. Comp. Neurol. 521:2439–2453, 2013. © 2013 Wiley Periodicals, Inc.     

Expression of glial fibrillary acidic protein by Müller cells in rd chick retina

Accumulation of glial fibrillary acidic protein (GFAP) in Müller cells has been observed in retinas of several mammalian species secondary to genetically induced degeneration and neuronal injury. In the present series of experiments, I have examined the effects of the rd (retinal degeneration) mutation on the expression of GFAP in retinas of chicks homozygous for the mutation (rd/rd) prior to and following the onset of photoreceptor degeneration, which first appears approximately 7 days posthatch (7 dph). Carrier (+/rd) and wild-type (+/+) retinas served as controls. Retinas taken from 1, 7, 21, and 33 dph rd/rd, +/rd, and +/+ chicks were analyzed for the presence of GFAP by immunocytochemical and SDS-PAGE/Western blot techniques. The following immunocytochemical observations were made: (1) GFAP immunostaining was limited to and located throughout the Müller cells. (2) The intensity of GFAP immunostaining increased with age in all three retina types in tissue sections, as well as on immunoblots. (3) The distribution of GFAP staining within rd/rd Müller cells following the onset of degeneration was slightly different from that observed in +/+ and +/rd retinas and was distinguished by increased staining of the cell bodies and the cell processes forming the outer limiting membrane. The results of these experiments show that Müller cells in chick retina contain GFAP. In addition, they suggest that, in contrast to Müller cells in degenerating mammalian retina, Müller cells in rd chick retina do not accumulate large amounts of GFAP in response to degeneration.     

Adenosine triphosphate‐induced photoreceptor death and retinal remodeling in rats

Many common causes of blindness involve the death of retinal photoreceptors, followed by progressive inner retinal cell remodeling. For an inducible model of retinal degeneration to be useful, it must recapitulate these changes. Intravitreal administration of adenosine triphosphate (ATP) has recently been found to induce acute photoreceptor death. The aim of this study was to characterize the chronic effects of ATP on retinal integrity. Five‐week‐old, dark agouti rats were administered 50 mM ATP into the vitreous of one eye and saline into the other. Vision was assessed using the electroretinogram and optokinetic response and retinal morphology investigated via histology. ATP caused significant loss of visual function within 1 day and loss of 50% of the photoreceptors within 1 week. At 3 months, 80% of photoreceptor nuclei were lost, and total photoreceptor loss occurred by 6 months. The degeneration and remodeling were similar to those found in heritable retinal dystrophies and age‐related macular degeneration and included inner retinal neuronal loss, migration, and formation of new synapses; Müller cell gliosis, migration, and scarring; blood vessel loss; and retinal pigment epithelium migration. In addition, extreme degeneration and remodeling events, such as neuronal and glial migration outside the neural retina and proliferative changes in glial cells, were observed. These extreme changes were also observed in the 2‐year‐old P23H rhodopsin transgenic rat model of retinitis pigmentosa. This ATP‐induced model of retinal degeneration may provide a valuable tool for developing pharmaceutical therapies or for testing electronic implants aimed at restoring vision. J. Comp. Neurol. 522:2928–2950, 2014. © 2014 Wiley Periodicals, Inc.     

Dysmorphic photoreceptors in a P23H mutant rhodopsin model of retinitis pigmentosa are metabolically active and capable of regenerating to reverse retinal degeneration

This study evaluated the capacity of Xenopus laevis retina to regenerate photoreceptor cells after cyclic light-mediated acute rod photoreceptor degeneration in a transgenic P23H mutant rhodopsin model of retinits pigmentosa. After discontinuation of cyclic light exposure, we monitored histologic progression of retinal regeneration over a 3 week recovery period. To assess their metabolomic states, contralateral eyes were processed for computational molecular phenotyping. We found that retinal degeneration in the P23H rhodopsin mutation could be partially reversed, with regeneration of rod photoreceptors recovering normal morphology (including full-length rod outer segments) by the end of the 3 week recovery period. In contrast, retinal degeneration mediated by directly induced apoptosis did not recover in the 3 week recovery period. Dystrophic rod photoreceptors with truncated rod outer segments were identified as the likely source of rod photoreceptor regeneration in the P23H retinas. These dystrophic photoreceptors remain metabolically active despite having lost most of their outer segments.     

Pigment epithelium-derived factor delays the death of photoreceptors in mouse models of inherited retinal degenerations

Pigment epithelium-derived factor (PEDF) is a member of the serine protease inhibitor superfamily produced by retinal pigment epithelial cells in the developing and adult retina. In vitro, it induces neuronal differentiation of retinoblastoma cells and promotes survival of cerebellar granule neurons. The pedf gene is closely linked to an autosomal-dominant locus for retinitis pigmentosa, suggesting that PEDF could be a survival factor for photoreceptors. We have investigated this possibility by injecting PEDF into the eyes of homozygous retinal degeneration (rd) and retinal degeneration slow (rds) mice, two mutants displaying apoptotic photoreceptor loss. This procedure resulted in a transient delay of photoreceptor loss in the rd mouse and a reduction in apoptotic photoreceptor profiles in the rds mouse. We conclude that PEDF can act as a survival-promoting factor for photoreceptors in vivo and could potentially be useful for the treatment of photoreceptor diseases.     

Lazy eyes zebrafish mutation affects Müller glial cells,compromising photoreceptor function and causing partial blindness

A behavioral assay based on the optokinetic reflex was used to screen chemically mutagenized zebrafish larvae for deficits in visual function. A homozygous recessive mutation, lazy eyes (lze), was isolated based on the observation that 5-day postfertilization (dpf) mutants displayed weaker and less frequent eye movements than wild-type fish in response to moving stripes. Electroretinographic (ERG) recordings revealed that mutants had severely reduced a- and b-wave amplitudes relative to wild-type fish, indicating outer retinal dysfunction. Retinal lamination and cellular differentiation were normal in the lze retina; however, mutant photoreceptor cells had small outer segments and pyknotic nuclei were occasionally observed in the outer retina and the marginal zone of lze. Cone, rod, amacrine, bipolar, and Müller cell marker analyses indicated that the typical lze retina contained fewer rod photoreceptors and fewer Müller cells than wild-type fish at 5 dpf. At 3 dpf, however, mutant retinas had normal numbers of rod photoreceptors and Müller cells, suggesting that the initial differentiation of these cell types occurred normally. Rod photoreceptor histology was normal at this early stage, but Müller cells were often hypertrophied, suggesting that they were unhealthy. Constant light rearing of mutant animals accelerated the Müller cell degeneration, severely worsened the visual deficit, but had no obvious affect on the photoreceptors. When ERG responses and Müller cell degeneration from the same mutant animals were analyzed, the extent of the Müller cell loss matched closely the degree to which ERG responses were reduced. In summary, the lze gene appears to be required for Müller cell viability and normal visual function. The lze mutant may be a model for the study of the involvement of Müller cells in photoreceptor development and function.     

Luteolin delays photoreceptor degeneration in a mouse model of retinitis pigmentosa

Luteolin is neuroprotective for retinal ganglion cells and retinal pigment epithelial cells after oxidative injury,whereby it can inhibit microglial neurotoxicity.Therefore,luteolin holds the potential to be useful for treatment of retinal diseases.The purpose of this study was to investigate whether luteolin exhibits neuroprotective effects on rod cells in rd10 mice,a slow photoreceptor-degenerative model of retinitis pigmentosa.Luteolin(100 mg/kg)intraperitoneally injected daily from postnatal day 14(P14)to P25 significantly enhanced the visual performance and retinal light responses of rd10 mice at P25.Moreover,it increased the survival of photoreceptors and improved retinal structure.Mechanistically,luteolin treatment attenuated increases in reactive oxygen species,photoreceptor apoptosis,and reactive gliosis;increased mRNA levels of anti-inflammatory cytokines while lowering that of pro-inflammatory and chemoattractant cytokines;and lowered the ratio of phospho-JNK/JNK.Application of the JNK inhibitor SP600125 exerted a similar protective effect to luteolin,suggesting that luteolin delays photoreceptor degeneration and functional deterioration in rd10 mice through regulation of retinal oxidation and inflammation by inhibiting the JNK pathway.Therefore,luteolin may be useful as a supplementary treatment for retinitis pigmentosa.This study was approved by the Qualified Ethics Committee of Jinan University,China(approval No.IACUC-20181217-02)on December 17,2018.     

Functional remodeling of glutamate receptors by inner retinal neurons occurs from an early stage of retinal degeneration

Retinitis pigmentosa reflects a family of diseases that result in retinal photoreceptor death and functional blindness. The natural course of retinal changes secondary to photoreceptor degeneration involves anatomical remodeling (cell process alterations and soma displacement) and neurochemical remodeling. Anatomical remodeling predominantly occurs late in the disease process and cannot explain the significant visual deficits that occur very early in the disease process. Neurochemical remodeling includes modified glutamate receptor disposition and altered responses secondary to functional activation of glutamate receptors. We investigated the neurochemical remodeling of retinal neurons in the rd/rd (rd1) mouse retina by tracking the functional activation of glutamate receptors with a cation probe, agmatine. We provide evidence that bipolar cells and amacrine cells undergo selective remodeling of glutamate receptors during the early phases of retinal degeneration. These early neurochemical changes in the rd/rd mouse retina include the expression of aberrant functional ionotropic glutamate receptors on the cone ON bipolar cells from postnatal day 15 (P15), poor functional activation of metabotropic glutamate receptors on both rod and cone ON bipolar cells throughout development/degeneration, and poor functional activation of N‐methyl‐D‐aspartate receptors on amacrine cells from P15. Our results suggest that major neurochemical remodeling occurs prior to anatomical remodeling, and likely accounts for the early visual deficits in the rd/rd mouse retina. J. Comp. Neurol. 514:473–491, 2009. © 2009 Wiley‐Liss, Inc.     

Development and postnatal neurogenesis in the retina: a comparison between altricial and precocial bird species

The visual system is affected by neurodegenerative diseases caused by the degeneration of specific retinal neurons, the leading cause of irreversible blindness in humans. Throughout vertebrate phylogeny, the retina has two kinds of specialized niches of constitutive neurogenesis: the retinal progenitors located in the circumferential marginal zone and Müller glia. The proliferative activity in the retinal progenitors located in the circumferential marginal zone in precocial birds such as the chicken, the commonest bird model used in developmental and regenerative studies, is very low. This region adds only a few retinal cells to the peripheral edge of the retina during several months after hatching, but does not seem to be involved in retinal regeneration. Müller cells in the chicken retina are not proliferative under physiological conditions, but after acute damage some of them undergo a reprogramming event, dedifferentiating into retinal stem cells and generating new retinal neurons. Therefore, regenerative response after injury occurs with low efficiency in the precocial avian retina. In contrast, it has recently been shown that neurogenesis is intense in the retina of altricial birds at hatching. In particular, abundant proliferative activity is detected both in the circumferential marginal zone and in the outer half of the inner nuclear layer. Therefore, stem cell niches are very active in the retina of altricial birds. Although more extensive research is needed to assess the potential of proliferating cells in the adult retina of altricial birds, it emerges as an attractive model for studying different aspects of neurogenesis and neural regeneration in vertebrates.     

Retinal organization in the retinal degeneration 10 (rd10) mutant mouse: a morphological and ERG study

Retinal degeneration 10 (rd10) mice are a model of autosomal recessive retinitis pigmentosa (RP), identified by Chang et al. in 2002 (Vision Res. 42:517-525). These mice carry a spontaneous mutation of the rod-phosphodiesterase (PDE) gene, leading to a rod degeneration that starts around P18. Later, cones are also lost. Because photoreceptor degeneration does not overlap with retinal development, and light responses can be recorded for about a month after birth, rd10 mice mimic typical human RP more closely than the well-known rd1 mutants. The aim of this study is to provide a comprehensive analysis of the morphology and function of the rd10 mouse retina during the period of maximum photoreceptor degeneration, thus contributing useful data for exploiting this novel model to study RP. We analyzed the morphology and survival of retinal cells in rd10 mice of various ages with quantitative immunocytochemistry and confocal microscopy; we also studied retinal function with the electroretinogram (ERG), recorded between P18 and P30. We found that photoreceptor death (peaking around P25) is accompanied and followed by dendritic retraction in bipolar and horizontal cells, which eventually undergo secondary degeneration. ERG reveals alterations in the physiology of the inner retina as early as P18 (before any obvious morphological change of inner neurons) and yet consistently with a reduced band amplification by bipolar cells. Thus, changes in the rd10 retina are very similar to what was previously found in rd1 mutants. However, an overall slower decay of retinal structure and function predicts that rd10 mice might become excellent models for rescue approaches.     

Systematic spatiotemporal mapping reveals divergent cell death pathways in three mouse models of hereditary retinal degeneration

Calcium (Ca²⁺) dysregulation has been linked to neuronal cell death, including in hereditary retinal degeneration. Ca²⁺ dysregulation is thought to cause rod and cone photoreceptor cell death. Spatial and temporal heterogeneities in retinal disease models have hampered validation of this hypothesis. We examined the role of Ca²⁺ in photoreceptor degeneration, assessing the activation pattern of Ca²⁺-dependent calpain proteases, generating spatiotemporal maps of the entire retina in the cpfl1 mouse model for primary cone degeneration, and in the rd1 and rd10 models for primary rod degeneration. We used Gaussian process models to distinguish the temporal sequences of degenerative molecular processes from other variability sources.In the rd1 and rd10 models, spatiotemporal pattern of increased calpain activity matched the progression of primary rod degeneration. High calpain activity coincided with activation of the calpain-2 isoform but not with calpain-1, suggesting differential roles for both calpain isoforms. Primary rod loss was linked to upregulation of apoptosis-inducing factor, although only a minute fraction of cells showed activity of the apoptotic marker caspase-3. After primary rod degeneration concluded, caspase-3 activation appeared in cones, suggesting apoptosis as the dominant mechanism for secondary cone loss. Gaussian process models highlighted calpain activity as a key event during primary rod photoreceptor cell death. Our data suggest a causal link between Ca²⁺ dysregulation and primary, nonapoptotic degeneration of photoreceptors and a role for apoptosis in secondary degeneration of cones, highlighting the importance of the spatial and temporal location of key molecular events, which may guide the evaluation of new therapies.     

PALS1 is essential for retinal pigment epithelium structure and neural retina stratification

The membrane-associated palmitoylated protein 5 (MPP5 or PALS1) is thought to organize intracellular PALS1-CRB-MUPP1 protein scaffolds in the retina that are involved in maintenance of photoreceptor-Müller glia cell adhesion. In humans, the Crumbs homolog 1 (CRB1) gene is mutated in progressive types of autosomal recessive retinitis pigmentosa and Leber congenital amaurosis. However, there is no clear genotype-phenotype correlation for CRB1 mutations, which suggests that other components of the CRB complex may influence the severity of retinal disease. Therefore, to understand the physiological role of the Crumbs complex proteins, especially PALS1, we generated and analyzed conditional knockdown mice for Pals1. Small irregularly shaped spots were detected throughout the PALS1 deficient retina by confocal scanning laser ophthalmoscopy and spectral domain optical coherence tomography. The electroretinography a- and b-wave was severely attenuated in the aged mutant retinas, suggesting progressive degeneration of photoreceptors. The histological analysis showed abnormal retinal pigment epithelium structure, ectopic photoreceptor nuclei in the subretinal space, an irregular outer limiting membrane, half rosettes of photoreceptors in the outer plexiform layer, and a thinner photoreceptor synaptic layer suggesting improper photoreceptor cell layering during retinal development. The PALS1 deficient retinas showed reduced levels of Crumbs complex proteins adjacent to adherens junctions, upregulation of glial fibrillary acidic protein indicative of gliosis, and persisting programmed cell death after retinal maturation. The phenotype suggests important functions of PALS1 in the retinal pigment epithelium in addition to the neural retina.     

Crb1 is a determinant of retinal apical Müller glia cell features

Mutations in the human Crumbs homologue-1 (CRB1) gene cause retinal blinding diseases, such as Leber congenital amaurosis and retinitis pigmentosa. In the previous studies we have shown that Crb1 resides in retinal Müller glia cells and that loss of Crb1 results in retinal degeneration (particularly in the inferior temporal quadrant of the mouse eye). Degeneration is increased by exposure to white light. Here, we studied the role of light and aging to gain a better understanding of the factors involved in the progress of retinal disease. Our data reveal that light is neither sufficient nor required to induce retinal disorganization and degeneration in young Crb1(-/-) mutant mice, suggesting that it rather modulates the retinal phenotype. Gene expression profiling showed that expression of five genes is altered in light-exposed Crb1(-/-) mutant retinas. Three of the five genes are involved in chromosome stabilization (Pituitary tumor transforming gene 1 or Pttg1, Establishment of cohesion 1 homolog 1 or Esco1, and a gene similar to histone H2B). In aged retinas, degeneration of photoreceptors, inner retinal neurons, and retinal pigment epithelium was practically limited to the inferior temporal quadrant. Loss of Crb1 in Müller glia cells resulted in an irregular number and size of their apical villi. We propose that Crb1 is required to regulate number and size of these Müller glia cell villi. The subsequent loss of retinal integrity resulted in neovascularization, in which blood vessels of the choroid protruded into the neural retina.     

Microglial phagocytosis and activation underlying photoreceptor degeneration is regulated by CX3CL1‐CX3CR1 signaling in a mouse model of retinitis pigmentosa

Retinitis pigmentosa (RP), a disease characterized by the progressive degeneration of mutation‐bearing photoreceptors, is a significant cause of incurable blindness in the young worldwide. Recent studies have found that activated retinal microglia contribute to photoreceptor demise via phagocytosis and proinflammatory factor production, however mechanisms regulating these contributions are not well‐defined. In this study, we investigate the role of CX3CR1, a microglia‐specific receptor, in regulating microglia‐mediated degeneration using the well‐established rd10 mouse model of RP. We found that in CX3CR1‐deficient (CX3CR1^GFP/GFP) rd10 mice microglial infiltration into the photoreceptor layer was significantly augmented and associated with accelerated photoreceptor apoptosis and atrophy compared with CX3CR1‐sufficient (CX3CR1^GFP/+) rd10 littermates. CX3CR1‐deficient microglia demonstrated increased phagocytosis as evidenced by (1) having increased numbers of phagosomes in vivo, (2) an increased rate of phagocytosis of fluorescent beads and photoreceptor cellular debris in vitro, and (3) increased photoreceptor phagocytosis dynamics on live cell imaging in retinal explants, indicating that CX3CR1 signaling in microglia regulates the phagocytic clearance of at‐risk photoreceptors. We also found that CX3CR1 deficiency in retinal microglia was associated with increased expression of inflammatory cytokines and microglial activation markers. Significantly, increasing CX3CL1‐CX3CR1 signaling in the rd10 retina via exogenous intravitreal delivery of recombinant CX3CL1 was effective in (1) decreasing microglial infiltration, phagocytosis and activation, and (2) improving structural and functional features of photoreceptor degeneration. These results indicate that CX3CL1‐CX3CR1 signaling is a molecular mechanism capable of modulating microglial‐mediated degeneration and represents a potential molecular target in therapeutic approaches to RP. GLIA 2016;64:1479–1491     

Effect of glucocorticoids on neuronal and vascular pathology in a transgenic model of selective Müller cell ablation

Retinal diseases such as macular telangiectasis type 2 (MacTel), age‐related macular degeneration (AMD) and diabetic retinopathy (DR) affect both neurons and blood vessels. Treatments addressing both at the same time might have advantages over more specific approaches, such as vascular endothelial growth factor (VEGF) inhibitors, which are used to treat vascular leak but are suspected to have a neurotoxic effect. Here, we studied the effects of an intravitreal injection of triamcinolone acetonide (TA) in a transgenic model in which patchy Müller cell ablation leads to photoreceptor degeneration, vascular leak, and intraretinal neovascularization. TA was injected 4 days before Müller cell ablation. Changes in photoreceptors, microglia and Müller cells, retinal vasculature, differential expression of p75 neurotrophin receptor (p75^NTR), tumor necrosis factor‐α (TNFα), the precursor and mature forms of neurotrophin 3 (pro‐NT3 and mature NT3) and activation of the p53 and p38 stress‐activated protein kinase (p38/SAPK) signaling pathways were examined. We found that TA prevented photoreceptor degeneration and inhibited activation of microglial and Müller cells. TA attenuated Müller cell loss and inhibited overexpression of p75^NTR, TNFα, pro‐NT, and the activation of p53 and p38/SAPK signaling pathways. TA not only prevented the development of retinal vascular lesions but also inhibited fluorescein leakage from established vascular lesions. TA inhibited overexpression of VEGF in transgenic mice but without affecting its basal level expression in the normal retina. Our data suggest that glucocorticoid treatment may be beneficial for treatment of retinal diseases such as MacTel, AMD, and DR that affect both neurons and the vasculature. GLIA 2014;62:1110–1124     

Differential effects of bFGF on development of the rat retina

A variety of growth factors can influence the expression of differentiated properties by cell types of the developing retina. One unresolved question has been whether these factors can direct the differentiation pathway of uncommitted precursors or whether they act to help the expression of properties by already committed cells. To address this question we have studied the effects of basic fibroblast growth factor (bFGF) on the differentiation of ganglion cells and rod photoreceptors in explant cultures of embryonic rat retinas. Incubation of retinas in the presence of bFGF accelerated the appearance of differentiated ganglion cells and incubation in the presence of anti-bFGF antibodies delayed the appearance. bFGF had no effect on the appearance of differentiated rod photoreceptors as judged by expression of opsin, although all-trans-retinoic acid did increase the number of cells expressing opsin. bFGF inhibited the formation of rod photoreceptor rosettes suggesting that it does influence some properties of rods or the adjacent Müller glial cells. The results suggest that bFGF can alter the timing of differentiation of retinal ganglion cells but not direct their production from retinal precursors.     

Functional and neurochemical development in the normal and degenerating mouse retina

The rd1 mouse is a well‐established animal model for human retinitis pigmentosa (RP). We used electroretinography (ERG) to evaluate retinal function and postembedding immunocytochemistry to determine the changes in cellular amino acid expression in the normal (C57Bl6) and degenerating mouse retina (rd1), as a function of age during development and the onset of degeneration. In the normal mouse retina, photoreceptoral and post‐photoreceptoral ERG responses improved simultaneously from eye‐opening until adult levels were achieved at approximately postnatal day (P) 30. Maturation of amino acid neurochemistry preceded the development of retinal function in the normal retina. Amino acid levels increased immediately from birth and reached stable levels by eye‐opening. In contrast, in the rd1 mouse, both rod and cone pathway function rapidly reduced from eye‐opening and by P21 became undetectable. Interestingly, at P18 cone responses were still comparable between the normal and degenerating retina. Before eye opening, the pattern of amino acid immunoreactivity in the rd1 retina was similar to the normal retina. Alterations in neurochemistry were observed after the onset of rod photoreceptor cell death. The most obvious change was the reduction in neurotransmitter immunoreactivity within the synaptic layers and some cell classes of the rd1 retina. Reduction of glutamine and glutamate was observed in Müller cells before established gliosis markers. Overall, these results suggest the rapid maturation of neurochemistry by eye opening followed by functional maturation by P30 in the normal retina. The dystrophic retina displays similar neurochemistry to control retina before eye opening but a subsequent decline. J. Comp. Neurol. 521:1251–1267, 2013. © 2012 Wiley Periodicals, Inc.     

Pro‐survival redox signalling in progesterone‐mediated retinal neuroprotection

Retinitis pigmentosa (RP) is a group of hereditary retinal diseases, characterised by photoreceptor cell loss. Despite a substantial understanding of the mechanisms leading to cell death, an effective therapeutic strategy is sought. Our laboratory has previously demonstrated the neuroprotective properties of Norgestrel, a progesterone analogue, in the degenerating retina, mediated in part by the neurotrophic factor basic fibroblast growth factor (bFGF). In other retinal studies, we have also presented a pro‐survival role for reactive oxygen species (ROS), downstream of bFGF. Thus, we hypothesized that Norgestrel utilises bFGF‐driven ROS production to promote photoreceptor survival. Using the 661W photoreceptor‐like cell line, we now show that Norgestrel, working through progesterone receptor membrane complex 1 (PGRMC1); generates an early burst of pro‐survival bFGF‐induced ROS. Using the rd10 mouse model of RP, we confirm that Norgestrel induces a similar early pro‐survival increase in retinal ROS. Norgestrel‐driven protection in the rd10 retina was attenuated in the presence of antioxidants. This study therefore presents an essential role for ROS signalling in Norgestrel‐mediated neuroprotection in vitro and demonstrates that Norgestrel employs a similar pro‐survival mechanism in the degenerating retina.