Efficacy and Safety of Ranibizumab 0.5 mg for the Treatment of Macular Edema Resulting from Uncommon Causes: Twelve-Month Findings from PROMETHEUS.

PURPOSE: To evaluate the efficacy and safety of ranibizumab 0.5 mg in adult patients with macular edema (ME) resulting from any cause other than diabetes, retinal vein occlusion, or neovascular age-related macular degeneration. DESIGN: A phase 3, 12-month, double-masked, randomized, sham-controlled, multicenter study. PARTICIPANTS: One hundred seventy-eight eligible patients aged ≥18 years. METHODS: Patients were randomized 2:1 to receive either ranibizumab 0.5 mg (n = 118) or sham (n = 60) at baseline and month 1. From month 2, patients in both arms received open-label individualized ranibizumab treatment based on disease activity. A preplanned subgroup analysis was conducted on the primary end point on 5 predefined baseline ME etiologies (inflammatory/post-uveitis, pseudophakic or aphakic, central serous chorioretinopathy, idiopathic, and miscellaneous). MAIN OUTCOME MEASURES: Changes in best-corrected visual acuity (BCVA; Early Treatment Diabetic Retinopathy Study letters) from baseline to month 2 (primary end point) and month 12 and safety over 12 months. RESULTS: Overall, 156 patients (87.6%) completed the study. The baseline characteristics were well balanced between the treatment arms. Overall, ranibizumab showed superior efficacy versus sham from baseline to month 2 (least squares mean BCVA, +5.7 letters vs. +2.9 letters; 1-sided P = 0.0111), that is, a treatment effect (TE) of +2.8 letters. The mean BCVA gain from baseline to month 12 was 9.6 letters with ranibizumab. The TE at month 2 was variable in the 5 predefined etiology subgroups, ranging from >5-letter gain to 0.5-letter loss. The safety findings were consistent with the well-established safety profile of ranibizumab. CONCLUSIONS: The primary end point was met and ranibizumab showed superiority in BCVA gain over sham in treating ME due to uncommon causes, with a TE of +2.8 letters versus sham at month 2. At month 12, the mean BCVA gain was high (9.6 letters) in the ranibizumab arm; however, the TE was observed to be variable across the different etiology subgroups, reaching a >1-line TE in BCVA in patients with ME resulting from inflammatory conditions/post-uveitis or after cataract surgery. Overall, ranibizumab was well tolerated with no new safety findings up to month 12.

Sustained Benefits of Ranibizumab with or without Laser in Branch Retinal Vein Occlusion: 24-Month Results of the BRIGHTER Study.

PURPOSE: To evaluate the long-term (24-month) efficacy and safety of ranibizumab 0.5 mg administered pro re nata (PRN) with or without laser using an individualized visual acuity (VA) stabilization criteria in patients with visual impairment due to macular edema secondary to branch retinal vein occlusion (BRVO). DESIGN: Phase IIIb, open-label, randomized, active-controlled, 3-arm, multicenter study. PARTICIPANTS: A total of 455 patients. METHODS: Patients were randomized (2:2:1) to ranibizumab 0.5 mg (n = 183), ranibizumab 0.5 mg with laser (n = 180), or laser (with optional ranibizumab 0.5 mg after month 6; n = 92). After initial 3 monthly injections, patients in the ranibizumab with or without laser arms received VA stabilization criteria-driven PRN treatment. Patients assigned to the laser arm received laser at the investigator's discretion. MAIN OUTCOME MEASURES: Mean (and mean average) change in best-corrected visual acuity (BCVA) and central subfield thickness (CSFT) from baseline to month 24, and safety over 24 months. RESULTS: A total of 380 patients (83.5%) completed the study. Ranibizumab with or without laser led to superior BCVA outcomes versus laser (monotherapy and combined with ranibizumab from month 6; 17.3/15.5 vs. 11.6 letters; P < 0.0001). Ranibizumab with laser was noninferior to ranibizumab monotherapy (mean average BCVA change: 15.4 vs. 15.0 letters; P < 0.0001). However, addition of laser did not reduce the number of ranibizumab injections (mean injections: 11.4 vs. 11.3; P = 0.4259). A greater reduction in CSFT was seen with ranibizumab with or without laser versus laser monotherapy over 24 months from baseline (ranibizumab monotherapy -224.7 µm, ranibizumab with laser -248.9 µm, laser [monotherapy and combined with ranibizumab from month 6] -197.5 µm). Presence of macular ischemia did not affect BCVA outcome or treatment frequency. There were no reports of neovascular glaucoma or iris neovascularization. No new safety signals were identified. CONCLUSIONS: The BRIGHTER study results confirmed the long-term efficacy and safety profile of PRN dosing driven by individualized VA stabilization criteria using ranibizumab 0.5 mg in patients with BRVO. Addition of laser did not lead to better functional outcomes or lower treatment need. The safety results were consistent with the well-established safety profile of ranibizumab.

Individualized Ranibizumab Regimen Driven by Stabilization Criteria for Central Retinal Vein Occlusion: Twelve-Month Results of the CRYSTAL Study.

PURPOSE: To assess the 12-month efficacy and safety profile of an individualized regimen of ranibizumab 0.5 mg driven by stabilization criteria in patients with macular edema secondary to central retinal vein occlusion (CRVO). DESIGN: A 24-month, prospective, open-label, single-arm, multicenter study. PARTICIPANTS: Three hundred fifty-seven patients. METHODS: Patients were treated with monthly ranibizumab 0.5-mg injections (minimum of 3 injections) until stable visual acuity (VA) was maintained for 3 consecutive months. Thereafter, ranibizumab 0.5 mg was dosed as needed if monthly monitoring indicated a loss of VA resulting from disease activity. MAIN OUTCOME MEASURES: Mean change from baseline at month 12 in best-corrected VA (BCVA; primary end point) and safety over 12 months. The efficacy of this regimen in subgroups categorized by baseline BCVA score, CRVO duration, or presence of macular ischemia (exploratory analysis). RESULTS: At baseline, the mean BCVA was 53.0 letters and mean CRVO duration was 8.9 months (median, 2.4 months). Ranibizumab 0.5-mg treatment resulted in a statistically significant mean gain in BCVA from baseline at month 12 of 12.3 letters (standard deviation [SD], 16.72 letters; P < 0.0001). The mean number of ranibizumab injections up to month 12 was 8.1 (SD, 2.77). At month 12, mean BCVA gains were similar with or without macular ischemia at baseline (11.6 vs. 12.1 letters); the mean BCVA gain was higher with baseline CRVO duration of less than 3 months (13.4 letters) than with a longer duration (≥3-<9 months, 11.1 letters; ≥9 months, 10.9 letters). Patients with lower baseline BCVA had larger mean BCVA gains at month 12 than those with higher baseline BCVA (≤39/40-59/≥60 and 18.0/12.7/8.9 letters, respectively), although the absolute BCVA at month 12 was higher with higher baseline BCVA. No new ocular or nonocular safety events were observed. CONCLUSIONS: An individualized dosing regimen of ranibizumab 0.5 mg driven by stabilization criteria for up to 12 months resulted in significant BCVA gain in a broad population of patients with macular edema secondary to CRVO, including those with macular ischemia at baseline. The safety findings were consistent with those reported in previous ranibizumab studies in patients with CRVO.

Individualized Stabilization Criteria-Driven Ranibizumab versus Laser in Branch Retinal Vein Occlusion: Six-Month Results of BRIGHTER.

PURPOSE: To compare the 6-month efficacy and safety profile of an individualized stabilization criteria-driven pro re nata (PRN) regimen of ranibizumab 0.5 mg with or without laser versus laser alone in patients with visual impairment due to macular edema secondary to branch retinal vein occlusion (BRVO). DESIGN: A 24-month, prospective, open-label, randomized, active-controlled, multicenter, phase IIIb study. PARTICIPANTS: A total of 455 patients. METHODS: Eligible patients were randomized 2:2:1 to receive ranibizumab (n = 183), ranibizumab with laser (n = 180), or laser only (n = 92). Patients treated with ranibizumab with or without laser received a minimum of 3 initial monthly ranibizumab injections until visual acuity (VA) stabilization, and VA-based PRN dosing thereafter. In the ranibizumab with laser and laser-only groups, laser was given at the investigator's discretion at a minimum interval of 4 months and if VA was <79 letters. MAIN OUTCOME MEASURES: Mean change from baseline at month 6 in best-corrected visual acuity (BCVA) (primary end point) and central subfield thickness, and safety over 6 months. Exploratory objectives were to evaluate the influence of baseline BCVA, disease duration, and ischemia on BCVA outcomes at month 6. RESULTS: Baseline mean BCVA was 57.7 letters, and mean BRVO duration was 9.9 months. Ranibizumab with or without laser was superior to laser only in improving mean BCVA from baseline at month 6 (14.8 and 14.8 vs. 6.0 letters; both P < 0.0001; primary end point met). Patients with a shorter BRVO duration at baseline had a higher mean BCVA gain than those with a longer BRVO duration. Patients with a poor baseline VA had a better BCVA gain than those with a higher baseline VA, although final BCVA was lower in those with poor baseline VA. In the ranibizumab with or without laser groups, the presence of some macular ischemia at baseline did not influence mean BCVA gains. There were no new ocular or nonocular safety events. CONCLUSIONS: Ranibizumab with an individualized VA-based regimen, with or without laser, showed statistically significant superior improvement in BCVA compared with laser alone in patients with BRVO. Overall, there were no new safety events other than those reported in previous studies.

Single-Chain Antibody Fragment VEGF Inhibitor RTH258 for Neovascular Age-Related Macular Degeneration: A Randomized Controlled Study.

PURPOSE: To assess the safety and efficacy of different doses of RTH258 applied as single intravitreal administration compared with ranibizumab 0.5 mg in patients with neovascular age-related macular degeneration (AMD). DESIGN: Six-month, phase 1/2, prospective, multicenter, double-masked, randomized, ascending single-dose, active-controlled, parallel-group study. PARTICIPANTS: A total of 194 treatment-naive patients, aged ≥50 years, with primary subfoveal choroidal neovascularization secondary to AMD. METHODS: Patients received a single intravitreal injection of RTH258 0.5 mg (n = 11), 3.0 mg (n = 31), 4.5 mg (n = 47), or 6.0 mg (n = 44), or ranibizumab 0.5 mg (n = 61). MAIN OUTCOME MEASURES: The primary efficacy end point was the change from baseline to month 1 in central subfield thickness (CSFT) measured by spectral-domain optical coherence tomography. The secondary efficacy end point was the duration of treatment effect measured as time from the initial injection to receipt of post-baseline therapy (PBT) guided by protocol-defined criteria. Adverse events (AEs) were recorded throughout the study. RESULTS: RTH258 demonstrated noninferiority compared with ranibizumab in mean change in CSFT from baseline to month 1 for the 4.5- and 6.0-mg dose groups (margin: 40 µm, 1-sided alpha 0.05). The difference in CSFT change at month 1 comparison with ranibizumab was 22.86 µm (90% confidence interval [CI], -9.28 to 54.99) and 19.40 µm (95% CI, -9.00 to 47.80) for RTH258 4.5 and 6 mg, respectively. The median time to PBT after baseline therapy was 60 and 75 days for patients in the RTH258 4.5- and 6.0-mg groups, respectively, compared with 45 days for ranibizumab. Changes in best-corrected visual acuity with RTH258 were comparable to those observed with ranibizumab. The most frequent AEs reported for the RTH258 groups were conjunctival hemorrhage, eye pain, and conjunctival hyperemia; the majority of these events were mild in intensity. CONCLUSIONS: This first-in-human study of RTH258 demonstrated noninferiority in the change in CSFT at 1 month for the 4.5- and 6.0-mg doses compared with ranibizumab and an increase of 30 days in the median time to PBT for the 6.0-mg dose. There were no unexpected safety concerns, and the results support the continued development of RTH258 for the treatment of neovascular AMD.

Visual Function Measurements in Eyes With Diabetic Retinopathy: An Expert Opinion on Available Measures.

Clinical Relevance: Visual function impairment from diabetic retinopathy can have a considerable impact on patient's quality of life. Best-corrected visual acuity (BCVA) is most commonly used to assess visual function and guide clinical trials. However, BCVA is affected late in the disease process, is not affected in early disease, and does not capture some of the visual disturbances described by patients with diabetes. The goal of this report is to evaluate the relationship between diabetic retinal disease (DRD) and visual function parameters to determine which if any of them may be used in a future DRD staging system. Methods: The visual functions working group was 1 of 6 areas of DRD studied as part of the DRD staging system update, a project of the Mary Tyler Moore Vision Initiative. The working group identified 12 variables of possible interest, 7 of which were judged to have sufficient preliminary data to suggest an association with DR to warrant further review: microperimetry, static automated perimetry, electroretinogram (ERG) oscillatory potentials, flicker ERG, low luminance visual acuity (LLVA), contrast sensitivity (CS), and BCVA. The objective field analyzer (OFA) was added after subsequent in-person workshops. Results: Currently, the only visual function test available for immediate use is BCVA; the remaining tests are either promising (within 5 years) or have potential (>5 years) use. Besides BCVA, most visual function tests had a limited role in current clinical care; however, LLVA, CS, flicker ERG, and OFA demonstrated potential for screening and research purposes. Conclusions: Although current visual function tests are promising, future prospective studies involving patients with early and more advanced retinopathy are necessary to determine if these tests can be used clinically or as endpoints for clinical studies. Financial Disclosures: Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Evidence for two apoptotic pathways in light-induced retinal degeneration.

Excessive phototransduction signaling is thought to be involved in light-induced and inherited retinal degeneration. Using knockout mice with defects in rhodopsin shut-off and transducin signaling, we show that two different pathways of photoreceptor-cell apoptosis are induced by light. Bright light induces apoptosis that is independent of transducin and accompanied by induction of the transcription factor AP-1. By contrast, low light induces an apoptotic pathway that requires transducin. We also provide evidence that additional genetic factors regulate sensitivity to light-induced damage. Our use of defined mouse mutants resolves some of the complexity underlying the mechanisms that regulate susceptibility to retinal degeneration.

In conditions of limited chromophore supply rods entrap 11-cis-retinal leading to loss of cone function and cell death.

RPE65 is a retinoid isomerase required for the production of 11-cis-retinal, the chromophore of both cone and rod visual pigments. We recently established an R91W knock-in mouse strain as homologous animal model for patients afflicted by this mutation in RPE65. These mice have impaired vision and can only synthesize minute amounts of 11-cis-retinal. Here, we investigated the consequences of this chromophore insufficiency on cone function and pathophysiology. We found that the R91W mutation caused cone opsin mislocalization and progressive geographic cone atrophy. Remnant visual function was mostly mediated by rods. Ablation of rod opsin corrected the localization of cone opsin and improved cone retinal function. Thus, our analyses indicate that under conditions of limited chromophore supply rods and cones compete for 11-cis-retinal that derives from regeneration pathway(s) which are reliant on RPE65. Due to their higher number and the instability of cone opsin, rods are privileged under this condition while cones suffer chromophore deficiency and degenerate. These findings reinforce the notion that in patients any effective gene therapy with RPE65 needs to target the cone-rich macula directly to locally restore the cones' chromophore supply outside the reach of rods.

HIF-1-induced erythropoietin in the hypoxic retina protects against light-induced retinal degeneration.

Erythropoietin (Epo) is upregulated by hypoxia and provides protection against apoptosis of erythroid progenitors in bone marrow and brain neurons. Here we show in the adult mouse retina that acute hypoxia dose-dependently stimulates expression of Epo, fibroblast growth factor 2 and vascular endothelial growth factor via hypoxia-inducible factor-1alpha (HIF-1alpha) stabilization. Hypoxic preconditioning protects retinal morphology and function against light-induced apoptosis by interfering with caspase-1 activation, a downstream event in the intracellular death cascade. In contrast, induction of activator protein-1, an early event in the light-stressed retina, is not affected by hypoxia. The Epo receptor required for Epo signaling localizes to photoreceptor cells. The protective effect of hypoxic preconditioning is mimicked by systemically applied Epo that crosses the blood retina barrier and prevents apoptosis even when given therapeutically after light insult. Application of Epo may, through the inhibition of apoptosis, be beneficial for the treatment of different forms of retinal disease.

R91W mutation in Rpe65 leads to milder early-onset retinal dystrophy due to the generation of low levels of 11-cis-retinal.

RPE65 is a retinal pigment epithelial protein essential for the regeneration of 11-cis-retinal, the chromophore of cone and rod visual pigments. Mutations in RPE65 lead to a spectrum of retinal dystrophies ranging from Leber's congenital amaurosis to autosomal recessive retinitis pigmentosa. One of the most frequent missense mutations is an amino acid substitution at position 91 (R91W). Affected patients have useful cone vision in the first decade of life, but progressively lose sight during adolescence. We generated R91W knock-in mice to understand the mechanism of retinal degeneration caused by this aberrant Rpe65 variant. We found that in contrast to Rpe65 null mice, low but substantial levels of both RPE65 and 11-cis-retinal were present. Whereas rod function was impaired already in young animals, cone function was less affected. Rhodopsin metabolism and photoreceptor morphology were disturbed, leading to a progressive loss of photoreceptor cells and retinal function. Thus, the consequences of the R91W mutation are clearly distinguishable from an Rpe65 null mutation as evidenced by the production of 11-cis-retinal and rhodopsin as well as by less severe morphological and functional disturbances at early age. Taken together, the pathology in R91W knock-in mice mimics many aspects of the corresponding human blinding disease. Therefore, this mouse mutant provides a valuable animal model to test therapeutic concepts for patients affected by RPE65 missense mutations.

Bone spicule pigment formation in retinitis pigmentosa: insights from a mouse model.

BACKGROUND: Bone spicule pigments (BSP) are a hallmark of retinitis pigmentosa (RP). In this study, we examined the process of BSP formation in the rhodopsin knockout (rho (-/-)) mouse, a murine model for human RP. METHODS: In rho (-/-) mice from 2 to 16 months of age, representing the range from early to late stages of degeneration, retinal sections and whole mounts were examined morphologically by light and electron microscopy. The results were compared to scanning laser ophthalmoscopy of BSP degeneration in human RP. RESULTS: After the loss of all photoreceptor cells in rho-/- mice, the outer retina successively degenerated, leading to approximation and finally a direct contact of inner retinal vessels and the retinal pigment epithelium (RPE). We could show that it was the event of proximity of retinal vessel and RPE that triggered migration of RPE cells along the contacting vessels towards the inner retina. Ultrastructurally, these mislocalized RPE cells partially sealed the vessels by tight junction linkage and deposited extracellular matrix perivascularly. Also, the vascular endothelium developed fenestrations similar to the RPE-choroid interface. In whole mounts, the pigmented cell clusters outlining retinal capillaries correlated well with BSPs in human RP. The structure of the inner retina remained well preserved, even in late stages. CONCLUSIONS: The Rho (-/-) mouse is the first animal model that depicts all major pathological changes, even in the late stages of RP. Using the rho (-/-) mouse model we were able to analyze the complete dynamic process of BSP formation. Therefore we conclude that: (1) In rho (-/-) retinas, BSPs only form in areas devoid of photoreceptors; (2) Direct contact between inner retinal vessels and RPE appears to be a major trigger for migration of RPE cells; (3) The distribution of the RPE cells in BSPs reflects the vascular network at the time of formation. The similarity of the disease process between mouse and human and the possibility to study all consecutive steps of the course of the disease makes the rho (-/-) mouse valuable for further insights in the dynamics of BSP formation in human RP.

Analysis of the retinal gene expression profile after hypoxic preconditioning identifies candidate genes for neuroprotection.

BACKGROUND: Retinal degeneration is a main cause of blindness in humans. Neuroprotective therapies may be used to rescue retinal cells and preserve vision. Hypoxic preconditioning stabilizes the transcription factor HIF-1alpha in the retina and strongly protects photoreceptors in an animal model of light-induced retinal degeneration. To address the molecular mechanisms of the protection, we analyzed the transcriptome of the hypoxic retina using microarrays and real-time PCR. RESULTS: Hypoxic exposure induced a marked alteration in the retinal transcriptome with significantly different expression levels of 431 genes immediately after hypoxic exposure. The normal expression profile was restored within 16 hours of reoxygenation. Among the differentially regulated genes, several candidates for neuroprotection were identified like metallothionein-1 and -2, the HIF-1 target gene adrenomedullin and the gene encoding the antioxidative and cytoprotective enzyme paraoxonase 1 which was previously not known to be a hypoxia responsive gene in the retina. The strongly upregulated cyclin dependent kinase inhibitor p21 was excluded from being essential for neuroprotection. CONCLUSION: Our data suggest that neuroprotection after hypoxic preconditioning is the result of the differential expression of a multitude of genes which may act in concert to protect visual cells against a toxic insult.

Sustained Benefits from Ranibizumab for Central Retinal Vein Occlusion with Macular Edema: 24-Month Results of the CRYSTAL Study.

PURPOSE: To assess the efficacy and safety profile of an individualized, stabilization criteria-driven regimen of ranibizumab 0.5 mg in patients with visual impairment due to macular edema secondary to central retinal vein occlusion (CRVO). DESIGN: A 24-month, prospective, open-label, single-arm, multicenter study. PARTICIPANTS: A total of 357 patients. METHODS: Patients received monthly ranibizumab 0.5 mg injections (minimum, 3 injections) until stable visual acuity (VA) was maintained for 3 consecutive months. Thereafter, ranibizumab 0.5 mg injections were administered if monitoring indicated a loss of VA due to disease activity. The primary outcome results have been published previously. MAIN SECONDARY OUTCOME MEASURES: Mean change from baseline at months 1 through 24 in best-corrected VA (BCVA) in the overall population and in subgroups categorized according to baseline BCVA, CRVO duration, or presence of macular ischemia. RESULTS: The baseline mean BCVA was 53.0 letters and baseline mean CRVO duration was 8.9 months (median, 2.4 months). The mean (standard deviation) gain in BCVA from baseline with ranibizumab 0.5 mg at month 24 was 12.1 (18.60) letters (P < 0.0001). Best-corrected VA gains at month 24 were similar in patients with or without baseline macular ischemia (mean change, 11.1 and 12.9 letters, respectively). The mean BCVA gain at month 24 was higher in patients with CRVO duration <3 months (13.2 letters) compared with that in those with CRVO duration >9 months (10.5 letters). Patients with lower baseline BCVA had larger mean BCVA gains at month 24 (≤39 letters; 18.5 letters) than those with higher baseline BCVA (40-59/≥60 letters; 13.9/7.2 letters), although the absolute BCVA values at month 24 were higher in patients with higher baseline BCVA. The mean (standard deviation) and median number of ranibizumab injections up to month 23 were 13.1 (6.39) and 15.0 injections, respectively. No new ocular or nonocular safety events were reported. CONCLUSION: An individualized, stabilization criteria-driven dosing regimen of ranibizumab 0.5 mg led to sustained BCVA gains for up to 24 months in patients with CRVO. The presence of macular ischemia at baseline did not influence VA gains. Shorter duration of CRVO at baseline was associated with better VA gains. Safety findings were consistent with those reported in previous ranibizumab studies in patients with CRVO.

RPE65 is essential for the function of cone photoreceptors in NRL-deficient mice.

PURPOSE: Phototransduction in cones is initiated by the bleaching of their visual pigment, which comprises a protein component-cone opsin-and a vitamin A derivative-11-cis retinal. Little is known about the source of 11-cis retinal for cones. In the current study, neural retina leucine zipper-deficient (Nrl(-/-)) and rod opsin (Rho(-/-))-deficient mice were used, two mouse models that have been described as having a "cone-only" retina, to analyze the retinoid metabolism of cones. In addition, these mice were bred to retinal pigment epithelial protein 65 (Rpe65(-/-))-deficient mice to study the role of RPE65. METHODS: Mice were analyzed using morphology, Western blot analysis, immunohistochemistry, electroretinography (ERG), and retinoid profiling by HPLC. RESULTS: In comparison to wild-type mice, the retina of Nrl(-/-) mice contained elevated levels of RPE65 and cellular retinaldehyde-binding protein (CRALBP), suggesting a particular role of these two proteins for the retinoid metabolism of cones. In Nrl(-/-) mice, different retinoid species were present in proportions similar to wild type. Ablation of RPE65 in Nrl(-/-) and Rho(-/-) mice led to the absence of 11-cis retinal, but increased the total retinoid content, with retinyl esters representing the most abundant retinoid species. In the absence of RPE65, retinal sensitivity in Nrl(-/-) mice dropped by a factor of a thousand. CONCLUSIONS: The data show that RPE65, previously shown to be essential for rod function, is also indispensable for the production of 11-cis retinal for cones and thus for cone function.

Differential role of Jak-STAT signaling in retinal degenerations.

Retinal degeneration is a major cause of severe visual impairment or blindness. Understanding the underlying molecular mechanisms is a prerequisite to develop therapeutic approaches for human patients. We show in three mouse models that induced and inherited retinal degeneration induces LIF and CLC as members of the interleukin (IL)-6 family of proteins, activates proteins of the Jak-STAT signaling pathway, and up-regulates suppressors of cytokine signaling as a negative feedback loop. Inhibition of Jak2 leads to protection of photoreceptors in a model of induced but not in a model of inherited retinal degeneration. Differential activation of Akt suggests alternative pathways for cell death and/or survival in different models. Proteins induced during photoreceptor degeneration are not mainly expressed in photoreceptors but in cells of other retinal layers. This suggests a model in which photoreceptor injury is signaled to cells of the inner retina, which in turn initiate a response either to support viability or accelerate death of injured cells.

Lentiviral gene transfer of RPE65 rescues survival and function of cones in a mouse model of Leber congenital amaurosis.

BACKGROUND: RPE65 is specifically expressed in the retinal pigment epithelium and is essential for the recycling of 11-cis-retinal, the chromophore of rod and cone opsins. In humans, mutations in RPE65 lead to Leber congenital amaurosis or early-onset retinal dystrophy, a severe form of retinitis pigmentosa. The proof of feasibility of gene therapy for RPE65 deficiency has already been established in a dog model of Leber congenital amaurosis, but rescue of the cone function, although crucial for human high-acuity vision, has never been strictly proven. In Rpe65 knockout mice, photoreceptors show a drastically reduced light sensitivity and are subject to degeneration, the cone photoreceptors being lost at early stages of the disease. In the present study, we address the question of whether application of a lentiviral vector expressing the Rpe65 mouse cDNA prevents cone degeneration and restores cone function in Rpe65 knockout mice. METHODS AND FINDINGS: Subretinal injection of the vector in Rpe65-deficient mice led to sustained expression of Rpe65 in the retinal pigment epithelium. Electroretinogram recordings showed that Rpe65 gene transfer restored retinal function to a near-normal pattern. We performed histological analyses using cone-specific markers and demonstrated that Rpe65 gene transfer completely prevented cone degeneration until at least four months, an age at which almost all cones have degenerated in the untreated Rpe65-deficient mouse. We established an algorithm that allows prediction of the cone-rescue area as a function of transgene expression, which should be a useful tool for future clinical trials. Finally, in mice deficient for both RPE65 and rod transducin, Rpe65 gene transfer restored cone function when applied at an early stage of the disease. CONCLUSIONS: By demonstrating that lentivirus-mediated Rpe65 gene transfer protects and restores the function of cones in the Rpe65(-/-) mouse, this study reinforces the therapeutic value of gene therapy for RPE65 deficiencies, suggests a cone-preserving treatment for the retina, and evaluates a potentially effective viral vector for this purpose.

Caspase-1 ablation protects photoreceptors in a model of autosomal dominant retinitis pigmentosa.

PURPOSE: Caspase-1 gene expression has been reported to be upregulated during light-induced retinal degeneration and to be reduced after neuroprotective treatments. Thus, caspase-1 may be proapoptotic in the retina. To test directly the role of caspase-1 in photoreceptor apoptosis, three mouse models were analyzed for retinal degeneration in the presence or absence of caspase-1. METHODS: Photoreceptor apoptosis was monitored in one model of induced (exposure to light) and in two models of inherited (rd1, VPP) retinal degeneration. Retinal degeneration was assessed qualitatively by light microscopy and quantitatively by the determination of free nucleosomes with ELISA or by rhodopsin measurements. Gene expression and protein levels were assessed by real-time RT-PCR and by Western blot analysis, respectively. RESULTS: Levels of caspase-1 proenzyme increased in all models of retinal degeneration concomitantly with the onset of cell death. Maturation or classic activity of caspase-1 was not detected in the retina. Ablation of caspase-1 was protective in the model of adRP (VPP mouse), but not in the two other models. Ablation of interleukin-1 receptor type 1 was without effect. Expression of monocyte chemoattractant protein (MCP)-1 increased in the model protected by caspase-1 ablation. CONCLUSIONS: Increased retinal expression of caspase-1 proenzyme may be a common marker for photoreceptor degeneration. The differential effects of caspase-1 ablation suggests a modulatory role of caspase-1 for photoreceptor apoptosis in some but not all models. Such a modulatory activity may involve a caspase-1 function different from the classic activation of interleukin-1beta.