To assess the efficacy of voretigene neparvovec (VN) treatment by objective fixation stability and chromatic pupillometry testing in clinical practice.
Retrospective cohort study with longitudinal ...follow-up.
Twelve patients (aged 7–34 years) with RPE65-related inherited retinal dystrophies were treated at the same center with VN in both eyes.
Patients treated at the same center with VN were evaluated over a 12-month posttreatment follow-up by subjective and objective tests. Furthermore, patients treated with VN who developed atrophy were compared with those who did not.
Best-corrected visual acuity (BCVA), full-field stimulus threshold test (FST), semiautomated kinetic visual field (SKVF), microperimetry, and chromatic pupillometry over a 12-month follow-up.
Significant improvements of BCVA (P < 0.001), SKVF (P < 0.05), and FST (P < 0.001) were already observed 45 days after treatment and were maintained at the 12-month timepoint. Fixation stability, assessed by microperimetry, improved significantly (P < 0.05) after treatment. Chromatic pupillometry showed significant improvements (P < 0.05) at the 6- and 12-month timepoints. The increase in maximum pupillary constriction significantly (P < 0.001) correlated with higher retinal sensitivity in FST. Four patients developed multifocal retinal atrophy in both eyes, detected at the 6-month timepoint, but this atrophy was not generally associated with worse visual function outcomes.
This study explores objective outcomes in order to demonstrate the efficacy of VN treatment in addition to the tests normally performed in clinical practice. Our findings show a significant improvement of retinal function both in subjective assessments, such as BCVA, SKVF, and FST, and in objective measurements of fixation stability and maximum pupillary constriction. Moreover, the significant correlation between maximum pupillary constriction and light sensitivity thresholds corroborates the introduction of chromatic pupillometry as an objective test to better assess treatment outcomes in patients with inherited retinal dystrophies.
Proprietary or commercial disclosure may be found after the references in the Footnotes and Disclosures at the end of this article.
Inherited retinal dystrophies caused by dominant mutations in photoreceptor (PR) cell expressed genes are a major cause of irreversible vision loss. Oligonucleotide therapy has been of interest in ...diseases that conventional medicine cannot target. In the early days, small interfering RNAs (siRNAs) were explored in clinical trials for retinal disorders with limited success due to a lack of stability and efficient cellular delivery. Thus, an unmet need exists to identify siRNA chemistry that targets PR cell expressed genes. Here, we evaluated 12 different fully chemically modified siRNA configurations, where the valency and conjugate structure were systematically altered. The impact on retinal distribution following intravitreal delivery was examined. We found that the increase in valency (tetravalent siRNA) supports the best PR accumulation. A single intravitreal administration induces multimonths efficacy in rodent and porcine retinas while demonstrating a good safety profile. The data suggest that this configuration can treat retinal diseases caused by PR cell expressed genes with 1–2 intravitreal injections per year.
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Punzo and colleagues have identified in a screen a chemically modified tetrameric siRNA that exhibits efficient long-term gene silencing in photoreceptor cells of mouse and swine eyes. This tetrameric siRNA chemistry may be used for the treatment of retinal diseases caused by mutations in photoreceptor cell expressed genes.
Background
With the promise of gene replacement therapy, eligible males and females with X‐linked inherited retinal dystrophy (XL‐IRD) should be identified.
Methods
Retrospective observational cohort ...study to establish the phenotypic and genotypic spectrum of XL‐IRD within New Zealand (NZ). Thirty‐two probands, including 9 females, with molecularly proven XL‐IRD due to RP2 or RPGR mutations, and 72 family members, of which 43 were affected, were identified from the NZ IRD Database. Comprehensive ophthalmic phenotyping, familial cosegregation, genotyping, and bioinformatics were undertaken. Main outcome measures were: RP2 and RPGR pathogenic variant spectrum, phenotype in males and females (symptoms, age of onset, visual acuity, refraction, electrophysiology, autofluorescence, retinal appearance), and genotype–phenotype correlation.
Results
For 32 families, 26 unique pathogenic variants were identified; in RP2 (n = 6, 21.9% of all families), RPGR exons 1–14 (n = 10, 43.75%), and RPGR‐ORF15 (n = 10, 34.3%). Three RP2 and 8 RPGR exons 1–14 variants are novel, rare, and cosegregate. Thirty‐one percent of carrier females were significantly affected, with 18.5% of families initially classified as autosomal dominant. Of five Polynesian families, 80% had novel disease‐causing variants. One Māori family showed keratoconus segregating with an ORF15 variant.
Conclusions
Significant disease was present in 31% of genetically proven female carriers, often leading to an erroneous presumption of the inheritance pattern. Pathogenic variants in 44% of the families were in exon 1–14 of RPGR, more frequent than usually described, which may inform the gene testing algorithm. Proving cosegregation in families for novel variants and identifying affected females and males translates to optimised clinical care and potential for gene therapy.
Conventional next‐generation sequencing methods, used in most gene panels, cannot separate maternally and paternally derived sequence information of distant variants. In recessive diseases, two or ...more equally plausible causative variants with unsolved phase information prevent accurate molecular diagnosis. In reality, close relatives might be unavailable for segregation analysis. Here, we utilized whole genome linked‐read sequencing to assign variants to haplotypes in two patients with inherited retinal dystrophies. Patient 1 with macular dystrophy had variants c.3442T>C, p.(Cys1148Arg), c.4209G>T, p.(Glu1403Asp), and c.1182C>T, p.(Cys394=) in CRB1, and Patient 2 with nonsyndromic retinitis pigmentosa had c.1328T>A, p.(Val443Asp) and c.3032C>G, p.(Ser1011*) in AHI1. The relatives were not available for genotyping. Using whole genome linked‐read sequencing we phased the variants to haplotypes providing genetic background for the retinal dystrophies. In future, when the price of sequencing methods that provides long‐read data decreases and their read‐depth and accuracy increases, they are probably considered the primary or adjunctive sequencing methods in genetic testing, allowing the immediate collection of phase information and thus obviating the need for the carrier testing and segregation analysis.
The purpose of this study was to assess the therapeutic efficacy of rAAV8-hGRK1-Tlcd3b in a Tlcd3b-/- mouse model of retinal generation and validate TLCD3B's role as a ceramide synthase in vivo.
...Using Tlcd3b-/- mice as an inherited retinal disease animal model, we performed subretinal injection of rAAV8-hGRK1-Tlcd3b and evaluated the efficacy of gene replacement therapy. Tlcd3b-/- mice were treated at two time points: postnatal day 21 (P21) and postnatal day 120 (P120) with various dosages.
Tlcd3b overexpression rescued retinal degeneration in the mutant mice, as indicated by significantly improved photoreceptor function and preservation of photoreceptor cells over the course of 1 year. Although Tlcd3b is expressed in all cell types in the retina, photoreceptor cell-specific expression of Tlcd3b is sufficient to rescue the phenotype, indicating the primary function of TLCD3B is in photoreceptors. Consistent with the idea that TLCD3B is a ceramide synthase, mass spectrometry analyses of the mutant retina indicate the reduction of C16-, C18-, and C20-ceramides in the retina, which are restored with Tlcd3b overexpression.
Our findings demonstrated the therapeutic efficacy of gene therapy in treating Tlcd3b mutant retina, laying the foundation for developing future therapy for TLCD3B retinopathy.
Induced pluripotent stem cells (iPSCs), reprogrammed from human somatic cells, hold the capacity to differentiate into most human body cells. iPSCs can be differentiated into retinal organoids, a ...three-dimensional structured retina containing various retinal cells. Patient-specific retinal organoids provide a powerful disease model to recapitulate the disease to study the pathogenesis of inherited retinal dystrophies, to screen or discover new drugs, and most importantly to supply an unlimited cell source for retinal regeneration.
Collectively, retinal neurodegenerative diseases are comprised of numerous subtypes of disorders which result in loss of a varying cell types in the retina. These diseases can range from glaucoma, ...which results in retinal ganglion cell death, to age-related macular degeneration and retinitis pigmentosa, which result in cell death of the retinal pigment epithelium, photoreceptors, or both. Regardless of the disease, it's been recently found that increased release of proinflammatory cytokines and proliferation of active microglia result in a remarkably proinflammatory microenvironment that assists in the pathogenesis of the disease; however, many of the details of these inflammatory events have yet to be elucidated. In an ongoing study, we have used systems genetics to identify possible models of spontaneous polygenic age-related macular degeneration by mining the BXD family of mice using single nucleotide polymorphism analyses of known genes associated with the human retinal disease. One BXD strain (BXD32) was removed from the study as the rate of degeneration observed in these animals was markedly increased with a resultant loss of most all photoreceptors by 6 months of age. Using functional and anatomical exams including optokinetic nystamography, funduscopy, fluorescein angiography, and optical coherence tomography, along with immunohistochemical analyses, we show that the BXD32 mouse strain exhibits a severe neurodegenerative phenotype accompanied by adverse effects on the retinal vasculature. We also expose the concurrent establishment of a chronic proinflammatory microenvironment including the TNFα secretion and activation of the NF-κB and JAK/STAT pathways with an associated increase in activated macrophages and phagoptosis. We conclude that the induced neuronal death and proinflammatory pathways work synergistically in the disease pathogenesis to enhance the rate of degeneration in this spontaneous polygenic model of inherited retinal dystrophy.
Increasing evidence has supported the role of ceramide as a mediator of photoreceptor dysfunction or cell death in ceramide accumulation and deficiency contexts. TLCD3B, a non-canonical ceramide ...synthase, was previously identified in addition to the six canonical ceramide synthases (CerSs), and the Tlcd3b-/- mouse model exhibited both retinal dysfunction and degeneration. As previous canonical CerS-deficient mouse models failed to display retinal degeneration, the mechanisms of how TLCD3B interacts with CerSs have not been investigated. Additionally, as the ceramide profile of each CerS is distinct, it is unclear whether the overall level or the homeostasis of different ceramide species plays a critical role in photoreceptor degeneration. Interactions between TLCD3B with canonical CerSs expressed in the retina were examined by subretinally injecting recombinant adeno-associated virus 8 vectors containing the Cers2 (rAAV8-CerS2), Cers4 (rAAV8-CerS4) and Cers5 (rAAV8-CerS5) genes. Injection of all three rAAV8-CerS vectors restored retinal functions as indicated by improved electroretinogram responses, but only rAAV8-CerS5 successfully retained retinal morphology in Tlcd3b-/- mice. CerSs and TLCD3B played partially redundant roles. Additionally, rather than acting as an integral entity, different ceramide species had different impacts on retinal cells, suggesting that the maintenance of the overall ceramide profile is critical for retinal function.
To report on the presence of autosomal dominant and compound dominant-null RP1-related retinitis pigmentosa in the same non-consanguineous family.
The father was minimally symptomatic and referred by ...his optometrist aged 38. He was diagnosed with rod-cone dystrophy, confirmed to be caused by the previously reported RP1 c.2613dupA mutation. He was reassured that his 11-year-old daughter had a 50% chance of inheriting the same mutation and that the condition, if she had it, would most likely be similar. Clinical phenotyping of his daughter however revealed an early onset cone-rod dystrophy. The mother was entirely asymptomatic and clinically normal. Sanger sequencing of the RP1 gene in the daughter confirmed the presence of biallelic mutations – the dominant c.2613dupA variant from her father and a c.3843dupT truncating variant inherited from her mother, both located in exon 4 of the RP1 gene. The maternal c.3843dupT has previously been reported.
Pathogenic variants in exon 4 of RP1 are known to cause differential dominant and recessive disease. The presence of both phenotypes in a single family has not yet been reported. The father, being minimally symptomatic, is affected by a known dominant variant which truncates the RP1 protein more proximally. However, inheritance of both variants in a compound heterozygous state in the daughter resulted in a much more severe, early onset cone-rod phenotype in a pattern akin to recessive disease. This raises challenges for genetic counselling and development of gene-based therapies for RP1 mutations.
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