Long-Term Follow-Up After Unilateral Intravitreal Gene Therapy for Leber Hereditary Optic Neuropathy: The RESTORE Study

BACKGROUND

RESCUE and REVERSE were 2 Phase 3 clinical trials that assessed the efficacy and safety of intravitreal gene therapy with lenadogene nolparvovec (rAAV2/2-ND4) for the treatment of Leber hereditary optic neuropathy (LHON). RESTORE is the long-term follow-up study of subjects treated in the RESCUE and REVERSE trials.

METHODS

In RESCUE and REVERSE, 76 subjects with LHON because of the m.11778 G>A mutation in the mitochondrial gene ND4 received a single unilateral intravitreal injection of lenadogene nolparvovec. After 96 weeks, 61 subjects were enrolled in the long-term follow-up study RESTORE. The best-corrected visual acuity (BCVA) was assessed over a period of up to 52 months after onset of vision loss. A locally estimated scatterplot smoothing regression model was used to analyze changes in BCVA over time. Vision-related quality of life was reported using the visual function questionnaire-25 (VFQ-25).

RESULTS

The population of MT-ND4 subjects enrolled in RESTORE was representative of the combined cohorts of RESCUE and REVERSE for mean age (35.1 years) and gender distribution (79% males). There was a progressive and sustained improvement of BCVA up to 52 months after the onset of vision loss. The final mean BCVA was 1.26 logarithm of the minimal angle of resolution 48 months after the onset of vision loss. The mean VFQ-25 composite score increased by 7 points compared with baseline.

CONCLUSION

The treatment effect of lenadogene nolparvovec on BCVA and vision-related quality of life observed 96 weeks (2 years) after treatment in RESCUE and REVERSE was sustained at 3 years in RESTORE, with a maximum follow-up of 52 months (4.3 years) after the onset of vision loss.

Cross-Sectional Analysis of Baseline Visual Parameters in Subjects Recruited Into the RESCUE and REVERSE ND4-LHON Gene Therapy Studies

OBJECTIVE

This report presents a cross-sectional analysis of the baseline characteristics of subjects with Leber hereditary optic neuropathy enrolled in the gene therapy trials RESCUE and REVERSE, to illustrate the evolution of visual parameters over the first year after vision loss.

METHODS

RESCUE and REVERSE were 2 phase III clinical trials designed to assess the efficacy of rAAV2/2-ND4 gene therapy in ND4-LHON subjects. At enrollment, subjects had vision loss for ≤6 months in RESCUE, and between 6 and 12 months in REVERSE. Functional visual parameters (best-corrected visual acuity [BCVA], contrast sensitivity [CS], and Humphrey Visual Field [HVF]) and structural parameters assessed by spectral-domain optical coherence tomography were analyzed in both cohorts before treatment. The cross-sectional analysis of functional and anatomic parameters included the baseline values collected in all eyes at 2 different visits (Screening and Inclusion).

RESULTS

Seventy-six subjects were included in total, 39 in RESCUE and 37 in REVERSE. Mean BCVA was significantly worse in RESCUE subjects compared with REVERSE subjects (1.29 and 1.61 LogMAR respectively, P = 0.0029). Similarly, mean CS and HVF were significantly more impaired in REVERSE vs RESCUE subjects (P < 0.005). The cross-sectional analysis showed that the monthly decrease in BCVA, ganglion cell layer macular volume, and retinal nerve fiber layer thickness was much more pronounced in the first 6 months after onset (+0.24 LogMAR, -0.06 mm3, and -6.00 μm respectively) than between 6 and 12 months after onset (+0.02 LogMAR, -0.01 mm3, and -0.43 μm respectively).

CONCLUSION

LHON progresses rapidly in the first months following onset during the subacute phase, followed by relative stabilization during the dynamic phase.

Visual Outcomes in Leber Hereditary Optic Neuropathy Patients With the m.11778G>A (MTND4) Mitochondrial DNA Mutation

BACKGROUND

Leber hereditary optic neuropathy (LHON) is a maternally inherited bilaterally blinding optic neuropathy, predominantly affecting otherwise healthy young individuals, mostly men. The visual prognosis is generally poor, with most patients worsening to at least 20/200 visual acuity. The m.11778G>A (MTND4) mitochondrial DNA mutation is the most common cause of LHON and is associated with poor outcomes and limited potential for meaningful visual recovery. Treatments for LHON are limited, and clinical trials are hampered by inadequate data regarding the natural history of visual loss and recovery. In this article, we review the current literature specifically related to visual function of LHON patients with the m.11778G>A mutation.

EVIDENCE ACQUISITION

Literature review was performed using MEDLINE through PubMed, Cochrane Reviews Library, and Orpha.net with search terms of "Leber hereditary optic neuropathy," "LHON," "ND4," "G11778A," "visual acuity," "nadir," "natural history," and "registry." All English-language, peer-reviewed publications with study cohorts of at least 5 LHON patients with the molecularly confirmed m.11778G>A mutation were included.

RESULTS

Meta-analysis of 12 retrospective and 3 prospective studies provided visual function information on 695 LHON patients with the m.11778G>A mutation, 100 (14.4%) of whom were reported to have "recovered" some vision, although definitions of "recovery" varied among studies and idebenone use could not always be excluded. When incorporating age at onset of visual loss into the analyses, and specifically addressing those patients aged 15 years or older, meaningful visual recovery occurred in 23 of 204 (11.3%) patients. A younger age at onset, especially less than 12 years, portends a better visual prognosis and a different natural history of visual loss progression and recovery than in adults.

CONCLUSIONS

The classic presentation of LHON patients with the m.11778G>A mutation of severe visual loss with rare or poor recovery from nadir still holds true for most affected individuals. Among patients 15 years and older, recovery of meaningful vision likely occurs in less than 20% of patients, irrespective of how recovery is defined, and ultimate visual acuities of better than 20/200 are rare. Adequate prospective studies with sufficient sample sizes of genotypically homogeneous untreated LHON patients stratified by age, immediately enrolled when symptomatic, followed regularly for adequate periods of time with consistent measures of visual function, and analyzed with a standard definition of visual improvement are unfortunately lacking. Future clinical trials for LHON will require more standardized reporting of the natural history of this disorder.

Real-World Clinical Experience With Idebenone in the Treatment of Leber Hereditary Optic Neuropathy

BACKGROUND

Leber hereditary optic neuropathy (LHON) leads to bilateral central vision loss. In a clinical trial setting, idebenone has been shown to be safe and to provide a trend toward improved visual acuity, but long-term evidence of effectiveness in real-world clinical practice is sparse.

METHODS

Open-label, multicenter, retrospective, noncontrolled analysis of long-term visual acuity and safety in 111 LHON patients treated with idebenone (900 mg/day) in an expanded access program. Eligible patients had a confirmed mitochondrial DNA mutation and had experienced the onset of symptoms (most recent eye) within 1 year before enrollment. Data on visual acuity and adverse events were collected as per normal clinical practice. Efficacy was assessed as the proportion of patients with either a clinically relevant recovery (CRR) or a clinically relevant stabilization (CRS) of visual acuity. In the case of CRR, time to and magnitude of recovery over the course of time were also assessed.

RESULTS

At time of analysis, 87 patients had provided longitudinal efficacy data. Average treatment duration was 25.6 months. CRR was observed in 46.0% of patients. Analysis of treatment effect by duration showed that the proportion of patients with recovery and the magnitude of recovery increased with treatment duration. Average gain in best-corrected visual acuity for responders was 0.72 logarithm of the minimal angle of resolution (logMAR), equivalent to more than 7 lines on the Early Treatment Diabetic Retinopathy Study (ETDRS) chart. Furthermore, 50% of patients who had a visual acuity below 1.0 logMAR in at least one eye at initiation of treatment successfully maintained their vision below this threshold by last observation. Idebenone was well tolerated, with most adverse events classified as minor.

CONCLUSIONS

These data demonstrate the benefit of idebenone treatment in recovering lost vision and maintaining good residual vision in a real-world setting. Together, these findings indicate that idebenone treatment should be initiated early and be maintained more than 24 months to maximize efficacy. Safety results were consistent with the known safety profile of idebenone.

What are the characteristics and progression of visual field defects in patients with Leber hereditary optic neuropathy: a prospective single-centre study in China

OBJECTIVE

To study the characteristics and progression of visual field defects in patients with Leber hereditary optic neuropathy.

DESIGN

Prospective study.

SETTING

3-A-class hospital in China; single-centre study.

PARTICIPANTS

From 100 patients diagnosed with Leber hereditary optic neuropathy, 80 (160 eyes; 68 men and 12 women; youngest patient, 6 years; oldest patient, 35 years) were recruited.

EXPOSURE

All patients were followed up for at least 12 months. Each patient underwent at least three visual field examinations. Patient groups 1-6 were created according to the time of visual field data acquisition. Patient group 7 included patients with a different onset of disease between eyes. Group 8 was composed of patients with a course of disease of 12-24 months when one of the examinations performed. Patients who performed the third examination made up patient group 9.

PRIMARY OUTCOME MEASURES

Prevalence of the different visual field defect types on the basis of severity in groups 1-6. Mean of the difference of visual function between eyes in group 7.

RESULT

In groups 1-6, the prevalences of defects classified using Visual Field Index values were significantly different between groups 1 and 3. In group 7, with the prolongation of the course of the disease, the mean of the difference of visual function between eyes decreased. There was no significant correlation between age and the severity of visual field defect. There was significant correlation between visual acuity and the severity of visual field defect.

CONCLUSION

Visual field defects in patients with Leber hereditary optic neuropathy (G11778A) may continuously progress within 6 months of disease development, and remain stable after 9 months. With the progression of the disease, the differences in visual function between eyes may decrease. The severity of visual field defect seems to be independent of age; however, could be related to visual acuity.

TRIAL REGISTRATION NUMBER

NCT03428178, NCT01267422.

Mitophagy activation repairs Leber's hereditary optic neuropathy-associated mitochondrial dysfunction and improves cell survival

Leber's hereditary optic neuropathy (LHON) is a classical mitochondrial disease caused by mutations in the mitochondrial DNA encoding complex I subunits. Oxidative stress associated with complex I defect has been implicated in developing LHON phenotype such as retinal ganglion cell (RGC) death and loss of vision. However, the mechanism of LHON pathogenesis is still not very clear and thus no effective therapies are available to date. Using cybrid models for LHON, we show that autophagy is significantly compromised in cells carrying LHON-specific mtDNA mutations, which results in reduced clearance of dysfunctional mitochondria contributing to cell death. We further show that pharmacological activation of autophagy selectively clears the damaged mitochondria and thus repairs mitochondrial defects and improves overall cell survival in LHON cell models. Our results suggest that compromised autophagy is the missing link from oxidative stress to LHON pathogenesis. Activation of mitophagy ameliorates mitochondrial defects and exerts a protective role by improving cell survival in cells carrying LHON mutations that could be utilized as a potential therapeutic target for LHON treatment.

Mitochondrial DNA copy number in affected and unaffected LHON mutation carriers

OBJECTIVES

Leber's hereditary optic neuropathy (LHON) is a mitochondrial genetic disease characterized by a variable and reduced penetrance. Individuals carrying a primary LHON-causing mitochondrial DNA (mtDNA) mutation may either remain asymptomatic lifelong, as unaffected carriers, or develop sudden central visual loss that rapidly aggravates over some weeks. Over the years several genetic/environmental triggers able to modulate the risk of developing LHON have been proposed. We provided data supporting a possible correlation between LHON penetrance and the mtDNA copy number, a raw index of mitochondrial mass, whose increase could represent a compensatory response that cells implement to alleviate the pathogenic effect of the primary LHON-causing mtDNA mutations.

DATA DESCRIPTION

We collected Italian and Spanish subjects harboring one of the three common LHON primary mutations, either in heteroplasmic or homoplasmic status. For each population we were able to discriminate between affected subjects presenting typical clinical tracts of LHON and LHON-causing mutation carriers showing no symptoms correlated with vision loss. Each subject has been characterized for the presence of a LHON primary mutation, for its status of homoplasmy or heteroplasmy, and for the mtDNA content per cell, expressed as relative mtDNA/nDNA ratio respect to controls. Additional clinical information is present for all the Italian subjects.

A Review of Mitochondrial Optic Neuropathies: From Inherited to Acquired Forms

In recent years, the term mitochondrial optic neuropathy (MON) has increasingly been used within the literature to describe a group of optic neuropathies that exhibit mitochondrial dysfunction in retinal ganglion cells (RGCs). Interestingly, MONs include genetic aetiologies, such as Leber hereditary optic neuropathy (LHON) and dominant optic atrophy (DOA), as well as acquired aetiologies resulting from drugs, nutritional deficiencies, and mixed aetiologies. Regardless of an inherited or acquired cause, patients exhibit the same clinical manifestations with selective loss of the RGCs due to mitochondrial dysfunction. Various novel therapies are being explored to reverse or limit damage to the RGCs. Here we review the pathophysiology, clinical manifestations, differential diagnosis, current treatment, and promising therapeutic targets of MON.

[Leber's hereditary optic neuropathy]

Lebers hereditary optic neuropathy (LHON) is a maternally inherited disease characterized by subacute severe visual loss in both eyes, which usually manifests in young adulthood. The disease has maternal inheritance due to mitochondrial DNA mutation. The final diagnosis is genetic. There is still no proven treatment, but there is significant progress in developments on the genetics of the disease to reach gene therapy. In this article we review the latest literature relevant to this disease.

Raised intraocular pressure as a potential risk factor for visual loss in Leber Hereditary Optic Neuropathy

Leber Hereditary Optic Neuropathy (LHON) is an important cause of inherited mitochondrial blindness among young adults. The majority of patients carry one of three mitochondrial DNA (mtDNA) point mutations: m.3460G>A, m.11778G>A and m.14484T>C, all of which affect critical complex I subunits of the mitochondrial respiratory chain. LHON is characterised by marked incomplete penetrance, clearly implying that the mtDNA mutation is insufficient on its own to trigger retinal ganglion cell dysfunction and visual loss. In this case series of three affected patients harbouring the m.11778G>A mutation, we provide evidence suggesting that raised intraocular pressure could be a risk factor triggering visual loss in at-risk LHON carriers.

[Clinical and molecular genetic analysis of hereditary optic neuropathies]

DNA samples of 50 patients with optic neuropathy (ON) associated with congenital cataract were studied to find 3 major mt-DNA mutations (m.11778G>A, m.3460G>A, m.14484T>C), mutations in "hot" regions of OPA 1 gene (exons 8, 14, 15, 16, 18, 27, 28) and in the entire coding sequence of OPA3 gene for molecular genetic confirmation of diagnosis of hereditary Leber and autosomal dominant ON. Primary mutations of mtDNA responsible for hereditary Leber ON were found in 16 patients (32%). Pathogenic mutations of OPAl gene (c.869G>A and c. 2850delT) were identified in 2 patients (4%), these mutations were not found in the literature. OPA3 gene mutations were not revealed.

Novel therapeutic approaches for Leber's hereditary optic neuropathy

Many human childhood mitochondrial disorders result from abnormal mitochondrial DNA (mtDNA) and altered bioenergetics. These abnormalities span most of the mtDNA, demonstrating that there are no "unique" positions on the mitochondrial genome that when deleted or mutated produce a disease phenotype. This diversity implies that the relationship between mitochondrial genotype and clinical phenotype is very complex. The origins of clinical phenotypes are thus unclear, fundamentally difficult-to-treat, and are usually clinically devastating. Current treatment is largely supportive and the disorders progress relentlessly causing significant morbidity and mortality. Vitamin supplements and pharmacological agents have been used in isolated cases and clinical trials, but the efficacy of these interventions is unclear. In spite of recent advances in the understanding of the pathogenesis of mitochondrial diseases, a cure remains elusive. An optimal cure would be gene therapy, which involves introducing the missing gene(s) into the mitochondria to complement the defect. Our recent research results indicate the feasibility of an innovative protein-transduction ("protofection") technology, consisting of a recombinant mitochondrial transcription factor A (TFAM) that avidly binds mtDNA and permits efficient targeting into mitochondria in situ and in vivo. Thus, the development of gene therapy for treating mitochondrial disease offers promise, because it may circumvent the clinical abnormalities and the current inability to treat individual disorders in affected individuals. This review aims to focus on current treatment options and future therapeutics in mitochondrial disease treatment with a special emphasis on Leber's hereditary optic neuropathy.

Mitochondrial optic neuropathies - disease mechanisms and therapeutic strategies

Leber hereditary optic neuropathy (LHON) and autosomal-dominant optic atrophy (DOA) are the two most common inherited optic neuropathies in the general population. Both disorders share striking pathological similarities, marked by the selective loss of retinal ganglion cells (RGCs) and the early involvement of the papillomacular bundle. Three mitochondrial DNA (mtDNA) point mutations; m.3460G>A, m.11778G>A, and m.14484T>C account for over 90% of LHON cases, and in DOA, the majority of affected families harbour mutations in the OPA1 gene, which codes for a mitochondrial inner membrane protein. Optic nerve degeneration in LHON and DOA is therefore due to disturbed mitochondrial function and a predominantly complex I respiratory chain defect has been identified using both in vitro and in vivo biochemical assays. However, the trigger for RGC loss is much more complex than a simple bioenergetic crisis and other important disease mechanisms have emerged relating to mitochondrial network dynamics, mtDNA maintenance, axonal transport, and the involvement of the cytoskeleton in maintaining a differential mitochondrial gradient at sites such as the lamina cribosa. The downstream consequences of these mitochondrial disturbances are likely to be influenced by the local cellular milieu. The vulnerability of RGCs in LHON and DOA could derive not only from tissue-specific, genetically-determined biological factors, but also from an increased susceptibility to exogenous influences such as light exposure, smoking, and pharmacological agents with putative mitochondrial toxic effects. Our concept of inherited mitochondrial optic neuropathies has evolved over the past decade, with the observation that patients with LHON and DOA can manifest a much broader phenotypic spectrum than pure optic nerve involvement. Interestingly, these phenotypes are sometimes clinically indistinguishable from other neurodegenerative disorders such as Charcot-Marie-Tooth disease, hereditary spastic paraplegia, and multiple sclerosis, where mitochondrial dysfunction is also thought to be an important pathophysiological player. A number of vertebrate and invertebrate disease models has recently been established to circumvent the lack of human tissues, and these have already provided considerable insight by allowing direct RGC experimentation. The ultimate goal is to translate these research advances into clinical practice and new treatment strategies are currently being investigated to improve the visual prognosis for patients with mitochondrial optic neuropathies.

Gene therapy for retinitis pigmentosa and Leber congenital amaurosis caused by defects in AIPL1: effective rescue of mouse models of partial and complete Aipl1 deficiency using AAV2/2 and AAV2/8 vectors

Defects in the photoreceptor-specific gene encoding aryl hydrocarbon receptor-interacting protein-like 1 (AIPL1) are clinically heterogeneous and present as Leber Congenital Amaurosis, the severest form of early-onset retinal dystrophy and milder forms of retinal dystrophies such as juvenile retinitis pigmentosa and dominant cone-rod dystrophy. [Perrault, I., Rozet, J.M., Gerber, S., Ghazi, I., Leowski, C., Ducroq, D., Souied, E., Dufier, J.L., Munnich, A. and Kaplan, J. (1999) Leber congenital amaurosis. Mol. Genet. Metab., 68, 200-208.] Although not yet fully elucidated, AIPL1 is likely to function as a specialized chaperone for rod phosphodiesterase (PDE). We evaluate whether AAV-mediated gene replacement therapy is able to improve photoreceptor function and survival in retinal degeneration associated with AIPL1 defects. We used two mouse models of AIPL1 deficiency simulating three different rates of photoreceptor degeneration. The Aipl1 hypomorphic (h/h) mouse has reduced Aipl1 levels and a relatively slow degeneration. Under light acceleration, the rate of degeneration in the Aipl1 h/h mouse is increased by 2-3-fold. The Aipl1-/- mouse has no functional Aipl1 and has a very rapid retinal degeneration. To treat the different rates of degeneration, two pseudotypes of recombinant adeno-associated virus (AAV) exhibiting different transduction kinetics are used for gene transfer. We demonstrate restoration of cellular function and preservation of photoreceptor cells and retinal function in Aipl1 h/h mice following gene replacement therapy using an AAV2/2 vector and in the light accelerated Aipl1 h/h model and Aipl1-/- mice using an AAV2/8 vector. We have thus established the potential of gene replacement therapy in varying rates of degeneration that reflect the clinical spectrum of disease. This is the first gene replacement study to report long-term rescue of a photoreceptor-specific defect and to demonstrate effective rescue of a rapid photoreceptor degeneration.

[A pedigree of Leber's hereditary optic neuropathy with mtDNA 14484 mutation]

OBJECTIVE

To analyze a pedigree of Leber's hereditary optic neuropathy, and its penetrance, anticipation, and spontaneous eyesight improvement, and its relationship with mitochondrial DNA mutation.

METHODS

Eighteen members in the family were undergone routine visual check. Five cases were taken visual evoked potential and visual field examination. DNA sequencing was performed on 6 cases to check the mtDNA 11778, 3460 and 14484 loci.

RESULTS

(1)The offsprings from the first wife in the first generation showed decreased acuity of the two eyes, which was optic atrophy identified by funduscopy. (2) The mtDNA had mutation at position 14484, but not at positions 11778 and 3460.

CONCLUSION

The pedigree showed a typical maternal inheritance of Leber's hereditary optic neuropathy. It was caused by mtDNA 14484 mutation.

Retinal degeneration in children: dark adapted visual threshold and arteriolar diameter

To assess the condition of the retina in children with retinal degeneration due to Bardet-Biedl syndrome (BBS, n=41), Leber congenital amaurosis (LCA, n=31), or Usher syndrome (USH, n=13), the dark adapted visual threshold (DAT) and arteriolar diameters were measured. Compared to controls, the initial DATs of nearly all (83/85) were significantly elevated, and in 26/62 with serial DATs, significant progressive elevation occurred. Arteriolar diameters were significantly attenuated and narrowed with age in BBS and USH, but not LCA. Higher DATs were associated with narrower arterioles. Such non-invasive procedures can document the natural history of these retinal diseases and have the potential to assess response to future treatment.

Woman with atypical unilateral Leber's hereditary optic neuropathy with visual improvement

We describe a patient with Leber's hereditary optic neuropathy (LHON) who had a unilateral involvement and a gradual recovery of vision. A 50-year-old woman was referred to our clinic in December 2004 for the treatment of left optic neuritis. The visual acuity was 0.01 in her left eye and 1.5 in her right eye. The left eye had a central scotoma and a relative afferent pupillary defect. Ophthalmoscopy revealed a hyperaemic optic disc with indistinct margins in the left eye. Fluorescein angiography showed circumpapillary microangiopathy in both eyes and staining of the left optic disc. An nt 11778 mutation was identified and she was diagnosed with LHON. The central scotoma gradually improved, and the visual acuity had recovered to 0.3 in August 2007. LHON should still be considered even in older female patients presenting with unilateral acute visual loss when microangiopathy is seen. In such cases, molecular testing is effective in confirming a diagnosis of LHON.

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.

[A case of Leber's hereditary optic neuropathy in a female patient with the recrudescence of hyperthyroidism]

BACKGROUND

Thyroid hormone increases oxygen consumption and regulates mitochondrial biogenesis. On the other hand, in Leber's hereditary optic neuropathy(LHON), retinal ganglion cells are exposed to the oxidative stress generated during the process of adenosine 5'-triphosphate (ATP) synthesis, eventually leading to a loss of vision. Although there is a possibility that the thyroid hormone may have a role in the development or the course of LHON, no case has been reported indicating a relation between them. We report a female case with LHON who also presented exacerbation of hyperthyroidism during the course of the disease.

CASE

The patient was a thirty-nine-year-old woman who complained of bilateral loss of vision. Her corrected visual acuity was 0.2 in the right eye, and 0.1 in the left. Fundus examination showed characteristic findings of LHON in both eyes. The blood free thyroxin(FT4) level at that time was abnormally high. The diagnosis of LHON was confirmed by the presence of mitochondrial DNA mutation at the nucleotide position 11778. Her visual acuity improved after one month of FT4 normalization. A year later, her corrected visual acuity recovered to 0.9 in the right eye and 1.0 in the left.

CONCLUSION

Hyperthyroidism may be a trigger in the development of LHON.

White matter changes in Leber's hereditary optic neuropathy: MRI findings

Leber's hereditary optic neuropathy is a mitochondrial disorder causing bilateral optic nerve degeneration. It is sometimes associated with clinical signs of multiple sclerosis. We report MRI findings in two patients with LHON-MS and comment on possible distinguishing features of this disease entity.

Leber hereditary optic neuropathy possibly triggered by exposure to tire fire

We report three members of one family, a mother and two daughters aged 4 and 7 years, who developed visual loss from Leber hereditary optic neuropathy within a 19-month period. All three had been exposed to smoke from two large rubber tire fires within the previous 24 months, suggesting the possibility of an epigenetic triggering factor.

Electroretinographic assessment and diagnostic reappraisal of children with visual dysfunction: A prospective study

PURPOSE

To assess the presence or absence of a retinal cause of visual impairment using electroretinography (ERG) in children with no obvious discernable cause on ocular examination.

DESIGN

Prospective observational case series.

MATERIALS AND METHODS

A prospective study was carried out involving 120 children with the mean age 4.4+/-3.2 years with visual dysfunction. All children underwent ERG under general anesthesia using a special handheld mini-Ganzfeld (Kurbisfeld) dome.

RESULTS

Fifty-two (43.3%) children were male and 68 (56.7%) were female. The clinical diagnosis was as follows: Leber's congenital amaurosis (LCA) (n=47), achromatopsia (n=25), congenital stationary night blindness (CSNB) (n=9) and others (unclassifiable, n=39). The visual acuity ranged from perception of light (PL) to PL with projection in children with LCA. In the rest (n=73), some sort of visually guided behavior was discernable. Following ERG, a diagnostic reappraisal resulted as follows: LCA (n=49), achromatopsia (n=28), CSNB (n=4), cone-rod dystrophy (n=22), rod-cone degeneration (n=7), normal (n=8) and others (unclassifiable, n=2). Except for the two unclassifiable cases, ERG was successful in the diagnosis or exclusion of retinal dysfunction in the rest. By Pearson Chi-square test, there was a statistically significant association between the clinical and ERG diagnosis (P < 0.001).

CONCLUSION

LCA was the commonest cause of visual dysfunction in our series. A statistically significant correlation between clinical and electrophysiological diagnosis was seen. ERG helped in firmly establishing the presence or absence of global retinal dysfunction in the majority (118/120) of pediatric patients with visual dysfunction.

Leber’s Hereditary Optic Neuropathy with Childhood Onset

PURPOSE

To characterize the clinical features of childhood-onset Leber's hereditary optic neuropathy (LHON) as defined by a pathogenic mtDNA mutation and age at onset equal to or less than 10 years of age.

METHODS

Fifty-six LHON Italian pedigrees including 180 affected individuals were reviewed, and 14 of 18 patients with childhood LHON were enrolled. LHON was classified as acute bilateral, acute unilateral, slowly progressive, and subclinical, according to disease features. All patients underwent a complete ophthalmic examination and optical coherence tomography (OCT), including retinal nerve fiber layer (RNFL) and optic nerve head analysis (ONH), and were compared with age- and optic disc size-matched control groups.

RESULTS

The prevalence of childhood LHON in this case series was 11.5%. Five patients had an acute bilateral course, three an acute unilateral course with subclinical signs in the fellow eye, and six a slowly progressive course. Four of five acute patients with acute bilateral disease experienced visual recovery. Slowly progressive cases presented a better visual acuity and visual field outcome than acute cases. A significant diffuse reduction of RNFL was evident in children with acute LHON compared with the control group, whereas a significant reduction of the temporal quadrant was present in the slowly progressive and subclinical LHON cases. Acute LHON children had a smaller disc area and vertical disc diameter than did the control subjects.

CONCLUSIONS

This study systematically characterized for the first time the subgroup of LHON with childhood onset. The peculiar clinical and anatomic features of childhood LHON offer insights for the understanding of LHON's pathophysiology as well as a basis for the differential diagnosis of visual loss in childhood.

Partial mitochondrial complex I inhibition induces oxidative damage and perturbs glutamate transport in primary retinal cultures. Relevance to Leber Hereditary Optic Neuropathy (LHON)

Leber Hereditary Optic Neuropathy (LHON) is a maternally inherited form of visual loss, due to selective degeneration of retinal ganglion cells. Despite the established aetiological association between LHON and mitochondrial DNA mutations affecting complex I of the electron transport chain, the pathophysiology of this disorder remains obscure. Primary rat retinal cultures were exposed to increasing concentrations of rotenone to titrate complex I inhibition. Neural cells were more sensitive than Müller glial cells to rotenone toxicity. Rotenone induced an increase in mitochondrial-derived free radicals and lipid peroxidation. Sodium-dependent glutamate uptake, which is mostly mediated by the glutamate transporter GLAST expressed by Müller glial cells, was reduced dose-dependently by rotenone with no changes in GLAST expression. Our findings suggest that complex I-derived free radicals and disruption of glutamate transport might represent key elements for explaining the selective retinal ganglion cell death in LHON.

Alterations in multifocal visual evoked potentials during the acute phase of Leber's hereditary optic neuropathy

PURPOSE

This report aimed to investigate alterations in multifocal visual evoked potentials (mfVEPs) during the acute stage of Leber's hereditary optic neuropathy (LHON).

METHODS

A 27-year-old woman with a point mutation at nucleotide 11778 in the mitochondrial DNA was examined during the acute phase of LHON, which is generally investigated only rarely because of its rapid progress. She was examined repeatedly, with testing of best corrected visual acuity, pupil function, Goldmann perimetry, ophthalmoscopy and frequent assessment of mfVEPs.

RESULTS

Multifocal VEPs, which reveal topographical information about different parts of the visual pathways, demonstrated reduced responses in all parts of the central visual field. The mean amplitude (summarized amplitude of the first two components) in the mfVEPs in the previously described sector C, which has been identified as a hallmark of other optic nerve disorders, was evaluated. This amplitude demonstrated a correlation with the progression of the disease during the acute period of LHON, which also correlated with the VA, pupil function and Goldmann perimetry.

CONCLUSIONS

These alterations in the components of mfVEPs reflect the reduction in the function of the visual pathways in different parts of the central field; the drop in amplitude in a localized area (sector C), not previously described, demonstrates the acute course of this disorder. Multifocal VEPs may be of further interest in evaluating the pathogenesis of this disorder and of clinical value in representing an objective method for monitoring the course of this disease.

Progression of visual field defects in leber hereditary optic neuropathy: experience of the LHON treatment trial

PURPOSE

To describe the visual fields of patients with Leber hereditary optic neuropathy (LHON), a maternally inherited disorder characterized by bilateral, often sequential vision loss, before and during progressive visual deterioration.

DESIGN

Prospective longitudinal follow-up of serial visual fields in patients enrolled onto an open-label, nonrandomized pilot study of topical brimonidine purite as prophylactic treatment after first eye involvement in LHON.

METHODS

Nine molecularly confirmed primary mutation patients with LHON with monocular vision loss for less than six months and normal visual function in the other eye were followed prospectively for up to two years. Visual fields were performed on automated perimetry at baseline and on many follow-up visits.

RESULTS

Despite normal visual acuity at baseline in all patients, seven patients had some minimal changes in the central visual field of the second eye. All patients had subsequent deterioration of visual acuity, mean deviation, and foveal sensitivity in their second eye. The earliest pattern of abnormality was typically a cecocentral defect enlarging to become a central defect, often with a superior or inferior predilection. The visual field defects in the two eyes of any given patient were remarkably similar.

CONCLUSIONS

LHON may be a bilateral condition at onset more frequently than appreciated. Automated static perimetry of the "normal" eye may reveal subclinical findings that typically worsen rapidly over weeks to months to similar central scotomatous damage. Quantitative automated static perimetry is helpful in elucidating the natural history of LHON and in understanding the underlying pathology and pathophysiology of this disease.

Influence of mutation type on clinical expression of Leber hereditary optic neuropathy

PURPOSE

The aim of this research was to determine the molecular factors of influence on the clinical expression of Leber hereditary optic neuropathy (LHON), which might aid in counseling LHON patients and families. The prevalence of LHON in the Dutch population was determined.

DESIGN

Observational, retrospective population cohort study.

METHODS

The clinical characteristics of LHON patients of 25 families, previously described in 1963, were reevaluated. The mutation and haplotype were determined in the DNA of one affected LHON patient per family. The genotype of their relatives could be deducted, enabling us to evaluate retrospectively the genotype-phenotype correlation. The prevalence of LHON was determined on the basis of anamnestic evaluation of patients in 1963 and by using population registers of that period.

RESULTS

The LHON mutation does not influence disease penetrance (50% in male subjects; 10% to 20% in female subjects). More than half of the patients with the 14484 mutation exhibit a partial recovery of vision, regardless of the acuteness of disease onset (P = .001), whereas only 22% of the 11778 carriers and 15.4% of the 3460 carriers recovered. The recovery did not take place within the first year after onset and was uncommon after four years. The onset of LHON is in general very acute but might be more gradual in 11778 carriers and in children. The calculated prevalence of LHON in the Dutch population (1/39,000) is very likely an underestimation caused by a selection bias of familial cases in the original study.

CONCLUSIONS

The LHON genotype influences the recovery of vision and disease onset but is unrelated to age, acuteness of onset, or gender. The genotype does not influence disease penetrance. Children might exhibit a slower onset of disease.

Caspase-independent death of Leber's hereditary optic neuropathy cybrids is driven by energetic failure and mediated by AIF and Endonuclease G

Leber's hereditary optic neuropathy (LHON) is associated with mitochondrial DNA point mutations affecting different subunits of complex I. By replacing glucose with galactose in the medium, cybrids harboring each of the three LHON pathogenic mutations (11778/ND4, 3460/ND1, 14484/ND6) suffered a profound ATP depletion over a few hours and underwent apoptotic cell death, which was caspase-independent. Control cybrids were unaffected. In addition to cytochrome c, apoptosis inducing factor (AIF) and endonuclease G (EndoG) were also released from the mitochondria into the cytosol in LHON cybrids, but not in control cells. Exposure of isolated nuclei to cytosolic fractions from LHON cybrids maintained in galactose medium caused nuclear fragmentation, which was strongly reduced by immuno-depletion with anti-AIF and anti-EndoG antibodies. In conclusion, the caspase-independent death of LHON cybrids incubated in galactose medium is triggered by rapid ATP depletion and mediated by AIF and EndoG.

Chromatic and luminance contrast sensitivities in asymptomatic carriers from a large Brazilian pedigree of 11778 Leber hereditary optic neuropathy

PURPOSE

To determine whether asymptomatic 11778 LHON carriers demonstrated impairments in (1) chromatic red/green (R/G) and blue/yellow (B/Y) contrast sensitivity functions (CSF) and in (2) luminance contrast sensitivity functions in the spatial CSF (SCSF) and temporal CSF (TCSF) domains.

METHODS

Twenty-five carriers (8 male, 17 female; 34.1 +/- 15.1 years of age) of homoplasmic 11778 LHON from the same well-described family and 30 age-matched controls (17 male, 13 female; 29.2 +/- 7.1 years of age) were tested in one eye, randomly selected. Of the 25 eyes tested, 18 had normal fundus, 5 had swelling and microangiopathy, and 2 had temporal pallor. The R/G and B/Y CSFs were obtained after equiluminance correction with bichromatic horizontal sinusoidal gratings at 0.3, 0.7, and 2 cycles per degree (cpd); the SCSFs were obtained with achromatic gratings at 0.3, 2, 6, and 12 cpd; and the TCSFs were obtained at 2, 10, 20, and 33 Hz with sinusoidal modulation of a 2.7 degrees field with a superimposed spatial Gabor function.

RESULTS

Differences between carriers and controls were statistically significant for all spatial frequencies of chromatic and luminance SCSFs, but not for the TCSFs. R/G equiluminance settings of carriers differed from those of controls (P < 0.001), requiring higher luminance in the green; B/Y equiluminance settings were not statistically different in carriers and controls. Fundus findings did not correlate with CS results.

CONCLUSIONS

Luminance and chromatic spatial CS losses that affected all tested spatial frequencies, are reported in LHON asymptomatic carriers with the mtDNA 11778 mutation. No losses were found in the temporal CSF. An intriguing finding is that the blue system is substantially spared in this LHON family. These represent subclinical visual impairments in otherwise asymptomatic LHON carriers.

[Leber's optic neuropathy: a case report]

INTRODUCTION

Leber's optic neuropathy is a hereditary disease that mainly affects young males and is produced by specific mutations of the mitochondrial DNA, which affect the complex I of the mitochondrial respiratory chain.

CASE REPORT

An 18-year-old male who presented with a 3-week history of progressive loss of sight in the right eye. Magnetic resonance imaging of the brain revealed numerous hyperintense lesions in the periventricular and subcortical white matter, and the visual evoked potentials showed bilateral optic neuropathy that was mild on the left side and severe on the right side. A spinal tap was performed and oligoclonal bands were detected in the cerebrospinal fluid. In the weeks that followed vision continued to get worse on both sides and the patient had hyalinised vessels in the papilla, with lower amplitude responses bilaterally in the electroretinogram. A genetic study was conducted that revealed a primary mutation 11778 in gene MTND4 and secondary mutation 15257 in gene MTCYB, which were compatible with a diagnosis of Leber's optic neuropathy.

CONCLUSIONS

The absence of inflammation of the optic disc, which could lead to the suspicion of a retrobulbar neuritis, must act as a warning to the physician that he or she is possibly before a case of Leber's optic neuropathy, especially when the loss of vision is still progressing, when there is early bilateral involvement or if there is a family history of optic neuritis or multiple sclerosis.

Leber's hereditary optic neuropathy with dystonia in a Japanese family

We investigated a Japanese family with generalized dystonia attributed to striatal degeneration, which occurred in childhood, and late-onset optic neuropathy. We determined the entire nucleotide sequence of mitochondrial DNA (mtDNA) from the proband and compared our findings with the 2001 Revised Cambridge Reference Sequence. The mtDNA of the proband showed a total of 42 nucleotide changes. We identified two A3203G and G14459A mutations, which were completely absent in a population of 200 healthy Japanese, by estimating the frequency of each nucleotide change. The nucleotide G14459A mutation occurs in NADH dehydrogenase subunit 6, and has been suggested previously as the disease-causing mutation in Hispanic, African-American and Caucasian families of Leber's hereditary optic neuropathy (LHON) and/or dystonia. The significance of the A3203G mutation remains unknown. To our knowledge, this is the first case of LHON with dystonia that revealed a mtDNA mutation in a Japanese family.

Restoring retinal function in a mouse model of hereditary blindness

Moore discusses a new study showing rescue of photoreceptor function using gene and drug therapies in a mouse model of Leber congenital amaurosis.

LHON/MELAS overlap syndrome associated with a mitochondrial MTND1 gene mutation

Pathogenic point mutations in the mitochondrial MTND1 gene have previously been described in association with two distinct clinical phenotypes -- Leber hereditary optic neuropathy (LHON) and mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS). Here we report the first heteroplasmic mitochondrial DNA (mtDNA) point mutation (3376G>A) in the MTND1 gene associated with an overlap syndrome comprising the clinical features of both LHON and MELAS. Muscle histochemistry revealed subtle mitochondrial abnormalities, while biochemical analysis showed an isolated complex I deficiency. Our findings serve to highlight the growing importance of mutations in mitochondrial complex I structural genes in MELAS and its associated overlap syndromes.

Hereditary optic neuropathies

AIMS

To provide a clinical update on the hereditary optic neuropathies.

METHODS

Review of the literature.

RESULTS

The hereditary optic neuropathies comprise a group of disorders in which the cause of optic nerve dysfunction appears to be hereditable, based on familial expression or genetic analysis. In some hereditary optic neuropathies, optic nerve dysfunction is typically the only manifestation of the disease. In others, various neurologic and systemic abnormalities are regularly observed.

CONCLUSION

The most common hereditary optic neuropathies are autosomal dominant optic atrophy (Kjer's disease) and maternally inherited Leber's hereditary optic neuropathy. We review the clinical phenotypes of these and other inherited disorders with optic nerve involvement.

Retinal degeneration in Aipl1-deficient mice: a new genetic model of Leber congenital amaurosis

Leber congenital amaurosis (LCA) is the most severe inherited retinopathy, with the earliest age of onset. Because this currently incurable disease is present from birth and is a relatively rare disorder, the development of animal models that closely resemble the phenotype in patients is especially important. Our previous genetic analyses of LCA patients identified mutations in the aryl-hydrocarbon interacting protein-like 1 (AIPL1) gene. Here we present development of an animal model of AIPL1-associated LCA, the Aipl1-deficient mouse. Aipl1 is expressed at low levels throughout human and mouse retinal development and is rapidly upregulated as photoreceptors differentiate. The mouse displays rapid retinal degeneration and massive Müler cell gliosis, resembling the phenotype of the rd mouse, which is caused by a mutation in the gene for the beta-subunit of the rod-specific phosphodiesterase. We confirm that this phenotype is consistent with the human disease using electroretinograms, and document the disease pathogenesis by analyzing the development of all retinal cell types and synaptogenesis during retinal histogenesis. Ectopic expression of AIPL1 led to deregulated retinal progenitor cell proliferation and alterations in cell fate specification; however, no gross abnormalities of proliferation during retinal development were detected. Data from analysis of proliferation and cell fate specification during retinal development of Aipl1-deficient mice suggests that there may be redundancy or compensation for Aipl1 loss by other related proteins. Because this mouse model closely mimics the human retinopathy caused by homozygous mutations in this gene, it provides a preclinical model for testing therapies to rescue the vision of children whose blindness is caused by AIPL1 mutations.

Bioenergetics shapes cellular death pathways in Leber's hereditary optic neuropathy: a model of mitochondrial neurodegeneration

Leber's hereditary optic neuropathy (LHON) was the first maternally inherited disease to be associated with point mutations in mitochondrial DNA and is now considered the most prevalent mitochondrial disorder. The pathology is characterized by selective loss of ganglion cells in the retina leading to central vision loss and optic atrophy, prevalently in young males. The pathogenic mtDNA point mutations for LHON affect complex I with the double effect of lowering the ATP synthesis driven by complex I substrates and increasing oxidative stress chronically. In this review, we first consider the biochemical changes associated with the proton-translocating NADH-quinone oxidoreductase of mitochondria in cybrid cells carrying the most common LHON mutations. However, the LHON cybrid bioenergetic dysfunction is essentially compensated under normal conditions, i.e. in glucose medium, but is unrevealed by stressful conditions such as growing cybrids in glucose free/galactose medium, which forces cells to rely only on respiratory chain for ATP synthesis. In fact, the second part of this review deals with the investigation of LHON cybrid death pathway in galactose medium. The parallel marked changes in antioxidant enzymes, during the time-course of galactose experiments, also reveal a relevant role played by oxidative stress. The LHON cybrid model sheds light on the complex interplay amongst the different levels of biochemical consequences deriving from complex I mutations in determining neurodegeneration in LHON, and suggests an unsuspected role of bioenergetics in shaping cell death pathways.

Cell response to oxidative stress induced apoptosis in patients with Leber's hereditary optic neuropathy

OBJECTIVES

Leber's hereditary optic neuropathy (LHON) is a maternally inherited disease in which acute or subacute bilateral visual loss occurs preferentially in young men. Over 95% of LHON cases are associated with one of three mitochondrial DNA (mtDNA) point mutations, but only 50% of men and 10% of women who harbour a pathogenetic mtDNA mutation develop optic neuropathy. This incomplete penetrance and preference for men suggests that additional genetic (nuclear or mitochondrial) and/or environmental factors must modulate phenotype expression in LHON. A role for reactive oxygen species (ROS) in mitochondrial diseases, secondary to mtDNA mutations, or as a result of the direct effect of ROS cytotoxicity, has been implicated in many mitochondrial disorders, including LHON. The purpose of this study was to investigate the role of oxidative stress induced apoptosis in LHON.

METHODS

The 2-deoxy-D-ribose induced apoptotic response of peripheral blood lymphocytes from six patients with LHON and six healthy subjects was investigated using light microscopy, flow cytometry, agarose gel electrophoresis, and the measurement of mitochondrial membrane potential.

RESULTS

Cells of patients with LHON had a higher rate of apoptosis than those of controls and there was evidence of mitochondrial involvement in the activation of the apoptotic cascade.

CONCLUSIONS

These differences in oxidative stress induced apoptosis are in line with the hypothesis that redox homeostasis could play a role in the expression of genetic mutations in different individuals and could represent a potential target in the development of new therapeutic strategies.

Visual electrophysiologic findings in patients from an extensive Brazilian family with Leber's hereditary optic neuropathy

Leber's hereditary optic neuropathy (LHON) is a maternally inherited disease, associated with mitochondrial DNA (mtDNA) point mutations and characterized by bilateral, usually sequential, rapid loss of central vision. The purpose of this study was to investigate electrophysiologically a small cohort of members from an extensive Brazilian family affected by LHON. Pattern-reversal visual evoked potentials (PVEP), and full-field electroretinograms (ERG) were performed on the four index members, all carrying the 11778 homoplasmic mtDNA mutation. They were a 14-year-old recently affected male, his unaffected mother, and her two affected brothers. The three affected members all had bilateral profound visual loss with visual acuities that ranged from 20/250 to CF, cecocentral defects, and severe dyschromatopsia (by FM-100). The unaffected (carrier) female had normal visual acuities, visual fields and color discrimination. Severely prolonged P100 latencies and decreased N75-P100 peak amplitudes were found in pattern-reversal VEPs for three affected members. Normal PVEP responses were found in the carrier female. Rod and cone ERG responses were normal in two affected members, but both the carrier mother and her affected son showed reduced peak-to-peak amplitude for single-flash cone response and 30 Hz flicker, with normal b-wave implicit times. Thus, optic nerve function, evaluated by PVEP, was severely reduced in LHON affected members and normal in the carrier female. However, reduced ERG cone responses suggest that LHON can also affect retinal elements, even in the absence of fundus and other clinical changes that constitute the full and classical expression of LHON.