ABSTRACT
Age-related macular degeneration (AMD) is the main cause of visual impairment and blindness in people aged over 65 years in developed countries. Vascular endothelial growth factor (VEGF) is a positive regulator of angiogenesis and its proven role in the pathological neovascularization in wet AMD has provided evidence for the use of anti-VEGF agents as potential therapies. In this study, we review the literature for the possible causes of failure after treatment with anti-VEGF agents and attempt to propose an algorithm of suggestive actions to increase the chances of successful management of such difficult cases.
Subject(s)
Macular Degeneration/drug therapy , Vascular Endothelial Growth Factor A/antagonists & inhibitors , Choroid Diseases/drug therapy , Drug Resistance , Humans , Macular Degeneration/genetics , Treatment FailureABSTRACT
Autosomal dominant optic atrophy (ADOA) is a slowly progressive optic neuropathy that has been associated with mutations of the OPA1 gene. In patients, the disease primarily affects the retinal ganglion cells (RGCs) and causes optic nerve atrophy and visual loss. A subset of RGCs are intrinsically photosensitive, express the photopigment melanopsin and drive non-image-forming (NIF) visual functions including light driven circadian and sleep behaviours and the pupil light reflex. Given the RGC pathology in ADOA, disruption of NIF functions might be predicted. Interestingly in ADOA patients the pupil light reflex was preserved, although NIF behavioural outputs were not examined. The B6; C3-Opa1(Q285STOP) mouse model of ADOA displays optic nerve abnormalities, RGC dendropathy and functional visual disruption. We performed a comprehensive assessment of light driven NIF functions in this mouse model using wheel running activity monitoring, videotracking and pupillometry. Opa1 mutant mice entrained their activity rhythm to the external light/dark cycle, suppressed their activity in response to acute light exposure at night, generated circadian phase shift responses to 480 nm and 525 nm pulses, demonstrated immobility-defined sleep induction following exposure to a brief light pulse at night and exhibited an intensity dependent pupil light reflex. There were no significant differences in any parameter tested relative to wildtype littermate controls. Furthermore, there was no significant difference in the number of melanopsin-expressing RGCs, cell morphology or melanopsin transcript levels between genotypes. Taken together, these findings suggest the preservation of NIF functions in Opa1 mutants. The results provide support to growing evidence that the melanopsin-expressing RGCs are protected in mitochondrial optic neuropathies.
Subject(s)
Light , Optic Atrophy, Autosomal Dominant/physiopathology , Animals , Behavior, Animal/radiation effects , Circadian Rhythm/radiation effects , Darkness , Disease Models, Animal , GTP Phosphohydrolases/deficiency , GTP Phosphohydrolases/genetics , Gene Expression Regulation/radiation effects , Male , Mice , Mutation , Optic Atrophy, Autosomal Dominant/genetics , Optic Atrophy, Autosomal Dominant/metabolism , Pupil/radiation effects , Retinal Ganglion Cells/metabolism , Retinal Ganglion Cells/radiation effects , Rod Opsins/metabolism , Sleep/physiology , Sleep/radiation effectsABSTRACT
Autosomal dominant optic atrophy (ADOA) is a slowly progressive optic neuropathy caused by mutations in the OPA1 gene. OPA1 is ubiquitously expressed and plays a key role in mitochondrial fusion. Heterozygous Opa1 mutant mice (B6; C3-Opa1(Q285STOP)), have previously been reported to develop visual defects and optic nerve changes. In this study, in vivo visual electrophysiological testing (ERGs and VEPs) was performed on 11-13 month old B6; C3-Opa1(Q285STOP) mice (n = 5) and age/sex matched wildtype littermate controls. Full intensity series were recorded in response to brief (4 ms) single flash stimuli delivered in a Ganzfeld dome under dark- and light-adapted conditions. The major ERG components (a-wave and b-wave) showed no detectable difference from wildtype in the amplitude or implicit time of dark-adapted ERGs across the full intensity range tested. This was also true for the components of the dark-adapted VEP. However, the light-adapted ERG responses revealed a significant reduction in the photopic negative response (PhNR) amplitude in Opa1(+/-) animals relative to wildtypes at the brighter intensities tested. Elements of the light-adapted VEP were also abnormal in mutant mice. Overall Opa1(+/-) mice display functional deficits in electrophysiology that are consistent with ganglion cell dysfunction. These deficits may correlate with a reduction in the dendritic arborisation of retinal ganglion cells, which has been previously reported to occur at a similar age in the same mutant mouse line (Williams et al., 2010). The functional phenotype we have described in this mouse model may be useful in the robust and accurate assessment of potential treatments for ADOA.
