99 research outputs found
Neuropilin 1 Involvement in Choroidal and Retinal Neovascularisation
Purpose
Inhibiting VEGF is the gold standard treatment for neovascular age-related macular degeneration (AMD). It is also effective in preventing retinal oedema and neovascularisation (NV) in diabetic retinopathy (DR) and retinal vein occlusions (RVO). Neuropilin 1 (Nrp1) is a co-receptor for VEGF and many other growth factors, and therefore a possible alternative drug target in intra ocular neovascular disease. Here we assessed choroidal and retinal NV in an inducible, endothelial specific knock out model for Nrp1.
Methods
Crossing Nrp1 floxed mice with Pdgfb-CreERT2 mice produced tamoxifen-inducible, endothelial specific Nrp1 knock out mice (Nrp1ΔEC) and Cre-negative, control littermates. Cre-recombinase activity was confirmed in the Ai3(RCL-EYFP) reporter strain. Animals were subjected to laser-induced CNV (532 nm) and spectral domain-optical coherence tomography (SD-OCT) was performed immediately after laser and at day 7. Fluorescein angiography (FA) evaluated leakage and postmortem lectin staining in flat mounted RPE/choroid complexes was also used to measure CNV. Furthermore, retinal neovascularisation in the oxygen induced retinopathy (OIR) model was assessed by immunohistochemistry in retinal flatmounts.
Results
In vivo FA, OCT and post-mortem lectin staining showed a statistically significant reduction in leakage (p<0.05), CNV volume (p<0.05) and CNV area (p<0.05) in the Nrp1ΔEC mice compared to their Cre-negative littermates. Also the OIR model showed reduced retinal NV in the mutant animals compared to wild types (p<0.001).
Conclusion
We have demonstrated reduced choroidal and retinal NV in animals that lack endothelial Nrp1, confirming a role of Nrp1 in those processes. Therefore, Nrp1 may be a promising drug target for neovascular diseases in the eye
Visual Impairment and Blindness
Blindness and vision impairment affect at least 2.2 billion people worldwide with most individuals having a preventable vision impairment. The majority of people with vision impairment are older than 50 years, however, vision loss can affect people of all ages. Reduced eyesight can have major and long-lasting effects on all aspects of life, including daily personal activities, interacting with the community, school and work opportunities, and the ability to access public services. This book provides an overview of the effects of blindness and visual impairment in the context of the most common causes of blindness in older adults as well as children, including retinal disorders, cataracts, glaucoma, and macular or corneal degeneration
Strategies for revascularizing the ischemic retina
Les rétinopathies ischémiques (RI) sont la cause majeure de cécité chez les
personnes âgées de moins de 65 ans. Il existe deux types de RIs soit la rétinopathie
du prématuré (ROP) ainsi que la rétinopathie diabétique (RD). Les RIs sont décrites
en deux phases soit la phase de vasooblitération, marquée par une perte importante
de vaisseaux sanguins, et une phase de néovascularisation secondaire à lʼischémie
menant à une croissance pathologique de vaisseaux. Cette seconde phase peut
générer des complications cliniques telles quʼun oedème dans lʼhumeur vitré ainsi que
le détachement de la rétine chez les patients déjà atteints dʼune RI. Les traitements
approuvés pour les RIs visent à réduire la formation des vaisseaux pathologiques ou
lʼoedème; mais ceux-ci malheureusement ne règlent pas les problèmes sous-jacents
tels que la perte vasculaire et lʼischémie.
La rétine est un tissu hautement vascularisé qui contribue à lʼirrigation et à
lʼhoméostasie des neurones. Lʼinteraction neurovasculaire, comprenant de neurones,
vaisseaux et cellules gliales, contribue au maintien de cette homéostasie. Durant le
développement, les neurones et les cellules gliales jouent un rôle important dans la
vascularisation de la rétine en sécrétant des facteurs qui stimulent l'angiogenèse.
Cependant, nos connaissances sur lʼinteraction neurovasculaire dans les RIs sont
limitées. En identifiant les interactions importantes entre les cellules composant cette
unité neurovasculaire dans la rétine, nous pourrons viser des cibles qui engendreront
une revascularisation seine afin de diminuer les signes pathologiques chez les
patients atteints dʼune RI.
Les travaux présentés dans cette thèse visent à mieux expliquer cette
interaction neurovasculaire en soulignant des concepts importants propres aux RIs.
En utilisant un modèle de rétinopathie induite par lʼoxygène chez la souris, qui
reproduit les caractéristiques importantes de la ROP (et en certaines instances, la
RD), nous identifions quelques molécules clés jouant un rôle significatif dans les RIs
soit la sémaphorine 3A (sema3A), lʼIL-1β, ainsi que le récepteur PAR2.
Nos résultats démontrent que Sema3A, sécrétée par les cellules
ganglionnaires rétiniennes (CGRs) durant une ischémie, empêche la
revascularisation normale et que cette expression est induite par lʼIL-1β provenant
des microglies activées. En bloquant Sema3A directement ou via lʼinhibition de lʼIL-
1β, nous remarquons une revascularisation seine ainsi quʼune diminution importante
des vaisseaux pathologiques. Cela nous indique que Sema3A est impliquée dans la
guidance vasculaire et quʼelle contribue à la pathogenèse des RIs. Lʼactivation de
façon exogène de PAR2, identifié aussi comme régulateur du récepteur de lʼIL-1β (IL-
1RI) sur les CGRs, se traduit par une diminution séquentielle de lʼIL-1RI et de
Sema3A ce qui mène également à une revascularisation seine.
En conclusion, ces travaux soulignent lʼimportance de lʼinteraction
neurovasculaire ainsi que la guidance vasculaire dans les RIs. Ils renforcent
lʼimportance de la communication entre neurone, vaisseau et microglie dans la
pathogenèse des RIs. Finalement, nous identifions quelques molécules clés qui
pourront servir comme cibles afin de lutter contre lʼischémie qui cause des problèmes
vasculaires chez les patients atteints dʼune RI.Ischemic retinopathies (IRs), namely, retinopathy of prematurity (ROP) and
diabetic retinopathy (DR), are the major cause of blindness in persons under the age
of 65. IRs are biphasic disorders described by an initial vasoobliterative phase
marked by a persistent microvascular degeneration, which leads to ischemia. Retinal
ischemia, secondary to vessel loss, incites a second neovascularization phase
represented by an aberrant, misdirected neovessel formation into the vitreous, which
can cause adverse clinical complications including vitreous hemorrhaging and
tractional retinal detachment. While current treatments aim at reducing vitreous/retinal
hemorrhaging and/or pathological pre-retinal neovascularization, these regimens fail
to address the underlying problem; that is, microvascular decay and retinal ischemia.
The retina is a highly metabolic tissue that requires a significant amount of
nutrients and oxygen. This is supplied by an intricate and highly regulated vascular
network required to maintain homeostasis and proper function. The intricate cellular
interactions in the neurovascular unit – the consortium of vessel, neurons and support
glia – are required for regulating and maintaining homeostasis under normal
conditions. However, the understanding of how this unit functions under ischemic
stress, that which is seen in patients suffering from IRs, is not well defined. The
present work underlines several important concepts of neurovascular coupling in IRs
in efforts to identify potential therapeutic agents that may help curb retinal ischemia by
stimulating normal revascularization.
Using a mouse model of oxygen-induced retinopathy (OIR), which reproduces
the salient features of ROP (and in some instances DR), we identified key players
involved in generating the pathophysiological signatures associated with IRs; namely,
semaphorin3A (Sema3A), interleukin-1β (IL-1β) and protease-activated receptor 2
(PAR2). Our results show that neuronal-derived Sema3A, secreted by ischemic
retinal ganglion cells (RGCs), acts as a potent vaso-repulsive molecules that impedes normal revascularization. Activated microglia contribute to this process by secreting IL-1β, which induces paracrine release of Sema3A expression contributing to
microvascular decay as well as pathological pre-retinal neovascularization. Inhibition
of Sema3A or IL-1β translates to rapid revascularization and, as a result, a significant
reduction in pathological neovessel formation. These results demonstrate that
Sema3A is directly involved in vascular guidance and precipitates the pathophysiological
features associated with IRs. PAR2, found on RGCs, was also identified
as a key regulatory mechanism involved in dampening IL-1β induced Sema3A mediated
vascular decay by reducing IL-1 receptor (IL-1RI). Exogenous activation of
neuronal PAR2 translates to a sequential reduction of both IL-1RI and Sema3A
resulting in accelerated revascularization and consequentially pre-retinal
neovascularization. In conclusion, these studies highlight the importance of neurovascular coupling associated with IRs. Herein, we demonstrate the consorted interaction between
neuron, vessel and glia and its impact on shaping the retinal vasculature during
disease. Moreover, we underscore the significant impact of neuronal guidance cues in
manifesting the salient vascular features of IRs. Finally, we identify key players that
may serve as potential therapeutic avenues in curbing retinal ischemia in efforts to
reduce vascular complications associated with IRs
Multimodal imaging in age-related macular degeneration
Age-related macular degeneration (AMD) is a leading cause of blindness and affects approximately one in seven
Australians aged 50 years and above. Currently, this complex condition is not easily and uniformly assessed. The
signs of AMD differ between eyes and also occur in other macular disorders. This hinders accurate diagnosis and
classification, which is fundamental to optimal patient care. Ocular imaging and visual function assessment have the
potential to minimise the devastating consequences of disease through early detection. However, multiple devices
are now commercially available and the impact of these technologies in clinical practice may not be straightforward.
For instance, their usefulness may depend on accessibility and the operator’s knowledge and clinical skills. The
impact on patient management, as well as alternative models of eye-care delivery, requires clarification.
This thesis aims to explore the current and potential utility of imaging technologies (optical coherence tomography,
infrared imaging, monochromatic retinal photography and fundus autofluorescence) in the assessment and
management of AMD and other diseases of retinal pigment epithelium dysfunction.
The findings show that optometrists self-describe high levels of practice competency and make ready use of imaging
in everyday practice. However, they also unwittingly demonstrated low awareness of the evidence base in AMD.
Furthermore, when their interpretation of images was tested using a series of case vignettes, their diagnostic
accuracy as a group improved by only five per cent (from 61 per cent to 66 per cent); their tendency to refer
increased by four per cent. These factors might be improved through education.
A series of open-access, chair-side reference charts were consequently devised to help optometrists use imaging
technologies more effectively in clinical practice. The additive contribution of multimodal structural and functional
testing was particularly emphasised. Finally, a novel model of intermediate-tier eye-care in Australia was shown to
substantially reduce the number of false positive cases or cases without a specific diagnosis. Interestingly, this model
was acclaimed by reviewers as “scoring highly for originality and of international relevance”. Most excitingly, the
thesis concludes with future directions regarding collaborative care and multimodal imaging, where detection of
disease might be facilitated via a computational approach
Fighting against atherosclerotic disease: From the endothelium to invasive cardiology
An insight into in vitro strategies to improve endothelial function and response to ischemia and into clinical strategies to improve the outcome after percutaneous interventions
Lipid keratopathy in the dog
Naturally occurring lipid keratopathy in the dog has been
investigated using a variety of examination techniques. The same
procedures have also been followed for a group of normal dogs
matched to the clinical cases by age, sex and breed and for a third
group of unmatched, normal, animals.Investigations have included general clinical and ophthalmoscopic
examination and detailed examination of the anterior segment,
including tonometry, temperature measurement and fluorescein
angiography. Laboratory examination has largely concentrated on
serum lipid and lipoprotein analysis.A number of microscopic methods have been applied to normal and
diseased corneas. A comprehensive selection of histochemical
techniques for identification of lipids have been used in
conjunction with light, polarising, interference contrast and phase
contrast microscopy. The physical properties of lipids have been
explored using squash or imprint preparations, a heated microscope
stage and polarised light (with a mica plate and a first order
red gypsum accessory plate). A variety of other non-1ipid methods
have also been used.Ultrastructural studies complemented those of light microscopy,
employing both scanning electron microscopy and transmission
electron microscopy and utilising a limited number of
ultrahistochemical staining techniques with the latter.The results of this study indicate that lipid keratopathy may
be associated with a variety of conditions involving the anterior
segment and that abnormalities of the serum lipids and lipoproteins
can often be demonstrated in affected animals. These findings are
of significance for diseases of lipid metabolism in other species
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