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Glaucoma at ARVO

April 25-29, 2004, Fort Lauderdale, Florida, USA

Rosario Hernandez - Top 10

• Novel imaging technique to visualize retinal ganglion cells undergoing apoptosis using intravitreal injections of fluorescent labeled annexin V in rats with elevated IOP. This promising imaging technology, already in use in humans, may be adapted to detect early glaucomatous damage.
• Evidence is presented for two novel loci for POAG in chromosomes 14 and 15. Several important genes that maybe relevant to glaucoma pathogenesis are located near or at these loci.
• Deletion of a-adrenergic receptors subtypes a-2A, a-2B and a-2C in mice did not alter IOP magnitude or circadian variation providing an example of using transgenic mice on mechanisms of control of IOP.
• RGC cell death in the DBA/2J mouse glaucoma model was delayed by using intravitreal injections of biodegradable microspheres containing glial derived growth factor (GDNF).
• Microarray cDNA analyses applied to human glaucomatous retinas and to study signaling interactions between RGC and glial cells in rat retina indicate that global gene expression analysis is a tool to study glaucoma pathogenesis.
• In vitro synthesis of pseudoexfoliation fibers by Tenon's capsule fibroblast will allow studies into the unknown molecular mechanisms involved in PEX synthesis.
• Two separate studies using gene therapy with active MEK to protect RGC in experimental glaucoma and a gene transfer approach using active MAPK protected axotomized RGC from cell death.
• Estrogen involvement in neuroprotection of RGC in the retina and neuroactive androgens involved in the maintenance of reactive astrocyte in glaucoma suggests widespread effects of steroids in the glaucomatous eye.
• New experimental evidence of the regulation of metalloproteinase activity by JNK-MAP kinases in trabecular meshwork may lead to new drugs to control outflow facility.
• A possible role for optineurin gene in glaucoma: oxidative stress and phagocytosis induce optineurin expression in trabecular meshwork cells.

Martin Wax - Top 8

• Francesca Cordeiro et al.: Annexin V: In Vivo Imaging of RGC Apoptosis
  This work reports the first direct visualization of RGCs undergoing apoptosis in vivo as demonstrated in three animal models. This technique might well be useful as a clinical tool to detect glaucomatous damage before it can be observed by any other known technique. Thus it may serve to monitor disease status and treatment efficacy. In addition, it can be a highly useful in vivo imaging procedure to test neuroprotectants in animal models, including man. See separate commentary.
• Simon John: Cogan Award and Lecture
  John described details of the DBA2J mouse genetic model of pigment dispersion glaucoma and dropped a 'bombshell' when he said that syngenic bone marrow transfer alleviates/prevents progression to glaucoma in these animals. This may alter the way we view classical neuroprotection and methods to achieve it in glaucoma therapeutics.
• Richard Libby (abstract #2293): Bax knockouts permit RGC but not axonal survival
  A holy grail in glaucoma is understanding whether the RGC death is a process that is initiated in the RGC soma or in the axon. In the DBA 2J mouse, Libby observed TUNEL labeling between 7 and 12 months, peaking at 10 months. Bax is a pro-apoptotic protein. They knocked out Bax and analyzed RGC survival at 12 months. They found rates of 60%, 80%, and 100% survival in the cell bodies of wild type,.heterozygotes, and homozygotes respectively, but not for the axons! Thus, the absence of Bax does not appear to protect these animals from axonal damage, although it did delay it. In the Bax knockout RGCs survived greater than 6 months without their axons. This work may suggest that perhaps injured axons can be rescued if the RGC bodies are intact.
• John Flanagan and John Thompson, University of Waterloo: siRNA-
  The beginning of small interfering RNA (siRNA) technology as it applies to potential therapy is beginning to appear in the ophthalmic field. This group showed that an siRNA against eI5A is capable of blocking apoptosis in lamina cribrosa cells against a wide variety of cytokines including TNF and interleukins,. The implications of this are significant for both retinal neuroprotection in glaucoma, as well as in ocular anterior surface inflammatory diseases such as dry eye.
• Crowston et al. (abstract #3532): Effect of a Single Dose of Latanoprost on Intraocular Pressure in FP Receptor Knockout Mice
  FP knockout mice showed little response to a single dose of Latanoprost, thus validating that latanoprost works at the FP receptor to mediate its hypotensive effect.. It is certainly interesting to speculate whether the negative hypotensive response would be similar to bimatoprost. A negative response to bimatoprost latanoprost would go a long way towards confirming the suspicion that the FP receptor is important in mediating the IOP lowering effect of this drug, in addition to those that are believed to work through the FP receptor, such as latanoprost and travoprost.
  
• Julia Song et al.: Statins lower IOP
  Statins lower IOP by possibly acting indirectly as rho kinase inhibitors (facilitate increased outflow).
• Mettu et al. (abstract #4371): U BA441-2272 for IOP-Lowering
  BA441-2272 is a soluble guanylyl cyclase activator that increases outflow facility in pig perfused organ culture. Activation of guanylyl cyclase by other means has long been known to lower IOP. However, this is a new candidate small molecule that might lower IOP and have therapeutic utility.
• Stefano Gandolfi and Roger Hitchings: Topical brimonidine appears to be neuroprotective
  Using Progressor software to monitor visual field changes in a small number prospective study, the authors suggested that topical brimonidine may have utility as a genuine neuroprotective agent since they found there was some modest visual field improvement that occurred in the brimonidine-treated patients that was indepent of IOP control which was matched between the brimonidine and non-brimonidine-treated groups. However, their sample size is nominal and the methods used to assess their results were not fully clear to this listener. This work will surely undergo rigorous evaluation as this work seeks to be published. Still, their findings are very provocative and may help modify our current treatment paradigms if it can be validated and reproduced.

Shlomo Melamed - Top 10

• Intra-venous injection of soluble K-114 dye allows fluorescent imaging of amyloid in eyes with chronic ocular hypertension model of rats.
• New hyperspectral imaging technique improves the evaluation of relative oxygen saturation of the optic nerve head in acutely elevated IOP model.
• Cholesterol lowering drugs from the statins family decrease aqueous humor outflow.
• In cases of progressive glaucoma, when compared with laser trabeculoplasty, topical brimonidine was found to better protect from visual fields damage progression despite a weaker effect on IOP.
• Systemic dosing of Minocycline was found to be neuroprotective for retinal ganglion cell loss in both chronic IOP elevation and optic nerve dissection models in the rat.
• Implantation of progenitor ciliary body cells into the retina in rats with experimental glaucoma may prove a valid method for repopulating retinal ganglion cells in the future.
• In human glaucoma, there are signs of neural degeneration involving the intra-cranial optic nerve, lateral geniculate body and the visual cortex.
• After a follow-up of two years, trabeculectomy and phacotrabeculectomy with intra-operative Mitomycin C show no difference in post-operative IOP.
• Perfusion of glaucomatous human eyes with cationized ferritin shows segmental alterations of aqueous flow in the trabecular meshwork and juxta-canalicular tissue adjacent to Schlemm's Canal.
• Choroidal expansion pushing the iris forward may be an important mechanism of acute primary angle closure glaucoma.

Norbert Pfeiffer - Top 6

• Eyes with ocular hypertension with an optic disc haemorrhage have a four-fold higher probability of developing glaucoma than eyes without.
• In failed filtering blebs needling with injection of MMC causes less corneal problems than injection of 5-Fluorouracil and is similarly effective.
• Ocular hypertensive patients that convert to glaucoma often show a nasal step and arcuate changes in the visual field.
• Glaucoma shows signs of an auto-immune disease. At the moment it is not clear whether these changes induce glaucoma or are an epiphenomenon.
• Visual field testing with Humphrey sita standard is more sensitive than full threshold on the occasion of the first examination.
• When comparing sensitivity and specificity of HRT, GDx and
  OCT, OCT and GDx performed better than HRT in detection of glaucoma.

Rodolfo Perez Grossman - Top 11

• The seventh gene for POAG was mapped in chromosome 5 (GLC1G).
• The eye with more advanced glaucomatous cupping has a decreased CCT compared with his fellow eye with less cupping.
• Eyes with thinner corneas have lower IOPs than those with thicker corneas in the treatnent with brimonidine, but not with latanoprost.
• Better measurements taken in a supine position during routine daytime office visits can predict peak nocturnal IOP.•
• A high percentage of POAG patients under medical therapy with controlled IOP on single office measurement, presents significantly higher IOP measurements when performing a modified diurnal tension curve and water drinking test.
• A longer interval (0-2-5 min) between instillation of multiple eye drops may not improve effectiveness, while the inconvenience of a longer delay could negatively impact compliance.
• Patients should be advised to wait at least two minutes between eyedrops, to maximize efficacy.
• Trabeculectomy and phacotrabeculectomy, each with MMC, appear to offer similar effectiveness in IOP control over two years, though trabeculectomy with MMC may offer greater reduction from the baseline.
• Increased peripheral bleb vascularity is the best predictor zone for future failure of trabeculectomy.
• The cholesterol lowering statin drugs induce cellular relaxation in the trabecular meshwork and ciliary muscle cells via effects on cell shape, actin citoskeletal integrity and myosin ligth chain phosphorilation, and demostrate the ability to decrease IOP in an organ culture perfution model.
• MYOC, OPTN and APOE were separately but not interactively associated with POAG, suggesting the monogenic nature, rather than digenic or poligenic.
  

Keith Martin - Top 5 on axonal degeneration, gene therapy and stem cell treatments for glaucoma

Although IOP reduction has now been shown conclusively to reduce the progression of glaucoma, we are all aware of patients who continue to deteriorate, even at very low pressures. An important goal of future research in glaucoma is therefore to understand the mechanisms of retinal ganglion cell (RGC) death and to develop new ways to treat them. Gene therapy and stem cell therapy are techniques that have received a lot of recent attention because of their possible application to glaucoma treatment. Several important advances were reported at ARVO 2004.

• It has long been suspected that RGC death in glaucoma is, at least partly, related to axonal injury at the optic nerve head causing retrograde degeneration that eventually kills the cell body in the retina. Richard Libby, working with Simon John (this year's Cogan Award winner) at the Jackson Laboratory, reported important findings on how RGC axons and cell bodies die that may well be relevant to those working to protect or regenerate RGC. The DBA/2J strain of mice develops a condition similar to human pigment dispersion syndrome, with IOP elevation and selective loss of RGC over a period of months. John's group have found that the pro-apoptotic molecule Bax is necessary for glaucomatous RGC body degeneration but, interestingly, Bax is not necessary for optic nerve degeneration. Bax deficient DBA/2J mutants lost axons but retained completely normal numbers of RGC bodies despite prolonged periods of IOP elevation. Thus, RGC axon and cell body degeneration appear to be mediated by completely different mechanisms. The exciting possibility arises that it might be possible to prevent the cell body from dying as a consequence of axonal damage, perhaps leaving a population of 'dormant' RGC bodies in the retinas of patients with severe glaucoma to await future axonal regenerative strategies.
• RGC survival is dependent on a sufficient supply of neurotrophic factors. It has been suggested that neurotrophin deprivation may be involved in RGC death in glaucoma. Adriana Di Polo and her group at the University of Montreal, using an experimental rat glaucoma model, found that neurotrophin-induced RGC survival is critically dependent on activation of the mitogen-activated protein kinase (MAPK) pathway. They went on to demonstrate that gene therapy using an adeno-associated viral vector incorporating the gene for MEK, an upstream inhibitor of the MAPK pathway, markedly improved RGC survival, at least temporarily. Further work to explore similar mechanisms in larger animals is eagerly awaited in the hope that such techniques may eventually benefit human patients.

Currently available treatments for glaucoma all aim to slow the progression of the disease, but we have no therapies that can restore visual function once it has been lost. The unique properties of stem cells are a topic of much current interest throughout the neuroscience research community, because of the possibility that they may be capable of restoring some degree of function to the damaged nervous system. This year's ARVO saw an exciting mini-symposium on the application of stem cell transplantation to the eye.

• Sean Morrison from the University of Michigan summarised the properties of stem cells, including their ability to self-renew and to give rise to multiple diverse cell types under the control of a variety of lineage-determining factors. He identified some of the current problems in the field, including a lack of any truly specific markers or genes unique to stem cells and the fact that stem cell properties do appear to change over time in culture. He also pointed out that stem cells from different parts of the nerfvous system really are different and therefore it may well be best to use cells for therapy derived from sites anatomically close to the site of pathology.
• Tom Reh from the University of Washington gave an overview of how the regenerative potential of the vertebrate peripheral retina has changed during the course of evolution. Amphibians and fish have have large numbers of retinal stem cells in the ciliary marginal zone (CMZ) of the retina. Birds have smaller numbers of similar cells with progressively fewer seen in rodents and primates. The hedgehog signaling pathway is a key regulator of neural development and Reh proposed this pathway may act as a regulator of both prenatal and postnatal retinal growth. He also suggested that progressive reduction over evolution in the extent of the CMZ-derived retina may be due to loss of hedgehog signalling in the CMZ. The hedgehog signalling pathway is worth further investigation to help understand the behaviour of stem cells in the adult mammalian retina.
• Harry Quigley from the Wilmer Eye Institute reported successful incorporation of ciliary-body derived neural progenitor cells into the inner retinal layers of rats with experimental glaucoma. Approximately 7% of the progenitor cells injected intravitreally were found to incorporate into the host retina, with incorporation 1.6 to 3.7 times greater in glaucoma than non-glaucoma retinas. It will be exciting to explore whether such progenitor cells are capable of functional integration into the host retina and whether they can have a beneficial effect suggestive of potential usefulness in the future treatment of glaucoma.