An impressive line-up of speakers descended on Dublin on November 9 and 10 to present their findings at the Retina 2012 conference, including Professor Eberhart Zrenner from the University Of Tübingen pictured here with his Irish patient Saba. These world-class clinicians and scientists, who are working at the leading edge of scientific research, came from across Europe, the USA and Ireland to the meeting organised by Fighting Blindness that was held at Certus headquarters, St. Stephen’s Green, Dublin.
Jose Alain Sahel
Professor Jose-Alain Sahel of the Vision Institute, Paris, opened the conference with the first of the two keynote presentations of the day with an overview of some of the innovative therapies that his group are developing for inherited retinal disease. At the beginning of his presentation, Jose-Alain emphasised the importance of patient communication and involvement in the development of new therapies as being of the utmost priority. For example, he explained that there are two main types of photoreceptor cells involved in vision, rods and cones. Rods are more numerous and more sensitive than cones, and are useful for our dark adapted vision at night time. For patients however, it is the loss of cones that leads to central vision loss, and devastating complete blindness. The loss of cones is a late, secondary event which starts with the outer segments shortening and may occur many years after initial symptoms of RP.
During his presentation, Jose-Alain quoted Alan Wright of the Medical Research Council in the UK, “Preserving cones would prevent 1.5 million people worldwide from becoming blind, since in an age of artificial lighting, we function very well without rods.”
His group have demonstrated that administration by viral gene therapy of Rod-derived Cone Viability Factor (RdCVF), a potent anti-oxidant, to mouse models of RP led to an increase in cone survival and cone function being preserved. Also interestingly, this effect was seen irrespective of the causative mutation for RP.
This approach is useful for preserving existing cones, but what of patients where the cone cells have already degenerated? Research from Jose-Alain’s team and others in his institute has also shown that in RP, most cone cells are actually dormant, and not dead. His team have employed a technology known as optogenetics in order to re-sensitise these dormant cone cells to light. This again involves using viral gene therapy to deliver a bacterial gene known as halorhodopsin to the cells. They showed that this “biologic implant” can rewire the neural circuitry of the eye and they have identified certain patients that may benefit from this technology. In the future, this therapy may be combined with other therapeutic approaches that either corrects the defective gene that cause the retinal degeneration or with those that increase the survival of cone cells. He is confident that this therapy will be used not only in RP, but in other retinal degenerative diseases.
Finally, Professor Sahel once again emphasised the importance of placing the patient perspective at the heart of new developments. He explained some of the new approaches to document the outcomes of new and potential therapies. In Paris they have developed virtual simulators that reproduce daily life situations, (such as an apartment, street, shop and obstacles) in order to better assess the usefulness of these novel therapies in real life situations.
Our next presentation of the morning by Professor Frans Cremers was of current interest to all at Fighting Blindness. As we embark on our Target 3000 project, it was an honour to listen to Frans who has over 20 years’ experience identifying the mutated genes that are the molecular basis for retinal degenerations and are world authorities in this area. Recently, his group have utilised a technology known as Next-Generation Sequencing in order to identify both existing and new mutations associated with these conditions. This technology is the same that will be employed by the research team in Trinity College Dublin as part of the Target 3000 project.
Frans outlined the workflow for their gene sequencing project that is known as RP5000 in the Netherlands. This consists of obtaining informed consent from the individual to take their blood for gene sequencing, performing the next generation sequencing on the patient sample, and analysing the genes that are known to be involved in retinal diseases for mutations. Any information about an identified mutation is then relayed directly back to the patient. In the event where the gene mutation cannot be identified, a follow up by a research group analyses the entire sequence for other disease causing mutations. Frans also presented some of the difficult case studies outlining the methodology that was employed where his team have identified mutations in isolated forms of RP where there is no family history.
Professor Wolfgang Drexler from the Medical University in Vienna was next to take to the stage in order to speak about a fascinating medical imaging technique known as Optical Coherence Tomography (OCT). This technology has found a very successful application in ophthalmology by allowing the clinician to produce a highly detailed picture of the retina, which is essentially a non-invasive biopsy. OCT allows unprecedented visualisation of each individual cell in the retina, which aids the ophthalmologist not only in their diagnosis but also provides a crucial tool in ophthalmology clinical research. Wolfgang noted that not only does OCT offer a resolution of the retina that is 10 to 100 times better than ultrasound or MRI, it can be performed at a much higher speed which is preferable for the patient. Wolfgang ended his talk by bringing the conference attendees on a journey inside and through a blood vessel reconstructed in 3D by OCT, demonstrating the imaging power of this cutting-edge imaging technology.
The focus of Professor Nicolás Cuenca’s laboratory in the University of Alicante is on developing new therapeutic compounds that reduce the rate of retinal degeneration. During degeneration the retina responds to injury by remodelling, beginning with subtle changes in the neuronal structure and later by large scale reorganisation. One of the key stages during this process is the loss of photoreceptor cells by cell death. Nicolás presented a compelling story where he presented data about a compound known as TUDCA which is a potent antioxidant that is found in high quantities in the bile of black bears and has been synthetically available since 1954. Animals treated with TUDCA demonstrated lower numbers of photoreceptor cell death compared to controls. He also showed that TUDCA prevents the reorganisation of the retina seen in late stage of retinal injury and maintains the network of blood vessels of the retina in a mouse model of RP. Similarly, Nicolás presented data on another compound known as safranal, which is an extract from saffron, noted for its antioxidant properties. He noted that dietary supplementation with safranal slowed photoreceptor cell degeneration and this work suggests that safranal could be useful to retard retinal degeneration in patients with RP.
Professor Cuenca ended his presentation by speaking about his team’s research focusing on pro-insulin as a therapy for RP. As many of Fighting Blindness members are aware, RP is characterised by a variety of mutations in at least 35 different genes. The broad genetic nature of the disease has long frustrated scientists and clinicians in developing therapeutic strategies for this disease. This has led his team to explore mechanisms that focus on maintaining photoreceptor numbers rather than treating the individual gene mutations. His team were the first to demonstrate that gene therapy delivery of the human gene pro-insulin (which is a hormone precursor to insulin) could preserve photoreceptor cells, leading to treated subjects maintaining 49% more photoreceptors than non-treated controls.
Professor Jane Farrar of Trinity College Dublin was on hand to adeptly fly the flag for Irish ocular research with her presentation. She, along with Professor Pete Humphries and Dr. Paul Kenna of Trinity have spent many pioneering years identifying the genetic basis of retinal degenerations and are now in the process of progressing this research towards the development of gene based therapies for these disorders. As mentioned previously, RP poses a huge challenge for gene therapy, for example in rhodopsin-linked autosomal dominant RP alone there are over 150 individual mutations in the rhodopsin gene that can cause the disorder. Jane explained how they have circumvented this problem using a novel and clever method. They employ clinically safe and effective gene therapy vectors to deliver a molecule that “silences” both the faulty and normal gene copies of Rhodopsin. At the same time they deliver a copy of Rhodopsin that codes for the normal protein but is subtly altered so it does not become silenced itself. They term this approach suppression and replacement (S&R). Jane discussed the excellent preclinical data in animal models and the plan to progress towards human clinical trials in the very near future.
Jane also spoke about the development of gene therapy for the mitochondrial disorder Leber Hereditry Optic Neuropathy (LHON). The mitochondria are often referred to as the “powerhouses of the cell” because the mitochondria take in glucose and produce energy. In LHON, a mutation in the mitochondrial DNA leads to a loss of energy transfer to the optic nerve and a degeneration of the cells, resulting in loss of vision. In their work, Jane explained how they employ viral technology to deliver a gene that provides energy back to the eye cells, preventing those cells from dying and has demonstrated the effectiveness of this treatment in a mouse model of LHON. This study also delivers the gene by direct injection into the eye, which is a more clinically relevant method of delivery as the therapy is directly targeted to the retinal ganglion cells. This animal study is the first step forward in the preparation towards a future clinical trial.
Our next speaker of the day, Professor Robin Ali, is a regular visitor to Ireland in his role as Chief Scientific Advisor to Fighting Blindness. The primary focus of Robin’s team in University College London and Moorfields Eye Hospital is the development of novel treatments for retinal disease. Over the past fifteen years they have been at the forefront of investigating the basic aspects of gene transfer to the eye and have already developed gene therapy protocols in over a dozen different animal models of retinal degenerations. They are now transferring this extensive knowledge to human clinical trials.
In 2008, Robin and his collaborators were the first in the world to perform a gene therapy clinical trial for inherited blindness, involving the disorder Leber Congenital Amaurosis (LCA) with RPE65 mutations. LCA is an acute form of inherited blindness resulting in a severe loss of sight from birth onwards. This initial trial proved the safety of the experimental therapy, but also encouragingly led to a regaining of some sight in the treated adults. Robin explained how they have now extended this trial to treat patients from the ages of 5 years old, in order to deliver the therapy before the rapid loss of photoreceptor cells.
During his presentation, Robin outlined his research group’s strategy of beginning their initial studies in rare conditions such as LCA that are more amenable to therapy and moving towards developing treatments involving gene therapy for some of the more common, but also more complicated disorders. One such disorder is X-linked Retinitis Pigmentosa, which is known to be caused by mutations in three genes. Robin presented data regarding one of these genes, RPGR, and their efforts to work on a continuous pipeline of treatments. Robin noted that the main challenge is to increase the number of gene therapies in clinical trials and to optimise these therapies for the patient.
The expertise of the group of Professor John Flannery of the University of California, Berkely is directed towards refining viral gene therapy. John explained that although gene therapy has gone through a period of exciting advancement, especially with three landmark clinical trials for Leber’s Congenital Amaurosis (LCA), there are still a number of technical shortcomings that need to be overcome in order to deliver this form of treatment successfully to other retinal diseases. For example, highly efficient gene delivery to photoreceptors currently requires a subretinal injection (injection in the space under the retina) which is invasive for the patient and can induce retinal damage. The Flannery lab noted that müller cells are a cell type that spans the entire retina, however they are difficult cells to infect with current viral therapy. In order to engineer new viral therapies, John explained how his team harness the process that created viruses in the first place: evolution. They used this “directed evolution” method to create a pool of mutants and screened them for those that had the ability to only infect the müller cells. Using this targeted approach, they have successfully delivered by injection into the vitreous (the thick clear substance that fills the centre of the eye) a replacement copy of RS1 in animal models of X-linked retinoschisis. This codes for retinoschisin, mutations in which cause this rare dehabilitating retinal degeneration, characterised by splitting of the retina and loss of central vision.
Another strand of research that John’s team are interested in is restoring light responsiveness to a cell type known as retinal ganglion cells that may help individuals at end stage degeneration i.e. where there are no functioning photoreceptor cells. Although blindness occurs following loss of photoreceptor cells, much of the architecture of the retina actually remains intact, and retinal ganglion cells are the longest surviving cells in most hereditary retinal disorders. His team introduced a light channel by gene therapy to these cells in mice and recently in dogs and showed that it could restore several light responses of the visual system. While at early stage, this work may be of huge benefit to individuals where there are all the photoreceptor cells have degenerated fully.
Our keynote speaker of the afternoon, Professor Eberhart Zrenner from the University Of Tübingen, delivered a fascinating and engaging talk entitled “What blind Retinitis Pigmentosa patients can see when using the new subretinal wireless implant Alpha-IMS.” Eberhart is the co-ordinating director of an international team that are developing microchips to be surgically implanted beneath the transparent top membrane of the retina and into the macular region. This is the area of the eye where clear sharp central vision is formed. The heart of the retinal implant is approximately 3 x 3 mm2 large and consists of a silicon chip with 1,500 light sensitive elements. The chip senses light and transmits light signals back to the brain. The implant is controlled by a handheld, battery powered device which receives signals from a small device that is implanted under the skin behind the ear.
All components of the retinal chip must be biocompatible and demonstrate long term stability for many years. This is a huge technological challenge, which has led the team to explore the use of new materials and combinations. The components that are in contact with the surrounding tissue must be in a sealed protective layer to protect the device from the corrosive environment of the body. Eberhart explained that the retinal implants are well tolerated, and reassuringly remarked that although it is seven years since the first chips were implanted, they still look like new.
Eberhart then played some footage of one of the success stories of the retinal chip, a Finnish man named Miikka Terho, who was implanted with the retinal implant in 2010. Miika was able to distinguish between letters, a clock and amusingly his own name. When researchers placed letters reading MIKA in front of him, Miikka replied, “Do you think I’m a Formula 1 driver?”, as the research staff had confused the spelling of his name with fellow Finn, the race car driver Mika Hakkinen. Although the images generated by the retinal chip are in black and white and are not high resolution, most patients have trained their brain to interpret the images that they see. Eberhart then played more video clips showing how his patients are adapting; a woman points out her cutlery, her drink and her plate in a café; a young man can tell that his fiancé is smiling and laughing; a father plays with his young daughter and spots her bracelet which is reflective and easy to distinguish.
Professor Zrenner emphasised that although the development of retinal chip technology is still very much in its infancy, it has shown promising results. He expressed the certainty that the technology is already improving the mobility and quality of life of his patients. He concluded his presentation with a personal anecdote reminiscing about watching the first televised World Cup Final in 1954 where West Germany beat Hungary 3-2 in Switzerland. “Although it was black and white and the picture wasn’t very good…..it was still great!”
We in Fighting Blindness would like to thank all of our speakers and attendees who helped make Retina 2012 such a great success this year. The opportunity for interaction with the highest calibre scientists and clinicians involved in vision research will help to inspire our next generation of Irish researchers. We would also like to express thanks to all our members and supporters for their optimism and drive in helping Fighting Blindness ensure that these new developments will lead to patient-focused treatments in the fastest possible timeframe.