A neurodegenerative perspective on mitochondrial optic neuropathies

Publication: www.ncbi.nlm.nih.gov | Publication Date: September 30, 2016

Authors: Patrick Yu-Wai-Man, Marcela Votruba, Florence Burté, Chiara La Morgia, Piero Barboni, and Valerio Carelli

Abstract

Mitochondrial optic neuropathies constitute an important cause of chronic visual morbidity and registrable blindness in both the paediatric and adult population. It is a genetically heterogeneous group of disorders caused by both mitochondrial DNA (mtDNA) mutations and a growing list of nuclear genetic defects that invariably affect a critical component of the mitochondrial machinery. The two classical paradigms are Leber hereditary optic neuropathy (LHON), which is a primary mtDNA disorder, and autosomal dominant optic atrophy (DOA) secondary to pathogenic mutations within the nuclear gene OPA1 that encodes for a mitochondrial inner membrane protein. The defining neuropathological feature is the preferential loss of retinal ganglion cells (RGCs) within the inner retina but, rather strikingly, the smaller calibre RGCs that constitute the papillomacular bundle are particularly vulnerable, whereas melanopsin-containing RGCs are relatively spared. Although the majority of patients with LHON and DOA will present with isolated optic nerve involvement, some individuals will also develop additional neurological complications pointing towards a greater vulnerability of the central nervous system (CNS) in susceptible mutation carriers. These so-called “plus” phenotypes are mechanistically important as they put the loss of RGCs within the broader perspective of neuronal loss and mitochondrial dysfunction, highlighting common pathways that could be modulated to halt progressive neurodegeneration in other related CNS disorders. The management of patients with mitochondrial optic neuropathies still remains largely supportive, but the development of effective disease-modifying treatments is now within tantalising reach helped by major advances in drug discovery and delivery, and targeted genetic manipulation.

Read the entire publication article here.

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3 Things on my Mind When I Work on Wolfram syndrome

While working on Wolfram syndrome there are three things that are always on my mind: improving clinical care, raising awareness, and providing a cure. These three things motivate myself and my team to work hard every day.

 

Improving Clinical Care

Our effort to understand the progression and neurological symptoms of Wolfram syndrome will help improve the clinical care we give our patients. Clinical trials throughout the world have specific qualifications before they begin and thanks to our researchers from around the globe in the last few years there has been significant progress and we now know the appropriate measurements to use in our clinical trials. There are also new hypotheses on how Wolfram syndrome affects the brain that will soon be tested in research models, which will lead to more targeted treatments for the neurological systems and improve the clinical care for the patients. This is all thanks to multiple foundations around the world like The Snow Foundation who are helping us raise awareness and helping us raise funds to make these trials possible.

 

Raising Awareness

Awareness for Wolfram syndrome has grown significantly with help from advocate groups such as The Snow Foundation and the Ellie White Foundation. We could not have accomplished the research we have conducted so far without these organizations and other advocate groups  and we want to thank and recognize all the groups for being a part of our research efforts. However we still depend heavily on NIH (National Institutes of Health) grants to help us with a significant amount of funds for our research to find a cure. NIH grants have increasingly difficult to get and we are working on getting more funding in the next year. The awareness and research funds play the largest part in helping us find a cure for Wolfram syndrome.

 

Providing a Cure

To provide a cure, we need to first delay the progression of the disease so that we have more time to develop regenerative therapies and gene therapies. To accomplish this milestone, I have been focusing on “repurposing” one of the FDA-approved drugs (i.e. existing drugs) for the treatment of patients with Wolfram syndrome.  We have been making steady progress on this.

As I reported before, we discovered that dantrolene sodium currently approved for the treatment of spasticity (muscle stiffness) could delay the progression of Wolfram syndrome in animal and cell models. We obtained the orphan drug designation of dantrolene sodium for the treatment of Wolfram syndrome from the US FDA early in 2016.

I have been working on the logistics to commence a clinical trial of dantrolene sodium for the treatment of Wolfram syndrome at our medical center. I hope to start the trial in December of this year and the plan is to enroll 25 patients or more. The trial may last 2 years. I plan to monitor safety, vision, neurological functions, and diabetes in our patients since those are the primary indicators of Wolfram syndrome. As I reported before, type 2 diabetes is associated with Wolfram syndrome 1 gene variations.

We are trying to get more funds from the National Institutes of Health to recruit more patients, and we want to thank The Snow Foundation and Ellie White Foundation for planning to support this trial financially.

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