Update from the Institute of Neurosciences, Montpellier
Our team’s goal is to discover, test and develop treatments in order to prevent or limit visual impairment and to improve the autonomy and the quality of life of patients. Our efforts focus on a very severe form of syndromic Inherited Optic Neuropathy: Wolfram Syndrome (WS). WS is characterized by a rapid degeneration of retinal ganglion cells (RGC) resulting to severe visual impairment before the age of 20 years. To date, there is no treatment to stop the progression of the disease.
The analysis of biological samples from patients with the recessive WS revealed that the WFS1 protein is absent, or less stable, compared to the normal protein. This reduced quantity of WFS1 suggests that the re- expression of WFS1 through gene augmentation therapy could restore the protein function and thus possibly protect the cells from degeneration.
It is important to say that the eye is a perfect model for applying gene therapy approach. It is small, transparent, allowing for very precise visual monitoring. It is also a closed organ, relatively isolated from the rest of the body. RGC are easily accessed by the ocular surgeon who targets them through intravitreal injection, a current routine procedure used to inject medications in various retinal pathologies. In this regard, gene complementation for Wolfram patients is an ideal therapeutic approach to treat visual impairment. Consequently, micro-injection of a vector expressing the human WFS1 cDNA, directly in the vitreous close to the retinal ganglion cell layer should allow to prevent RGC dysfunction and degeneration.
We have studied mice models of WS. Our results indicate that mice reproduced the optic atrophy of WS patients with loss of visual acuity starting at 1 month. We designed a therapeutic vector expressing human WFS1 that we microinjected into the vitreous of Wfs1 mutant mice. We showed that the animals injected with the therapeutic vector have a stabilization of their visual acuity between 3 and 6 months post-injection, a decrease of optic disc pallor and axonal damages. A parallel approach is applied on wild type animals using the same vector in order to assess the innocuousness of the treatment and the transgene expression and distribution. These promising results lead us to continue these therapeutic approach.
Our project consists in demonstrating the validity of the pre-clinical approach to treat Wolfram Syndrome by gene therapy. Obtaining this proof of concept will allow to transfer the protocol to patients assess the therapeutic benefits in the short and medium.
Dr. Cécile Delettre, PhD
cecile.delettre@inserm.fr
http://www.inmfrance.com/inm/en/