American and Arab researchers are currently working together on a breakthrough study to develop a gene therapy that would help treat a rare, hereditary retinal disease.
The therapy has been shown to restore lost vision in animal models of retinitis pigmentosa (RP).
The RP patients first experience defective dark adaptation or "night blindness," followed by reduction of the peripheral visual field known as tunnel vision, sometimes followed by loss of central vision late in the course of the disease.
The team led by Dr Kang Zhang, professor of ophthalmology at the University of California, San Diego School's Shiley Eye Center and director of the UCSD Institute for Genomic Medicine, and Dr Fowzan Alkuraya, senior clinical scientist and head of developmental genetics unit at King Faisal Specialist Hospital and Research Centre, Saudi Arabia are using receptor protein called MERTK that is expressed in the retinal pigment epithelium,
It is the pigmented cell layer just outside the retina that closely interacts with photoreceptors in the maintenance of visual function.
Patients with loss of MERTK function have a defect in phagocytosis - a mechanism used to remove pathogens and cell debris.
As a result of this defect, debris accumulates between the photoreceptors and retinal pigment epithelium, resulting in death of photoreceptors and loss of vision.
The researchers plan to deliver the MERTK gene in a viral vector a carrier commonly used to deliver genetic material to treat these cells in order to restore function of photoreceptors.
It showed that viral vector delivery of MERTK corrected the mutant gene and restored vision.
The same type of vector has been successfully tested in both animals and humans for a similar type of early-onset retinal degeneration called Leber's congenital amaurosis.
The research team's next step is to show that such gene therapy is safe in further animal studies, to be conducted in China, along with additional rat studies that will be conducted at UC San Diego and at the University of Florida.