Developing Cell-Based Therapies for RPE-Associated Degenerative Eye Diseases.

In developed countries, blindness and visual impairment are caused mainly by diseases affecting the retina. These retinal degenerative diseases, including age-related macular dystrophy (AMD) and inherited retinal diseases such as retinitis pigmentosa (RP), are the predominant causes of human blindness worldwide and are responsible for more than 1.5 million cases in France and more than 30 million cases worldwide. Global prevalence and disease burden projections for next 20 years are alarming (Wong et al., Lancet Glob Health 2(2):e106-e116, 2014) and strongly argue toward designing innovative eye-care strategies. At present, despite the scientific advances achieved in the last years, there is no cure for such diseases, making retinal degenerative diseases an unmet medical need.The majority of the inherited retinal disease (IRD) genes codes for proteins acting directly in photoreceptors. Yet, a few of them are expressed in the retinal pigment epithelium (RPE), the supporting tissue necessary for proper functioning of the photoreceptors. Among retinal degenerative diseases, impairment of some RPE genes engenders a spectrum of conditions ranging from stationary visual defects to very severe forms of retinal dystrophies in which the RPE dysfunction leads to photoreceptors cell death and consecutive irreversible vision loss. The accessibility of the eye and the immune privilege of the retina, together with the availability of noninvasive imaging technologies, make such inherited retinal dystrophies a particularly attractive disease model for innovative cell therapy approaches to replace, regenerate, and/or repair the injured RPE tissue. Proof-of-concept studies in animal models have demonstrated the safety and efficacy of the engraftment of therapeutic cells either to support RPE cell functions or to provide a trophic support to photoreceptors. These different approaches are now in the pipeline of drug development with objective to provide first cell-based treatments by 2020.This chapter will focus on the different cell-based strategies developed in the past and current approaches to prevent photoreceptor death in RPE-associated degenerative eye diseases.