Retinal degeneration represents a group of blinding diseases that are increasingly impacting the health and well-being of affected patients. More than 150 genes are known and more being discovered causing retinal disorders upon mutation. About 45 million people are blind worldwide (Europe 10 million, Germany 0.1 million). It is estimated that by 2020, over 76 million (www.vision2020.org) will suffer from vision loss or blindness due to age-related macular degen eration (AMD), the most common cause of retinal degeneration in the elderly. In Germany 1 million patients already suffer from high vision loss and about 2 million people have been diagnosed with AMD (1:10 above age 60). AMD is anticipated to be epidemic by increasing 6-fold until 2025 (NIH, USA; BMBF Roadmap 2007). Although loss of photoreceptors is the major reason for vision loss, in other retinal diseases, like glaucoma (ganglion cell loss), damage of other neurons is causative. Development of various therapies targeting prevention, progression and repair is thus pressing and will not only contribute to maintain mobility, life quality and indepen dence, but also to reduce the social annual cost due to vision loss (>500 million € in Germany today).
Frontiers of retinal research: Fortunately recent research provided remarkable proof-of-principle evidence on neuronal regeneration, retinal tissue engineering as well as neuronal replacement by cell transplantation in the retina opening up a new field of basic science of regenerative medicine. In the retina of adult mice a limited amount of neuronal regeneration by endogenous de-novo neurogenesis could be stimulated after neuron loss in vivo. Further, protocols for deriving retinal progenitor from human stem cell lines have been developed and derived photoreceptors integrate into adult mouse retina after transplantation.
Research in regeneration is motivated by the goals of attaining a fundamental description of the plasticity of the retina, such as its role in health and disease as well as understanding the retina’s endogenous potentials for prevention, compensation and regeneration in neurodegenerative and age-related diseases. Although fundamentally driven by the quest for knowledge, the ensuing research is performed at the edge of what is feasible in regenerative medicine and hence drives the development of novel therapeutic approaches in many areas. We propose that by studying regeneration we might glean novel knowledge towards the development of defined strategies for cell neuroprotection, replacement, repair, reprogramming and engineering from the regenerative programs. The ultimate goal is to make the research also available to the human retina, where loss of neurons frequently leads to permanent functional impairment.
