1. Neuroprotection

Degenerative processes of the retina, as they occur in age-related macular degeneration or glaucoma, result in death of essential neuronal cells such as retinal ganglion cells or photoreceptors. Due to the multifactorial causes and the various genes involved, specific targeted therapies are often difficult in these diseases. There-fore, treatment is usually only symptomatic, e.g. by prevention or reduction of cell death. Aptamers, which specifically bind to their target molecules and thus exert neuroprotective effects, offer the possibility to de-velop new therapeutic options for retinal diseases. Our projects aim to generate novel therapeutic options currently based on tree aptamers. The first aptamer activates the signalling cascade of neurotrophic growth factors via receptor binding. The second aptamer binds and inhibits a central regulator of apoptosis and is thus expected to reduce the final cell death pathway. The third aptamer binds and inhibits a central proin-flammatory Interleukin, which prevents a further activation of the immune response. Similar to aptamers DNA-motifs offer the possibility to enhance neuroprotective effects, which we currently evaluate for AMD treatment. In addition, a stress regulated therapy system via expression vectors is under development. Furthermore, all these therapeutics extent our understanding of the underlying molecular pathomechanisms of retinal degenerative diseases.

2. Drug Delivery Systems

In case of many eye conditions, including AMD or glaucoma, the only effective medication is very frequent administration of highly concentrated eye drops or repeated intravitreal injections. Our drug-delivery system is a patent protected carrier system for efficient delivery of drugs to the eye. Our DNA-based nanoparticles can be loaded with various active compounds using different loading strategies. Thus a much lower concen-tration of the drug is needed resulting in reduction of side effects. Additionally, less frequent administration of medication can be achieved. Thereby improved therapy options can be offered and even substances which have been banned due to side effects or delivery problems can be used. We have developed and validated our carrier system with glaucoma drugs and antibiotics. As our nanoparticles show excellent adherence to impaired corneal tissue we conduct further research on treatment options for dry eye disease. In addition, we are linking the prior mentioned aptamers and DNA-motifs to our nanoparticles for improved delivery.

3. Gene delivery Systems

The effective transfer of genetic material into the target cells with as few side effects as possible is crucial for the efficacy of gene therapies. Currently, mainly adeno-associated viruses (AAV) are used as vector sys-tem in ocular gene therapy. Despite multiple positive study results, there is increasing evidence that local and systemic immune responses and ocular inflammation occur. Unfortunately, AAV can only transfer nucleic acid sequences of relatively small size (max. 4.8 kB). Consequently, the need for novel non-viral gene therapy approaches is high. There are two main obstacles to overcome: limited uptake into the cell and nucleus, and limited long-term stability or transient gene expression. The other disadvantage of the current therapy is that the current mode of subretinal application is very invasive. The stress caused by this injection is consid-ered to be very high for the cells already damaged in the patient, so that a gentler, more minimally invasive, method should lead to a significantly better therapeutic effect. Via biodegradable magnetic microparticles controlled by magnetic force, we pursue the goal of introducing larger DNA sequences than previously possible or entire plasmids into the retina in a minimally invasive manner and thus realizing a new approach to gene therapy. My very soon arriving junior group leader will further support this field by investigating on inorganic polymers provided with specific ligands to enable uptake via cell-typical receptors and thus enable targeted gene delivery.

4 . Organ cultures and spheroids

Models with simulated retinal degeneration are necessary to understand the underlying pathological pro-cesses and for testing innovative therapies. Not only public pressure and increasing regulations but also un-satisfactory results with rodent disease models demand for better and more robust disease models. A good alternative are organ cultures. We were able to establish different porcine retinal degeneration models over the last years. For example, oxidative stress is induced by H2O2, hypoxic mechanisms are activated by CoCl2 and degeneration via light-induced stress. Currently we are establishing a model for diabetic retinopathy. As a result, different disease-like pathways are activated in neuronal cells ultimately resulting in their cell death. In addition, we are working on more complex co-culture models to simulate AMD-like processes ex vivo. Furthermore, we are using spheroids. Spheroids consisting of different cell types are grown from adult primary porcine human ocular cell lines. The hanging drop method is mainly used for this purpose. Our sphe-roids are used for angiogenesis studies, biocompatibility studies and transfection experiments. Our organ culture models and spheroids, which can be used to model the pathogenesis of several diseases like glauco-ma or AMD, are used to evaluate neuroprotective effects of drugs/substances and to extent our understand-ing of the underlying molecular pathomechanisms of retinal degenerative diseases