siRNA-basierte Therapie von Tauopathien
Final Report Abstract
Aggregation and hyperphosophorylation of the microtubule-associated protein Tau (MAPT) are major factors in the development of brain diseases, collectively called Tauopathies. These includes disorders such as Alzheimer´s disease, Progessive Supranuclear Palsy and others. Until today there is no current treatment for Tauopathies and options for symptomatic treatment are very limited. A novel treatment strategy might be down-regulation of mutated and malign Tau protein expression. Such a strategy would lead to less protein accumulation and concomitant slower disease progression, or even a remission of the disease. Small interference RNA (siRNA) has been developed as a powerful tool to silence specific genes of interest and their corresponding protein expression. We have here explored the siRNA interference technique to knockdown the expression of specific disease-related proteins in postmitotic neurons in vitro and in vivo. In order to deliver siRNA into cells, several techniques had been suggested. We have specifically investigated multiple transfection agents for postmitotic neurons in vitro. We found that, in our hands, most previously used transfection agents were not effective in or toxic to cultured neurons. When administered in the living brain, most transfection agents were limited by high toxicity, low diffusibility, or limited efficacy. Finally, however, we managed to identify one particular approach, which showed significant knockdown in primary neuronal cultures and in the living brain, leading to profound silencing of Tau in absence of neuronal loss and of astroglial or microglial reaction. We then used a subacute model of neurodegeneration to provide the proof-of-principle that knockdown of specific proteins by siRNA injection can rescue neurons in vivo from degeneration. This approach does not rely on the previously reported use of viral vectors for shRNAs, which have the disadvantage of long production time, high cost, irreversibility of the effects, and inflammatory responses to the virus, but is a rather versatile, inexpensive, and apparently safe method. Our data represent an important step forward in investigating the effect of siRNA interference in postmitotic neurons in vitro and in the brain parenchyma. We are now aiming to extend our approach to more chronic situations, as they are typically relevant for neurodegenerative diseases. More research effort is required to bring these promising new applications nearer to potential applications in clinical practice.
