Development and preclinical assessment of novel therapies for Epilepsy. Exploring the potential of human-derived cell lines and glial cell line-derived neurotrophic factor for network inhibition

Sammanfattning: Epilepsy is one of the leading neurological disorders affecting not only patients who suffer from seizures but also people around them and society in general. The striking one third of patients not responding to pharmacological treatments implies the necessity of developing alternative options for controlling seizures in these individuals. Moreover, the possibility to stop the progression of the disease before seizures occur would pose a viable option in the future. A rising treatment approach targeting focal epilepsies, such as temporal lobe epilepsy (TLE), commonly diagnosed as pharmacoresistant, is cell therapy. The results presented in this thesis, reflect the efforts to suppress seizures in the chronic phase of epilepsy by transplanting inhibitory GABAergic interneurons, and to ameliorate the outcomes of epileptogenesis after a brain-damaging insult by transplanting mesenchymal stem cells (MSCs) alone or modified to release glial cell line-derived neurotrophic factor (GDNF). These studies were performed in the post-status epilepticus (SE) rat model of TLE induced by systemic kainic acid injections.Using electrophysiology and optogenetics, the maturation and synaptic integration of human embryonic stem cell-derived GABAergic interneurons (hdInts) was confirmed in vitro in human neuronal networks and in vivo in the hippocampi of the rat TLE model. In both cases the cells differentiated mostly into calretinin and calbindin interneuron subtypes confirmed by immunohistochemistry. In hippocampal slices from the epileptic animals the optogenetic activation of these cells reduced epileptiform activity and with video monitoring, fewer seizures were detected in animals treated with hdInts.GDNF has reported anti-seizure effects in animal epilepsy models. The mechanism of this inhibitory potential was investigated, specifically how GDNF acts on principal neurons in the mouse and human hippocampus. An increase in frequency and amplitude of inhibitory postsynaptic currents was observed electrophysiologically. Additionally, this effect was attributed to the GDNF family receptor alpha-1 and the transmembrane receptor tyrosine kinase signalling pathway using electrophysiology and western blot.Next, the use of GDNF was combined with the use of MSCs as carriers. This approach was implemented to modify epileptogenesis by transplanting either naïve MSCs or GDNF-releasing MSCs into the hippocampi of rats one day after SE. Both cell types altered the progress of epileptogenesis as seen by analysing 35 days of continuous video-EEG recordings, the MSCs alone reducing seizure occurrence and the GDNF-MSCs prolonging the intervals between seizures. Some behavioural alterations of the epileptic animals were partially corrected after 5 weeks of monitoring, however, the elevated microglia activation was not changed by either of the cell types.In summary, the data presented in this thesis contribute to the development of the growing field of novel therapeutic approaches for epilepsy which may in the future benefit those patients whose seizures cannot be controlled by conventional drugs, or even prevent seizures from occurring.