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With its high prevalence among the elderly, the movement disorder Parkinson’s disease (PD) poses a major challenge for our society. Unfortunately, despite continuous efforts from the research community, we still lack the disease-modifying treatments for this condition. Therefore, it is of great importance to develop suitable models, which can be employed to better understand the molecular mechanisms underlying PD. In this context, iPSC technology offers a possibility to study the disease pathogenesis using patient-derived brain cells. In recent years, astrocytes have come into the spotlight as potential major contributors to PD development. Yet, there is a limited number of studies utilizing iPSC-derived models to examine PD-linked mutations at endogenous levels. This thesis aims to address the described gap by studying the effect of the A53T α-synuclein on the physiology of human iPSC-derived astrocytes. To identify a suitable model, we first compared two published protocols for the generation of iPSC astrocytes, referred to as Oksanen and Palm method, respectively. A transcriptomic analysis revealed higher maturation characteristics for Oksanen astrocytes. Furthermore, these astrocytes showed a higher similarity to their human postmortem counterparts. Applying the Oksanen protocol, we generated astrocytes derived from a healthy individual and a patient carrying the G209A mutation in SNCA, corresponding to p.A53T substitution in α-synuclein. The utilization of single-cell RNA sequencing allowed us to identify perturbed molecular mechanisms exclusively in pure astrocytic populations. We could demonstrate that astrocytes have a decreased capacity to differentiate. Furthermore, we observed a distinct response of the two cell lines to triggers of activation. Interestingly, activated patient astrocytes also showed changes in pathways related to mitochondrial homeostasis. Taken together, we show that A53T α-synuclein has a profound effect on the function of iPSC-derived astrocytes. In particular, we could demonstrate that patient astrocytes differ from healthy control cells in their activation status and with respect to mitochondrial biology. Further investigation will be required to elucidate the impact of the identified perturbations on the astrocyte-neuron interplay in the context of PD.

Converging evidence made clear that declining brain energetics contribute to aging and are implicated in the initiation and progression of neurodegenerative disorders such as Alzheimer's and Parkinson's disease. Indeed, both pathologies involve instances of hypometabolism of glucose and oxygen in the brain causing mitochondrial dysfunction, energetic failure and oxidative stress. Importantly, recent evidence suggests that astrocytes, which play a key role in supporting neuronal function and metabolism, might contribute to the development of neurodegenerative diseases. Therefore, exploring how the neuro-supportive role of astrocytes may be impaired in the context of these disorders has great therapeutic potential. In the following, we will discuss some of the so far identified features underlining the astrocyte-neuron metabolic crosstalk. Thereby, special focus will be given to the role of mitochondria. Furthermore, we will report on recent advancements concerning iPSC-derived models used to unravel the metabolic contribution of astrocytes to neuronal demise. Finally, we discuss how mitochondrial dysfunction in astrocytes could contribute to inflammatory signaling in neurodegenerative diseases.