|Ph.D Student||Robicsek Odile|
|Subject||Human Hair-Derived Induced Pluripotent Stem Cells (iPSC)|
as a Model to Study Neurodevelopment in
|Department||Department of Medicine||Supervisor||Professor Dorit Ben-Shachar|
|Full Thesis text|
One of the prevailing hypotheses suggests schizophrenia as a neurodevelopmental disorder, involving dysfunction of dopaminergic and glutamatergic systems. Accumulating evidence proposes mitochondria as an additional pathological factor in schizophrenia. An attractive model to study processes related to neurodevelopment in schizophrenia is reprogramming of somatic cells into induced pluripotent stem cells (iPSC) and differentiating them into different neuronal lineages.
iPSC from three patients suffering from severe paranoid schizophrenia and from two controls were reprogrammed from hair follicle keratinocytes, because of their accessibility and common ectodermal origin with neurons. iPSC were differentiated into Pax6 ? /Nestin ? neuronal precursors and then further differentiated into β3-Tubulin ? /TH ? /DAT ? dopaminergic neurons. In addition, iPSC were differentiated through embryonic bodies into β3-Tubulin ? /Tbr1 glutamatergic neurons. Schizophrenia patients-derived dopaminergic cells showed severely impaired ability to differentiate, whereas glutamatergic cells were unable to maturate. Mitochondrial respiration and its sensitivity to dopamine-induced inhibition were impaired in schizophrenia patients-derived keratinocytes and iPSC. Moreover, we observed dissipation of mitochondrial membrane potential and perturbations in mitochondrial network structure and connectivity in dopaminergic cells along the differentiation process and in glutamatergic cells. Further we transferred isolated active normal mitochondria (IAN-MIT) into schizophrenia patient various cells to study the link between impaired neuronal differentiation and mitochondrial dysfunction. A few studies have shown the ability of mitochondria to transfer between cells and improve their function. We studied the ability of IAN-MIT to enter the cells inducing long lasting improvement of mitochondrial function and of the differentiation in schizophrenia patients-derived iPSC into glutamatergic neurons. We found improved mitochondrial cellular respiration, membrane potential (Δym) and network dynamics in IAN-MIT transferred schizophrenia patients cells. In addition, we observed increased expression of glutamatergic neuronal markers including β3-Tubulin, Tbr1, synapsin 1 and the number of synaptic contacts expressed by synapsin 1 and PSD-95 co-localization, as well as a higher activation of the glutamate-glutamine cycle in IAN-MIT transferred schizophrenia patients-derived cells. Finally, transfer of IAN-MIT had no significant effect on the impaired spontaneous or peroxide-induced apoptosis in schizophrenia patients-derived cells, suggesting that the improvement in neuronal differentiation following IAN-MIT transfer was not related to apoptotic processes in our experimental model. Additionally, it implies that the IAN-MIT transfer was not particularly toxic under the study conditions.
Our data unravel perturbations in neural differentiation and mitochondrial function, which may be interconnected, and of relevance to dysfunctional neurodevelopmental processes in schizophrenia.