The Impact of Oxidative Stress on Amyotrophic Lateral Sclerosis Induced Pluripotent Stem Cells and Their Neuronal Differentiation

Abstract

Amyotrophic Lateral Sclerosis (ALS) is a progressive, fatal neurodegenerative disease that affects motor nerve cells in the brain and spinal cord. There is currently no effective treatment for ALS disease. Although the etiology of the disease is not yet clearly known, environmental and genetic factors are effective in the development of the disease. It is known that oxidative damage is among the important factors in the development and progression of ALS. SOD1 mutation is encountered in approximately 20% of ALS cases. SOD1 is a Cu-Zn metalloprotein responsible for the conversion of superoxide to O2 and H2O2. This enzyme plays a key role in the antioxidant defense of the cell; it regulates cellular respiration and energy metabolism. For this reason, SOD1 mutation renders the defense mechanisms of the cells dysfunctional to a certain extent against oxidative stress. Oxidative stress associated with increased reactive oxygen species (ROS) levels can also cause genomic instability, differentiation, aging and even death in pluripotent stem cells (PSCs). In this thesis study, the effect of oxidative stress exposure of induced PSCs (iPSCs) on neuronal stem cells, motor neuron progenitor cells and on the motor neuron (MN) differentiation process were investigated. Although it is known that ALS MNs are sensitive to oxidative stress, its effects on the differentiation process has not been clarified. iPSCs of healthy donors and ALS patients were exposed to oxidative stress agents (50 μM H2O2 and 0.5 μg/mL LPS) and examined for changes in pluripotency markers and apoptosis-related gene expressions after 4- and 24-hour exposures followed by induced MN differentiation through lipofectamine mediated transfection of MN transcription factors. The changes in the gene expressions related to neuronal markers and pluripotency markers on the 1st, 3rd and 9th days of differentiation were comparatively examined. This preliminary study may contribute to accumulation of information in enlightening the potential link between early intrauterine exposures and dysfunctional MN differentiation and ALS pathogenesis