RESUMEN
Disease modeling has become challenging in the context of amyotrophic lateral sclerosis (ALS), as obtaining viable spinal motor neurons from postmortem patient tissue is an unlikely possibility. Limitations in the animal models due to their phylogenetic distance from human species hamper the success of translating possible findings into therapeutic options. Accordingly, there is a need for developing humanized models as a lead towards identifying successful therapeutic possibilities. In this study, human embryonic stem cells-BJNHem20-were differentiated into motor neurons expressing HB9, Islet1, and choline acetyl transferase using retinoic acid and purmorphamine. These motor neurons discharged spontaneous action potentials with two different frequencies (< 5 and > 5 Hz), and majority of them were principal neurons firing with < 5 Hz. Exposure to cerebrospinal fluid from ALS patients for 48 h induced several degenerative changes in the motor neurons as follows: cytoplasmic changes such as beading of neurites and vacuolation; morphological alterations, viz., dilation and vacuolation of mitochondria, curled and closed Golgi architecture, dilated endoplasmic reticulum, and chromatin condensation in the nucleus; lowered activity of different mitochondrial complex enzymes; reduced expression of brain-derived neurotrophic factor; up-regulated neurofilament phosphorylation and hyperexcitability represented by increased number of spikes. All these changes along with the enhanced expression of pro-apoptotic proteins-Bax and caspase 9-culminated in the death of motor neurons.