Fig. 4. Neural progenitor cells (NPCs) overexpressing arginine decarboxylase (ADC) genes (ADC-NPCs) accumulate intracellular calcium by regulating mitochondrial function during ischemic stress. (A) Fluo-4AM-labeled ADC-NPCs were observed by live cell imaging analysis under both normal and ischemic conditions; the graph depicts the increased [Ca²⁺_i] levels in the ADC-NPCs in the resting state (Fluo-4AM only). (B) The graph shows the higher [Ca²⁺_i] levels in the ADC-NPCs in the excitation state (1 µM ionomycin treatment). (C and D) Small interfering RNA (siRNA)-treated and Fluo-4AM-labeled ADC-NPCs following oxygen-glucose deprivation (OGD. The graph shows the [Ca²⁺_i] levels in the resting (Fluo-4AM only; C) and excitation (1 µM ionomycin treatment; D) states. (E) The oxygen consumption rate (OCR) principle and (F) the OCR graph; all the NPCs were investigated using a Seahorse XF24 Extracellular Flux Analyzer (n=6~7 per condition). (G–I) The graphs depict the analysis of the area under the curve of the oxygen consumption rate (OCR-AUC) in the NPCs under normal and ischemic conditions. (G) Basal respiration, (H) ATP-linked respiration, and (I) maximal respiration under both normal and ischemic conditions. The error bars represent the mean±SEM.