Comparing the mitochondrial signatures in ESCs and iPSCs and their neural derivations.

Embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) have distinct origins: ESCs are derived from pre-implanted embryos while iPSCs are reprogrammed somatic cells. Both have their own characteristics and lineage specificity, and both are valuable tools for studying human neurological development and disease. Thus far, few studies have analyzed how differences between stem cell types influence mitochondrial function and mitochondrial DNA (mtDNA) homeostasis during differentiation into neural and glial lineages. In this study, we compared mitochondrial function and mtDNA replication in human ESCs and iPSCs at three different stages - pluripotent, neural progenitor and astrocyte. We found that while ESCs and iPSCs have a similar mitochondrial signature, neural and astrocyte derivations manifested differences. At the neural stem cell (NSC) stage, iPSC-NSCs displayed decreased ATP production and a reduction in mitochondrial respiratory chain (MRC) complex IV expression compared to ESC-NSCs. IPSC-astrocytes showed increased mitochondrial activity including elevated ATP production, MRC complex IV expression, mtDNA copy number and mitochondrial biogenesis relative to those derived from ESCs. These findings show that while ESCs and iPSCs are similar at the pluripotent stage, differences in mitochondrial function may develop during differentiation and must be taken into account when extrapolating results from different cell types.Abbreviation: BSA: Bovine serum albumin; DCFDA: 2',7'-dichlorodihydrofluorescein diacetate; DCX: Doublecortin; EAAT-1: Excitatory amino acid transporter 1; ESCs: Embryonic stem cells; GFAP: Glial fibrillary acidic protein; GS: Glutamine synthetase; iPSCs: Induced pluripotent stem cells; LC3B: Microtubule-associated protein 1 light chain 3β; LC-MS: Liquid chromatography-mass spectrometry; mito-ROS: Mitochondrial ROS; MMP: Mitochondrial membrane potential; MRC: Mitochondrial respiratory chain; mtDNA: Mitochondrial DNA; MTDR: MitoTracker Deep Red; MTG: MitoTracker Green; NSCs: Neural stem cells; PDL: Poly-D-lysine; PFA: Paraformaldehyde; PGC-1α: PPAR-γ coactivator-1 alpha; PPAR-γ: Peroxisome proliferator-activated receptor-gamma; p-SIRT1: Phosphorylated sirtuin 1; p-ULK1: Phosphorylated unc-51 like autophagy activating kinase 1; qPCR: Quantitative PCR; RT: Room temperature; RT-qPCR: Quantitative reverse transcription PCR; SEM: Standard error of the mean; TFAM: Mitochondrial transcription factor A; TMRE: Tetramethylrhodamine ethyl ester; TOMM20: Translocase of outer mitochondrial membrane 20.