Distinct Mitochondrial Remodeling During Mesoderm Differentiation in a Human-Based Stem Cell Model

Abstract

Given the considerable interest in using stem cells for modeling and treating disease, it is essential to understand what regulates self-renewal and differentiation. Remodeling of mitochondria and metabolism, with the shift from glycolysis to oxidative phosphorylation (OXPHOS), plays a fundamental role in maintaining pluripotency and stem cell fate. It has been suggested that the metabolic “switch” from glycolysis to OXPHOS is germ layer-specific as glycolysis remains active during early ectoderm commitment but is downregulated during the transition to mesoderm and endoderm lineages. How mitochondria adapt during these metabolic changes and whether mitochondria remodeling is tissue specific remain unclear. Here, we address the question of mitochondrial adaptation by examining the differentiation of human pluripotent stem cells to cardiac progenitors and further to differentiated mesodermal derivatives, including functional cardiomyocytes. In contrast to recent findings in neuronal differentiation, we found that mitochondrial content decreases continuously during mesoderm differentiation, despite increased mitochondrial activity and higher levels of ATP-linked respiration. Thus, our work highlights similarities in mitochondrial remodeling during the transition from pluripotent to multipotent state in ectodermal and mesodermal lineages, while at the same time demonstrating cell-lineage-specific adaptations upon further differentiation. Our results improve the understanding of how mitochondrial remodeling and the metabolism interact during mesoderm differentiation and show that it is erroneous to assume that increased OXPHOS activity during differentiation requires a simultaneous expansion of mitochondrial content.

Early dynamic changes in iPSC oxygen consumption rate predict future cardiomyocyte differentiation

“…Our results indicate that on average lower oxygen consumption during the first 6 days of the CM differentiation protocol results in higher cTnT‐positive signal (Figure 2b). The decrease in mitochondrial content has been reported during mesoderm differentiation (Mostafavi et al, 2021) which our findings may capture and attribute to the subsequent successful CM differentiation.…”

“…However, the suggested approach can be translated to the data acquired from the bioreactor and the model can be re‐trained, given that the predictive power of the derived metrics is already proven in principle. The Wnt signaling modulation protocol used to differentiate CMs in this article drives iPSCs to commit to mesoderm in the first 48 hours of differentiation and to cardiac mesoderm in the first 72 hours accompanied by a significant drop in mitochondrial DNA copy number (Mostafavi et al, 2021). Our results highlight the metabolic shift occurring in critical time window of the first 72 hours of the CM differentiation.…”

1H NMR Metabolite Monitoring during the Differentiation of Human Induced Pluripotent Stem Cells Provides New Insights into the Molecular Events That Regulate Embryonic Chondrogenesis

“…Pyruvate was significantly increased between Stage 1 and Stage 2, consistent with it being a key metabolic promoter of differentiation to mesodermal cell lineages [ 57 , 58 ]. The increase in pyruvate also correlates with previous studies that report the maturation of mitochondria in differentiating hESC as being at a stage equivalent to mesoderm formation [ 59 ]. Increased pyruvate and acetate (the precursor of acetyl Co-A) within our Stage 2 cultures may therefore reflect the bioenergetic shift in favour of oxidative phosphorylation, and this is further supported by the increase in levels of taurine required to maintain the health and function of mitochondria [ 60 ] and the significant decrease in lactate corresponding to a reduction in aerobic glycolysis.…”

DOT1L regulates lung developmental epithelial cell fate and adult alveolar stem cell differentiation after acute injury

“…Loss of Dot1l led to the emergence of a novel AT2 cell state characterized by elevated OxPhos gene expression and elevated expression of a subset of important transcription and epigenetic factors. The increase in OxPhos gene expression is interesting as it is also associated with differentiation in other cellular systems including T cells ( Shin et al., 2020 ) and stem cells ( Mostafavi et al., 2021 ). While the emergence of an OxPhox metabolic signature could represent the enhanced differentiation of AT1 cells from AT2 cells after loss of Dot1l , the increase in OxPhox gene expression observed in the AT2b state was significantly greater than that observed in AT1 cells.…”