Metabolites can regulate stem cell behavior through the STAT3/AKT pathway in a similar trend to that under hypoxic conditions

Exendin-4 attenuates atherosclerosis progression via controlling hematopoietic stem/progenitor cell proliferation

Beyond glycemic control, applications of glucagon-like peptide-1 receptor (GLP-1r) agonists (GLP-1 RAs) inhibit inflammation and plaque development in murine atherosclerotic models. However, whether they modulate hematopoietic stem/progenitor cells (HSPCs) to prohibit skewed myelopoiesis in hypercholesteremia remains unknown. In this study, GLP-1r expression in fluorescence-activated cell sorting (FACS)-sorted wild-type HSPCs was determined by capillary western blotting. Bone marrow cells (BMCs) of wild-type or GLP-1r-/- mice were transplanted into lethally irradiated low-density lipoprotein receptor deficient (LDLr-/-) recipients followed by high-fat diet (HFD) for chimerism analysis by FACS. In parallel, LDLr-/- mice were placed on HFD for 6 weeks and then treated with saline or Exendin-4 (Ex-4) for another 6 weeks. HSPC frequency and cell cycle were analyzed by FACS, and intracellular metabolite levels were assessed by targeted metabolomics. The results demonstrated that HSPCs expressed GLP-1r and transplantation of GLP-1r-/- BMCs resulted in skewed myelopoiesis in hypercholesterolemic LDLr-/- recipients. In vitro, Ex-4 treatment of FACS-purified HSPCs suppressed cell expansion and granulocyte production induced by LDL. In vivo, Ex-4 treatment inhibited plaque progression, suppressed HSPC proliferation, and modified glycolytic and lipid metabolism in HSPCs of hypercholesteremic LDLr-/- mice. In conclusion, Ex-4 could directly inhibit HSPC proliferation induced by hypercholesteremia.

Phosphoenolpyruvate regulates the Th17 transcriptional program and inhibits autoimmunity

Aerobic glycolysis, a metabolic pathway essential for effector T cell survival and proliferation, regulates differentiation of autoimmune T helper (Th) 17 cells, but the mechanism underlying this regulation is largely unknown. Here, we identify a glycolytic intermediate metabolite, phosphoenolpyruvate (PEP), as a negative regulator of Th17 differentiation. PEP supplementation or inhibition of downstream glycolytic enzymes in differentiating Th17 cells increases intracellular PEP levels and inhibits interleukin (IL)-17A expression. PEP supplementation inhibits expression of signature molecules for Th17 and Th2 cells but does not significantly affect glycolysis, cell proliferation, or survival of T helper cells. Mechanistically, PEP binds to JunB and inhibits DNA binding of the JunB/basic leucine zipper transcription factor ATF-like (BATF)/interferon regulatory factor 4 (IRF4) complex, thereby modulating the Th17 transcriptional program. Furthermore, daily administration of PEP to mice inhibits generation of Th17 cells and ameliorates Th17-dependent autoimmune encephalomyelitis. These data demonstrate that PEP links aerobic glycolysis to the Th17 transcriptional program, suggesting the therapeutic potential of PEP for autoimmune diseases.

Metabolism and Sex Differentiation in Animals from a Starvation Perspective

Animals determine their sex genetically (GSD: genetic sex determination) and/or environmentally (ESD: environmental sex determination). Medaka (Oryzias latipes) employ a XX/XY GSD system, however, they display female-to-male sex reversal in response to various environmental changes such as temperature, hypoxia, and green light. Interestingly, we found that 5 days of starvation during sex differentiation caused female-to-male sex reversal. In this situation, the metabolism of pantothenate and fatty acid synthesis plays an important role in sex reversal. Metabolism is associated with other biological factors such as germ cells, HPG axis, lipids, and epigenetics, and supplys substances and acts as signal transducers. In this review, we discuss the importance of metabolism during sex differentiation and how metabolism contributes to sex differentiation.

Agitation in a Microcarrier-based Spinner Flask Bioreactor Modulates Homeostasis of Human Mesenchymal Stem Cells

Human mesenchymal stem cells (hMSCs) are well known in cell therapy due to their secretion of trophic factors, multipotent differentiation potential, and ability for self-renewal. As a result, the number of clinical trials has been steadily increasing over the last decade highlighting the need for in vitro systems capable of producing large quantities of cells to meet growing demands. However, hMSCs are highly sensitive to microenvironment conditions, including shear stress caused by dynamic bioreactor systems, and can lead to alteration of cellular homeostasis. In this study, hMSCs were expanded on microcarriers within a 125 mL spinner flask bioreactor system. Our results demonstrate a three-fold expansion over seven days. Furthermore, our results show that culturing hMSCs in the microcarrier-based suspension bioreactor (compared to static planar culture) results in smaller cell size and higher levels of reactive oxidative species (ROS) and ROS regulator Sirtuin-3, which have implications on the nicotinamide adenine dinucleotide metabolic pathway and metabolic homeostasis. In addition, hMSCs in the bioreactor showed the increased Prostaglandin E₂ secretion as well as reduced the Indoleamine-pyrrole 2,3-dioxygenase secretion upon stimulus with interferon gamma. The results of this study provide understanding of potential hMSC physiology alterations impacted by bioreactor microenvironment during scalable production of hMSCs for biomanufacturing and clinical trials.

Stem Cell Metabolism: Powering Cell-Based Therapeutics

Cell-based therapeutics for cardiac repair have been extensively used during the last decade. Preclinical studies have demonstrated the effectiveness of adoptively transferred stem cells for enhancement of cardiac function. Nevertheless, several cell-based clinical trials have provided largely underwhelming outcomes. A major limitation is the lack of survival in the harsh cardiac milieu as only less than 1% donated cells survive. Recent efforts have focused on enhancing cell-based therapeutics and understanding the biology of stem cells and their response to environmental changes. Stem cell metabolism has recently emerged as a critical determinant of cellular processes and is uniquely adapted to support proliferation, stemness, and commitment. Metabolic signaling pathways are remarkably sensitive to different environmental signals with a profound effect on cell survival after adoptive transfer. Stem cells mainly generate energy through glycolysis while maintaining low oxidative phosphorylation (OxPhos), providing metabolites for biosynthesis of macromolecules. During commitment, there is a shift in cellular metabolism, which alters cell function. Reprogramming stem cell metabolism may represent an attractive strategy to enhance stem cell therapy for cardiac repair. This review summarizes the current literature on how metabolism drives stem cell function and how this knowledge can be applied to improve cell-based therapeutics for cardiac repair.

Interplay between Metabolites and the Epigenome in Regulating Embryonic and Adult Stem Cell Potency and Maintenance

The environment surrounding stem cells has the ability to elicit profound, heritable epigenetic changes orchestrated by multiple epigenetic mechanisms, which can be modulated by the level of specific metabolites. In this review, we highlight the significance of metabolism in regulating stem cell homeostasis, cell state, and differentiation capacity, using metabolic regulation of embryonic and adult muscle stem cells as examples, and cast light on the interaction between cellular metabolism and epigenetics. These new regulatory networks, based on the dynamic interplay between metabolism and epigenetics in stem cell biology, are important, not only for understanding tissue homeostasis, but to determine in vitro culture conditions which accurately support normal cell physiology.

Metabolic Regulation and Related Molecular Mechanisms in Various Stem Cell Functions

Recent studies on the mechanisms that link metabolic changes with stem cell fate have deepened our understanding of how specific metabolic pathways can regulate various stem cell functions during the development of an organism. Although it was originally thought to be merely a consequence of the specific cell state, metabolism is currently known to play a critical role in regulating the self-renewal capacity, differentiation potential, and quiescence of stem cells. Many studies in recent years have revealed that metabolic pathways regulate various stem cell behaviors (e.g., selfrenewal, migration, and differentiation) by modulating energy production through glycolysis or oxidative phosphorylation and by regulating the generation of metabolites, which can modulate multiple signaling pathways. Therefore, a more comprehensive understanding of stem cell metabolism could allow us to establish optimal culture conditions and differentiation methods that would increase stem cell expansion and function for cell-based therapies. However, little is known about how metabolic pathways regulate various stem cell functions. In this context, we review the current advances in metabolic research that have revealed functional roles for mitochondrial oxidative phosphorylation, anaerobic glycolysis, and oxidative stress during the self-renewal, differentiation and aging of various adult stem cell types. These approaches could provide novel strategies for the development of metabolic or pharmacological therapies to promote the regenerative potential of stem cells and subsequently promote their therapeutic utility.

Epigenetic metabolites license stem cell states

It has become clear during recent years that stem cells undergo metabolic remodeling during their activation process. While these metabolic switches take place in pluripotency as well as adult stem cell populations, the rules that govern the switch are not clear. In this review, we summarize some of the transitions in adult and pluripotent cell types and will propose that the key function in this process is the generation of epigenetic metabolites that govern critical epigenetic modifications, and therefore stem cell states.

Simulated microgravity significantly altered metabolism in epidermal stem cells

Simulated microgravity can significantly affect various cell types and multiple systems of the human body, such as cardiovascular system, skeletal muscle system, and immune system, and is known to cause anemia and loss of electrolyte and fluids. Epidermal stem cells (EpSCs) were cultured in a rotary cell culture system (RCCS) bioreactor to simulate microgravity. The metabolites of EpSCs were identified by liquid chromatography-mass spectrometry (LC-MS). Compared with normal gravity (NG) group, a total of 57 different metabolites of EpSCs were identified (P < 0.05, VIP > 1), including lipids and lipid-like molecules (51 molecules), amino acids (5 molecules), nucleosides, nucleotides, and analogues (1 molecule). According to the partial least squares discriminant analysis (PLS-DA) score plot, a VIP > 1 and P < 0.05 were obtained for the 57 different metabolites, of which 23 molecules were significantly downregulated and 34 were significantly upregulated in simulated microgravity (SMG) group. These results showed that SMG has a significant impact on different pathways, and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis indicated that multiple pathways were involved, mainly the amino acid metabolism pathway, lipid metabolism pathway, membrane transport pathway, and cell growth and death pathways. Thus, the metabolic profile of EpSCs was changed under SMG. Exploring the metabolic profile of EpSCs would be helpful to further understand the growth characteristics of EpSCs under SMG, which will provide a new approach to explore the metabolomics mechanism of stress injury and repair trauma under SMG.