A single metabolite which modulates lipid metabolism alters hematopoietic stem/progenitor cell behavior and promotes lymphoid reconstitution
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ABSTRACT: Fatty acid beta-oxidation (FAO), the breakdown of lipids, is a metabolic pathway used by various stem cells. FAO levels are generally high during quiescence and downregulated with proliferation. The endogenous metabolite malonyl-CoA modulates lipid metabolism as a reversible FAO inhibitor and as a substrate for de novo lipogenesis. Here we assessed whether malonyl-CoA can be exploited to steer the behavior of hematopoietic stem/progenitor cells (HSPCs), quiescent stem cells of clinical relevance. Treatment of mouse HSPCs in vitro with malonyl-CoA increases HSPC numbers compared to non-treated controls and ameliorates blood reconstitution capacity when transplanted in vivo, mainly through enhanced lymphoid reconstitution. Similarly, human HSPC numbers also increase upon malonyl-CoA treatment in vitro. These data corroborate that lipid metabolism can be targeted to direct cell fate and stem cell proliferation. Physiological modulation of metabolic pathways, rather than genetic or pharmacological inhibition, provides unique perspectives for stem cell manipulations in health and disease.
Project description:Mitochondrial fatty acid oxidation (FAO) is an important energy provider for cardiac work and changes in cardiac substrate preference are associated with different heart diseases. Carnitine palmitoyltransferase 1B (CPT1B) is thought to perform the rate limiting enzyme step in FAO and is inhibited by malonyl-CoA. The role of CPT1B in cardiac metabolism has been addressed by inhibiting or decreasing CPT1B protein or after modulation of tissue malonyl-CoA metabolism. We assessed the role of CPT1B malonyl-CoA sensitivity in cardiac metabolism.
Project description:Adult hippocampal neurogenesis is important for certain forms of cognition and failing neurogenesis has been implicated in neuropsychiatric diseases. The neurogenic capacity of hippocampal neural stem/progenitor cells (NSPCs) depends on a balance between quiescent and proliferative states. However, how this balance is regulated remains poorly understood. Here we show that the rate of fatty acid oxidation (FAO) defines quiescence vs. proliferation in NSPCs. Quiescent NSPCs show high levels of carnitine palmitoyltransferase 1a (Cpt1a)-dependent FAO, which is downregulated in proliferating NSPCs. Pharmacological inhibition and conditional deletion of Cpt1a in vitro and in vivo leads to altered NSPC behavior, showing that Cpt1a-dependent FAO is required for stem cell maintenance and proper neurogenesis. Strikingly, experimental manipulation of malonyl-CoA, the metabolite that regulates levels of FAO, is sufficient to induce exit from quiescence and to enhance NSPC proliferation. Thus, the data presented here identify a shift in FAO metabolism that governs NSPC behavior and suggest an instructive role for fatty acid metabolism in regulating NSPC activity.
Project description:Polycomb Repressive Complex 2 (PRC2) has been shown to play a key role in hematopoietic stem and progenitor cell (HSPC) function. Analyses of mouse mutants harboring deletions of core components have implicated PRC2 in fine-tuning multiple pathways that instruct HSPC behavior, yet how PRC2 is targeted to specific genomic loci within HSPCs remains unknown. Here we use shRNA-mediated knockdown to survey the function of known PRC2 accessory factors in HSPCs by testing the competitive reconstitution capacity of transduced murine fetal liver cells. We find that similar to the phenotype observed upon depletion of core subunit Suz12, depleting Jarid2 enhances the competitive transplantation capacity of both fetal and adult, mouse and human HSPCs. Gene expression profiling revealed common Suz12 and Jarid2 target genes that are enriched for the H3K27me3 mark established by PRC2. These data implicate Jarid2 as an important component of PRC2 that has a central role in coordinating HSPC function. RNA-seq of jarid knockdown, suz knockdown and control from HSPC in 16 week old mice.
Project description:Ex-vivo gene editing in T cells and hematopoietic stem/progenitor cells (HSPCs) holds promise for treating diseases by non-homologous end joining (NHEJ) gene disruption or homology-driven repair (HDR) gene correction. Gene editing encompasses delivery of nucleases by electroporation and, when aiming to HDR, of a DNA template often provided by viral vectors. Whereas HSPCs activate robust p53-dependent DNA damage response (DDR) upon editing, the responses triggered in T cells remain poorly characterized. Here, we performed comprehensive multi-omics analyses and found that electroporation is the culprit of cytotoxicity in T cells, causing death and cell cycle delay, perturbing metabolism and inducing inflammatory response. Nuclease delivery by lipid nanoparticles (LNPs) nearly abolished cell death and ameliorated cell growth, improving tolerance to the procedure and yielding higher number of edited cells compared to electroporation. Transient transcriptomic changes upon LNP treatment were mostly caused by cellular loading with exogenous cholesterol, whose potentially detrimental impact could be overcome by limiting exposure. Notably, LNP-based HSPC editing dampened p53 pathway induction and supported higher reconstitution by long-term repopulating HSPCs compared to electroporation, reaching similar editing efficiencies. Overall, LNPs may allow efficient and stealthier ex-vivo gene editing in hematopoietic cells for treatment of human diseases.
Project description:Cellular crosstalk within the bone marrow niche maintains hematopoietic stem and progenitor cell (HSPC) integrity and safeguards lifelong blood and immune cell production. Deeper understanding of reciprocal niche signals governing crucial properties of HSPCs is relevant to the pathophysiology of blood disorders and improving HSPC transplantation. Extracellular vesicles (EVs) are key factors of the HSPC secretome, providing signals that regulate homeostasis and stemness. Here we demonstrate ex vivo blockade of ceramide-dependent vesicle secretion from HSPCs activates an integrated stress response (ISR), promoting downstream mTOR inhibition and metabolic quiescence. Crucially, ceramide-EV depletion leads to striking improvements in long-term transplantation. The aggregate findings link ceramide-dependent EV secretion and the ISR as a regulatory dyad guarding HSPC homeostasis and long-term fitness. Translationally, these data support exploration of ceramide inhibition during ex vivo maintenance of HSPCs for adoptive transfer.
Project description:Although lipid-derived acetyl-CoA is a major carbon source for histone acetylation, the contribution of fatty acid -oxidation (FAO) to this process remains poorly characterized. To investigate this, we generated mitochondrial acetyl-CoA acetyltransferase 1 (ACAT1, distal FAO enzyme) knockout macrophages. 13C-carbon tracing confirmed reduced FA-derived carbon incorporation into histone H3 and RNA-seq identified diminished interferon stimulated gene expression in the absence of ACAT1. Chromatin accessibility at Stat1 locus was diminished in ACAT1-/- cells. CHIP analysis demonstrated reduced acetyl-H3 binding to Stat1 promoter/enhancer regions and increasing histone acetylation rescued Stat1 expression. IFNβ release was blunted in ACAT1-/- and recovered by ACAT1 reconstitution. Furthermore, ACAT1-dependent histone acetylation required an intact acetylcarnitine shuttle. Finally, obese subjects’ monocytes exhibited increased ACAT1 and histone acetylation levels. Thus, our study identifies a novel link between FAO-mediated epigenetic control of type 1 interferon signaling and uncovers a potential mechanistic link between obesity and type I inferon signaling.
Project description:Fundamental alterations in lipid metabolism including increased rates of de novo lipogenesis (DNL), reduced fatty acid oxidation (FAOX) and ectopic lipid accumulation in skeletal muscle and liver are characteristic of type 2 diabetes mellitus (T2DM) and have been hypothesized to directly contribute to the molecular pathogenesis of the disease. Acetyl-CoA carboxylase (ACC) catalyzes the formation of malonyl-CoA, the rate limiting substrate for DML and key regulator of FAOX. ACC inhibitors have the potential to pharmacologically rebalance these metabolic alterations. In the present study, PF-04923503, a potent dual ACC1/ACC2 inhibitor with properties optimized for in vivo studies, suppressed levels of malonyl-CoA in primary hepatocytes, rat skeletal muscle ex vivo, as well as rat liver and skeletal muscle in vivo. This impact on malonyl-CoA was directly correlated (r2>0.9) with reduced hepatic DNL and inversely correlated with incresed rates of FAOX (r2>0.9). The pharmacological eccfect of PF-04923503 persisted with chronic treatment. High-fat fed rats treated with PF-04923503 for six weeks showed dose-dependent reductions in skeletal muscle and liver lipid accumulation. These changes correlated directly with markers for improved insulin sensitization. However, liver gene expression indicates that pharmacological inhibition results in compensation by up-regualtion of genes involved with DNL. These results suggest that pharmacological inhibition of ACC may have utility to help rebalance metabolic abnormalities in T2DM and improve insulin sensitivity. Differential gene expression was assessed by Affymetrix microarray experiments for 15 liver samples across 3 pharmacological treatment groups (vehicle control 0.5% methylcellulose had 5 samples, PF-04923503 10mpk had 5 samples, PF-04923503 30mpk had 5 samples)
Project description:Fundamental alterations in lipid metabolism including increased rates of de novo lipogenesis (DNL), reduced fatty acid oxidation (FAOX) and ectopic lipid accumulation in skeletal muscle and liver are characteristic of type 2 diabetes mellitus (T2DM) and have been hypothesized to directly contribute to the molecular pathogenesis of the disease. Acetyl-CoA carboxylase (ACC) catalyzes the formation of malonyl-CoA, the rate limiting substrate for DML and key regulator of FAOX. ACC inhibitors have the potential to pharmacologically rebalance these metabolic alterations. In the present study, PF-04923503, a potent dual ACC1/ACC2 inhibitor with properties optimized for in vivo studies, suppressed levels of malonyl-CoA in primary hepatocytes, rat skeletal muscle ex vivo, as well as rat liver and skeletal muscle in vivo. This impact on malonyl-CoA was directly correlated (r2>0.9) with reduced hepatic DNL and inversely correlated with incresed rates of FAOX (r2>0.9). The pharmacological eccfect of PF-04923503 persisted with chronic treatment. High-fat fed rats treated with PF-04923503 for six weeks showed dose-dependent reductions in skeletal muscle and liver lipid accumulation. These changes correlated directly with markers for improved insulin sensitization. However, liver gene expression indicates that pharmacological inhibition results in compensation by up-regualtion of genes involved with DNL. These results suggest that pharmacological inhibition of ACC may have utility to help rebalance metabolic abnormalities in T2DM and improve insulin sensitivity.
Project description:It has long been known that leukemic cells disrupt normal patterns of blood cell formation, but little is understood about mechanisms. It has generally been assumed that normal hematopoietic stem and progenitor cells (HSPC) are simply out-competed for space by malignant cells. We designed a strategy to determine if leukemic cells alter intrinsic properties and functions of normal HSPCs. Chimeric mice were generated by transplantation of normal marrow and marrow from an inducible transgenic model of chronic myelogenous leukemia (CML). With induction of CML, the composition of the marrow changed dramatically, and normal HSPCs divided more readily and lost their ability to produce lymphocytes. In contrast, only modest changes were recorded in numbers of normal hematopoietic stem cells (HSCs). However, these stem cells were not unscathed, and had reduced reconstitution and self-renewal potential upon transplantation. Interestingly, the normal bystander cells acquired gene expression patterns resembling their neighboring malignant counterparts. This suggested that much of the leukemia signature is mediated by extrinsic factors in the environment.
Project description:Osteolineage cell-derived extracellular vesicles (EVs) play a regulatory role in hematopoiesis and have been shown to promote the ex vivo expansion of human hematopoietic stem and progenitor cells (HSPCs). Here, we demonstrate that EVs from different human osteolineage sources do not have the same HSPC expansion promoting potential. Comparison of stimulatory and non-stimulatory osteolineage EVs by next-generation sequencing and mass spectrometry analyses revealed distinct microRNA and protein signatures identifying EV-derived candidate regulators of ex vivo HSPC expansion. Accordingly, the treatment of umbilical cord blood-derived CD34+ HSPCs with stimulatory EVs altered HSPC transcriptome, including genes with known roles in cell proliferation. An integrative bioinformatics approach, which connects the HSPC gene expression data with the candidate cargo in stimulatory EVs, delineated the potentially targeted biological functions and pathways during hematopoietic cell expansion and development. In conclusion, our study gives novel insights into the complex biological role of EVs in osteolineage cell-HSPC crosstalk and promotes the utility of EVs and their cargo as therapeutic agents in regenerative medicine.