Stem Cell Field Research Articles

Umbilical Cord Blood Donation: An Evolving Lifeline for the Stem Cell Field

Umbilical Cord Blood Donation: An Evolving Lifeline for the Stem Cell Field

Biological Characteristics and Multilineage Differentiation of Kidney Mesenchymal Stem Cells Derived from the Tibetan Mastiff

Of all the significant researches that have taken place in isolation, culture and characterization of mesenchymal stem cells (MSCs), the field of kidney-derived mesenchymal stem cells (KMSCs) in Tibetan mastiff is still a blank. Therefore, the purpose of this study is to isolate, culture and characterize the Tibetan mastiff KMSCs. The KMSCs were successfully isolated from one-day year old Tibetan mastiff kidney, cultured for 16 passages and distinguished by two methods: immunofluorescence staining and RT-PCR. The Tibetan mastiff KMSCs expressed specific surface marker genes (VIM, CD44, FN1, CD90, CD109, CD73, FN1) and kidney marker gene PAX2. The proliferation ability of Tibetan mastiff KMSCs was measured through cell count and clonality. Furthermore, cells differentiated into different cell types (hepatocellular cells, osteogenic cells, adipogenic cells and chondrogenic cells) under special induced medium, and the marker genes of induced cells were identified with Immunofluorescence staining and RT-PCR. All of these results indicated that the Tibetan mastiff KMSCs were obtained successfully, which possessed certain characteristics of multipotent stem cells. Therefore, MSCs in Tibetan mastiff kidney hold potential for clinical applications for regenerative therapy and their further studies are waiting to be required to investigate their functions.

Tissue Engineering for Clean Meat Production

Increasing public awareness of foodborne illnesses, factory farming and the ecological footprint of the meat industry, has generated the need for animal-free meat alternatives. In the last decade, scientists have begun to leverage the knowledge and tools accumulated in the fields of stem cells and tissue engineering towards the development of cell-based meat (i.e., clean meat). In tissue engineering, the physical and biochemical features of the native tissue can be mimicked; cells and biomaterials are integrated under suitable culture conditions to form mature tissues. More specifically, in skeletal muscle tissue engineering, a plurality of cell types can be co-cultured on a 3D scaffold to generate muscle fibers, blood vessels and a dense extracellular matrix (ECM). This review focuses on tissue engineering of skeletal muscle and the adjustments needed for clean meat development. We discuss the skeletal muscle structure and composition, and elaborate on cell types from farm animals that have the potential to recapitulate the muscle ECM, blood vessels, muscle fibers and fat deposits. We also review relevant biomaterials, primarily for fabricating scaffolds that can mimic the intramuscular connective tissues, as well as gene expression studies on the biological pathways that influence meat quality.

Remodeling of mitochondrial morphology and function: an emerging hallmark of cellular reprogramming.

Research in the stem cell field has traditionally focused on understanding key transcriptional factors that provide pluripotent cell identity. However, much less is known about other critical non-transcriptional signaling networks that govern stem cell identity. Although we continue to gain critical insights into the mechanisms underlying mitochondrial morphology and function during cellular reprogramming – the process of reverting the fate of a differentiated cell into a stem cell, many uncertainties remain. Recent studies suggest an emerging landscape in which mitochondrial morphology and function have an active role in maintaining and regulating changes in cell identity. In this review, we will focus on these emerging concepts as crucial modulators of cellular reprogramming. Recognition of the widespread applicability of these concepts will increase our understanding of the mitochondrial mechanisms involved in cell identity, cell fate and disease.

Circulating exosomes derived from transplanted progenitor cells aid the functional recovery of ischemic myocardium.

The stem cell field is hindered by its inability to noninvasively monitor transplanted cells within the target organ in a repeatable, time-sensitive, and condition-specific manner. We hypothesized that quantifying and characterizing transplanted cell-derived exosomes in the recipient plasma would enable reliable, noninvasive surveillance of the conditional activity of the transplanted cells. To test this hypothesis, we used a human-into-rat xenogeneic myocardial infarction model comparing two well-studied progenitor cell types: cardiosphere-derived cells (CDCs) and c-kit+ cardiac progenitor cells (CPCs), both derived from the right atrial appendage of adults undergoing cardiopulmonary bypass. CPCs outperformed the CDCs in cell-based and in vivo regenerative assays. To noninvasively monitor the activity of transplanted CDCs or CPCs in vivo, we purified progenitor cell-specific exosomes from recipient total plasma exosomes. Seven days after transplantation, the concentration of plasma CPC-specific exosomes increased about twofold compared to CDC-specific exosomes. Computational pathway analysis failed to link CPC or CDC cellular messenger RNA (mRNA) with observed myocardial recovery, although recovery was linked to the microRNA (miRNA) cargo of CPC exosomes purified from recipient plasma. We further identified mechanistic pathways governing specific outcomes related to myocardial recovery associated with transplanted CPCs. Collectively, these findings demonstrate the potential of circulating progenitor cell-specific exosomes as a liquid biopsy that provides a noninvasive window into the conditional state of the transplanted cells. These data implicate the surveillance potential of cell-specific exosomes for allogeneic cell therapies.

Generation of human midbrain organoids from induced pluripotent stem cells

The development of brain organoids represents a major technological advance in the stem cell field, a novel bridge between traditional 2D cultures and in vivo animal models. In particular, the development of midbrain organoids containing functional dopaminergic neurons producing neuromelanin granules, a by-product of dopamine synthesis, represents a potential new model for Parkinson’s disease. To generate human midbrain organoids, we introduce specific inductive cues, at defined timepoints, during the 3D culture process to drive the stem cells towards a midbrain fate. In this method paper, we describe a standardized protocol to generate human midbrain organoids (hMOs) from induced pluripotent stem cells (iPSCs). This protocol was developed to demonstrate how human iPSCs can be successfully differentiated into numerous, high quality midbrain organoids in one batch. We also describe adaptations for cryosectioning of fixed organoids for subsequent histological analysis.

The effect of activated pure platelete rich plasma (P-PRP) on the proliferation of adipose -derived mesenchymal stem cells (AD-MSCs) as a substitute for fetal bovine serum (FBS)

The field of stem cells has attracted the attention of many researchers as a hope to treat many incurable diseases because of their ability of self-renewal and differentiation into a specific type of cells that compensates damaged cells. Many studies have been published to confirm their effectiveness but there are some obstacles that limit their clinical applications. One of these obstacles is xenogenic fetal bovine serum (FBS); the main proliferative source for stem cell culture with subsequent risk of infection transmission or immunogenic problems. So, in our study, we aimed to replace the xenogenic FBS with xeno-free blood derivative. We tested the effect of different concentrations of activated pure platelet rich plasma (P-PRP); one of the blood derivatives on proliferation of adipose derived mesenchymal stem cells (AD-MSCs) in comparison to FBS and found that 20% activated P-PRP followed by 10% activated P-PRP increased the proliferation rate of AD-MSCs more than 10% FBS. KEYWORDS AD-MSCs, P-PRP, FBS.

The effect of activated pure platelete rich plasma (P-PRP) on the proliferation of adipose -derived mesenchymal stem cells (AD-MSCs) as a substitute for fetal bovine serum (FBS)

The field of stem cells has attracted the attention of many researchers as a hope to treat many incurable diseases because of their ability of self-renewal and differentiation into a specific type of cells that compensates damaged cells. Many studies have been published to confirm their effectiveness but there are some obstacles that limit their clinical applications. One of these obstacles is xenogenic fetal bovine serum (FBS); the main proliferative source for stem cell culture with subsequent risk of infection transmission or immunogenic problems. So, in our study, we aimed to replace the xenogenic FBS with xeno-free blood derivative. We tested the effect of different concentrations of activated pure platelet rich plasma (P-PRP); one of the blood derivatives on proliferation of adipose derived mesenchymal stem cells (AD-MSCs) in comparison to FBS and found that 20% activated P-PRP followed by 10% activated P-PRP increased the proliferation rate of AD-MSCs more than 10% FBS.

Inhibition of PTGS1 promotes osteogenic differentiation of adipose-derived stem cells by suppressing NF-kB signaling

BackgroundTissue inflammation is an important problem in the field of human adipose-derived stem cell (ASC)-based therapeutic bone regeneration. Many studies indicate that inflammatory cytokines are disadvantageous for osteogenic differentiation and bone formation. Therefore, overcoming inflammation would be greatly beneficial in promoting ASC-mediated bone regeneration. The present study aims to investigate the potential anti-inflammatory role of Prostaglandin G/H synthase 1 (PTGS1) during the osteogenic differentiation of ASCs.MethodsWe performed TNFα treatment to investigate the response of PTGS1 to inflammation. Loss- and gain-of-function experiments were applied to investigate the function of PTGS1 in the osteogenic differentiation of ASCs ex vivo and in vivo. Western blot and confocal analyses were used to determine the molecular mechanism of PTGS1-regulated osteogenic differentiation.ResultsOur work demonstrates that PTGS1 expression is significantly increased upon inflammatory cytokine treatment. Both ex vivo and in vivo studies indicate that PTGS1 is required for the osteogenic differentiation of ASCs. Mechanistically, we show that PTGS1 regulates osteogenesis of ASCs via modulating the NF-κB signaling pathway.ConclusionsCollectively, this work confirms that the PTGS1-NF-κB signaling pathway is a novel molecular target for ASC-mediated regenerative medicine.

Various Mathematical Models of Tumor Growth with Reference to Cancer Stem Cells: A Review

Using mathematical models to simulate biological systems has a long history. An increasing number of such models have been applied to various aspects of tumor growth, with the ultimate goal of controlling cancer. Nevertheless, very little has been done in the field of cancer stem cells. Herein, we have reviewed some mathematical models of tumor growth and their specific properties. Considering the importance of the role cancer stem cells play in the production, progression and recurrence of cancer, we have also examined a mathematical growth model describing the dynamics of tumor growth in the presence of cancer stem cells.

LIVER CANCER STEM CELLS

Recent studies have shown that many tumours are containing small population of stem cell-like cells, in other words, cancer stem cells. The rapid development of the cancer stem cell field has allowed the scientists and the clinicians to focus on another challenge, which targets cancer stem cells for new therapeutic strategies. Studies showed that novel therapeutic approaches on the selective targeting of cancer stem cells might be extremely successful for prevention of invasion, metastasis, and the relapses of tumors. Liver cancer is the 5th most common cancer type. It has also been reported as the third most common cause of cancer related death. Recently, progression of hepatocellular carcinoma is thought to be driven by cancer stem cells. There are tremendous efforts to clarify the features of liver cancer stem cells, to identify them within other tumor cells, and finally to develop the new therapeutic models that target those cells. This review summarizes the features of liver cancer stem cells, and its importance for therapeutic approaches.

Simultaneous Electrical and Mechanical Stimulation to Enhance Cells' Cardiomyogenic Potential.

Cardiovascular diseases are the leading cause of death in developed countries. Consequently, the demand for effective cardiac cell therapies has motivated researchers in the stem cell and bioengineering fields to develop in vitro high-fidelity human myocardium for both basic research and clinical applications. However, the immature phenotype of cardiac cells is a limitation on obtaining tissues that functionally mimic the adult myocardium, which is mainly characterized by mechanical and electrical signals. Thus, the purpose of this protocol is to prepare and mature the target cell population through electromechanical stimulation, recapitulating physiological parameters. Cardiac tissue engineering is evolving toward more biological approaches, and strategies based on biophysical stimuli, thus, are gaining momentum. The device developed for this purpose is unique and allows individual or simultaneous electrical and mechanical stimulation, carefully characterized and validated. In addition, although the methodology has been optimized for this stimulator and a specific cell population, it can easily be adapted to other devices and cell lines. The results here offer evidence of the increased cardiac commitment of the cell population after electromechanical stimulation. Electromechanically stimulated cells show an increased expression of main cardiac markers, including early, structural, and calcium-regulating genes. This cell conditioning could be useful for further regenerative cell therapy, disease modeling, and high-throughput drug screening.

Two decades of embryonic stem cells: a historical overview.

STUDY QUESTIONHow did the field of stem cell research develop in the years following the derivation of the first human embryonic stem cell (hESC) line?SUMMARY ANSWERSupported by the increasing number of clinical trials to date, significant technological advances in the past two decades have brought us ever closer to clinical therapies derived from pluripotent cells.WHAT IS KNOWN ALREADYSince their discovery 20 years ago, the use of human pluripotent stem cells has progressed tremendously from bench to bedside. Here, we provide a concise review of the main keystones of this journey and focus on ongoing clinical trials, while indicating the most relevant future research directions.STUDY DESIGN, SIZE, DURATIONThis is a historical narrative, including relevant publications in the field of pluripotent stem cells (PSC) derivation and differentiation, recounted both through scholarly research of published evidence and interviews of six pioneers who participated in some of the most relevant discoveries in the field.PARTICIPANTS/MATERIALS, SETTING, METHODSThe authors all contributed by researching the literature and agreed upon body of works. Portions of the interviews of the field pioneers have been integrated into the review and have also been included in full for advanced reader interest.MAIN RESULTS AND THE ROLE OF CHANCEThe stem cell field is ever expanding. We find that in the 20 years since the derivation of the first hESC lines, several relevant developments have shaped the pluripotent cell field, from the discovery of different states of pluripotency, the derivation of induced PSC, the refinement of differentiation protocols with several clinical trials underway, as well as the recent development of organoids. The challenge for the years to come will be to validate and refine PSCs for clinical use, from the production of highly defined cell populations in clinical grade conditions to the possibility of creating replacement organoids for functional, if not anatomical, function restoration.LIMITATIONS, REASONS FOR CAUTIONThis is a non-systematic review of current literature. Some references may have escaped the experts’ analysis due to the exceedingly diverse nature of the field. As the field of regenerative medicine is rapidly advancing, some of the most recent developments may have not been captured entirely.WIDER IMPLICATIONS OF THE FINDINGSThe multi-disciplinary nature and tremendous potential of the stem cell field has important implications for basic as well as translational research. Recounting these activities will serve to provide an in-depth overview of the field, fostering a further understanding of human stem cell and developmental biology. The comprehensive overview of clinical trials and expert opinions included in this narrative may serve as a valuable scientific resource, supporting future efforts in translational approaches.STUDY FUNDING/COMPETING INTEREST(S)ESHRE provided funding for the authors’ on-site meeting and discussion during the preparation of this manuscript. S.M.C.S.L. is funded by the European Research Council Consolidator (ERC-CoG-725722-OVOGROWTH). M.P. is supported by the Special Research Fund, Bijzonder Onderzoeksfonds (BOF01D08114). M.G. is supported by the Methusalem grant of Vrije Universiteit Brussel, in the name of Prof. Karen Sermon and by Innovation by Science and Technology in Flanders (IWT, Project Number: 150042). A.V. and B.A. are supported by the Plataforma de Proteomica, Genotipado y Líneas Celulares (PT1770019/0015) (PRB3), Instituto de Salud Carlos III. Research grant to B.H. by the Research Foundation—Flanders (FWO) (FWO.KAN.2016.0005.01 and FWO.Project G051516N). There are no conflicts of interest to declare.TRIAL REGISTRATION NUMBERNot applicable.ESHRE Pages are not externally peer reviewed. This article has been approved by the Executive Committee of ESHRE.

Dental stem cells – Sources and identification methods

The banking of mesenchymal cells from the umbilical cord and harvesting them for future use is the current trend in medical science. Such sources are reservoirs of stem cells. Over the past decade, the field of dentistry has embossed its presence by taking major lead in the field of regenerative medicine and more precisely in the field of stem cells. These stem cells have the capacity for regeneration and repair by converting into any other cell type. However, these cells require signals for differentiation in a timely manner. Tooth and its associated structures have been discovered as the latest reservoirs of stem cells. In this review, a light has been thrown on such sources and their identification has been emphasized.

Molecular understanding of hierarchy and lineage of mesenchymal stem cells in vivo

Mesenchymal stem cell (MSC) is a type of tissue stem cell. In clinical studies, cultured MSCs have shown important therapeutic effects on diseases via the reduction of neurological defects and regulation of immune responses. However, in vivo MSC localization, function, and properties are poorly understood; therefore, the molecular understanding of MSCs hierarchy is less advanced compared to hematopoietic stem cell hierarchy. To address these issues, we developed a method that enables us to visualize MSCs, manipulate their function, and analyze their molecular biology in vivo. Paired-related homeobox 1 (Prrx1)-positive cells are transiently observed during limb skeletal development in mice. Prrx1-positive cells form heterogeneous populations comprising multiple mesenchymal progenitors with different lineages that are developing into osteoblasts, chondrocytes, adipocytes, fibroblasts, and tendon and ligament cells. Our results suggest that osteoblast differentiation in the calvaria begins at the Prrx1+Sca1+ MSC stage with sequential progression to Prrx1+Sca1- cells, then Osterix+Prrx1-Sca1- osteoblast precursors, which eventually form mature α1(I)-collagen+ osteoblasts. Using Runt-related transcription factor 2 (Runx2) conditional knockout mice, furthermore, we found that the essential period of Runx2 function in intramembranous ossification likely begins at the Prrx1+Sca1+ MSC stage and ends at the Osterix+Prrx1-Sca1- osteoblast precursor stage (before mature the α1(I)-collagen+ osteoblasts appear). This approach will enable us to understand the in vivo molecular biology features of MSCs, leading to their therapeutic applications for tissue repair and regeneration. This development can also contribute to the field of pluripotent stem cell by enabling the transplantation of lineage-restricted mesenchymal progenitors.

Stem and Progenitor Cells in thePathogenesis and Treatment of Digestive Diseases.

The global epidemic of chronic degenerative diseases expands rapidly. The pathogenesis of these noncommunicable disorders revolves around innate immunity, microbiome, and stem cell alterations. Understanding the mechanisms behind stem cell biology and their regulatory pathways is a key to understanding the origin of human disease. Stem cells are involved in tissue and organ damage and regeneration. The evidence is mounting that not only eukaryotic cells but also gut microbiota may release extracellular microvesicles that are absorbed from the gut into the portal and systemic circulation. Linking the fields of stem cells, innate immunity and microbiome research opens up new avenues to develop novel diagnostic (e.g., biomarkers), therapeutic (e.g., microbiome modulation, stem cell-based medicines), and prognostic (personalized diets) tools. In this chapter, we present the short overview of various stem and progenitor cells of adult tissues circulating in peripheral blood and their role in the pathogenesis and treatment of digestive diseases. We also briefly discuss the role of host-stem cell-microbial interactions as a new frontier of research in gastroenterology.

Heterogeneous, dynamic, and stochastic nature of mammalian spermatogenic stem cells.

Mammalian testes produce a huge number of sperm over a long period. This process, essential for the continuity of life, depends on the delicate balance of self-renewal and differentiation of resident stem cells, termed spermatogenic (spermatogonial) stem cells or SSCs. SSCs have motivated many researchers to query their identity, behavior, and regulation in the tissue microenvironment. The study of SSCs has a long and prominent history: Taking advantage of the unique organization of the seminiferous tubules, and the accompanying seminiferous epithelial cycle and spermatogenic wave, intricate concepts of SSC dynamics were established from the early days. This is represented by the "As model" first published in 1971. Then, numerous technical breakthroughs including transplantation, stem cell culture, organ culture, intravital live-imaging, and lineage tracing have made SSCs an invaluable model for tissue stem cell research. Further progress is likely to come from emerging technologies, such as in vitro gametogenesis and single cell omics. An ensemble of these experimental systems has lead to the identification of the dynamic and heterogeneous nature of SSCs, underpinning their context-dependent and flexible behavior. In addition, active migration of SSCs over the open (or facultative) niche microenvironment of the seminiferous tubules is in stark contrast to stem cell regulations within anatomically defined niches such as in the Drosophila ovary and testis (see chapter "Germline stem cell homeostasis" by Nelson et al.). By revealing novel mechanisms of stem cell regulation, research on mouse spermatogenesis will continually make significant contributions to the understanding of general concepts in the tissue stem-cell field.

Use of mesenchymal stemcells in dogs

Mesenchymal stem cells (MSC) are multipotent cells, which are able to differentiate into various cell types of the body, as for example in osteogenic, chondrogenic, adipogenic and myogenic directions. In human medicine, the application of stem cells represents a well-established clinical procedure already applied for several decades. Addition-ally, in veterinary medicine, the stem-cell field is a rapidly growing sector for clinical use, particularly in horses. Recently, this treatment moda lity has also been commonly applied in dogs. The main field of application are diseases of the musculoskeletal system. Furthermore MSC are predominantly used for the treatment of lameness because of osteoarthritic changes of the large joints. In veterinary medicine, MSC are mainly isolated from bone marrow or adipose tissue. This artic le provides an overview of the removal site, isolation, characterisation and application of MSC. Moreover, studies available in the litera ture concerning the therapy of orthopaedic diseases in the dog using MSC are presented.

Ovarian cancer stem cells and their role in drug resistance.

Ovarian cancer is typically diagnosed at advanced stages (III or IV), with metastasis ensuing at stage III. Complete remission is infrequent and is not achieved in almost half of the women diagnosed with ovarian cancer. Consequently, management and treatment of this disease is challenging as many patients are faced with tumour recurrence disseminating to surrounding organs further complicated with acquired chemo-resistance. The cancer stem cell theory proposes the idea that a drug resistant subset of tumour cells drive tumour progression, metastasis and ultimately, recurrent disease. In the ovarian cancer field, cancer stem cells remain elusive with significant gaps in our knowledge. The characteristics and specific role of ovarian cancer stem cells in recurrence still requires further research since different studies often arrive at contradictory conclusions. Here we present a review and critical analysis of current research conducted in the field of ovarian cancer stem cells and their potential role in drug resistance including several signalling pathways within these cells that affect the viability of targeted therapies.

Sphingolipid Perturbation Activates Proteostasis Programs to Govern Human Hematopoietic Stem Cell Self-Renewal

The hematopoietic stem cells (HSC) field has long been perplexed by how the blood system d (~10e12 cells produced daily) - yet hematologic malignancies remain relatively rare. The risk of malignancy is mitigated in part by a complex hierarchy in which the quiescent long-term hematopoietic stem cells (LT-HSC) with high self-renewal capacity undergo a restricted number of cell divisions. Nonetheless, such a high production demand over a lifetime raises an inherent risk of malignancy due to DNA replication errors, misfolded proteins and metabolic stress that cause cellular damage in HSC. Previously, HSC dormancy, largely thought to be controlled by transcription factor networks, was held responsible for preventing mutation acquisition. However, recent studies suggest that LT-HSC contain critical cellular networks centered around the coordination of distinct HSC metabolic programs with proteostasis, which serve as crucial decision nodes to balance persistence or culling of HSC for lifelong blood production. While HSC culling mechanisms are known, the linkage between cellular stress programs and the self-renewal properties that underlie human HSC persistence remains unknown. Here, we ask how this HSC fate choice is influenced by lipid biosynthesis - an underexplored area of HSC metabolism.We observed a distinct sphingolipid transcriptional signature in human HSC and examined the consequences of sphingolipid perturbation in human cord blood (CB) stem cells during ex vivo activation. DEGS1 (Delta 4-Desaturase, Sphingolipid 1) is the final enzyme in de novo sphingolipid synthesis, converting dihydroceramide (dhCer) to ceramide (Cer); ablation of DEGS1 either genetically or by treatment with the synthetic retinoid fenretinide/N-(4-hydroxyphenyl) retinamide (4HPR) is sufficient to activate autophagy in mouse cells and human cell lines. DEGS1 gene expression was higher in HSC than in progenitors and was significantly increased in LT-HSC following 6 hours of cytokine stimulation, suggesting that it plays a role in cellular activation. Sphingolipid composition was altered in CB cultured with 4HPR for 8 days with an increase in dhCer levels and decrease in Cer levels shown by lipidomics. Remarkably, 4HPR treatment significantly increased in vitro colony forming efficiency from LT-HSC (50% over control), but not from short-term HSC or granulocyte-macrophage progenitors. Ex vivo 4HPR treatment of CB followed by serial xenotransplantation resulted in a 2.5-fold increase in long-term repopulation cell (LTRC) frequency over control-treated cells, suggesting that 4HPR treatment affects HSC self-renewal.RNA-seq analysis showed that 4HPR activates a set of proteostatic quality control (QC) programs that coalesce around the unfolded protein response (UPR) and autophagy, the latter confirmed by immunofluorescence and flow cytometry in CB stem cells. Ex vivo culture perturbs these programs and results in loss of chromatin accessibility at sites associated with uncultured LT-HSC as determined by ATAC-Seq. Addition of 4HPR to the culture activates these proteostatic programs to sustain immunophenotypic and functional HSC. These results suggest that ceramide, the central component to all sphingolipids, may act as a “lipid biostat” for measuring cellular stress and activating stress responses.We further asked if 4HPR could synergize with known compounds to enhance HSC self-renewal. Treatment of CB with a combination of 4HPR plus CD34+ agonists UM171 and StemRegenin-1 during ex vivo culture maintains a chromatin state more similar to uncultured LT-HSC as demonstrated by ATAC-seq, and led to a 4-fold increase in serial repopulating ability in xenotransplant assays over treatment with UM171 and SR1 alone. These results suggest that sphingolipid perturbation not only activates proteostatic mechanisms that protect HSC organelles from damage incurred during cellular activation, but also regulates the landscape of chromatin accessibility in cultured HSC when combined with CD34+ agonists. This work identifies a new linkage between sphingolipid metabolism, proteostatic QC systems and HSC self-renewal, and identifies novel strategies by which to expand HSC numbers and improve HSC quality for clinical applications. DisclosuresTakayama:Megakaryon co. Ltd.: Research Funding.