Hematopoietic stem cells (HSCs) exhibit considerable cell-intrinsic changes with age. Here, we present an integrated analysis of transcriptome and chromatin accessibility of aged HSCs and downstream ...progenitors. Alterations in chromatin accessibility preferentially take place in HSCs with aging, which gradually resolve with differentiation. Differentially open accessible regions (open DARs) in aged HSCs are enriched for enhancers and show enrichment of binding motifs of the STAT, ATF, and CNC family transcription factors that are activated in response to external stresses. Genes linked to open DARs show significantly higher levels of basal expression and their expression reaches significantly higher peaks after cytokine stimulation in aged HSCs than in young HSCs, suggesting that open DARs contribute to augmented transcriptional responses under stress conditions. However, a short-term stress challenge that mimics infection is not sufficient to induce persistent chromatin accessibility changes in young HSCs. These results indicate that the ongoing and/or history of exposure to external stresses may be epigenetically inscribed in HSCs to augment their responses to external stimuli.
In a classical view of hematopoiesis, the various blood cell lineages arise via a hierarchical scheme starting with multipotent stem cells that become increasingly restricted in their differentiation ...potential through oligopotent and then unipotent progenitors. We developed a cell-sorting scheme to resolve myeloid (My), erythroid (Er), and megakaryocytic (Mk) fates from single CD34(+) cells and then mapped the progenitor hierarchy across human development. Fetal liver contained large numbers of distinct oligopotent progenitors with intermingled My, Er, and Mk fates. However, few oligopotent progenitor intermediates were present in the adult bone marrow. Instead, only two progenitor classes predominate, multipotent and unipotent, with Er-Mk lineages emerging from multipotent cells. The developmental shift to an adult "two-tier" hierarchy challenges current dogma and provides a revised framework to understand normal and disease states of human hematopoiesis.
Several real-world problems are modeled as multi-objective sequential decision-making problems with multiple competing objectives, and multi-objective reinforcement learning (MORL) has garnered ...attention as a solution to this problem. One of the challenges in obtaining the desired policy using MORL is that the priorities (hereafter, weights) for each objective must be designed in advance to scalarize the reward vector. Determining weights through trial-and-error burdens system designers, and methods to estimate weights are needed. The existing methods use inverse reinforcement learning (IRL), which is not scalable because it requires reinforcement learning several times until an optimal policy is obtained. This study proposes a weight interval estimation (WInter) method using adversarial IRL (AIRL). AIRL is a scalable framework that reduces the computational complexity of IRL by simultaneously estimating rewards and policies. WInter estimates the weight interval using the expert neighborhoods obtained during AIRL training. We successfully estimated the weight interval through experiments in a benchmark environment for multi-objective sequential decision-making problems in a continuous state space while reducing computational complexity compared to the existing methods.
Obesity is a worldwide epidemic that predisposes individuals to many age-associated diseases, but its exact effects on organ dysfunction are largely unknown
. Hair follicles-mini-epithelial organs ...that grow hair-are miniaturized by ageing to cause hair loss through the depletion of hair follicle stem cells (HFSCs)
. Here we report that obesity-induced stress, such as that induced by a high-fat diet (HFD), targets HFSCs to accelerate hair thinning. Chronological gene expression analysis revealed that HFD feeding for four consecutive days in young mice directed activated HFSCs towards epidermal keratinization by generating excess reactive oxygen species, but did not reduce the pool of HFSCs. Integrative analysis using stem cell fate tracing, epigenetics and reverse genetics showed that further feeding with an HFD subsequently induced lipid droplets and NF-κB activation within HFSCs via autocrine and/or paracrine IL-1R signalling. These integrated factors converge on the marked inhibition of Sonic hedgehog (SHH) signal transduction in HFSCs, thereby further depleting lipid-laden HFSCs through their aberrant differentiation and inducing hair follicle miniaturization and eventual hair loss. Conversely, transgenic or pharmacological activation of SHH rescued HFD-induced hair loss. These data collectively demonstrate that stem cell inflammatory signals induced by obesity robustly represses organ regeneration signals to accelerate the miniaturization of mini-organs, and suggests the importance of daily prevention of organ dysfunction.
The donor-dependent supply of platelets is frequently insufficient to meet transfusion needs. To address this issue, we developed a clinically applicable strategy for the derivation of functional ...platelets from human pluripotent stem cells (PSCs). This approach involves the establishment of stable immortalized megakaryocyte progenitor cell lines (imMKCLs) from PSC-derived hematopoietic progenitors through the overexpression of BMI1 and BCL-XL to respectively suppress senescence and apoptosis and the constrained overexpression of c-MYC to promote proliferation. The resulting imMKCLs can be expanded in culture over extended periods (4–5 months), even after cryopreservation. Halting the overexpression of c-MYC, BMI1, and BCL-XL in growing imMKCLs led to the production of CD42b+ platelets with functionality comparable to that of native platelets on the basis of a range of assays in vitro and in vivo. The combination of robust expansion capacity and efficient platelet production means that appropriately selected imMKCL clones represent a potentially inexhaustible source of hPSC-derived platelets for clinical application.
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•Expandable megakaryocyte progenitors were established from human PSCs•BMI1 and BCL-XL suppress senescence and apoptosis induced by c-MYC in imMKCLs•imMKCLs differentiate into mature megakaryocytes and release functional platelets•Rapid and efficient platelet yield provides key advantages for clinical application
This study describes a clinically applicable strategy for the derivation of functional platelets from human induced pluripotent stem cells (iPSCs) using the establishment of stable immortalized megakaryocyte progenitor lines from the iPSCs.
Hepatocytes generated from human induced pluripotent stem cells (hiPSCs) are unprecedented resources for pharmaceuticals and cell therapy. However, the in vitro directed differentiation of human ...pluripotent stem cells into mature hepatocytes remains challenging. Little attention has so far been paid to variations among hiPSC lines in terms of their hepatic differentiation. In the current study, we developed an improved hepatic differentiation protocol and compared 28 hiPSC lines originated from various somatic cells and derived using retroviruses, Sendai viruses, or episomal plasmids. This comparison indicated that the origins, but not the derivation methods, may be a major determinant of variation in hepatic differentiation. The hiPSC clones derived from peripheral blood cells consistently showed good differentiation efficiency, whereas many hiPSC clones from adult dermal fibroblasts showed poor differentiation. However, when we compared hiPSCs from peripheral blood and dermal fibroblasts from the same individuals, we found that variations in hepatic differentiation were largely attributable to donor differences, rather than to the types of the original cells. These data underscore the importance of donor differences when comparing the differentiation propensities of hiPSC clones.
Weight is a parameter used for measuring the priority in multi-objective reinforcement learning when linearly scalarizing the reward vector for each objective. The weights need to be set in advance; ...however, most real-world problems have numerous objectives. Therefore, adjusting the weights requires many trials and errors by the designer. In addition, a method to automatically estimate weights is needed to reduce the burden on designers to set weights. In this paper, we propose a novel method for estimating the weights based on the reward vector for each objective and the expert trajectories using the framework of inverse reinforcement learning (IRL). In particular, we adopt deep IRL with deep reinforcement learning and multiplicative weights apprenticeship learning for fast weight estimation in a continuous state space. Through experiments in a benchmark environment for multi-objective sequential decision-making problems in a continuous state space, we verified that our novel weight estimation method is superior to the projection method and Bayesian optimization.
Human embryonic stem cells (hESCs) represent a potential source of blood cells for transfusion therapies and a promising tool for studying the ontogeny of hematopoiesis. Moreover, human-induced ...pluripotent stem cells (hiPSCs), recently established by defined reprogramming factors expressed in somatic cells, represent a further source for the generation of hematopoietic cells. When undifferentiated hESCs or hiPSCs are cultured on either mesenchymal C3H10T1/2 cells or OP-9 stromal cells, they can be differentiated into a hematopoietic niche that concentrates hematopoietic progenitors, which we named "embryonic stem cell-derived sacs" (ES-sacs). We have optimized the in vitro culture condition for obtaining mature megakaryocytes derived from the hematopoietic progenitors within ES-sacs, which are then able to release platelets. These in vitro-generated platelets display integrin activation capability, indicating normal hemostatic function. This novel protocol thus provides a means of generating platelets from hESCs as well as hiPSCs, for the study of normal human thrombopoiesis and also thrombopoiesis in disease conditions using patient-specific hiPSCs.
Human (h) induced pluripotent stem cells (iPSCs) are a potentially abundant source of blood cells, but how best to select iPSC clones suitable for this purpose from among the many clones that can be ...simultaneously established from an identical source is not clear. Using an in vitro culture system yielding a hematopoietic niche that concentrates hematopoietic progenitors, we show that the pattern of c-MYC reactivation after reprogramming influences platelet generation from hiPSCs. During differentiation, reduction of c-MYC expression after initial reactivation of c-MYC expression in selected hiPSC clones was associated with more efficient in vitro generation of CD41a(+)CD42b(+) platelets. This effect was recapitulated in virus integration-free hiPSCs using a doxycycline-controlled c-MYC expression vector. In vivo imaging revealed that these CD42b(+) platelets were present in thrombi after laser-induced vessel wall injury. In contrast, sustained and excessive c-MYC expression in megakaryocytes was accompanied by increased p14 (ARF) and p16 (INK4A) expression, decreased GATA1 expression, and impaired production of functional platelets. These findings suggest that the pattern of c-MYC expression, particularly its later decline, is key to producing functional platelets from selected iPSC clones.
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