Comparative analysis of pressure ulcer development in stroke patients within and outside healthcare facilities: A systematic review and meta-analysis.

The risk of pressure ulcers in stroke patients is a significant concern, impacting their recovery and quality of life. This systematic review and meta-analysis investigate the prevalence and risk factors of pressure ulcers in stroke patients, comparing those in healthcare facilities with those in home-based or non-clinical environments. The study aims to elucidate how different care settings affect the development of pressure ulcers, serving as a crucial indicator of patient care quality and management across diverse healthcare contexts. Following PRISMA guidelines, a comprehensive search was conducted across PubMed, Embase, Web of Science and the Cochrane Library. Inclusion criteria encompassed studies on stroke patients in various settings, reporting on the incidence or prevalence of pressure ulcers. Exclusion criteria included non-stroke patients, non-original research and studies with incomplete data. The Newcastle-Ottawa scale was used for quality assessment, and statistical analyses involved both fixed-effect and random-effects models, depending on the heterogeneity observed. A total of 1542 articles were initially identified, with 11 studies meeting the inclusion criteria. The studies exhibited significant heterogeneity, necessitating the use of a random-effects model. The pooled prevalence of pressure injuries was 9.53% in patients without family medical services and 2.64% in patients with medical services. Sensitivity analysis confirmed the stability of these results, and no significant publication bias was detected through funnel plot analysis and Egger's linear regression test. The meta-analysis underscores the heightened risk of pressure injuries in stroke patients, especially post-discharge. It calls for concerted efforts among healthcare providers, policymakers and caregivers to implement targeted strategies tailored to the specific needs of different care environments. Future research should focus on developing and evaluating interventions to effectively integrate into routine care and reduce the incidence of pressure injuries in stroke patients.

Risk assessment and pathogen profile of surgical site infections in traumatic brain injury patients undergoing emergency craniotomy: A retrospective study.

Emergency craniotomy in patients with traumatic brain injury poses a significant risk for surgical site infections (SSIs). Understanding the risk factors and pathogenic characteristics of SSIs in this context is crucial for improving outcomes. This comprehensive retrospective analysis spanned from February 2020 to February 2023 at our institution. We included 25 patients with SSIs post-emergency craniotomy and a control group of 50 patients without SSIs. Data on various potential risk factors were collected, including demographic information, preoperative conditions, and intraoperative details. The BACT/ALERT3D Automated Bacterial Culture and Detection System was utilized for rapid bacterial pathogen identification. Statistical analyses included univariate and multivariate logistic regression to identify significant risk factors for SSIs. The study identified Klebsiella pneumoniae, Escherichia coli, and Staphylococcus aureus as the most prevalent pathogens in SSIs. Significant risk factors for SSIs included the lack of preoperative antibiotic use, postoperative drainage tube placement, diabetes mellitus, and the incorporation of invasive procedures, all of which showed a significant association with SSIs in the univariate analysis. The multivariate analysis further highlighted the protective effect of preoperative antibiotics and the increased risks associated with anaemia, diabetes mellitus, postoperative drainage tube placement, and the incorporation of invasive procedures. Our research underscores the critical role of factors like insufficient preoperative antibiotics, postoperative drainage, invasive techniques, anaemia, and diabetes mellitus in elevating the risk of surgical site infections in traumatic brain injury patients undergoing emergency craniotomy. Enhanced focus on these areas is essential for improving surgical outcomes.

A comprehensive RNA editome reveals that edited Azin1 partners with DDX1 to enable hematopoietic stem cell differentiation.

Adenosine-to-inosine RNA editing and the catalyzing enzyme adenosine deaminase are both essential for hematopoietic development and differentiation. However, the RNA editome during hematopoiesis and the underlying mechanisms are poorly defined. Here, we sorted 12 murine adult hematopoietic cell populations at different stages and identified 30 796 editing sites through RNA sequencing. The dynamic landscape of the RNA editome comprises stage- and group-specific and stable editing patterns, but undergoes significant changes during lineage commitment. Notably, we found that antizyme inhibitor 1 (Azin1) was highly edited in hematopoietic stem and progenitor cells (HSPCs). Azin1 editing results in an amino acid change to induce Azin1 protein (AZI) translocation to the nucleus, enhanced AZI binding affinity for DEAD box polypeptide 1 to alter the chromatin distribution of the latter, and altered expression of multiple hematopoietic regulators that ultimately promote HSPC differentiation. Our findings have delineated an essential role for Azin1 RNA editing in hematopoietic cells, and our data set is a valuable resource for studying RNA editing on a more general basis.

Radiation-induced bystander effects impair transplanted human hematopoietic stem cells via oxidative DNA damage.

Total body irradiation (TBI) is commonly used in host conditioning regimens for human hematopoietic stem cell (HSC) transplantation to treat various hematological disorders. Exposure to TBI not only induces acute myelosuppression and immunosuppression, but also injures the various components of the HSC niche in recipients. Our previous study demonstrated that radiation-induced bystander effects (RIBE) of irradiated recipients decreased the long-term repopulating ability of transplanted mouse HSCs. However, RIBE on transplanted human HSCs have not been studied. Here, we report that RIBE impaired the long-term hematopoietic reconstitution of human HSCs as well as the colony-forming ability of human hematopoietic progenitor cells (HPCs). Our further analyses revealed that the RIBE-affected human hematopoietic cells showed enhanced DNA damage responses, cell-cycle arrest, and p53-dependent apoptosis, mainly because of oxidative stress. Moreover, multiple antioxidants could mitigate these bystander effects, though at different efficacies in vitro and in vivo. Taken together, these findings suggest that RIBE impair human HSCs and HPCs by oxidative DNA damage. This study provides definitive evidence for RIBE on transplanted human HSCs and further justifies the necessity of conducting clinical trials to evaluate different antioxidants to improve the efficacy of HSC transplantation for the patients with hematological or nonhematological disorders.

Loss of Nupr1 promotes engraftment by tuning the quiescence threshold of hematopoietic stem cell repository via regulating p53-checkpoint pathway.

Hematopoietic stem cells (HSCs) are dominantly quiescent under homeostasis, which is a key mechanism of maintaining the HSC pool for life-long hematopoiesis. Dormant HSCs poise to be immediately activated on urgent conditions and can return to quiescence after regaining homeostasis. To date, the molecular networks of regulating the threshold of HSC dormancy, if exist, remain largely unknown. Here, we unveiled that deletion of Nupr1, a gene preferentially expressed in HSCs, activated the quiescence HSCs under homeostatic status, which conferred engraftment competitive advantage on HSCs without compromising their stemness and multi-lineage differentiation abilities in serial transplantation settings. Following an expansion protocol, the Nupr1-/- HSCs proliferate more robustly than their wild type counterparts in vitro. Nupr1 inhibits the expression of p53 and the rescue of which offsets the engraftment advantage. Our data unveil the de novo role of Nupr1 as an HSC quiescence-regulator, which provides insights into accelerating the engraftment efficacy of HSC transplantation by targeting the HSC quiescence-controlling network.

Bone marrow endothelial cell-derived interleukin-4 contributes to thrombocytopenia in acute myeloid leukemia.

Normal hematopoiesis can be disrupted by the leukemic bone marrow microenvironment, which leads to cytopenia-associated symptoms including anemia, hemorrhage and infection. Thrombocytopenia is a major and sometimes fatal complication in patients with acute leukemia. However, the mechanisms underlying defective thrombopoiesis in leukemia have not been fully elucidated. In the steady state, platelets are continuously produced by megakaryocytes. Using an MLL-AF9-induced acute myeloid leukemia mouse model, we demonstrated a preserved number and proportion of megakaryocyte-primed hematopoietic stem cell subsets, but weakened megakaryocytic differentiation via both canonical and non-canonical routes. This primarily accounted for the dramatic reduction of megakaryocytic progenitors observed in acute myeloid leukemia bone marrow and a severe disruption of the maturation of megakaryocytes. Additionally, we discovered overproduction of interleukin-4 from bone marrow endothelial cells in acute myeloid leukemia and observed inhibitory effects of interleukin-4 throughout the process of megakaryopoiesis in vivo Furthermore, we observed that inhibition of interleukin-4 in combination with induction chemotherapy not only promoted recovery of platelet counts, but also prolonged the duration of remission in our acute myeloid leukemia mouse model. Our study elucidates a new link between interleukin-4 signaling and defective megakaryopoiesis in acute myeloid leukemia bone marrow, thereby offering a potential therapeutic target in acute myeloid leukemia.

Leukemic marrow infiltration reveals a novel role for Egr3 as a potent inhibitor of normal hematopoietic stem cell proliferation.

Cytopenias resulting from the impaired generation of normal blood cells from hematopoietic precursors are important contributors to morbidity and mortality in patients with leukemia. However, the process by which normal hematopoietic cells are overtaken by emerging leukemia cells and how different subsets of hematopoietic stem cells (HSCs) and hematopoietic progenitor cells (HPCs) are distinctly influenced during leukemic cell infiltration is poorly understood. To investigate these important questions, we used a robust nonirradiated mouse model of human MLL-AF9 leukemia to examine the suppression of HSCs and HPCs during leukemia cell expansion in vivo. Among all the hematopoietic subsets, long-term repopulating HSCs were the least reduced, whereas megakaryocytic-erythroid progenitors were the most significantly suppressed. Notably, nearly all of the HSCs were forced into a noncycling state in leukemic marrow at late stages, but their reconstitution potential appeared to be intact upon transplantation into nonleukemic hosts. Gene expression profiling and further functional validation revealed that Egr3 was a strong limiting factor for the proliferative potential of HSCs. Therefore, this study provides not only a molecular basis for the more tightened quiescence of HSCs in leukemia, but also a novel approach for defining functional regulators of HSCs in disease.

ATF4 plays a pivotal role in the development of functional hematopoietic stem cells in mouse fetal liver.

The fetal liver (FL) serves as a predominant site for expansion of functional hematopoietic stem cells (HSCs) during mouse embryogenesis. However, the mechanisms for HSC development in FL remain poorly understood. In this study, we demonstrate that deletion of activating transcription factor 4 (ATF4) significantly impaired hematopoietic development and reduced HSC self-renewal in FL. In contrast, generation of the first HSC population in the aorta-gonad-mesonephros region was not affected. The migration activity of ATF4(-/-) HSCs was moderately reduced. Interestingly, the HSC-supporting ability of both endothelial and stromal cells in FL was significantly compromised in the absence of ATF4. Gene profiling using RNA-seq revealed downregulated expression of a panel of cytokines in ATF4(-/-) stromal cells, including angiopoietin-like protein 3 (Angptl3) and vascular endothelial growth factor A (VEGFA). Addition of Angptl3, but not VEGFA, partially rescued the repopulating defect of ATF4(-/-) HSCs in the culture. Furthermore, chromatin immunoprecipitation assay in conjunction with silencing RNA-mediated silencing and complementary DNA overexpression showed transcriptional control of Angptl3 by ATF4. To summarize, ATF4 plays a pivotal role in functional expansion and repopulating efficiency of HSCs in developing FL, and it acts through upregulating transcription of cytokines such as Angptl3 in the microenvironment.

Multiple genes of the renin-angiotensin system are novel targets of Wnt/ß-catenin signaling.

Activation of the renin-angiotensin system (RAS) plays an essential role in the pathogenesis of CKD and cardiovascular disease. However, current anti-RAS therapy only has limited efficacy, partly because of compensatory upregulation of renin expression. Therefore, a treatment strategy to simultaneously target multiple RAS genes is necessary to achieve greater efficacy. By bioinformatics analyses, we discovered that the promoter regions of all RAS genes contained putative T-cell factor (TCF)/lymphoid enhancer factor (LEF)-binding sites, and ß-catenin induced the binding of LEF-1 to these sites in kidney tubular cells. Overexpression of either ß-catenin or different Wnt ligands induced the expression of all RAS genes. Conversely, a small-molecule ß-catenin inhibitor ICG-001 abolished RAS induction. In a mouse model of nephropathy induced by adriamycin, either transient therapy or late administration of ICG-001 abolished established proteinuria and kidney lesions. ICG-001 inhibited renal expression of multiple RAS genes in vivo and abolished the expression of other Wnt/ß-catenin target genes. Moreover, ICG-001 therapy restored expression of nephrin, podocin, and Wilms' tumor 1, attenuated interstitial myofibroblast activation, repressed matrix expression, and inhibited renal inflammation and fibrosis. Collectively, these studies identify all RAS genes as novel downstream targets of Wnt/ß-catenin. Our results indicate that blockade of Wnt/ß-catenin signaling can simultaneously repress multiple RAS genes, thereby leading to the reversal of established proteinuria and kidney injury.

[Physiological regulation of hematopoietic stem cell and its molecular basis].

As a classical type of tissue stem cells, hematopoietic stem cell (HSC) is the earliest discovered and has been widely applied in the clinic as a great successful example for stem cell therapy. Thus, HSC research represents a leading field in stem cell biology and regenerative medicine. Self-renewal, differentiation, quiescence, apoptosis and trafficking constitute major characteristics of functional HSCs. These characteristics also signify different dynamic states of HSC through physiological interactions with the microenvironment cues in vivo. This review covers our current knowledge on the physiological regulation of HSC and its underlying molecular mechanisms. It is our hope that this review will not only help our colleagues to understand how HSC is physiologically regulated but also serve as a good reference for the studies on stem cell and regenerative medicine in general.

Sonic hedgehog signaling mediates epithelial-mesenchymal communication and promotes renal fibrosis.

Sonic hedgehog (Shh) signaling is a developmental signal cascade that plays an essential role in regulating embryogenesis and tissue homeostasis. Here, we investigated the potential role of Shh signaling in renal interstitial fibrogenesis. Ureteral obstruction induced Shh, predominantly in the renal tubular epithelium of the fibrotic kidneys. Using Gli1(lacZ) knock-in mice, we identified renal interstitial fibroblasts as Shh-responding cells. In cultured renal fibroblasts, recombinant Shh protein activated Gli1 and induced α-smooth muscle actin (α-SMA), desmin, fibronectin, and collagen I expression, suggesting that Shh signaling promotes myofibroblast activation and matrix production. Blockade of Shh signaling with cyclopamine abolished the Shh-mediated induction of Gli1, Snail1, α-SMA, fibronectin, and collagen I. In vivo, the kidneys of Gli1-deficient mice were protected against the development of interstitial fibrosis after obstructive injury. In wild-type mice, cyclopamine did not affect renal Shh expression but did inhibit induction of Gli1, Snail1, and α-SMA. In addition, cyclopamine reduced matrix expression and mitigated fibrotic lesions. These results suggest that tubule-derived Shh mediates epithelial-mesenchymal communication by targeting interstitial fibroblasts after kidney injury. We conclude that Shh/Gli1 signaling plays a critical role in promoting fibroblast activation, production of extracellular matrix, and development of renal interstitial fibrosis.

Interlukin-4 weakens resistance to stress injury and megakaryocytic differentiation of hematopoietic stem cells by inhibiting Psmd13 expression.

Thrombocytopenia is a major and fatal complication in patients with acute myeloid leukemia (AML), which results from disrupted megakaryopoiesis by leukemic niche and blasts. Our previous research revealed that elevated interleukin-4 (IL-4) in AML bone marrow had adverse impact on multiple stages throughout megakaryopoiesis including hematopoietic stem cells (HSCs), but the specific mechanism remains unknown. In the present study, we performed single-cell transcriptome analysis and discovered activated oxidative stress pathway and apoptosis pathway in IL-4Rαhigh versus IL-4Rαlow HSCs. IL-4 stimulation in vitro led to apoptosis of HSCs and down-regulation of megakaryocyte-associated transcription factors. Functional assays displayed higher susceptibility of IL-4Rαhigh HSCs to tunicamycin and irradiation-induced apoptosis, demonstrating their vulnerability to endoplasmic reticulum (ER) stress injury. To clarify the downstream signaling of IL-4, we analyzed the transcriptomes of HSCs from AML bone marrow and found a remarkable down-regulation of the proteasome component Psmd13, whose expression was required for megakaryocytic-erythroid development but could be inhibited by IL-4 in vitro. We knocked down Psmd13 by shRNA in HSCs, and found their repopulating capacity and megakaryocytic differentiation were severely compromised, with increased apoptosis in vivo. In summary, our study uncovered a previous unrecognized regulatory role of IL-4-Psmd13 signaling in anti-stress and megakaryocytic differentiation capability of HSCs.

Single-cell dissection of human hematopoietic reconstitution after allogeneic hematopoietic stem cell transplantation.

Hematopoietic stem cell transplantation is an effective regenerative therapy for many malignant, inherited, or autoimmune diseases. However, our understanding of reconstituted hematopoiesis in transplant patients remains limited. Here, we uncover the reconstitution dynamics of human allogeneic hematopoietic stem and progenitor cells (HSPCs) at single-cell resolution after transplantation. Transplanted HSPCs underwent rapid and measurable changes during the first 30 days after transplantation, characterized by a strong proliferative response on the first day. Transcriptomic analysis of HSPCs enabled us to observe that immunoregulatory neutrophil progenitors expressing high levels of the S100A gene family were enriched in granulocyte colony-stimulating factor-mobilized peripheral blood stem cells. Transplant recipients who developed acute graft-versus-host disease (aGVHD) infused fewer S100Ahigh immunoregulatory neutrophil progenitors, immunophenotyped as Lin-CD34+CD66b+CD177+, than those who did not develop aGVHD. Therefore, our study provides insights into the regenerative process of transplanted HSPCs in human patients and identifies a potential criterion for identifying patients at high risk for developing aGVHD early after transplant.

CEA cell adhesion molecule 5 enriches functional human hematopoietic stem cells capable of long-term multi-lineage engraftment.

Hematopoietic stem cell (HSC) surface markers improve the understanding of cell identity and function. Here, we report that human HSCs can be distinguished by their expression of the CEA Cell Adhesion Molecule 5 (CEACAM5, CD66e), which serves as a marker and a regulator of HSC function. CD66e+ cells exhibited a 5.5-fold enrichment for functional long term HSCs compared to CD66e- cells. CD66e+CD34+CD90+CD45RA- cells displayed robust multi-lineage repopulation and serial reconstitution ability in immunodeficient mice compared to CD66e-CD34+CD90+CD45RA-cells. CD66e expression also identified almost all repopulating HSCs within the CD34+CD90+CD45RA- population. Together, these results indicated that CEACAM5 is a marker that enriches functional human hematopoietic stem cells capable of long-term multi-lineage engraftment.

Targeted inhibition of ß-catenin/CBP signaling ameliorates renal interstitial fibrosis.

Because fibrotic kidneys exhibit aberrant activation of ß-catenin signaling, this pathway may be a potential target for antifibrotic therapy. In this study, we examined the effects of ß-catenin activation on tubular epithelial-mesenchymal transition (EMT) in vitro and evaluated the therapeutic efficacy of the peptidomimetic small molecule ICG-001, which specifically disrupts ß-catenin-mediated gene transcription, in obstructive nephropathy. In vitro, ectopic expression of stabilized ß-catenin in tubular epithelial (HKC-8) cells suppressed E-cadherin and induced Snail1, fibronectin, and plasminogen activator inhibitor-1 (PAI-1) expression. ICG-001 suppressed ß-catenin-driven gene transcription in a dose-dependent manner and abolished TGF-ß1-induced expression of Snail1, PAI-1, collagen I, fibronectin, and α-smooth muscle actin (α-SMA). This antifibrotic effect of ICG-001 did not involve disruption of Smad signaling. In the unilateral ureteral obstruction model, ICG-001 ameliorated renal interstitial fibrosis and suppressed renal expression of fibronectin, collagen I, collagen III, α-SMA, PAI-1, fibroblast-specific protein-1, Snail1, and Snail2. Late administration of ICG-001 also effectively attenuated fibrotic lesions in obstructive nephropathy. In conclusion, inhibiting ß-catenin signaling may be an effective approach to the treatment of fibrotic kidney diseases.

Temporal molecular program of human hematopoietic stem and progenitor cells after birth.

Hematopoietic stem and progenitor cells (HSPCs) give rise to the blood system and maintain hematopoiesis throughout the human lifespan. Here, we report a transcriptional census of human bone-marrow-derived HSPCs from the neonate, infant, child, adult, and aging stages, showing two subpopulations of multipotent progenitors separated by CD52 expression. From birth to the adult stage, stem and multipotent progenitors shared similar transcriptional alterations, and erythroid potential was enhanced after the infant stage. By integrating transcriptome, chromatin accessibility, and functional data, we further showed that aging hematopoietic stem cells (HSCs) exhibited a bias toward megakaryocytic differentiation. Finally, in comparison with the HSCs from the cord blood, neonate bone-marrow-derived HSCs were more quiescent and had higher long-term regeneration capability and durable self-renewal. Taken together, this work provides an integral transcriptome landscape of HSPCs and identifies their dynamics in post-natal steady-state hemopoiesis, thereby helping explore hematopoiesis in development and diseases.

Plasminogen activator inhibitor-1 is a transcriptional target of the canonical pathway of Wnt/beta-catenin signaling.

Plasminogen activator inhibitor-1 (PAI-1) is a multifunctional glycoprotein that plays a critical role in the pathogenesis of chronic kidney and cardiovascular diseases. Although transforming growth factor (TGF)-beta1 is a known inducer of PAI-1, how it controls PAI-1 expression remains enigmatic. Here we investigated the mechanism underlying TGF-beta1 regulation of PAI-1 in kidney tubular epithelial cells (HKC-8). Surprisingly, overexpression of Smad2 or Smad3 in HKC-8 cells blocked PAI-1 induction by TGF-beta1, whereas knockdown of them sensitized the cells to TGF-beta1 stimulation, suggesting that Smad signaling is not responsible for PAI-1 induction. Blockade of several TGF-beta1 downstream pathways such as p38 MAPK or JNK, but not phosphatidylinositol 3-kinase/Akt and ERK1/2, only partially inhibited PAI-1 expression. TGF-beta1 stimulated beta-catenin activation in tubular epithelial cells, and ectopic expression of beta-catenin induced PAI-1 expression, whereas inhibition of beta-catenin abolished its induction. A functional T cell factor/lymphoid enhancer-binding factor-binding site was identified in the promoter region of the PAI-1 gene, which interacted with T cell factor upon beta-catenin activation. Deletion or site-directed mutation of this site abolished PAI-1 response to beta-catenin or TGF-beta1 stimulation. Similarly, ectopic expression of Wnt1 also activated PAI-1 expression and promoter activity. In vivo, PAI-1 was induced in kidney tubular epithelia in obstructive nephropathy. Delivery of Wnt1 gene activated beta-catenin and promoted PAI-1 expression after obstructive injury, whereas blockade of Wnt/beta-catenin signaling by Dickkopf-1 gene inhibited PAI-1 induction. Collectively, these studies identify PAI-1 as a direct downstream target of Wnt/beta-catenin signaling and demonstrate that PAI-1 induction could play a role in mediating the fibrogenic action of this signaling.

tPA is a potent mitogen for renal interstitial fibroblasts: role of beta1 integrin/focal adhesion kinase signaling.

Proliferation and expansion of interstitial fibroblasts are predominant features of progressive chronic kidney diseases. However, how interstitial fibroblast proliferation is controlled remains ambiguous. Here we show that tissue-type plasminogen activator (tPA) is a potent mitogen that promotes interstitial fibroblast proliferation through a cascade of signaling events. In vitro, tPA promoted cell proliferation of rat kidney fibroblasts (NRK-49F), as assessed by cell counting, cell proliferation assay, and bromodeoxyuridine labeling. tPA also accelerated NRK-49F cell cycle progression. Fibroblast proliferation induced by tPA was associated with an increased expression of numerous proliferation-related genes, including c-fos, c-myc, proliferating cell nuclear antigen, and cyclin D1. The mitogenic effect of tPA was independent of its protease activity, but required LDL receptor-related protein 1. Interestingly, inhibition of beta1 integrin signaling prevented tPA-mediated fibroblast proliferation. tPA rapidly induced tyrosine phosphorylation of focal adhesion kinase (FAK), which led to activation of its downstream mitogen-activated protein kinase signaling. Blockade of FAK, but not integrin-linked kinase, abolished the tPA-triggered extracellular signal-regulated protein kinase 1/2 activation, proliferation-related gene induction, and fibroblast proliferation. In vivo, proliferation of interstitial myofibroblasts in tPA null mice was attenuated after obstructive injury, compared with the wild-type controls. These studies illustrate that tPA is a potent mitogen that promotes renal interstitial fibroblast proliferation through LDL receptor-related protein 1-mediated beta1 integrin and FAK signaling.

Single-cell transcriptomes of peripheral blood cells indicate and elucidate severity of COVID-19.

The blood and immune system of coronavirus disease 2019 (COVID-19) infected patients are dysfunctional, and numerous studies have been conducted to resolve their characteristics and pathogenic mechanisms. Nevertheless, the variations of immune responses along with disease severity have not been comprehensively documented. Here, we profiled the single-cell transcriptomes of 96,313 peripheral blood mononuclear cells (PBMCs) derived from 12 COVID-19 patients (including four moderate, four severe and four critical cases) and three healthy donors. We showed that proliferative CD8 effector T cells with declined immune functions and cytotoxicity accumulated in the critical stage. By contrast, the quantity of natural killer (NK) cells was significantly reduced, while they exhibited enhanced immune activities. Notably, a gradually attenuated responseto COVID-19 along with disease severity was observed in monocytes, in terms of cellular composition, transcriptional discrepancy and transcription factor regulatory network. Furthermore, we identified immune cell-type dependent cytokine signatures distinguishing the severity of COVID-19 patients. In addition, cell interactions between CD8 effector T/NK cells and monocytes mediated by inflammatory cytokines were enhanced in moderate and severe stages, but weakened in critical cases. Collectively, our work uncovers the cellular and molecular players underlying the disordered and heterogeneous immune responses associated with COVID-19 severity, which could provide valuable insights for the treatment of critical COVID-19 patients.

Single-cell transcriptomic landscape of human blood cells.

High throughput single-cell RNA-seq has been successfully implemented to dissect the cellular and molecular features underlying hematopoiesis. However, an elaborate and comprehensive transcriptome reference of the whole blood system is lacking. Here, we profiled the transcriptomes of 7551 human blood cells representing 32 immunophenotypic cell types, including hematopoietic stem cells, progenitors and mature blood cells derived from 21 healthy donors. With high sequencing depth and coverage, we constructed a single-cell transcriptional atlas of blood cells (ABC) on the basis of both protein-coding genes and long noncoding RNAs (lncRNAs), and showed a high consistence between them. Notably, putative lncRNAs and transcription factors regulating hematopoietic cell differentiation were identified. While common transcription factor regulatory networks were activated in neutrophils and monocytes, lymphoid cells dramatically changed their regulatory networks during differentiation. Furthermore, we showed a subset of nucleated erythrocytes actively expressing immune signals, suggesting the existence of erythroid precursors with immune functions. Finally, a web portal offering transcriptome browsing and blood cell type prediction has been established. Thus, our work provides a transcriptional map of human blood cells at single-cell resolution, thereby offering a comprehensive reference for the exploration of physiological and pathological hematopoiesis.