Search

Haematopoietic stem cells (HSCs) are derived early from embryonic precursors, such as haemogenic endothelial cells and pre-haematopoietic stem cells (pre-HSCs), the molecular identity of which still remains elusive. Here we use potent surface markers to capture the nascent pre-HSCs at high purity, as rigorously validated by single-cell-initiated serial transplantation. Then we apply single-cell RNA sequencing to analyse endothelial cells, CD45.sup.- and CD45.sup.+ pre-HSCs in the aorta-gonad-mesonephros region, and HSCs in fetal liver. Pre-HSCs show unique features in transcriptional machinery, arterial signature, metabolism state, signalling pathway, and transcription factor network. Functionally, activation of mechanistic targets of rapamycin (mTOR) is shown to be indispensable for the emergence of HSCs but not haematopoietic progenitors. Transcriptome data-based functional analysis reveals remarkable heterogeneity in cell-cycle status of pre-HSCs. Finally, the core molecular signature of pre-HSCs is identified. Collectively, our work paves the way for dissection of complex molecular mechanisms regulating stepwise generation of HSCs in vivo, informing future efforts to engineer HSCs for clinical applications. Successful identification of mouse embryonic pre-haematopoietic stem cells at single-cell resolution. Haematopoietic stem cell formation dissected Fuchou Tang and colleagues have isolated the earliest haematopoietic stem cell (HSC) precursors -- rare CD45-negative pre-HSCs -- from developing mouse embryos using a combination of surface marker expression and single-cell-based transplantation assays, assessing blood-forming capacity. Single-cell RNA-seq was used to analyse the transcriptomes for five types of cells related to HSC formation, revealing a role for mTOR activation in the emergence of HSCs but not haematopoietic progenitors., Author(s): Fan Zhou [sup.1] , Xianlong Li [sup.2] , Weili Wang [sup.3] , Ping Zhu [sup.2] [sup.4] , Jie Zhou [sup.1] , Wenyan He [sup.1] , Meng Ding [sup.1] , [...]

In the aorta of mid‐gestational mouse embryos, a specialized endothelial subpopulation termed hemogenic endothelial cells (HECs) develops into hematopoietic stem and progenitor cells (HSPCs), through a conserved process of endothelial‐to‐hematopoietic transition (EHT). EHT is tightly controlled by multiple intrinsic and extrinsic mechanisms. Nevertheless, the molecular regulators restraining this process remain poorly understood. Here, it is uncovered that, one of the previously identified HEC signature genes, Nupr1, negatively regulates the EHT process. Nupr1 deletion in endothelial cells results in increased HSPC generation in the aorta‐gonad‐mesonephros region. Furthermore, single‐cell transcriptomics combined with serial functional assays reveals that loss of Nupr1 promotes the EHT process by promoting the specification of hematopoiesis‐primed functional HECs and strengthening their subsequent hematopoietic differentiation potential toward HSPCs. This study further finds that the proinflammatory cytokine, tumor necrosis factor α (TNF‐α), is significantly upregulated in Nupr1‐deficient HECs, and the use of a specific TNF‐α neutralizing antibody partially reduces excessive HSPC generation in the explant cultures from Nupr1‐deficient embryos. This study identifies a novel negative regulator of EHT and the findings indicate that Nupr1 is a new potential target for future hematopoietic stem cell regeneration research. [ABSTRACT FROM AUTHOR]

Abstract: Aim: Thermal ablation therapy has recently emerged as a promising noninvasive treatment modality for localized solid malignancies. Except its direct tumor‐cell‐killing effect on local tumor tissues, the immunomodulatory effect has also long been noticed which too has substantial effect on clinical outcome, but it is complicated. Though much has been investigated and rich evidences have been achieved, the fundamental state and profile of immunomodulation by thermal ablation in cancer patients, its exact mechanism, especially the systematic mechanism, and its effect on antitumor immunity remain unclear. Methods: In this study, we dynamically monitored the immunomodulation by thermal ablation through combined analysis of peripheral lymphocyte populations, functional T cell subtype Th1 (CD3+CD4+IFN‐r+), Th2 (CD3+CD4+IL‐4+), Tc1 (CD3+CD8+IFN‐r+), Tc2 (CD3+CD8+IL‐4+) and mRNA expression of several immune‐active and ‐suppressive molecules including CD25, CD28, cytotoxic T‐lymphocyte‐associated protein 4, programmed cell death protein 1, Foxp3, transforming growth factor beta (TGF‐β) and interleukin (IL‐10) in 16 cancer patients. Results: The results show that local cancer thermal ablation modulated the cellular immunity characterized by obviously downregulation of regulatory T cells (Treg) and cytotoxicity T cells followed by CD4, CD8 and suppressor T cells (Ts), but upregulation of natural killer (NK) cells and mRNA expression of TGF‐β and IL‐10, suggesting a slight inhibition of the cellular immunity which may affect antitumor immunity. Conclusions: We suggest a further immunomodulation therapy after thermal therapy for recovering a Th1‐ and Tc1‐dominant immune response for pursuing a better long‐term antitumor immunity. [ABSTRACT FROM AUTHOR]

Intrahepatic cholangiocarcinoma (ICC) is the second most common liver malignancy. ICC typically features remarkable cellular heterogeneity and a dense stromal reaction. Therefore, a comprehensive understanding of cellular diversity and the interplay between malignant cells and niche cells is essential to elucidate the mechanisms driving ICC progression and to develop therapeutic approaches. Herein, we performed single-cell RNA sequencing (scRNA-seq) analysis on unselected viable cells from 8 human ICCs and adjacent samples to elucidate the comprehensive transcriptomic landscape and intercellular communication network. Additionally, we applied a negative selection strategy to enrich fibroblast populations in 2 other ICC samples to investigate fibroblast diversity. The results of the analyses were validated using multiplex immunofluorescence staining, bulk transcriptomic datasets, and functional in vitro and in vivo experiments. We sequenced a total of 56,871 single cells derived from human ICC and adjacent tissues and identified diverse tumor, immune, and stromal cells. Malignant cells displayed a high degree of inter-tumor heterogeneity. Moreover, tumor-infiltrating CD4 regulatory T cells exhibited highly immunosuppressive characteristics. We identified 6 distinct fibroblast subsets, of which the majority were CD146-positive vascular cancer-associated fibroblasts (vCAFs), with highly expressed microvasculature signatures and high levels of interleukin (IL)-6. Functional assays indicated that IL-6 secreted by vCAFs induced significant epigenetic alterations in ICC cells, particularly upregulating enhancer of zeste homolog 2 (EZH2) and thereby enhancing malignancy. Furthermore, ICC cell-derived exosomal miR-9-5p elicited high expression of IL-6 in vCAFs to promote tumor progression. Our single-cell transcriptomic dataset delineates the inter-tumor heterogeneity of human ICCs, underlining the importance of intercellular crosstalk between ICC cells and vCAFs, and revealing potential therapeutic targets. Intrahepatic cholangiocarcinoma is an aggressive and chemoresistant malignancy. Better understanding the complex transcriptional architecture and intercellular crosstalk of these tumors will help in the development of more effective therapies. Herein, we have identified important interactions between cancer cells and cancer-associated fibroblasts in the tumor stroma, which could have therapeutic implications. • Single cell transcriptomic datasets are a valuable resource to dissect cellular diversity and intercellular crosstalk of human ICCs. • Malignant cells displayed remarkable inter-tumor heterogeneity and Tregs revealed highly immunosuppressive characteristics. • Six distinct fibroblast subsets were defined in ICCs and adjacent tissues. • CD146+ vCAFs, comprising most of the fibroblasts, had tight interactions with malignant cells through IL-6/IL-6R axis. • Tumor exosomal miR-9-5p elicited IL-6 expression in vCAFs, contributing to ICC progression via upregulation of EZH2. [ABSTRACT FROM AUTHOR]

Generation of the first T lymphocytes in the human embryo involves the emergence, migration, and thymus seeding of lymphoid progenitors together with concomitant thymus organogenesis, which is the initial step to establish the entire adaptive immune system. However, the cellular and molecular programs regulating this process remain unclear. We constructed a single-cell transcriptional landscape of human early T lymphopoiesis by using cells from multiple hemogenic and hematopoietic sites spanning embryonic and fetal stages. Among heterogenous early thymic progenitors, one subtype shared common features with a subset of lymphoid progenitors in fetal liver that are known as thymus-seeding progenitors. Unbiased bioinformatics analysis identified a distinct type of pre-thymic lymphoid progenitors in the aorta-gonad-mesonephros (AGM) region. In parallel, we investigated thymic epithelial cell development and potential cell-cell interactions during thymus organogenesis. Together, our data provide insights into human early T lymphopoiesis that prospectively direct T lymphocyte regeneration, which might lead to development of clinical applications. • Single-cell RNA-seq resolves human early T lymphopoiesis and thymus organogenesis • The first ETPs in the thymus share transcriptional features of TSPs in human fetal liver • Pre-thymic lymphoid progenitors are transcriptomically identified in human AGM region • Cortical TECs mature earlier than medullary TECs in human thymic primordium A comprehensive and precise understanding of early T lymphopoiesis and thymus organogenesis in human embryo is lacking. By performing single-cell transcriptomic analysis on human embryonic and fetal hematopoietic organs, Zeng et al. reveal distinct subpopulations of early thymic progenitors, identify thymus-seeding progenitors in fetal liver and pre-thymic lymphoid progenitors in the aorta-gonad-mesonephros region, and characterize early development of thymic epithelial cells. [ABSTRACT FROM AUTHOR]