Search

Monoclonal antibody therapies targeting tumour antigens drive cancer cell elimination in large part by triggering macrophage phagocytosis of cancer cells.sup.1-7. However, cancer cells evade phagocytosis using mechanisms that are incompletely understood. Here we develop a platform for unbiased identification of factors that impede antibody-dependent cellular phagocytosis (ADCP) using complementary genome-wide CRISPR knockout and overexpression screens in both cancer cells and macrophages. In cancer cells, beyond known factors such as CD47, we identify many regulators of susceptibility to ADCP, including the poorly characterized enzyme adipocyte plasma membrane-associated protein (APMAP). We find that loss of APMAP synergizes with tumour antigen-targeting monoclonal antibodies and/or CD47-blocking monoclonal antibodies to drive markedly increased phagocytosis across a wide range of cancer cell types, including those that are otherwise resistant to ADCP. Additionally, we show that APMAP loss synergizes with several different tumour-targeting monoclonal antibodies to inhibit tumour growth in mice. Using genome-wide counterscreens in macrophages, we find that the G-protein-coupled receptor GPR84 mediates enhanced phagocytosis of APMAP-deficient cancer cells. This work reveals a cancer-intrinsic regulator of susceptibility to antibody-driven phagocytosis and, more broadly, expands our knowledge of the mechanisms governing cancer resistance to macrophage phagocytosis. CRISPR-mediated gene knockout and activation are used to identify molecules in cancer cells and macrophages that regulate antibody-dependent cancer cell phagocytosis., Author(s): Roarke A. Kamber [sup.1] , Yoko Nishiga [sup.1] [sup.2] [sup.3] , Bhek Morton [sup.1] , Allison M. Banuelos [sup.4] [sup.5] [sup.6] , Amira A. Barkal [sup.4] [sup.5] [sup.6] [sup.7] [...]

Ageing of the immune system is characterized by decreased lymphopoiesis and adaptive immunity, and increased inflammation and myeloid pathologies1,2. Age-related changes in populations of self-renewing haematopoietic stem cells (HSCs) are thought to underlie these phenomena3. During youth, HSCs with balanced output of lymphoid and myeloid cells (bal-HSCs) predominate over HSCs with myeloid-biased output (my-HSCs), thereby promoting the lymphopoiesis required for initiating adaptive immune responses, while limiting the production of myeloid cells, which can be pro-inflammatory4. Ageing is associated with increased proportions of my-HSCs, resulting in decreased lymphopoiesis and increased myelopoiesis3,5,6. Transfer of bal-HSCs results in abundant lymphoid and myeloid cells, a stable phenotype that is retained after secondary transfer; my-HSCs also retain their patterns of production after secondary transfer5. The origin and potential interconversion of these two subsets is still unclear. If they are separate subsets postnatally, it might be possible to reverse the ageing phenotype by eliminating my-HSCs in aged mice. Here we demonstrate that antibody-mediated depletion of my-HSCs in aged mice restores characteristic features of a more youthful immune system, including increasing common lymphocyte progenitors, naive T cells and B cells, while decreasing age-related markers of immune decline. Depletion of my-HSCs in aged mice improves primary and secondary adaptive immune responses to viral infection. These findings may have relevance to the understanding and intervention of diseases exacerbated or caused by dominance of the haematopoietic system by my-HSCs.Antibody-mediated depletion of myeloid-biased haematopoietic stem cells in aged mice restores characteristic features of a more youthful immune system. [ABSTRACT FROM AUTHOR]

Atherosclerosis is the disease process that underlies heart attack and stroke (1). Advanced lesions at risk of rupture are characterized by the pathological accumulation of diseased vascular cells and apoptotic cellular debris (2). Why these cells are not cleared remains unknown (3). Here we show that atherogenesis is associated with upregulation of CD47, a key anti-phagocytic molecule that is known to render malignant cells resistant to programmed cell removal, or 'efferocytosis' (4-7). We find that administration of CD47-blocking antibodies reverses this defect in efferocytosis, normalizes the clearance of diseased vascular tissue, and ameliorates atherosclerosis in multiple mouse models. Mechanistic studies implicate the pro-atherosclerotic factor TNF-α as a fundamental driver of impaired programmed cell removal, explaining why this process is compromised in vascular disease. Similar to recent observations in cancer (5), impaired efferocytosis appears to play a pathogenic role in cardiovascular disease, but is not a fixed defect and may represent a novel therapeutic target., Each day the human body turns over more than 100 billion cells (8). To prevent the inflammatory consequences associated with the accumulation of apoptotic debris (9), these cells are rapidly [...]

Haematopoietic stem cells (HSCs) are arguably the most extensively characterized tissue stem cells. Since the identification of HSCs by prospective isolation (1), complex multi-parameter flow cytometric isolation of phenotypic subsets [...]

The regrowth of amputated limbs and the distal tips of digits represent models of tissue regeneration in amphibians, fish and mice. For decades it had been assumed that limb regeneration derived from the blastema, an undifferentiated pluripotent cell population thought to be derived from mature cells via dedifferentiation. Here we show that a wide range of tissue stem/progenitor cells contribute towards the restoration of the mouse distal digit. Genetic fate mapping and clonal analysis of individual cells revealed that these stem cells are lineage restricted, mimicking digit growth during development. Transplantation of cyan-fluorescent-protein-expressing haematopoietic stem cells, and parabiosis between genetically marked mice, confirmed that the stem/progenitor cells are tissue resident, including the cells involved in angiogenesis. These results, combined with those from appendage regeneration in other vertebrate subphyla, collectively demonstrate that tissue stem cells rather than pluripotent blastema cells are an evolutionarily conserved cellular mode for limb regeneration after amputation., Although whole-body regeneration from blood and vascular structures can occur in protochordate colonial tunicates (1,3), regeneration of body parts is highly restricted in vertebrates, especially in mammals (4). Therefore, digit [...]

Epigenetic modifications must underlie lineage-specific differentiation as terminally differentiated cells express tissue-specific genes, but their DNA sequence is unchanged. Haematopoiesis provides a well-defined model to study epigenetic modifications during cell-fate decisions, as multipotent progenitors (MPPs) differentiate into progressively restricted myeloid or lymphoid progenitors. Although DNA methylation is critical for myeloid versus lymphoid differentiation, as demonstrated by the myeloerythroid bias in Dnmt1 hypomorphs (1), a comprehensive DNA methylation map of haematopoietic progenitors, or of any multipotent/oligopotent lineage, does not exist. Here we examined 4.6 million CpG sites throughout the genome for MPPs, common lymphoid progenitors (CLPs), common myeloid progenitors (CMPs), granulocyte/macrophage progenitors (GMPs), and thymocyte progenitors (DN1, DN2, DN3). Marked epigenetic plasticity accompanied both lymphoid and myeloid restriction. Myeloid commitment involved less global DNA methylation than lymphoid commitment, supported functionally by myeloid skewing of progenitors following treatment with a DNA methyltransferase inhibitor. Differential DNA methylation correlated with gene expression more strongly at CpG island shores than CpG islands. Many examples of genes and pathways not previously known to be involved in choice between lymphoid/myeloid differentiation have been identified, such as Arl4c and Jdp2. Several transcription factors, including Meis1, were methylated and silenced during differentiation, indicating a role in maintaining an undifferentiated state. Additionally, epigenetic modification of modifiers of the epigenome seems to be important in haematopoietic differentiation. Our results directly demonstrate that modulation of DNA methylation occurs during lineage-specific differentiation and defines a comprehensive map of the methylation and transcriptional changes that accompany myeloid versus lymphoid fate decisions., Haematopoietic stem cells (HSC) can self renew for life and differentiate into all myeloid and lymphoid blood lineages (2) (Fig. 1a). Recent evidence indicates that DNA methylation has a direct [...]

The question of whether tumorigenic cancer stem cells exist in human melanomas has arisen in the last few years (1). Here we show that in melanomas, tumour stem cells (MTSCs, for melanoma tumour stem cells) can be isolated prospectively as a highly enriched [CD271.sup.+] MTSC population using a process that maximizes viable cell transplantation (1,2). The tumours sampled in this study were taken from a broad spectrum of sites and stages. High-viability cells isolated by fluorescence-activated cell sorting and re-suspended in a matrigel vehicle were implanted into T-, B- and natural-killer-deficient [Rag2.sup.-/-] γ[c.sup.-/-] mice. The [CD271.sup.+] subset of cells was the tumour-initiating population in 90% (nine out of ten) of melanomas tested. Transplantation of isolated [CD271.sup.+] melanoma cells into engrafted human skin or bone in [Rag2.sup.-/-] γ[c.sup.-/-] mice resulted in melanoma; however, melanoma did not develop after transplantation of isolated [CD271.sup.-] cells. We also show that in mice, tumours derived from transplanted human [CD271.sup.+] melanoma cells were capable of metastatsis in vivo. [CD271.sup.+] melanoma cells lacked expression of TYR, MART1 and MAGE in 86%, 69% and 68% of melanoma patients, respectively, which helps to explain why T-cell therapies directed at these antigens usually result in only temporary tumour shrinkage., Cancers derive by clonal progression to appear as abnormal growths. At diagnosis, they can be at a stage ranging from low risk of metastasis and probable cure, to highly aggressive [...]

Coronary artery disease is the leading cause of death worldwide. Determining the coronary artery developmental program could aid understanding of the disease and lead to new treatments, but many aspects of the process, including their developmental origin, remain obscure. Here we show, using histological and clonal analysis in mice and cardiac organ culture, that coronary vessels arise from angiogenic sprouts of the sinus venosus--the vein that returns blood to the embryonic heart. Sprouting venous endothelial cells dedifferentiate as they migrate over and invade the myocardium. Invading cells differentiate into arteries and capillaries; cells on the surface redifferentiate into veins. These results show that some differentiated venous cells retain developmental plasticity, and indicate that position-specific cardiac signals trigger their dedifferentiation and conversion into coronary arteries, capillaries and veins. Understanding this new reprogramming process and identifying the endogenous signals should suggest more natural ways of engineering coronary bypass grafts and revascularizing the heart., There has been tremendous progress during the past two decades in elucidating the general principles of blood vessel development and the factors that control it (1-4), especially during tumour angiogenesis [...]

The metabolism of oxygen, although central to life, produces reactive oxygen species (ROS) that have been implicated in processes as diverse as cancer, cardiovascular disease and ageing. It has recently been shown that central nervous system stem cells (1,2) and haematopoietic stem cells and early progenitors (3-6) contain lower levels of ROS than their more mature progeny, and that these differences are critical for maintaining stem cell function. We proposed that epithelial tissue stem cells and their cancer stem cell (CSC) counterparts may also share this property. Here we show that normal mammary epithelial stem cells contain lower concentrations of ROS than their more mature progeny cells. Notably, subsets of CSCs in some human and murine breast tumours contain lower ROS levels than corresponding non-tumorigenic cells (NTCs). Consistent with ROS being critical mediators of ionizing-radiation- induced cell killing (7,8), CSCs in these tumours develop less DNA damage and are preferentially spared after irradiation compared to NTCs. Lower ROS levels in CSCs are associated with increased expression of free radical scavenging systems. Pharmacological depletion of ROS scavengers in CSCs markedly decreases their clonogenicity and results in radiosensitization. These results indicate that, similar to normal tissue stem cells, subsets of CSCs in some tumours contain lower ROS levels and enhanced ROS defences compared to their non-tumorigenic progeny, which may contribute to tumour radioresistance., We began by addressing whether the low ROS concentrations that seem to be critical for self-renewal of haematopoietic stem cells (HSCS) (3,5) are also a property of mammary epithelial stem [...]

Little is known about the formation of niches, local micro-environments required for stem-cell maintenance. Here we develop an in vivo assay for adult haematopoietic stem-cell (HSC) niche formation (1,2). With this assay, we identified a population of progenitor cells with surface markers [CD45.sup.-][Tie2.sup.-][α.sub.v.sup.+][CD105.sup.+][Thy1.1.sup.-] ([CD105.sup.+][Thy1.sup.-]) that, when sorted from 15.5 days post-coitum fetal bones and transplanted under the adult mouse kidney capsule, could recruit host-derived blood vessels, produce donor-derived ectopic bones through a cartilage intermediate and generate a marrow cavity populated by host-derived long-term reconstituting HSC (LT-HSC). In contrast, [CD45.sup.-][Tie2.sup.-][α.sub.v.sup.+][CD105.sup.+][Thy1.sup.+] ([CD105.sup.+][Thy1.sup.+]) fetal bone progenitors form bone that does not contain a marrow cavity. Suppressing expression of factors involved in endochondral ossification, such as osterix and vascular endothelial growth factor (VEGF), inhibited niche generation. [CD105.sup.+][Thy1.sup.-] progenitor populations derived from regions of the fetal mandible or calvaria that do not undergo endochondral ossification formed only bone without marrow in our assay. Collectively, our data implicate endochondral ossification, bone formation that proceeds through a cartilage intermediate, as a requirement for adult HSC niche formation., Growth and renewal in many tissues are initiated by stem cells, supported by the niches in which they reside (1-3). Although recent work has begun to describe functional interactions between [...]

Author(s): Sydney R. Gordon [1, 2, 3, 4, 5]; Roy L. Maute [1, 3, 4, 5]; Ben W. Dulken [1, 6]; Gregor Hutter [1, 7, 8]; Benson M. George [1, [...]

Author(s): Kelley S. Yan [1, 2]; Claudia Y. Janda [3]; Junlei Chang [1]; Grace X. Y. Zheng [4]; Kathryn A. Larkin [1]; Vincent C. Luca [3]; Luis A. Chia [1]; [...]

Author(s): Derrick J. Rossi (corresponding author) [1, 4]; David Bryder [1, 4, 5]; Jun Seita [1]; Andre Nussenzweig [2]; Jan Hoeijmakers [3]; Irving L. Weissman [1] A diminished capacity to [...]

Author(s): Anthony W. De Tomaso (corresponding author) [1]; Spencer V. Nyholm [1]; Karla J. Palmeri [1]; Katherine J. Ishizuka [1]; William B. Ludington [1]; Katrina Mitchel [1]; Irving L. Weissman [...]

Author(s): Irina M. Conboy [1, 4, 5]; Michael J. Conboy [1, 4]; Amy J. Wagers [2, 5]; Eric R. Girma [1]; Irving L. Weissman [2]; Thomas A. Rando (corresponding author) [...]

Author(s): Leora B. Balsam [1]; Amy J. Wagers [2, 3]; Julie L. Christensen [2, 3]; Theo Kofidis [1]; Irving L. Weissman [2, 3]; Robert C. Robbins (corresponding author) [1] Under [...]

Author(s): Karl Willert [1]; Jeffrey D. Brown [1]; Esther Danenberg [1]; Andrew W. Duncan [2]; Irving L. Weissman [3]; Tannishtha Reya [2]; John R. Yates, III [4]; Roel Nusse (corresponding [...]

Author(s): Tannishtha Reya (corresponding author) [1, 2]; Andrew W. Duncan [1, 2]; Laurie Ailles [3]; Jos Domen [4]; David C. Scherer [3]; Karl Willert [5]; Lindsay Hintz [1]; Roel Nusse [...]

Author(s): In-kyung Park [1]; Dalong Qian [1]; Mark Kiel [2]; Michael W. Becker [1]; Michael Pihalja [1]; Irving L. Weissman [3]; Sean J. Morrison [2]; Michael F. Clarke (corresponding author) [...]

Author(s): Tannishtha Reya [1, 4, 5]; Sean J. Morrison [2, 5]; Michael F. Clarke [3]; Irving L. Weissman (corresponding author) [1] Stem cells are defined as cells that have the [...]

Author(s): Motonari Kondo [1]; David C. Scherer [1]; Toshihiro Miyamoto [1]; Angela G. King [1]; Koichi Akashi [1]; Kazuo Sugamura [2]; Irving L. Weissman [1] The primary role of cytokines [...]

Author(s): Koichi Akashi (corresponding author) [1, 2]; David Traver [1]; Toshihiro Miyamoto; Irving L. Weissman Haematopoietic stem cells give rise to progeny that progressively lose self-renewal capacity and become restricted [...]

Ageing is characterized by the development of persistent pro-inflammatory responses that contribute to atherosclerosis, metabolic syndrome, cancer and frailty1–3. The ageing brain is also vulnerable to inflammation, as demonstrated by the high prevalence of age-associated cognitive decline and Alzheimer’s disease4–6. Systemically, circulating pro-inflammatory factors can promote cognitive decline7,8, and in the brain, microglia lose the ability to clear misfolded proteins that are associated with neurodegeneration9,10. However, the underlying mechanisms that initiate and sustain maladaptive inflammation with ageing are not well defined. Here we show that in ageing mice myeloid cell bioenergetics are suppressed in response to increased signalling by the lipid messenger prostaglandin E2 (PGE2), a major modulator of inflammation11. In ageing macrophages and microglia, PGE2 signalling through its EP2 receptor promotes the sequestration of glucose into glycogen, reducing glucose flux and mitochondrial respiration. This energy-deficient state, which drives maladaptive pro-inflammatory responses, is further augmented by a dependence of aged myeloid cells on glucose as a principal fuel source. In aged mice, inhibition of myeloid EP2 signalling rejuvenates cellular bioenergetics, systemic and brain inflammatory states, hippocampal synaptic plasticity and spatial memory. Moreover, blockade of peripheral myeloid EP2 signalling is sufficient to restore cognition in aged mice. Our study suggests that cognitive ageing is not a static or irrevocable condition but can be reversed by reprogramming myeloid glucose metabolism to restore youthful immune functions.In aged mice, inhibition of prostaglandin E2 (PGE2) signalling through its receptor EP2 improves cellular bioenergetics, reduces inflammatory responses and restores hippocampal plasticity to youthful levels, resulting in an improvement in spatial memory and cognition. [ABSTRACT FROM AUTHOR]

Ovarian cancer and triple-negative breast cancer are among the most lethal diseases affecting women, with few targeted therapies and high rates of metastasis. Cancer cells are capable of evading clearance by macrophages through the overexpression of anti-phagocytic surface proteins called 'don't eat me' signals—including CD471, programmed cell death ligand 1 (PD-L1)2 and the beta-2 microglobulin subunit of the major histocompatibility class I complex (B2M)3. Monoclonal antibodies that antagonize the interaction of 'don't eat me' signals with their macrophage-expressed receptors have demonstrated therapeutic potential in several cancers4,5. However, variability in the magnitude and durability of the response to these agents has suggested the presence of additional, as yet unknown 'don't eat me' signals. Here we show that CD24 can be the dominant innate immune checkpoint in ovarian cancer and breast cancer, and is a promising target for cancer immunotherapy. We demonstrate a role for tumour-expressed CD24 in promoting immune evasion through its interaction with the inhibitory receptor sialic-acid-binding Ig-like lectin 10 (Siglec-10), which is expressed by tumour-associated macrophages. We find that many tumours overexpress CD24 and that tumour-associated macrophages express high levels of Siglec-10. Genetic ablation of either CD24 or Siglec-10, as well as blockade of the CD24–Siglec-10 interaction using monoclonal antibodies, robustly augment the phagocytosis of all CD24-expressing human tumours that we tested. Genetic ablation and therapeutic blockade of CD24 resulted in a macrophage-dependent reduction of tumour growth in vivo and an increase in survival time. These data reveal CD24 as a highly expressed, anti-phagocytic signal in several cancers and demonstrate the therapeutic potential for CD24 blockade in cancer immunotherapy. CD24 interacts with the tumour-associated-macrophage receptor Siglec-10 to inhibit the macrophage-mediated clearance of cancer cells, revealing a new 'don't eat me' signal as a potential target for cancer immunotherapy. [ABSTRACT FROM AUTHOR]

The mammalian brain contains neurogenic niches that comprise neural stem cells and other cell types. Neurogenic niches become less functional with age, but how they change during ageing remains unclear. Here we perform single-cell RNA sequencing of young and old neurogenic niches in mice. The analysis of 14,685 single-cell transcriptomes reveals a decrease in activated neural stem cells, changes in endothelial cells and microglia, and an infiltration of T cells in old neurogenic niches. T cells in old brains are clonally expanded and are generally distinct from those in old blood, which suggests that they may experience specific antigens. T cells in old brains also express interferon-γ, and the subset of neural stem cells that has a high interferon response shows decreased proliferation in vivo. We find that T cells can inhibit the proliferation of neural stem cells in co-cultures and in vivo, in part by secreting interferon-γ. Our study reveals an interaction between T cells and neural stem cells in old brains, opening potential avenues through which to counteract age-related decline in brain function. Single-cell transcriptomic analysis of neurogenic niches in young and old mice reveals that T cells infiltrate the neurogenic niches of old mice and inhibit the proliferation of neural stem cells, in part through expression of interferon-γ. [ABSTRACT FROM AUTHOR]

Haematopoiesis is an essential process that evolved in multicellular animals. At the heart of this process are haematopoietic stem cells (HSCs), which are multipotent and self-renewing, and generate the entire repertoire of blood and immune cells throughout an animal's life1. Although there have been comprehensive studies on self-renewal, differentiation, physiological regulation and niche occupation in vertebrate HSCs, relatively little is known about the evolutionary origin and niches of these cells. Here we describe the haematopoietic system of Botryllus schlosseri, a colonial tunicate that has a vasculature and circulating blood cells, and interesting stem-cell biology and immunity characteristics2-8. Self-recognition between genetically compatible B. schlosseri colonies leads to the formation of natural parabionts with shared circulation, whereas incompatible colonies reject each other3,4,7. Using flow cytometry, whole-transcriptome sequencing of defined cell populations and diverse functional assays, we identify HSCs, progenitors, immune effector cells and an HSC niche, and demonstrate that self-recognition inhibits allospecific cytotoxic reactions. Our results show that HSC and myeloid lineage immune cells emerged in a common ancestor of tunicates and vertebrates, and also suggest that haematopoietic bone marrow and the B. schlosseri endostyle niche evolved from a common origin. The identification of a complex haematopoietic system in a colonial tunicate sheds light on the evolution of the mammalian blood system. [ABSTRACT FROM AUTHOR]

Epigenetic modifications must underlie lineage-specific differentiation as terminally differentiated cells express tissue-specific genes, but their DNA sequence is unchanged. Haematopoiesis provides a well-defined model to study epigenetic modifications during cell-fate decisions, as multipotent progenitors (MPPs) differentiate into progressively restricted myeloid or lymphoid progenitors. Although DNA methylation is critical for myeloid versus lymphoid differentiation, as demonstrated by the myeloerythroid bias in Dnmt1 hypomorphs, a comprehensive DNA methylation map of haematopoietic progenitors, or of any multipotent/oligopotent lineage, does not exist. Here we examined 4.6 million CpG sites throughout the genome for MPPs, common lymphoid progenitors (CLPs), common myeloid progenitors (CMPs), granulocyte/macrophage progenitors (GMPs), and thymocyte progenitors (DN1, DN2, DN3). Marked epigenetic plasticity accompanied both lymphoid and myeloid restriction. Myeloid commitment involved less global DNA methylation than lymphoid commitment, supported functionally by myeloid skewing of progenitors following treatment with a DNA methyltransferase inhibitor. Differential DNA methylation correlated with gene expression more strongly at CpG island shores than CpG islands. Many examples of genes and pathways not previously known to be involved in choice between lymphoid/myeloid differentiation have been identified, such as Arl4c and Jdp2. Several transcription factors, including Meis1, were methylated and silenced during differentiation, indicating a role in maintaining an undifferentiated state. Additionally, epigenetic modification of modifiers of the epigenome seems to be important in haematopoietic differentiation. Our results directly demonstrate that modulation of DNA methylation occurs during lineage-specific differentiation and defines a comprehensive map of the methylation and transcriptional changes that accompany myeloid versus lymphoid fate decisions. [ABSTRACT FROM AUTHOR]

A correction to the article "Human melanoma-initiating cells express neural crest nerve growth factor receptor CD271" that was published in the 2010 issue is presented.

Adoptively transferred T cells and agents designed to block the CD47-SIRPα axis are promising cancer therapeutics that activate distinct arms of the immune system 1,2 . Here we administered anti-CD47 antibodies in combination with adoptively transferred T cells with the goal of enhancing antitumour efficacy but observed abrogated therapeutic benefit due to rapid macrophage-mediated clearance of T cells expressing chimeric antigen receptors (CARs) or engineered T cell receptors. Anti-CD47-antibody-mediated CAR T cell clearance was potent and rapid enough to serve as an effective safety switch. To overcome this challenge, we engineered the CD47 variant CD47(Q31P) (47 E ), which engages SIRPα and provides a 'don't eat me' signal that is not blocked by anti-CD47 antibodies. TCR or CAR T cells expressing 47 E are resistant to clearance by macrophages after treatment with anti-CD47 antibodies, and mediate substantial, sustained macrophage recruitment to the tumour microenvironment. Although many of the recruited macrophages manifested an M2-like profile 3 , the combined therapy synergistically enhanced antitumour efficacy. Our study identifies macrophages as major regulators of T cell persistence and illustrates the fundamental challenge of combining T-cell-directed therapeutics with those designed to activate macrophages. It delivers a therapeutic approach that is capable of simultaneously harnessing the antitumour effects of T cells and macrophages, offering enhanced potency against solid tumours., (© 2024. The Author(s).)

Loss of skeletal integrity during ageing and disease is associated with an imbalance in the opposing actions of osteoblasts and osteoclasts 1 . Here we show that intrinsic ageing of skeletal stem cells (SSCs) 2 in mice alters signalling in the bone marrow niche and skews the differentiation of bone and blood lineages, leading to fragile bones that regenerate poorly. Functionally, aged SSCs have a decreased bone- and cartilage-forming potential but produce more stromal lineages that express high levels of pro-inflammatory and pro-resorptive cytokines. Single-cell RNA-sequencing studies link the functional loss to a diminished transcriptomic diversity of SSCs in aged mice, which thereby contributes to the transformation of the bone marrow niche. Exposure to a youthful circulation through heterochronic parabiosis or systemic reconstitution with young haematopoietic stem cells did not reverse the diminished osteochondrogenic activity of aged SSCs, or improve bone mass or skeletal healing parameters in aged mice. Conversely, the aged SSC lineage promoted osteoclastic activity and myeloid skewing by haematopoietic stem and progenitor cells, suggesting that the ageing of SSCs is a driver of haematopoietic ageing. Deficient bone regeneration in aged mice could only be returned to youthful levels by applying a combinatorial treatment of BMP2 and a CSF1 antagonist locally to fractures, which reactivated aged SSCs and simultaneously ablated the inflammatory, pro-osteoclastic milieu. Our findings provide mechanistic insights into the complex, multifactorial mechanisms that underlie skeletal ageing and offer prospects for rejuvenating the aged skeletal system., (© 2021. The Author(s), under exclusive licence to Springer Nature Limited.)

Although single-cell RNA sequencing studies have begun to provide compendia of cell expression profiles 1-9 , it has been difficult to systematically identify and localize all molecular cell types in individual organs to create a full molecular cell atlas. Here, using droplet- and plate-based single-cell RNA sequencing of approximately 75,000 human cells across all lung tissue compartments and circulating blood, combined with a multi-pronged cell annotation approach, we create an extensive cell atlas of the human lung. We define the gene expression profiles and anatomical locations of 58 cell populations in the human lung, including 41 out of 45 previously known cell types and 14 previously unknown ones. This comprehensive molecular atlas identifies the biochemical functions of lung cells and the transcription factors and markers for making and monitoring them; defines the cell targets of circulating hormones and predicts local signalling interactions and immune cell homing; and identifies cell types that are directly affected by lung disease genes and respiratory viruses. By comparing human and mouse data, we identified 17 molecular cell types that have been gained or lost during lung evolution and others with substantially altered expression profiles, revealing extensive plasticity of cell types and cell-type-specific gene expression during organ evolution including expression switches between cell types. This atlas provides the molecular foundation for investigating how lung cell identities, functions and interactions are achieved in development and tissue engineering and altered in disease and evolution.