C/EBPß-induced lymphoid-to-myeloid transdifferentiation emulates granulocyte-monocyte progenitor biology.

CCAAT/enhancer-binding protein beta (C/EBPß) induces primary v-Abl immortalized mouse B cells to transdifferentiate (BT, B cell transdifferentiation) into granulocyte-macrophage progenitor-like cells (GMPBTs). GMPBTs maintain cytokine-independent self-renewal, lineage choice, and multilineage differentiation. Single-cell transcriptomics demonstrated that GMPBTs comprise a continuum of myelomonopoietic differentiation states that seamlessly fit into state-to-fate maps of normal granulocyte-macrophage progenitors (GMPs). Inactivating v-Abl kinase revealed the dependence on activated CSF2-JAK2-STAT5 signaling. Deleting IRF8 diminished monopoiesis and enhanced granulopoiesis while removing C/EBPß-abrogated self-renewal and granulopoiesis but permitted macrophage differentiation. The GMPBT culture system is easily scalable to explore the basics of GMP biology and lineage commitment and largely reduces ethically and legislatively debatable, labor-intensive, and costly animal experiments.

Immune cell C/EBPß deficiency is associated with hepatic mononuclear defects and spontaneous hepatitis but not steatohepatitis induced liver fibrosis.

BACKGROUND: CCAAT/enhancer-binding protein ß (C/EBPß) is a transcription factor known to be involved in macrophage differentiation and function, steatohepatitis and liver fibrosis. METHODS: Immune restricted C/EBPß deficient and control mice were investigated in steady-state and in the CDA-HFD steatohepatitis model. Mice were assessed for weight change, liver biochemical profile, histology and hepatic phagocytes composition. RESULTS: Flow cytometry analysis of hepatic nonparenchymal cells revealed reduced numbers of hepatic monocytes and Kupffer cells and an increase in hepatic MHC class II positive myeloid cells in immune cells restricted C/EBPß deficient mice. Immune-restricted C/EBPß deficiency resulted in decreased weight gain and appearance of mild spontaneous liver inflammation. Nevertheless, In the CDA-HFD steatohepatitis model, immune restricted C/EBPß deficient and proficient mice exhibit similar grade of hepatic steatosis, liver enzymes levels and fibrosis stage. CONCLUSIONS: Immune-restricted C/EBPß deficiency leads to significant alteration in hepatic mononuclear phagocytes composition associated with spontaneous mild hepatitis. Steatohepatitis associated fibrosis is not dependent on C/EBPß expression by immune cells.

Identification of environmental factors that promote intestinal inflammation.

Genome-wide association studies have identified risk loci linked to inflammatory bowel disease (IBD)1-a complex chronic inflammatory disorder of the gastrointestinal tract. The increasing prevalence of IBD in industrialized countries and the augmented disease risk observed in migrants who move into areas of higher disease prevalence suggest that environmental factors are also important determinants of IBD susceptibility and severity2. However, the identification of environmental factors relevant to IBD and the mechanisms by which they influence disease has been hampered by the lack of platforms for their systematic investigation. Here we describe an integrated systems approach, combining publicly available databases, zebrafish chemical screens, machine learning and mouse preclinical models to identify environmental factors that control intestinal inflammation. This approach established that the herbicide propyzamide increases inflammation in the small and large intestine. Moreover, we show that an AHR-NF-κB-C/EBPß signalling axis operates in T cells and dendritic cells to promote intestinal inflammation, and is targeted by propyzamide. In conclusion, we developed a pipeline for the identification of environmental factors and mechanisms of pathogenesis in IBD and, potentially, other inflammatory diseases.

C/EBPß regulates lipid metabolism and Pparg isoform 2 expression in alveolar macrophages.

Pulmonary alveolar proteinosis (PAP) is a syndrome characterized by accumulation of surfactant lipoproteins within the lung alveoli. Alveolar macrophages (AMs) are crucial for surfactant clearance, and their differentiation depends on colony-stimulating factor 2 (CSF2), which regulates the establishment of an AM-characteristic gene regulatory network. Here, we report that the transcription factor CCAAT/enhancer binding protein ß (C/EBPß) is essential for the development of the AM identity, as demonstrated by transcriptome and chromatin accessibility analysis. Furthermore, C/EBPß-deficient AMs showed severe defects in proliferation, phagocytosis, and lipid metabolism, collectively resulting in a PAP-like syndrome. Mechanistically, the long C/EBPß protein variants LAP* and LAP together with CSF2 signaling induced the expression of Pparg isoform 2 but not Pparg isoform 1, a molecular regulatory mechanism that was also observed in other CSF2-primed macrophages. These results uncover C/EBPß as a key regulator of AM cell fate and shed light on the molecular networks controlling lipid metabolism in macrophages.

Tongue immune compartment analysis reveals spatial macrophage heterogeneity.

The tongue is a unique muscular organ situated in the oral cavity where it is involved in taste sensation, mastication, and articulation. As a barrier organ, which is constantly exposed to environmental pathogens, the tongue is expected to host an immune cell network ensuring local immune defence. However, the composition and the transcriptional landscape of the tongue immune system are currently not completely defined. Here, we characterised the tissue-resident immune compartment of the murine tongue during development, health and disease, combining single-cell RNA-sequencing with in situ immunophenotyping. We identified distinct local immune cell populations and described two specific subsets of tongue-resident macrophages occupying discrete anatomical niches. Cx3cr1+ macrophages were located specifically in the highly innervated lamina propria beneath the tongue epidermis and at times in close proximity to fungiform papillae. Folr2+ macrophages were detected in deeper muscular tissue. In silico analysis indicated that the two macrophage subsets originate from a common proliferative precursor during early postnatal development and responded differently to systemic LPS in vivo. Our description of the under-investigated tongue immune system sets a starting point to facilitate research on tongue immune-physiology and pathology including cancer and taste disorders.

TAT-MeCP2 protein variants rescue disease phenotypes in human and mouse models of Rett syndrome.

Rett syndrome (RTT) is a neurodevelopmental disorder caused by pathogenic variants leading to functional impairment of the MeCP2 protein. Here, we used purified recombinant MeCP2e1 and MeCP2e2 protein variants fused to a TAT protein transduction domain (PTD) to evaluate their transduction ability into RTT patient-derived fibroblasts and the ability to carry out their cellular function. We then assessed their transduction ability and therapeutic effects in a RTT mouse model. In vitro, TAT-MeCP2e2-eGFP reversed the pathological hyperacetylation of histones H3K9 and H4K16, a hallmark of abolition of MeCP2 function. In vivo, intraperitoneal administration of TAT-MeCP2e1 and TAT-MeCP2e2 extended the lifespan of Mecp2-/y mice by >50%. This was accompanied by rescue of hippocampal CA2 neuron size in animals treated with TAT-MeCP2e1. Taken together, these findings provide a strong indication that recombinant TAT-MeCP2 can reach mouse brains following peripheral injection and can ameliorate the phenotype of RTT mouse models. Thus, our study serves as a first step in the development of a potentially novel RTT therapy.

CSF2-dependent monocyte education in the pathogenesis of ANCA-induced glomerulonephritis.

OBJECTIVES: Myeloid cell activation by antineutrophil cytoplasmic antibody (ANCA) is pivotal for necrotising vasculitis, including necrotising crescentic glomerulonephritis (NCGN). In contrast to neutrophils, the contribution of classical monocyte (CM) and non-classical monocyte (NCM) remains poorly defined. We tested the hypothesis that CMs contribute to antineutrophil cytoplasmic antibody-associated vasculitis (AAV) and that colony-stimulating factor-2 (CSF2, granulocyte-macrophage colony-stimulating factor (GM-CSF)) is an important monocyte-directed disease modifier. METHODS: Myeloperoxidase (MPO)-immunised MPO-/- mice were transplanted with haematopoietic cells from wild-type (WT) mice, C-C chemokine receptor 2 (CCR2)-/- mice to abrogate CM, or transcription factor CCAAT-enhancer-binding protein beta (C/EBPß)-/- mice to reduce NCM, respectively. Monocytes were stimulated with CSF2, and CSF2 receptor subunit beta (CSF2rb)-deficient mice were used. Urinary monocytes and CSF2 were quantified and kidney Csf2 expression was analysed. CSF2-blocking antibody was used in the nephrotoxic nephritis (NTN) model. RESULTS: Compared with WT mice, CCR2-/- chimeric mice showed reduced circulating CM and were protected from NCGN. C/EBPß-/- chimeric mice lacked NCM but developed NCGN similar to WT chimeric mice. Kidney and urinary CSF2 were upregulated in AAV mice. CSF2 increased the ability of ANCA-stimulated monocytes to generate interleukin-1ß and to promote TH17 effector cell polarisation. CSF2rb-/- chimeric mice harboured reduced numbers of kidney TH17 cells and were protected from NCGN. CSF2 neutralisation reduced renal damage in the NTN model. Finally, patients with active AAV displayed increased urinary CM numbers, CSF2 levels and expression of GM-CSF in infiltrating renal cells. CONCLUSIONS: CMs but not NCMs are important for inducing kidney damage in AAV. CSF2 is a crucial pathological factor by modulating monocyte proinflammatory functions and thereby TH17 cell polarisation.

Myeloid transformation by MLL-ENL depends strictly on C/EBP.

Chromosomal rearrangements of the mixed-lineage leukemia gene MLL1 are the hallmark of infant acute leukemia. The granulocyte-macrophage progenitor state forms the epigenetic basis for myelomonocytic leukemia stemness and transformation by MLL-type oncoproteins. Previously, it was shown that the establishment of murine myelomonocytic MLL-ENL transformation, but not its maintenance, depends on the transcription factor C/EBPα, suggesting an epigenetic hit-and-run mechanism of MLL-driven oncogenesis. Here, we demonstrate that compound deletion of Cebpa/Cebpb almost entirely abrogated the growth and survival of MLL-ENL-transformed cells. Rare, slow-growing, and apoptosis-prone MLL-ENL-transformed escapees were recovered from compound Cebpa/Cebpb deletions. The escapees were uniformly characterized by high expression of the resident Cebpe gene, suggesting inferior functional compensation of C/EBPα/C/EBPß deficiency by C/EBPε. Complementation was augmented by ectopic C/EBPß expression and downstream activation of IGF1 that enhanced growth. Cebpe gene inactivation was accomplished only in the presence of complementing C/EBPß, but not in its absence, confirming the Cebpe dependency of the Cebpa/Cebpb double knockouts. Our data show that MLL-transformed myeloid cells are dependent on C/EBPs during the initiation and maintenance of transformation.

Author Correction: Cxcl10+ monocytes define a pathogenic subset in the central nervous system during autoimmune neuroinflammation.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Publisher Correction: Cxcl10+ monocytes define a pathogenic subset in the central nervous system during autoimmune neuroinflammation.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Cxcl10+ monocytes define a pathogenic subset in the central nervous system during autoimmune neuroinflammation.

Multiple sclerosis (MS) is characterized by pathological inflammation that results from the recruitment of lymphoid and myeloid immune cells from the blood into the brain. Due to subset heterogeneity, defining the functional roles of the various cell subsets in acute and chronic stages of MS has been challenging. Here, we used index and transcriptional single-cell sorting to characterize the mononuclear phagocytes that infiltrate the central nervous system from the periphery in mice with experimentally induced autoimmune encephalomyelitis, a model of MS. We identified eight monocyte and three dendritic cell subsets at acute and chronic disease stages in which the defined transcriptional programs pointed toward distinct functions. Monocyte-specific cell ablation identified Cxcl10+ and Saa3+ monocytic subsets with a pathogenic potential. Transfer experiments with different monocyte and precursor subsets indicated that these Cxcl10+ and Saa3+ pathogenic cells were not derived from Ly6C+ monocytes but from early myeloid cell progenitors. These results suggest that blocking specific pathogenic monocytic subsets, including Cxcl10+ and Saa3+ monocytes, could be used for targeted therapeutic interventions.

C/EBPß-Dependent Epigenetic Memory Induces Trained Immunity in Hematopoietic Stem Cells.

Hematopoietic stem cells (HSCs) maintain life-long production of immune cells and can directly respond to infection, but sustained effects on the immune response remain unclear. We show that acute immune stimulation with lipopolysaccharide (LPS) induced only transient changes in HSC abundance, composition, progeny, and gene expression, but persistent alterations in accessibility of specific myeloid lineage enhancers occurred, which increased responsiveness of associated immune genes to secondary stimulation. Functionally, this was associated with increased myelopoiesis of pre-exposed HSCs and improved innate immunity against the gram-negative bacterium P. aeruginosa. The accessible myeloid enhancers were enriched for C/EBPß targets, and C/EBPß deletion erased the long-term inscription of LPS-induced epigenetic marks and gene expression. Thus, short-term immune signaling can induce C/EBPß-dependent chromatin accessibility, resulting in HSC-trained immunity, during secondary infection. This establishes a mechanism for how infection history can be epigenetically inscribed in HSCs as an integral memory function of innate immunity.

Good things come in threes.

Ectopic expression of PU.1, IRF8, and BATF3 reprograms mouse and human fibroblasts into dendritic cells. See related Research Article by Rosa et al.

Developmental and Functional Heterogeneity of Monocytes.

Novel experimental approaches such as fate-mapping and single-cell analysis have brought fresh insight into monocyte development and function over the past decade and helped redefine the monocyte field. Monocytes are now known to consist of multiple subsets generated through distinct developmental pathways with diverse functional specializations. Their fates under homeostatic conditions include the accumulation in peripheral reservoirs and the engraftment into certain resident macrophage pools. Under pathological conditions, monocytes acquire inflammatory effector functions, but can also develop regulatory properties essential for tissue repair. Importantly, monocytes recruited during inflammation are often functionally distinct from resident macrophages or conventional dendritic cells. Here we outline emerging concepts in monocyte heterogeneity, emergency monopoiesis, and trained immunity and discuss how these bring new perspectives to monocyte research.

From SOMDA to application - integration strategies in the OR.NET demonstration sites.

The effective development and dissemination of the open integration for the next generation of operating rooms require a comprehensive testing environment. In this paper, we present the various challenges to be addressed in demonstration applications, and we discuss the implementation approach, the foci of the demonstration sites and the evaluation efforts. Overall, the demonstrator setups have proven the feasibility of the service-oriented medical device architecture (SOMDA) and real-time approaches with a large variety of example applications. The applications demonstrate the potentials of open device interoperability. The demonstrator implementations were technically evaluated as well as discussed with many clinicians from various disciplines. However, the evaluation is still an ongoing research at the demonstration sites. Technical evaluation focused on the properties of a network of medical devices, latencies in data transmission and stability. A careful evaluation of the SOMDA design decisions and implementations are essential to a safe and reliable interoperability of integrated medical devices and information technology (IT) system in the especially critical working environment. The clinical evaluation addressed the demands of future users and stakeholders, especially surgeons, anesthesiologists, scrub nurses and hospital operators. The opinions were carefully collected to gain further insights into the potential benefits of the technology and pitfalls in future work.

Extended device profiles and testing procedures for the approval process of integrated medical devices using the IEEE 11073 communication standard.

Nowadays, only closed and proprietary integrated operating room systems (IORS) from big manufacturers are available on the market. Hence, the interconnection of components from third-party vendors is only possible with increased time and costs. In the context of the German Federal Ministry of Education and Research (BMBF)-funded project OR.NET (2012-2016), the open integration of medical devices from different manufacturers was addressed. An integrated operating theater based on the open communication standard IEEE 11073 shall give clinical operators the opportunity to choose medical devices independently of the manufacturer. This approach would be advantageous especially for hospital operators and small- and medium-sized enterprises (SME) of medical devices. Actual standards and concepts regarding technical feasibility and the approval process do not cope with the requirements for a modular integration of medical devices in the operating room (OR), based on an open communication standard. Therefore, innovative approval strategies and corresponding certification and test procedures, which cover actual legal and normative standards, have to be developed in order to support the future risk management and the usability engineering process of open integrated medical devices in the OR. The use of standardized device and service profiles and a three-step testing procedure, including conformity, interoperability and integration tests are described in this paper and shall support the manufacturers to integrate their medical devices without disclosing the medical devices' risk analysis and related confidential expertise or proprietary information.