Environmental signals rather than layered ontogeny imprint the function of type 2 conventional dendritic cells in young and adult mice

Conventional dendritic cells (cDC) are key activators of naive T cells, and can be targeted in adults to induce adaptive immunity, but in early life are considered under-developed or functionally immature. Here we show that, in early life, when the immune system develops, cDC2 exhibit a dual hematopoietic origin and, like other myeloid and lymphoid cells, develop in waves. Developmentally distinct cDC2 in early life, despite being distinguishable by fate mapping, are transcriptionally and functionally similar. cDC2 in early and adult life, however, are exposed to distinct cytokine environments that shape their transcriptional profile and alter their ability to sense pathogens, secrete cytokines and polarize T cells. We further show that cDC2 in early life, despite being distinct from cDC2 in adult life, are functionally competent and can induce T cell responses. Our results thus highlight the potential of harnessing cDC2 for boosting immunity in early life.</p

Resident and recruited macrophages differentially contribute to cardiac healing after myocardial ischemia

Cardiac macrophages are heterogenous in phenotype and functions, which has been associated with differences in their ontogeny. Despite extensive research, our understanding of the precise role of different subsets of macrophages in ischemia/reperfusion (I/R) injury remains incomplete. We here investigated macrophage lineages and ablated tissue macrophages in homeostasis and after I/R injury in a CSF1R-dependent manner. Genomic deletion of a fms-intronic regulatory element (FIRE) in the Csf1r locus resulted in specific absence of resident homeostatic and antigen-presenting macrophages, without affecting the recruitment of monocyte-derived macrophages to the infarcted heart. Specific absence of homeostatic, monocyte-independent macrophages altered the immune cell crosstalk in response to injury and induced proinflammatory neutrophil polarization, resulting in impaired cardiac remodeling without influencing infarct size. In contrast, continuous CSF1R inhibition led to depletion of both resident and recruited macrophage populations. This augmented adverse remodeling after I/R and led to an increased infarct size and deterioration of cardiac function. In summary, resident macrophages orchestrate inflammatory responses improving cardiac remodeling, while recruited macrophages determine infarct size after I/R injury. These findings attribute distinct beneficial effects to different macrophage populations in the context of myocardial infarction.</p

Deciphering sources of PET signals in the tumor microenvironment of glioblastoma at cellular resolution

Various cellular sources hamper interpretation of positron emission tomography (PET) biomarkers in the tumor microenvironment (TME). We developed an approach of immunomagnetic cell sorting after in vivo radiotracer injection (scRadiotracing) with three-dimensional (3D) histology to dissect the cellular allocation of PET signals in the TME. In mice with implanted glioblastoma, translocator protein (TSPO) radiotracer uptake per tumor cell was higher compared to tumor-associated microglia/macrophages (TAMs), validated by protein levels. Translation of in vitro scRadiotracing to patients with glioma immediately after tumor resection confirmed higher single-cell TSPO tracer uptake of tumor cells compared to immune cells. Across species, cellular radiotracer uptake explained the heterogeneity of individual TSPO-PET signals. In consideration of cellular tracer uptake and cell type abundance, tumor cells were the main contributor to TSPO enrichment in glioblastoma;however, proteomics identified potential PET targets highly specific for TAMs. Combining cellular tracer uptake measures with 3D histology facilitates precise allocation of PET signals and serves to validate emerging novel TAM-specific radioligands

Modulation of Rxr&alpha; Expression in Mononuclear Phagocytes Impacts on Cardiac Remodeling after Ischemia-Reperfusion Injury

Retinoid X receptors (RXRs), as members of the steroid/thyroid hormone superfamily of nuclear receptors, are crucial regulators of immune response during health and disease. RXR subtype expression is dependent on tissue and cell type, RXR&alpha; being the relevant isoform in monocytes and macrophages. Previous studies have assessed different functions of RXRs and positive implications of RXR agonists on outcomes after ischemic injuries have been described. However, the impact of a reduced Rxr&alpha; expression in mononuclear phagocytes on cardiac remodeling after myocardial infarction (MI) has not been investigated to date. Here, we use a temporally controlled deletion of Rxr&alpha; in monocytes and macrophages to determine its role in ischemia-reperfusion injury. We show that reduced expression of Rxr&alpha; in mononuclear phagocytes leads to a decreased phagocytic activity and an accumulation of apoptotic cells in the myocardium, reduces angiogenesis and cardiac macrophage proliferation in the infarct border zone/infarct area, and has an impact on monocyte/macrophage subset composition. These changes are associated with a greater myocardial defect 30 days after ischemia/reperfusion injury. Overall, the reduction of Rxr&alpha; levels in monocytes and macrophages negatively impacts cardiac remodeling after myocardial infarction. Thus, RXR&alpha; might represent a therapeutic target to regulate the immune response after MI in order to improve cardiac remodeling

Comparison of transient and permanent LAD ligation in mice using 18F-FDG PET imaging

Objective Animal models for myocardial injuries represent important cornerstones in cardiovascular research to monitor the pathological processes and therapeutic approaches. We investigated the association of 18F-FDG derived left ventricular metabolic volume (LVMV), defect area and cardiac function in mice after permanent or transient ligation of the left anterior descending artery (LAD). Methods Serial non-invasive ECG-gated 2-deoxy-2-[18F]fluoro-d-glucose positron emission tomography (18F-FDG PET) after permanent or transient LAD ligation enabled a longitudinal in vivo correlation of 18F-FDG derived left ventricular metabolic volume to functional parameters and myocardial defect. Results The LVMV shows a more prominent drop after permanent than transient LAD ligation and recovers after 30 days. The loss of LVMV correlates with the defect area assessed by QPS software. Cardiac function parameters (e.g., EDV, ESV, SV) by the QGS software positively correlate with LVMV after permanent and transient LAD ligation. Conclusions This study provides novel insight into 18F-FDG derived LVMV after permanent and transient LAD ligation by longitudinal in 18F-FDG PET imaging and underlines the associations of the FDG derived parameter and cardiac function

Need for additional professional psychosocial and spiritual support in patients with advanced diseases in the course of specialist palliative care – a longitudinal observational study

Background: We investigated the need for additional professional support and associated factors in patients (pts) at initiation and in the course of in- and outpatient specialist palliative care (I-SPC/O-SPC). Methods: Pts entering an urban SPC network consecutively completed questionnaires on psychosocial/spiritual problems and support needs within 72 h (T0) as well as within the first 6 weeks (T1) of SPC. Hierarchical linear regression analysis was used to investigate the impact of sociodemographic / disease-related variables, psychological / physical burden, social support, and SPC setting on the extent of support needs. Results: Four hundred twenty-five pts (70 years, 48% female, 91% cancer, 67% O-SPC) answered at T0, and 167 at T1. At T0, main problems related to transportation, usual activities, and dependency (83-89%). At T1, most prevalent problems also related to transportation and usual activities and additionally to light housework (82-86%). At T0, support needs were highest for transportation, light housework, and usual activities (35-41%). Cross-sectional comparisons of SPC settings revealed higher problem scores in O-SPC compared to I-SPC at T0 (p = .039), but not at T1. Support need scores were higher in O-SPC at T0 (p &amp;lt; .001), but lower at T1 (p = .039). Longitudinal analyses showed a decrease of support need scores over time, independent from the SPC setting. At T0, higher distress (p = .047), anxiety/depression (p &amp;lt; .001), physical symptom burden (p &amp;lt; .001) and I-SPC (p &amp;lt; .001) were associated with higher support need scores (at T1: only higher distress, p = .037). Conclusion: Need for additional professional psychosocial/spiritual support was identified in up to 40% of pts. with higher need at the beginning of O-SPC than of I-SPC. During SPC, this need decreased in both settings, but got lower in O-SPC than in I-SPC over time. Support need scores were not only associated with psychological, but also physical burden

18 kDa translocator protein positron emission tomography facilitates early and robust tumor detection in the immunocompetent SB28 glioblastoma mouse model

IntroductionThe 18 kDa translocator protein (TSPO) receives growing interest as a biomarker in glioblastoma. Mouse models can serve as an important tool for the investigation of biomarkers in glioblastoma, but several glioblastoma models indicated only low TSPO-PET signals in contrast to high TSPO-PET signals of human glioblastoma. Thus, we aimed to investigate TSPO-PET imaging in the syngeneic immunocompetent SB28 mouse model, which is thought to closely represent the tumor microenvironment (TME) of human glioblastoma. MethodsDynamic TSPO-PET/CT imaging was performed for 60 min after injection of 13.6 +/- 4.2 MBq [F-18]GE-180. Contrast enhanced CT (ceCT) was acquired prior to PET and served for assessment of tumor volumes and attenuation correction. SB28 and sham mice were imaged at an early (week-1; n = 6 SB28, n = 6 sham) and a late time-point (week-3; n = 8 SB28, n = 9 sham) after inoculation. Standard of truth ex vivo tumor volumes were obtained for SB28 mice at the late time-point. Tracer kinetics were analyzed for the lesion site and the carotid arteries to establish an image derived input function (IDIF). TSPO-PET and ceCT lesion volumes were compared with ex vivo volumes by calculation of root-mean-square-errors (RMSE). Volumes of distribution (VTmax/mean) in the lesion were calculated using carotid IDIF and standardized uptake values (SUVmax/mean) were obtained for a 40-60 min time frame. ResultsHigher uptake rate constants (K1) were observed for week-1 SB28 tumor lesions when compared to week-3 SB28 tumor lesions. Highest agreement between TSPO-PET lesion volumes and ex vivo tumor volumes was achieved with a 50% maximum threshold (RMSE-VT: 39.7%; RMSE-SUV: 34.4%), similar to the agreement of ceCT tumor volumes (RMSE: 30.1%). Lesions of SB28 mice had higher PET signal when compared to sham mice at week-1 (VTmax 6.6 +/- 2.9 vs. 3.9 +/- 0.8, p = 0.035; SUVmax 2.3 +/- 0.5 vs. 1.2 +/- 0.1, p < 0.001) and PET signals remained at a similar level at week-3 (VTmax 5.0 +/- 1.6 vs. 2.7 +/- 0.8, p = 0.029; SUVmax 1.9 +/- 0.5 vs. 1.2 +/- 0.2, p = 0.0012). VTmax correlated with SUVmax (R-2 = 0.532, p < 0.001). ConclusionTSPO-PET imaging of immunocompetent SB28 mice facilitates early detection of tumor signals over sham lesions. SB28 tumors mirror high TSPO-PET signals of human glioblastoma and could serve as a valuable translational model to study TSPO as an imaging biomarker

Ontogeny of arterial macrophages defines their functions in homeostasis and inflammation

International audienceAbstract Arterial macrophages have different developmental origins, but the association of macrophage ontogeny with their phenotypes and functions in adulthood is still unclear. Here, we combine macrophage fate-mapping analysis with single-cell RNA sequencing to establish their cellular identity during homeostasis, and in response to angiotensin-II (AngII)-induced arterial inflammation. Yolk sac erythro-myeloid progenitors (EMP) contribute substantially to adventitial macrophages and give rise to a defined cluster of resident immune cells with homeostatic functions that is stable in adult mice, but declines in numbers during ageing and is not replenished by bone marrow (BM)-derived macrophages. In response to AngII inflammation, increase in adventitial macrophages is driven by recruitment of BM monocytes, while EMP-derived macrophages proliferate locally and provide a distinct transcriptional response that is linked to tissue regeneration. Our findings thus contribute to the understanding of macrophage heterogeneity, and associate macrophage ontogeny with distinct functions in health and disease