Project description:The transcriptomes of FACS-sorted siglec-F+ alveolar macrophages and siglec-f- CD11b+ exudative macrophages from inducible airway GM-CSF over-expressing transgenic mice (DTGM) were compared to non-inducible littermate controls during influenza A virus infection.
Project description:Bacterial lung infections are associated with strong infiltration of CD11b+ myeloid cells, which limit life-threatening disease, but also severely damage lung tissue. In a murine lung infection model with Streptococcus pneumoniae, we found intrinsic upregulation of CD11b on resident alveolar macrophages. Such CD11b expression was associated with transcriptomic and proteomic adaptations by alveolar macrophages, leading to the identification of specific molecules and pathways that depended on CD11b. In the absence of CD11b, the antimicrobial defense of alveolar macrophages was strongly reduced, and the production of neutrophil-recruiting chemokines was more pronounced. Moreover, CD11b expression limited the infection and prevented excessive alveolar damage. In conclusion, our study provides detailed molecular insights into the alveolar macrophage-specific immune response to Streptococcus pneumoniae lung infection and reveals profound CD11b-dependent alterations that are critical for effective antimicrobial immunity, neutrophil recruitment, and prevention of alveolar damage.
Project description:Macrophages (MΦ) have been shown to contribute to fibrogenesis, however the underlying mechanisms and specific MΦ subsets involved remain unclear. Lung MΦ can be divided into two subsets: Siglec-Fhi resident alveolar MΦ and CD11bhi MΦ that primarily arise from immigrating monocytes. RNA-seq analysis was performed to compare these MΦ subsets during fibrosis. CD11bhi MΦ, not Siglec-Fhi MΦ, expressed high levels of pro-fibrotic chemokines and growth factors.
Project description:Recent studies suggest that training of innate immune cells such as tissue-resident macrophages by repeated noxious stimuli can heighten host defense responses. However, it remains unclear whether trained immunity of tissue-resident macrophages also comprises enhanced injury resolution capacity to counterbalance the heightened inflammatory responses. Here, we studied lung-resident alveolar macrophages (AMs) pre-challenged with either the bacterial endotoxin or with Pseudomonas aeruginosa and observed that these trained AMs showed greater resilience to pathogen-induced cell death. Transcriptomic analysis, and functional assays showed greater capacity of trained AMs to efferocytosis of cellular- debris, and facilitate injury resolution. Single-cell high-dimensional mass-cytometry analysis and lineage tracing demonstrated that training induces an expansion of a MERTKhiMarcohiCD163+F4/80low lung-resident AMs subset with pro-resolving phenotypes. Training epigenetically reprogrammed AMs to express a higher level of the transcription factor KLF4 which in turn upregulates the efferocytosis receptor MERTK. Adoptive transfer of these trained AMs restricted inflammatory lung injury in recipient mice exposed to lethal Pseudomonas aeruginosa. Thus, our study has identified a unique subset of tissue-resident trained macrophages which prevent hyper-inflammation and restore tissue homeostasis following pathogen challenge.
Project description:Recent studies suggest that training of innate immune cells such as tissue-resident macrophages by repeated noxious stimuli can heighten host defense responses. However, it remains unclear whether trained immunity of tissue-resident macrophages also comprises enhanced injury resolution capacity to counterbalance the heightened inflammatory responses. Here, we studied lung-resident alveolar macrophages (AMs) pre-challenged with either the bacterial endotoxin or with Pseudomonas aeruginosa and observed that these trained AMs showed greater resilience to pathogen-induced cell death. Transcriptomic analysis, and functional assays showed greater capacity of trained AMs to efferocytosis of cellular- debris, and facilitate injury resolution. Single-cell high-dimensional mass-cytometry analysis and lineage tracing demonstrated that training induces an expansion of a MERTKhiMarcohiCD163+F4/80low lung-resident AMs subset with pro-resolving phenotypes. Training epigenetically reprogrammed AMs to express a higher level of the transcription factor KLF4 which in turn upregulates the efferocytosis receptor MERTK. Adoptive transfer of these trained AMs restricted inflammatory lung injury in recipient mice exposed to lethal Pseudomonas aeruginosa. Thus, our study has identified a unique subset of tissue-resident trained macrophages which prevent hyper-inflammation and restore tissue homeostasis following pathogen challenge.
Project description:Idiopathic pulmonary fibrosis (IPF) is a common form of interstitial lung disease (ILD) resulting in alveolar remodeling and progressive loss of pulmonary function due to chronic alveolar injury and failure to regenerate the respiratory epithelium. Histologically, fibrotic lesions and honeycomb structures expressing atypical proximal airway epithelial markers replace alveolar structures, the latter normally lined by alveolar type 1 (AT1) and AT2 cells. Bronchial epithelial stem cells (BESCs) can give rise to AT2 and AT1 cells or honeycomb cysts following bleomycin-mediated lung injury. However, little is known about what controls this binary decision or whether this decision can be reversed. Here we report that inactivation of Fgfr2b in BESCs impairs their contribution to both alveolar epithelial regeneration and honeycomb cysts after bleomycin injury. By contrast overexpression of Fgf10 in BESCs enhances fibrosis resolution by favoring the more desirable outcome of alveolar epithelial regeneration over the development of pathologic honeycomb cysts.
Project description:Following all types of neurological injury, resident macrophages are activated locally, and blood-derived macrophages are recruited. Distinguishing the role of resident and blood-derived macrophages is complicated by the difficulty in distinguishing between these cell types because they mostly express the same molecular markers in a diseased state. To begin to understand the complexity of functions of resident and blood-derived macrophages following acute injury in the central nervous system (CNS) we ablated microglia, but not infiltrating macrophages, to determine their contribution following lysolecithin-induced demyelination .
Project description:Mononuclear phagocytes promote injury and repair following myocardial infarction but discriminating functions within mixed populations remains challenging. We utilized fate mapping and single cell RNA-sequencing to delineate fate specification trajectories of heterogeneous cardiac macrophage subpopulations. In steady state, TIMD4 expression tracked with a dominant resident cardiac macrophage subset that persisted via in situ self-renewal with minimal monocyte input. Following ischemic injury, monocytes displayed significant plasticity, ultimately adopting transcriptional states similar to resident macrophages, but also multiple unique states. Ischemic injury reduced resident macrophage abundance within infarct tissue, and despite transcriptional similarity, TIMD4 expression distinguished resident from recruited macrophages. Specific lineage-based depletion of resident cardiac macrophages resulted in depressed cardiac function and adverse remodeling primarily within the peri-infarct zone, the only region of the myocardium where resident macrophages expanded numerically following injury. Together, these data highlight a non-redundant, cardioprotective role of resident cardiac macrophages, and the diverse transcriptional fates recruited monocytes can adopt.
Project description:Siglec-E is a murine CD33-related siglec that functions as an inhibitory receptor and is expressed mainly on neutrophils and macrophage populations. Recent studies have suggested that siglec-E is an important negative regulator of LPS-TLR4 signalling and one report (Wu et al 2016) claimed that siglec-E is required for TLR4 endocytosis following uptake of Escherichia coli by macrophages and dendritic cells (DCs). Our attempts to reproduce these observations using cells from wildtype (WT) and siglec E deficient mice were unsuccessful. We used a variety of assays to determine if siglec-E expressed by different macrophage populations can regulate TLR-4 signalling in response to LPS, but found no consistent differences in cytokine secretion in vitro and in vivo, comparing 3 different strains of siglec-E-deficient mice with matched WT controls. No evidence was found that the siglec-E deficiency was compensated by expression of siglecs-F and –G, the other murine inhibitory CD33-related siglecs. Quantitative proteomics was used as an unbiased approach and provided additional evidence that siglec-E does not suppress inflammatory TLR4 signaling. Interestingly, proteomics revealed a siglec E dependent alteration in macrophage phenotype that could be relevant to functional responses in host defence. In support of this, siglec-E-deficient mice exhibited enhanced growth of Salmonella enterica serovar Typhimurium in the liver following intravenous infection, but macrophages lacking siglec-E did not show altered uptake or killing of bacteria in vitro. Using various cell types including bone marrow derived DCs (BMDC), splenic DCs and macrophages from WT and siglec-E-deficient mice, we showed that siglec-E is not required for TLR4 endocytosis following E.coli uptake or LPS challenge. We failed to see expression of siglec-E by BMDC even after LPS-induced maturation, but confirmed previous studies that splenic DCs express low levels of siglec-E. Taken together, our findings do not support a major role of siglec-E in regulation of TLR4 signalling functions or TLR4 endocytosis in macrophages or DCs. Instead, they reveal that induction of siglec-E by LPS can modulate the phenotype of macrophages, the functional significance of which is currently unclear.
Project description:Idiopathic pulmonary fibrosis (IPF) is a complex disease involving various cell types. Macrophages are essential in maintenance of physiological homeostasis, wound repair and fibrosis in the lung. Macrophages play a crucial role in repair and remodeling by altering their phenotype and secretory pattern in response to injury. The secretome of induced pluripotent stem cells (iPSC-cm) attenuates injury and fibrosis in bleomycin injured rat lungs. In the current study, we evaluate the effect of iPSC-cm on interstitial macrophage gene expression and phenotype in bleomycin injured rat lungs in vivo. Â iPSC-cm was intratracheally instilled 7 days after bleomycin induced lung injury and assessed 7 days later and single cell isolation was performed. Macrophages were FACS sorted and microarray analysis was performed. We characterized changes in the rat lung interstitial macrophages using transcriptional profiling.