Tissue-resident Macrophages Research Articles

Early ART reduces viral seeding and innate immunity in liver and lungs of SIV-infected macaques.

Identifying immune cells and anatomical tissues that contribute to the establishment of viral reservoirs is of central importance in HIV-1 cure research. Herein, we used rhesus macaques (RMs) infected with SIVmac251 to analyze viral seeding in the liver and lungs of either untreated or early antiretroviral therapy-treated (ART-treated) RMs. Consistent with viral replication and sensing, transcriptomic analyses showed higher levels of inflammation, pyroptosis, and chemokine genes as well as of interferon-stimulating gene (ISG) transcripts, in the absence of ART. Our results highlighted the infiltration of monocyte-derived macrophages (HLA-DR+CD11b+CD14+CD16+) in inflamed liver and lung tissues associated with the expression of CD183 and CX3CR1 but also with markers of tissue-resident macrophages (CD206+ and LYVE+). Sorting of myeloid cell subsets demonstrated that CD14+CD206-, CD14+CD206+, and CD14-CD206+ cell populations were infected, in the liver and lungs, in SIVmac251-infected RMs. Of importance, early ART drastically reduced viral seeding consistent with the absence of ISG detection but also of genes related to inflammation and tissue damage. Viral DNA was only detected in CD206+HLA-DR+CD11b+ cells in ART-treated RMs. The observation of pulmonary and hepatic viral rebound after ART interruption reinforces the importance of early ART implementation to limit viral seeding and inflammatory reactions.

Moderate hypoxia induces metabolic divergence in circulating monocytes and tissue resident macrophages from Berkeley sickle cell anemia mice.

Human and murine sickle cell disease (SCD) associated pulmonary hypertension (PH) is defined by hemolysis, nitric oxide depletion, inflammation, and thrombosis. Further, hemoglobin (Hb), heme, and iron accumulation are consistently observed in pulmonary adventitial macrophages at autopsy and in hypoxia driven rodent models of SCD, which show distribution of ferric and ferrous Hb as well as HO-1 and ferritin heavy chain. The anatomic localization of these macrophages is consistent with areas of significant vascular remodeling. However, their contributions toward progressive disease may include unique, but also common mechanisms, that overlap with idiopathic and other forms of pulmonary hypertension. These processes likely extend to the vasculature of other organs that are consistently impaired in advanced SCD. To date, limited information is available on the metabolism of macrophages or monocytes isolated from lung, spleen, and peripheral blood in humans or murine models of SCD. Here we hypothesize that metabolism of macrophages and monocytes isolated from this triad of tissue differs between Berkley SCD mice exposed for ten weeks to moderate hypobaric hypoxia (simulated 8,000 ft, 15.4% O2) or normoxia (Denver altitude, 5000 ft) with normoxia exposed wild type mice evaluated as controls. This study represents an initial set of data that describes the metabolism in monocytes and macrophages isolated from moderately hypoxic SCD mice peripheral lung, spleen, and blood mononuclear cells.

Monocyte-endothelial cell interactions in vascular and tissue remodeling.

Monocytes are circulating leukocytes of innate immunity derived from the bone marrow that interact with endothelial cells under physiological or pathophysiological conditions to orchestrate inflammation, angiogenesis, or tissue remodeling. Monocytes are attracted by chemokines and specific receptors to precise areas in vessels or tissues and transdifferentiate into macrophages with tissue damage or infection. Adherent monocytes and infiltrated monocyte-derived macrophages locally release a myriad of cytokines, vasoactive agents, matrix metalloproteinases, and growth factors to induce vascular and tissue remodeling or for propagation of inflammatory responses. Infiltrated macrophages cooperate with tissue-resident macrophages during all the phases of tissue injury, repair, and regeneration. Substances released by infiltrated and resident macrophages serve not only to coordinate vessel and tissue growth but cellular interactions as well by attracting more circulating monocytes (e.g. MCP-1) and stimulating nearby endothelial cells (e.g. TNF-α) to expose monocyte adhesion molecules. Prolonged tissue accumulation and activation of infiltrated monocytes may result in alterations in extracellular matrix turnover, tissue functions, and vascular leakage. In this review, we highlight the link between interactions of infiltrating monocytes and endothelial cells to regulate vascular and tissue remodeling with a special focus on how these interactions contribute to pathophysiological conditions such as cardiovascular and chronic liver diseases.

Examining the Effects of Gestational Physical Activity and Hofbauer Cell Polarization on Angiogenic Factors.

While gestational physical activity (PA) has demonstrated health benefits for both birthing parent and fetus, the mechanisms still need to be fully understood. Placental macrophages, or Hofbauer cells (HBCs), comprise a heterogenous population containing inflammatory (CD206-) and anti-inflammatory (CD206+) phenotypes. Similar to other tissue-resident macrophages (TRMs), HBCs are potential mediators of angiogenesis due to their secretion of both pro- and anti-angiogenic factors, including FGF2, VEGF, and SPRY2. While PA is associated with an increase in the proportion of VEGF- and FGF2-producing CD206+ macrophages in other tissues, the phenotypes producing FGF2, VEGF, and SPRY2 in the placenta and the associated relationships with gestational PA have not been studied. Using accelerometry, pregnant participants were classified as physically active or inactive in mid- and late-gestation. Term placenta tissue was collected at delivery and used for Western blotting and immunofluorescence to examine the protein expression of FGF2 and SPRY2, and to localize FGF2 in histological samples, respectively. Primary cultures of HBCs were used to examine the phenotypic differences in FGF2, SPRY2, and VEGF production. While no differences in the placental expression of SPRY2, total FGF2, or high-molecular-weight FGF2 were observed based on PA status, active individuals had significantly reduced levels of low-molecular-weight FGF2. Additionally, HBCs of all polarizations produce VEGF, FGF2, and SPRY2, and can form intercellular junctions and multinucleated giant cells. These findings suggest a possible relationship between PA and HBC-driven angiogenesis, providing an avenue for future exploration.

A macrophage subpopulation promotes airineme-mediated intercellular communication in a matrix metalloproteinase-9 dependent manner

Tissue-resident macrophages are heterogeneous and perform location-dependent functions. Skin resident macrophages play intriguing roles in long-distance intercellular signaling by mediating cellular protrusions called airinemes in zebrafish. These macrophages relay signaling molecules containing airineme vesicles between pigment cells, and their absence disrupts airineme-mediated signaling and pigment pattern formation. It is unknown if the same macrophages control both these signaling and typical immune functions or if a separate subpopulation functions in intercellular communication. With high-resolution imaging and genetic ablation approaches, we identify a macrophage subpopulation responsible for airineme-mediated signaling. These seem to be distinct from conventional skin-resident macrophages by their ameboid morphology and faster or expansive migratory behaviors. They resemble ectoderm-derived macrophages termed metaphocytes. Metaphocyte ablation markedly decreases airineme extension and signaling. In addition, these ameboid/metaphocytes require matrix metalloproteinase-9 for their migration and airineme-mediated signaling. These results reveal a macrophage subpopulation with specialized functions in airineme-mediated signaling, which may play roles in other aspects of intercellular communication.

Cross-organ single-cell transcriptome profiling reveals macrophage and dendritic cell heterogeneity in zebrafish

Tissue-resident macrophages (TRMs) and dendritic cells (DCs) are highly heterogeneous and essential for immunity, tissue regeneration, and homeostasis maintenance. Here, we comprehensively profile the heterogeneity of TRMs and DCs across adult zebrafish organs via single-cell RNA sequencing. We identify two macrophage subsets: pro-inflammatory macrophages with potent phagocytosis signatures and pro-remodeling macrophages with tissue regeneration signatures in barrier tissues, liver, and heart. In parallel, one conventional dendritic cell (cDC) population with prominent antigen presentation capacity and plasmacytoid dendritic cells (pDCs) featured by anti-virus properties are also observed in these organs. Remarkably, in addition to a single macrophage/microglia population with potent phagocytosis capacity, a pDC population and two distinct cDC populations are identified in the brain. Finally, we generate specific reporter lines for invivo tracking of macrophage and DC subsets. Our study depicts the landscape of TRMs and DCs and creates valuable tools for in-depth study of these cells in zebrafish.

Functional diversity of disorder-specific macrophage subtype

Macrophages have been discovered more than 100 years ago. Recent studies indicated that monocytes and macrophages can be categorized into several distinct phenotypes and their respective differentiation mechanisms are known. We also reported that the Jmjd3 is critical for the macrophage subtype activated by allergic stimuli and that the tissue resident macrophage subtype in adipose tissue, which is controlled by Trib1, is responsible for maintaining homeostasis of peripheral tissues such as adipocyte. Thus, it is considered that various macrophage/monocyte subtypes corresponding to certain disorders were existed in our body. Furthermore, in order to investigate the relationship between macrophage subtype and disease, we focused on fibrosis as the next target disease. Its pathogenesis is poorly understood, and there are few effective therapies. Previously we found that a new macrophage/monocyte subtype, which their markers are Msr1+Ceacam1+Ly6C-Mac1+F4/80-monocyte and share granulocyte characteristics, involved in development of fibrosis was accumulated in the affected area in the lungs at the beginning of fibrosis. We termed the monocyte/ macrophage subtype segregated-nucleus-containing atypical monocytes (SatM). Towards understanding the mechanism of fibrosis onset, we next focused on investigation of non-haematopoietic cells involved in activation of immune cell such as SatM during fibrotic phase.

Senescent alveolar macrophages promote early-stage lung tumorigenesis.

Senescent cells play relevant but context-dependent roles during tumorigenesis. Here, in an oncogenic Kras-driven lung cancer mouse model, we found that senescent cells, specifically alveolar macrophages, accumulate early in neoplasia. These macrophages have upregulated expression of p16INK4a and Cxcr1, are distinct from previously defined subsets and are sensitive to senolytic interventions, and suppress cytotoxic Tcell responses. Their removal attenuates adenoma development and progression in mice, indicating their tumorigenesis-promoting role. Importantly, we found that alveolar macrophages with these properties increase with normal aging in mouse lung and in human lung adenocarcinoma in situ. Collectively, our study indicates that a subset of tissue-resident macrophages can support neoplastic transformation through altering their local microenvironment, suggesting that therapeutic interventions targeting senescent macrophages may attenuate lung cancer progression during early stages of disease.

Tumor-specific CD4 T cells instruct monocyte fate in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDA) orchestrates a suppressive tumor microenvironment that fosters immunotherapy resistance. Tumor-associated macrophages (TAMs) are the principal immune cell infiltrating PDA and are heterogeneous. Here, by employing macrophage fate-mapping approaches and single-cell RNA sequencing, we show that monocytes give rise to most macrophage subsets in PDA. Tumor-specific CD4, but not CD8, Tcells promote monocyte differentiation into MHCIIhi anti-tumor macrophages. By conditional major histocompatibility complex (MHC) class II deletion on monocyte-derived macrophages, we show that tumor antigen presentation is required for instructing monocyte differentiation into anti-tumor macrophages, promoting Th1 cells, abrogating Treg cells, and mitigating CD8 Tcell exhaustion. Non-redundant IFNγ and CD40 promote MHCIIhi anti-tumor macrophages. Intratumoral monocytes adopt a pro-tumor fate indistinguishable from that of tissue-resident macrophages following loss of macrophage MHC class II or tumor-specific CD4 Tcells. Thus, tumor antigen presentation by macrophages to CD4 Tcells dictates TAM fate and is a major determinant of macrophage heterogeneity in cancer.

VSIG4 interaction with heparan sulfates inhibits VSIG4-complement binding.

V-set and immunoglobulin domain-containing 4 (VSIG4) is a complement receptor of the immunoglobulin superfamily that is specifically expressed on tissue resident macrophages, and its many reported functions and binding partners suggest a complex role in immune function. VSIG4 is reported to have a role in immune surveillance as well as in modulating diverse disease phenotypes such as infections, autoimmune conditions, and cancer. However, the mechanism(s) governing VSIG4's complex, context-dependent role in immune regulation remains elusive. Here, we identify cell surface and soluble glycosaminoglycans, specifically heparan sulfates, as novel binding partners of VSIG4. We demonstrate that genetic deletion of heparan sulfate synthesis enzymes or cleavage of cell-surface heparan sulfates reduced VSIG4 binding to the cell surface. Furthermore, binding studies demonstrate that VSIG4 interacts directly with heparan sulfates, with a preference for highly sulfated moieties and longer glycosaminoglycan chains. To assess the impact on VSIG4 biology, we show that heparan sulfates compete with known VSIG4 binding partners C3b and iC3b. Furthermore, mutagenesis studies indicate that this competition occurs through overlapping binding epitopes for heparan sulfates and complement on VSIG4. Together these data suggest a novel role for heparan sulfates in VSIG4-dependent immune modulation.

Physiology and diseases of tissue-resident macrophages.

Embryo-derived tissue-resident macrophages are the first representatives of the haematopoietic lineage to emerge in metazoans. In mammals, resident macrophages originate from early yolk sac progenitors and are specified into tissue-specific subsets during organogenesis-establishing stable spatial and functional relationships with specialized tissue cells-and persist in adults. Resident macrophages are an integral part of tissues together with specialized cells: for instance, microglia reside with neurons in brain, osteoclasts reside with osteoblasts in bone, and fat-associated macrophages reside with white adipocytes in adipose tissue. This ancillary cell type, which is developmentally and functionally distinct from haematopoietic stem cell and monocyte-derived macrophages, senses and integrates local and systemic information to provide specialized tissue cells with the growth factors, nutrient recycling and waste removal that are critical for tissue growth, homeostasis and repair. Resident macrophages contribute to organogenesis, promote tissue regeneration following damage and contribute to tissue metabolism and defence against infectious disease. A correlate is that genetic or environment-driven resident macrophage dysfunction is a cause of degenerative, metabolic and possibly inflammatory and tumoural diseases. In this Review, we aim to provide a conceptual outline of our current understanding of macrophage physiology and its importance in human diseases, which may inform and serve the design of future studies.

Selective oxidative protection leads to tissue topological changes orchestrated by macrophage during ulcerative colitis

Ulcerative colitis is a chronic inflammatory bowel disorder with cellular heterogeneity. To understand the composition and spatial changes of the ulcerative colitis ecosystem, here we use imaging mass cytometry and single-cell RNA sequencing to depict the single-cell landscape of the human colon ecosystem. We find tissue topological changes featured with macrophage disappearance reaction in the ulcerative colitis region, occurring only for tissue-resident macrophages. Reactive oxygen species levels are higher in the ulcerative colitis region, but reactive oxygen species scavenging enzyme SOD2 is barely detected in resident macrophages, resulting in distinct reactive oxygen species vulnerability for inflammatory macrophages and resident macrophages. Inflammatory macrophages replace resident macrophages and cause a spatial shift of TNF production during ulcerative colitis via a cytokine production network formed with T and B cells. Our study suggests components of a mechanism for the observed macrophage disappearance reaction of resident macrophages, providing mechanistic hints for macrophage disappearance reaction in other inflammation or infection situations.

#4549 INTEGRATIVE SPATIAL AND SINGLE-CELL ANALYSIS IDENTIFIES MACROPHAGE HETEROGENEITY AND A UNIQUE MULTI-IDENTITY SUBSET IN AKI TO CKD TRANSITION

Abstract Background and Aims The pathogenesis of acute kidney injury (AKI) transformed to chronic kidney disease (CKD) is still largely unclear. Previous studies have suggested the heterogeneity of macrophages might play a critical role in this pathological process. Here we demonstrated the spatiotemporal dynamics of macrophages and its potential function in AKI to CKD in unilateral ischemia-reperfusion injury (UIR) mice model. Method We generated an integrative high-resolution map of kidney injury and repair in a mouse model of failed repaired UIR using single-cell RNA-sequencing (scRNA-seq) and spatial transcriptomic profiling of multiple zones at five time points. We identified cell types through unsupervised clustering analysis. Differential gene expression, enrichment analysis and main function scoring were applied to define functional heterogeneity of macrophages. Next, pseudotime analysis of differentiation transitions was performed to create the diverse macrophage lineages. Finally, using ligand-receptor analysis, we identified the interaction between macrophage and other cells. Results We identified 13 main cell clusters and the dynamic changes in the process of AKI to CKD transition were analysed. A remarkable increasing proportion of macrophages after injury at day 1 followed with second peak at day 14 post AKI. Spatiotemporal profiles of main cells showed injured tubules and macrophages co-localized in outer stripe of outer medullary region early after AKI, whereas in late chronic stages macrophages had spatial proximity to fibroblasts. The subtypes of macrophage after AKI were identified as pro-inflammatory, pro-repair, proliferative, and immature populations. Notably, a novel multi-identity macrophage cluster which is recruited to the kidney early after AKI and remained in the kidney until chronic stages. In the multi-identity cluster, elevated expression of genes such as Trem2, Ctsd, Fn1, and Ccl7 was observed. Importantly, the upregulation of Trem2 is a marker of transition from M1 to M2 type. Multi-identity cluster was characterized with the highest fibrosis and phagocytosis scores as well as second high inflammation scores among the diverse clusters. In the early phase of UIR (days 1 and 3), GO terms for multi-identity cluster were more enriched in acute inflammatory response and phagocytosis; however, its functions were more turned to fibrosis and extracellular matrix in the late phase of UIR (days 14 and 28). These data indicated that multi-identity cluster was rapidly adopting a pro-inflammatory phenotype early after AKI, which present a profibrotic phenotype in late chronic stages. We retrieved two distinct trajectories of macrophage populations, tissue-resident and monocyte-recruited. Starting at monocyte, multi-identity cluster progressed along lineage 1 towards pro-inflammatory cluster, suggesting that the monocyte-derived infiltrating multi-identity macrophages significantly contributed to the formation of the pro-inflammatory M1 cells. On the other hand, proliferative and immature cluster branched off along lineage 2 towards an endpoint of pro-repair cells, indicating that tissue-resident macrophages contribute to repair of kidney by local proliferation. Furthermore, ligand-receptor analysis identified enhanced interaction between diverse macrophage clusters and neighboring cells in the failed repaired stages after AKI, supporting that intercellular communication drives kidney fibrosis. Importantly, we identified that the Igf1-Igf1r interaction was highly specific in multi-identity macrophage and fibroblast intercellular communication. Conclusion Our study demonstrated the spatiotemporal dynamics of macrophage heterogeneity and the transitionary functions of multi-identity macrophages in the process of AKI to CKD transition.

Reduced mitochondrial calcium uptake in macrophages is a major driver of inflammaging

Mitochondrial dysfunction is linked to age-associated inflammation or inflammaging, but underlying mechanisms are not understood. Analyses of 700 human blood transcriptomes revealed clear signs of age-associated low-grade inflammation. Among changes in mitochondrial components, we found that the expression of mitochondrial calcium uniporter (MCU) and its regulatory subunit MICU1, genes central to mitochondrial Ca2+ (mCa2+) signaling, correlated inversely with age. Indeed, mCa2+ uptake capacity of mouse macrophages decreased significantly with age. We show that in both human and mouse macrophages, reduced mCa2+ uptake amplifies cytosolic Ca2+ oscillations and potentiates downstream nuclear factor kappa B activation, which is central to inflammation. Our findings pinpoint the mitochondrial calcium uniporter complex as a keystone molecular apparatus that links age-related changes in mitochondrial physiology to systemic macrophage-mediated age-associated inflammation. The findings raise the exciting possibility that restoring mCa2+ uptake capacity in tissue-resident macrophages may decrease inflammaging of specific organs and alleviate age-associated conditions such as neurodegenerative and cardiometabolic diseases.

Leveraging Macrophage-Mediated Cancer Immunotherapy via a Cascading Effect Induced by a Molecularly Imprinted Nanocoordinator.

Reprogramming tumor-associated macrophages (TAMs) has emerged as a promising strategy in cancer immunotherapy. Targeted therapeutics integrating multiple functions to fully leverage the antitumor immune functions of macrophages without affecting systemic or tissue-resident macrophages are crucial for TAM reprogramming. Herein, by integrating molecular imprinting and nanotechnology, we rationally designed and engineered an unprecedented nanocoordinator for targeted remolding of TAMs to fully leverage the antitumor efficacy of macrophages by inducing a cascade effect. The nanocoordinator features a magnetic iron oxide nanoinner core and sialic acid-imprinted shell. Intravenously administered into systemic circulation, the nanocoordinator can rapidly accumulate at the tumor site in response to an external magnet. Then, by specifically binding to sialic acid overexpressed on tumor cells, the nanocoordinator anchors at the tumor site with prolonged retention time. Via binding with the nanocoordinator, tumor cells are tagged with a foreign substance, which promotes the intrinsic phagocytosis of macrophages. Subsequently, the nanocoordinator taken up by macrophages effectively promotes the polarization of macrophages toward the M1 phenotype, thus activating the immunotherapeutic efficacy of macrophages. Synergized by the cascade effect, this nanocoordinator effectively harnesses TAMs for macrophage-mediated immunotherapy. This study offers new TAM-targeted therapeutics that allows us to fully leverage the antitumor immune functions of macrophages without affecting the normal tissue.

Therapeutic effect of a VSIG4-specific mAb EU103 in a preclinical model of patient-derived ascites of ovarian cancer.

e14516 Background: V-set and immunoglobulin domain-containing 4 (VSIG4) is one of the B7 family-related proteins that includes PD-L1, VISTA, and CTLA4 ligand. VSIG4 overexpression is correlated with poor prognosis in patients with ovarian cancer, lung cancer, gastric cancer, high-grade glioma, and multiple myeloma. VSIG4 is also known to function as a receptor for complements and the negative regulation of T cell proliferation. Although VSIG4 is highly expressed in tissue-resident macrophages and tumor-associated macrophages (TAM), its role in the tumor microenvironment (TME) is not fully elucidated. Methods: We previously developed a therapeutic antibody, EU103, in a humanized form of a VSIG4-specific antibody. Most importantly, we demonstrated that EU103 directly acts on the tumor-associated macrophages (TAM) and mechanistically induces repolarization of TAM to tumor killing M1 macrophages and blocks VSIG4-mediated T cell suppression, eventually leading to CD8+ T cell proliferation and tumor suppression in a PBMC-humanized human lung cancer mouse model. Results: Expanding our previous findings with the therapeutic potential of EU103 in a non-small cell lung carcinoma (NSCLC), here, we also proved its therapeutic effect in human ovarian cancer. Firstly, TAMs isolated from ovarian cancer patients express high levels of VSIG4 with immunosuppressive M2 macrophage phenotype. Secondly, EU103 treatment of the TAMs in in vitro studies induces M2-to-M1 conversion and activation of T cells in the ascites leading to ovarian tumor cell killing in a dose-dependent manner. Thirdly, in vivo therapeutic efficacy of EU103 in ovarian cancer, especially through M2-to-M1 conversion, is also verified in both CD34+ cell and peripheral blood mononuclear cell (PBMC) humanized mouse models. Finally, we validate the results above by treating ovarian cancer patient-derived ascites with EU103. Conclusions: Almost 300,000 women are diagnosed with ovarian cancer worldwide each year, and ovarian cancer ranks fifth in cancer deaths among women. In the United States alone, we expect approximately 20,000 new diagnoses and more than 12,000 deaths for this year. Given our findings in this study and clinical significance, we propose here the therapeutic potential of EU103, previously developed by our proprietary antibody discovery and engineering technology, in ovarian cancer.

The role of monocyte-derived macrophages in the lung: it's all about context.

Macrophages are present in every tissue of the body where they play crucial roles in maintaining tissue homeostasis and providing front line defence against pathogens. Arguably, this is most important at mucosal barrier tissues, such as the lung and gut, which are major ports of entry for pathogens. However, a common feature of inflammation, infection or injury is the loss of tissue resident macrophages and accumulation of monocytes from the circulation, which differentiate, to different extents, into macrophages. The exact fate and function of these elicited, monocyte-derived macrophages in infection, injury and inflammation remains contentious. While some studies have documented the indispensable nature of monocytes and their macrophage derivatives in combatting infection and restoration of lung homeostasis following insult, observations from clinical studies and preclinical models of lung infection/injury shows that monocytes and their progeny can become dysregulated in severe pathology, often perpetuating rather than resolving the insult. In this Mini Review, we aim to bring together these somewhat contradictory reports by discussing how the plasticity of monocytes allow them to assume distinct functions in different contexts in the lung, from health to infection, and effective tissue repair to fibrotic disease.

Multi-omics analysis reveals the chemoresistance mechanism of proliferating tissue-resident macrophages in PDAC via metabolic adaptation

Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal cancer that typically demonstrates resistance to chemotherapy. Tumor-associated macrophages (TAMs) are essential in tumor microenvironment (TME) regulation, including promoting chemoresistance. However, the specific TAM subset and mechanisms behind this promotion remain unclear. We employ multi-omics strategies, including single-cell RNA sequencing (scRNA-seq), transcriptomics, multicolor immunohistochemistry (mIHC), flow cytometry, and metabolomics, to analyze chemotherapy-treated samples from both humans and mice. We identify four major TAM subsets within PDAC, among which proliferating resident macrophages (proliferating rMφs) are strongly associated with poor clinical outcomes. These macrophages are able to survive chemotherapy by producing more deoxycytidine (dC) and fewer dC kinases (dCKs) to decrease the absorption of gemcitabine. Moreover, proliferating rMφs promote fibrosis and immunosuppression in PDAC. Eliminating them in the transgenic mouse model alleviates fibrosis and immunosuppression, thereby re-sensitizing PDAC to chemotherapy. Consequently, targeting proliferating rMφs may become a potential treatment strategy for PDAC to enhance chemotherapy.

The Role of Macrophages in Atherosclerosis: Pathophysiologic Mechanisms and Treatment Considerations.

Atherosclerotic diseases are a leading cause of morbidity and mortality worldwide, despite the recent diagnostic and therapeutic advances. A thorough understanding of the pathophysiologic mechanisms is thus essential to improve the care of affected individuals. Macrophages are crucial mediators of the atherosclerotic cascade, but their role has not been fully elucidated. The two main subtypes, tissue-resident and monocyte-derived macrophages, have distinct functions that contribute to atherosclerosis development or regression. Since polarization of macrophages to an M2 phenotype and induction of macrophage autophagy have been demonstrated to be atheroprotective, targeting these pathways could represent an appealing approach. Interestingly, macrophage receptors could act as drug targets, as seen in recent experimental studies. Last but not least, macrophage-membrane-coated carriers have been investigated with encouraging results.

Analysis of the microglia transcriptome across the human lifespan using single cell RNA sequencing

BackgroundMicroglia are tissue resident macrophages with a wide range of critically important functions in central nervous system development and homeostasis.MethodIn this study, we aimed to characterize the transcriptional landscape of ex vivo human microglia across different developmental ages using cells derived from pre-natal, pediatric, adolescent, and adult brain samples. We further confirmed our transcriptional observations using ELISA and RNAscope.ResultsWe showed that pre-natal microglia have a distinct transcriptional and regulatory signature relative to their post-natal counterparts that includes an upregulation of phagocytic pathways. We confirmed upregulation of CD36, a positive regulator of phagocytosis, in pre-natal samples compared to adult samples in situ. Moreover, we showed adult microglia have more pro-inflammatory signature compared to microglia from other developmental ages. We indicated that adult microglia are more immune responsive by secreting increased levels of pro-inflammatory cytokines in response to LPS treatment compared to the pre-natal microglia. We further validated in situ up-regulation of IL18 and CXCR4 in human adult brain section compared to the pre-natal brain section. Finally, trajectory analysis indicated that the transcriptional signatures adopted by microglia throughout development are in response to a changing brain microenvironment and do not reflect predetermined developmental states.ConclusionIn all, this study provides unique insight into the development of human microglia and a useful reference for understanding microglial contribution to developmental and age-related human disease.