Trajectory analysis quantifies transcriptional plasticity during macrophage polarization

Clustered macrophages cooperate to eliminate tumors via coordinated intrudopodia

Macrophages often pervade solid tumors, but their nearest neighbor organization is understudied and potentially enables key functions such as phagocytosis. Here, we observe dynamic macrophage clusters in tumors under conditions that maximize cancer cell phagocytosis and use reductionist approaches to uncover pathways to cluster formation and roles for tumor-intrusive pseudopodia, which we term 'intrudopodia'. Macrophage clusters form over hours on low- adhesion substrates after M1 polarization with interferons, including T cell-derived cytokines, and yet clusters prove fluid on timescales of minutes. Clusters also sort from M2 macrophages that disperse on the same substrates. M1 macrophages upregulate specific cell-cell adhesion receptors but suppress actomyosin contractility, and while both pathways contribute to cluster formation, decreased cortical tension was predicted to unleash pseudopodia. Macrophage neighbors in tumor spheroids indeed extend intrudopodia between adjacent cancer cell junctions - at least when phagocytosis conditions are maximized, and coordinated intrudopodia help detach and individualize cancer cells for rapid engulfment. Macrophage clusters thereby provide a cooperative advantage for phagocytosis to overcome solid tumor cohesion.

Macrophage fate: to kill or not to kill?

Macrophages are dynamic innate immune cells that either reside in tissue, serving as sentinels, or recruited as monocytes from bone marrow into inflamed and infected tissue. In response to cues in the tissue microenvironment (TME), macrophages polarize on a continuum toward M1 or M2 with diverse roles in progression and resolution of disease. M1-like macrophages exhibit proinflammatory functions with antimicrobial and anti-tumorigenic activities, while M2-like macrophages have anti-inflammatory functions that generally resolve inflammatory responses and orchestrate a tissue healing process. Given these opposite phenotypes, proper spatiotemporal coordination of macrophage polarization in response to cues within the TME is critical to effectively resolve infectious disease and regulate wound healing. However, if this spatiotemporal coordination becomes disrupted due to persistent infection or dysregulated coagulation, macrophages' inappropriate response to these cues will result in the development of diseases with clinically unfavorable outcomes. Since plasticity and heterogeneity are hallmarks of macrophages, they are attractive targets for therapies to reprogram toward specific phenotypes that could resolve disease and favor clinical prognosis. In this review, we discuss how basic science studies have elucidated macrophage polarization mechanisms in TMEs during infections and inflammation, particularly coagulation. Therefore, understanding the dynamics of macrophage polarization within TMEs in diseases is important in further development of targeted therapies.

Stimulus-response signaling dynamics characterize macrophage polarization states

The functional state of cells is dependent on their microenvironmental context. Prior studies described how polarizing cytokines alter macrophage transcriptomes and epigenomes. Here, we characterized the functional responses of 6 differentially polarized macrophage populations by measuring the dynamics of transcription factor nuclear factor κB (NF-κB) in response to 8 stimuli. The resulting dataset of single-cell NF-κB trajectories was analyzed by three approaches: (1) machine learning on time-series data revealed losses of stimulus distinguishability with polarization, reflecting canalized effector functions. (2) Informative trajectory features driving stimulus distinguishability ("signaling codons") were identified and used for mapping a cell state landscape that could then locate macrophages conditioned by an unrelated condition. (3) Kinetic parameters, inferred using a mechanistic NF-κB network model, provided an alternative mapping of cell states and correctly predicted biochemical findings. Together, this work demonstrates that a single analyte's dynamic trajectories may distinguish the functional states of single cells and molecular network states underlying them. A record of this paper's transparent peer review process is included in the supplemental information.

Neither injury induced macrophages within the nerve, nor the environment created by Wallerian degeneration is necessary for enhanced in vivo axon regeneration after peripheral nerve injury

BACKGROUND

Since the 1990s, evidence has accumulated that macrophages promote peripheral nerve regeneration and are required for enhancing regeneration in the conditioning lesion (CL) response. After a sciatic nerve injury, macrophages accumulate in the injury site, the nerve distal to that site, and the axotomized dorsal root ganglia (DRGs). In the peripheral nervous system, as in other tissues, the macrophage response is derived from both resident macrophages and recruited monocyte-derived macrophages (MDMs). Unresolved questions are: at which sites do macrophages enhance nerve regeneration, and is a particular population needed.

METHODS

Ccr2 knock-out (KO) and Ccr2gfp/gfp knock-in/KO mice were used to prevent MDM recruitment. Using these strains in a sciatic CL paradigm, we examined the necessity of MDMs and residents for CL-enhanced regeneration in vivo and characterized injury-induced nerve inflammation. CL paradigm variants, including the addition of pharmacological macrophage depletion methods, tested the role of various macrophage populations in initiating or sustaining the CL response. In vivo regeneration, measured from bilateral proximal test lesions (TLs) after 2 d, and macrophages were quantified by immunofluorescent staining.

RESULTS

Peripheral CL-enhanced regeneration was equivalent between crush and transection CLs and was sustained for 28 days in both Ccr2 KO and WT mice despite MDM depletion. Similarly, the central CL response measured in dorsal roots was unchanged in Ccr2 KO mice. Macrophages at both the TL and CL, but not between them, stained for the pro-regenerative marker, arginase 1. TL macrophages were primarily CCR2-dependent MDMs and nearly absent in Ccr2 KO and Ccr2gfp/gfp KO mice. However, there were only slightly fewer Arg1+ macrophages in CCR2 null CLs than controls due to resident macrophage compensation. Zymosan injection into an intact WT sciatic nerve recruited Arg1+ macrophages but did not enhance regeneration. Finally, clodronate injection into Ccr2gfp KO CLs dramatically reduced CL macrophages. Combined with the Ccr2gfp KO background, depleting MDMs and TL macrophages, and a transection CL, physically removing the distal nerve environment, nearly all macrophages in the nerve were removed, yet CL-enhanced regeneration was not impaired.

CONCLUSIONS

Macrophages in the sciatic nerve are neither necessary nor sufficient to produce a CL response.

Harnessing anti-inflammatory pathways and macrophage nano delivery to treat inflammatory and fibrotic disorders

Targeting specific organs and cell types using nanotechnology and sophisticated delivery methods has been at the forefront of applicative biomedical sciences lately. Macrophages are an appealing target for immunomodulation by nanodelivery as they are heavily involved in various aspects of many diseases and are highly plastic in their nature. Their continuum of functional "polarization" states has been a research focus for many years yielding a profound understanding of various aspects of these cells. The ability of monocyte-derived macrophages to metamorphose from pro-inflammatory to reparative and consequently to pro-resolving effectors has raised significant interest in its therapeutic potential. Here, we briefly survey macrophages' ontogeny and various polarization phenotypes, highlighting their function in the inflammation-resolution shift. We review their inducing mediators, signaling pathways, and biological programs with emphasis on the nucleic acid sensing-IFN-I axis. We also portray the polarization spectrum of macrophages and the characteristics of their transition between different subtypes. Finally, we highlighted different current drug delivery methods for targeting macrophages with emphasis on nanotargeting that might lead to breakthroughs in the treatment of wound healing, bone regeneration, autoimmune, and fibrotic diseases.

The metabolic cofactor Coenzyme A enhances alternative macrophage activation via MyD88-linked signaling

Metabolites and metabolic co-factors can shape the innate immune response, though the pathways by which these molecules adjust inflammation remain incompletely understood. Here we show that the metabolic cofactor Coenzyme A (CoA) enhances IL-4 driven alternative macrophage activation [m(IL-4)] in vitro and in vivo. Unexpectedly, we found that perturbations in intracellular CoA metabolism did not influence m(IL-4) differentiation. Rather, we discovered that exogenous CoA provides a weak TLR4 signal which primes macrophages for increased receptivity to IL-4 signals and resolution of inflammation via MyD88. Mechanistic studies revealed MyD88-linked signals prime for IL-4 responsiveness, in part, by reshaping chromatin accessibility to enhance transcription of IL-4-linked genes. The results identify CoA as a host metabolic co-factor that influences macrophage function through an extrinsic TLR4-dependent mechanism, and suggests that damage-associated molecular patterns (DAMPs) can prime macrophages for alternative activation and resolution of inflammation.

Single-cell RNA sequencing combined with proteomics of infected macrophages reveals prothymosin-α as a target for treatment of apical periodontitis

INTRODUCTION

Chronic apical periodontitis (CAP) is a common infectious disease of the oral cavity. Immune responses and osteoclastogenesis of monocytes/macrophages play a crucial role in CAP progression, and this study want to clarify role of monocytes/macrophages in CAP, which will contribute to treatment of CAP.

OBJECTIVES

We aim to explore the heterogeneity of monocyte populations in periapical lesion of CAP tissues and healthy control (HC) periodontal tissues by single-cell RNA sequencing (scRNA-seq), search novel targets for alleviating CAP, and further validate it by proteomics and in vitro and in vivo evaluations.

METHODS

ScRNA-seq was used to analyze the heterogeneity of monocyte populations in CAP, and proteomics of THP-1-derived macrophages with porphyromonas gingivalis infection were intersected with the differentially expressed genes (DEGs) of macrophages between CAP and HC tissues. The upregulated PTMA (prothymosin-α) were validated by immunofluorescence staining and quantitative real time polymerase chain reaction. We evaluated the effect of thymosin α1 (an amino-terminal proteolytic cleavage product of PTMA protein) on inflammatory factors and osteoclast differentiation of macrophages infected by P. gingivalis. Furthermore, we constructed mouse and rat mandibular bone lesions caused by apical periodontitis, and estimated treatment of systemic and topical administration of PTMA for CAP. Statistical analyses were performed using GraphPad Prism software (v9.2) RESULTS: Monocytes were divided into seven sub-clusters comprising monocyte-macrophage-osteoclast (MMO) differentiation in CAP. 14 up-regulated and 21 down-regulated genes and proteins were intersected between the DEGs of scRNA-seq data and proteomics, including the high expression of PTMA. Thymosin α1 may decrease several inflammatory cytokine expressions and osteoclastogenesis of THP-1-derived macrophages. Both systemic administration in mice and topical administration in the pulp chamber of rats alleviated periapical lesions.

CONCLUSIONS

PTMA upregulation in CAP moderates the inflammatory response and prevents the osteoclastogenesis of macrophages, which provides a basis for targeted therapeutic strategies for CAP.

Diesel exhaust particles induce polarization state-dependent functional and transcriptional changes in human monocyte-derived macrophages

Macrophage populations exist on a spectrum between the proinflammatory M1 and proresolution M2 states and have demonstrated the ability to reprogram between them after exposure to opposing polarization stimuli. Particulate matter (PM) has been repeatedly linked to worsening morbidity and mortality following respiratory infections and has been demonstrated to modify macrophage function and polarization. The purpose of this study was to determine whether diesel exhaust particles (DEP), a key component of airborne PM, would demonstrate polarization state-dependent effects on human monocyte-derived macrophages (hMDMs) and whether DEP would modify macrophage reprogramming. CD14+CD16- monocytes were isolated from the blood of healthy human volunteers and differentiated into macrophages with macrophage colony-stimulating factor (M-CSF). Resulting macrophages were left unpolarized or polarized into the proresolution M2 state before being exposed to DEP, M1-polarizing conditions (IFN-γ and LPS), or both and tested for phagocytic function, secretory profile, gene expression patterns, and bioenergetic properties. Contrary to previous reports, we observed a mixed M1/M2 phenotype in reprogrammed M2 cells when considering the broader range of functional readouts. In addition, we determined that DEP exposure dampens phagocytic function in all polarization states while modifying bioenergetic properties in M1 macrophages preferentially. Together, these data suggest that DEP exposure of reprogrammed M2 macrophages results in a highly inflammatory, highly energetic subpopulation of macrophages that may contribute to the poor health outcomes following PM exposure during respiratory infections.NEW & NOTEWORTHY We determined that reprogramming M2 macrophages in the presence of diesel exhaust particles (DEP) results in a highly inflammatory mixed M1/M2 phenotype. We also demonstrated that M1 macrophages are particularly vulnerable to particulate matter (PM) exposure as seen by dampened phagocytic function and modified bioenergetics. Our study suggests that PM causes reprogrammed M2 macrophages to become a highly energetic, highly secretory subpopulation of macrophages that may contribute to negative health outcomes observed in humans after PM exposure.

Multi-omics computational analysis unveils the involvement of AP-1 and CTCF in hysteresis of chromatin states during macrophage polarization

Macrophages display extreme plasticity, and the mechanisms and applications of polarization and de-/repolarization of macrophages have been extensively investigated. However, the regulation of macrophage hysteresis after de-/repolarization remains unclear. In this study, by using a large-scale computational analysis of macrophage multi-omics data, we report a list of hysteresis genes that maintain their expression patterns after polarization and de-/repolarization. While the polarization in M1 macrophages leads to a higher level of hysteresis in genes associated with cell cycle progression, cell migration, and enhancement of the immune response, we found weak levels of hysteresis after M2 polarization. During the polarization process from M0 to M1 and back to M0, the factors IRFs/STAT, AP-1, and CTCF regulate hysteresis by altering their binding sites to the chromatin. Overall, our results show that a history of polarization can lead to hysteresis in gene expression and chromatin accessibility over a given period. This study contributes to the understanding of de-/repolarization memory in macrophages.

Anti-inflammatory mechanisms in cancer research: Characterization of a distinct M2-like macrophage model derived from the THP-1 cell line

AIMS

Macrophages play an essential role in cancer development. Tumor-associated macrophages (TAMs) have predominantly M2-like attributes that are associated with tumor progression and poor patient survival. Numerous methods have been reported for differentiating and polarizing macrophages in vitro, but there is no standardized and validated model for creating TAMs. Primary cells show varying cytokine responses depending on their origin and functional studies utilizing these cells may lack generalization and validity. A distinct cell line-derived TAM-like M2 subtype is required to investigate the mechanisms mediated by anti-inflammatory TAMs in vitro. Our previous work demonstrated a standardized protocol for creating an M2 subtype derived from a human THP-1 cell line. The cell expression profile, however, has not been validated. The aim of this study was to characterize and validate the TAM-like M2 subtype macrophage created based on our protocol to introduce them as a standardized model for cancer research.

METHODS AND RESULTS

Using qRT-PCR and ELISA, we demonstrated that proinflammatory, anti-inflammatory, and tumor-associated marker expression changed during THP-1-derived marcrophage development in vitro, mimicking a TAM-related profile (e.g., TNFα, IL-1β). The anti-inflammatory marker IL-8/CXCL8, however, is most highly expressed in young M0 macrophages. Flow cytometry showed increased expression of CD206 in the final TAM-like M2 macrophage. Single-cell RNA-sequencing analysis of primary human monocytes and colon cancer tissue macrophages demonstrated that cell line-derived M2 macrophages resembled a TAM-related gene profile.

CONCLUSIONS

The THP-1-derived M2 macrophage based on a standardized cell line model represents a distinct anti-inflammatory TAM-like phenotype with an M2a subtype profile. This model may provide a basis for in vitro investigation of functional mechanisms in a variety of anti-inflammatory settings, particularly colon cancer development.

Histological and Immunohistochemical Characterization of Osteoimmunological Processes in Scaffold-Guided Bone Regeneration in an Ovine Large Segmental Defect Model

Large-volume bone defect regeneration is complex and demands time to complete. Several regeneration phases with unique characteristics, including immune responses, follow, overlap, and interdepend on each other and, if successful, lead to the regeneration of the organ bone's form and function. However, during traumatic, infectious, or neoplastic clinical cases, the intrinsic bone regeneration capacity may exceed, and surgical intervention is indicated. Scaffold-guided bone regeneration (SGBR) has recently shown efficacy in preclinical and clinical studies. To investigate different SGBR strategies over periods of up to three years, we have established a well-characterized ovine large segmental tibial bone defect model, for which we have developed and optimized immunohistochemistry (IHC) protocols. We present an overview of the immunohistochemical characterization of different experimental groups, in which all ovine segmental defects were treated with a bone grafting technique combined with an additively manufactured medical-grade polycaprolactone/tricalcium phosphate (mPCL-TCP) scaffold. The qualitative dataset was based on osteoimmunological findings gained from IHC analyses of over 350 sheep surgeries over the past two decades. Our systematic and standardized IHC protocols enabled us to gain further insight into the complex and long-drawn-out bone regeneration processes, which ultimately proved to be a critical element for successful translational research.

Leprosy-specific subsets of macrophages and Schwann cells identified by single-cell RNA-sequencing

In Mycobacterium leprae (M. leprae)-infection, inflammatory cells' subsets and dynamics as well as the interactions with Schwann cells have remained elusive. We investigated individual cells in M. leprae-inoculated nude mice by single-cell RNA-sequencing (scRNA-seq). For macrophages, we dissected two M1-like subsets and five M2-like subsets, where lipid-associated signatures were pervasive in both M1-like and M2-like subsets. There were four macrophage trajectories showing: (i) pro-inflammatory (M1), (ii) lipid metabolism-related (M2), (iii) anti-inflammatory (M2), and (iv) interferon-stimulated gene-related (M2) fates. They displayed early divergence without ever rejoining along the paths, suggesting simultaneous or continuous stimuli for macrophage activation in leprosy. The scRNA-seq predicted Schwann cell-macrophage interactions (Notch1-Jag1, Plxnb1-Sema4d interactions). An immature Schwann cell subset showing Tfap2a expression was identified, indicating Schwann cell dedifferentiation in leprosy tissues. Expressions of Notch1, Jag1, Plxnb1, Sema4d, and Tfap2a were validated in mouse or human leprosy tissues by immunohistochemistry. We identified both pro-inflammatory and inflammation-resolution signatures, where lipid-associated signatures were pervasive to the macrophages, representing leprosy-specific macrophage states for prolonged and repeated episodes of inflammation and resolution. Our study identified refined molecular states and interactions of macrophages and Schwann cells, suggesting novel insights into the pathogenesis of unhealed inflammation with neuropathy and potential therapeutic targets for leprosy.

CXCL9:SPP1 macrophage polarity identifies a network of cellular programs that control human cancers

Tumor microenvironments (TMEs) influence cancer progression but are complex and often differ between patients. Considering that microenvironment variations may reveal rules governing intratumoral cellular programs and disease outcome, we focused on tumor-to-tumor variation to examine 52 head and neck squamous cell carcinomas. We found that macrophage polarity-defined by CXCL9 and SPP1 (CS) expression but not by conventional M1 and M2 markers-had a noticeably strong prognostic association. CS macrophage polarity also identified a highly coordinated network of either pro- or antitumor variables, which involved each tumor-associated cell type and was spatially organized. We extended these findings to other cancer indications. Overall, these results suggest that, despite their complexity, TMEs coordinate coherent responses that control human cancers and for which CS macrophage polarity is a relevant yet simple variable.

Deciphering the Biology of Circulating Tumor Cells through Single-Cell RNA Sequencing: Implications for Precision Medicine in Cancer

Circulating tumor cells (CTCs) hold unique biological characteristics that directly involve them in hematogenous dissemination. Studying CTCs systematically is technically challenging due to their extreme rarity and heterogeneity and the lack of specific markers to specify metastasis-initiating CTCs. With cutting-edge technology, single-cell RNA sequencing (scRNA-seq) provides insights into the biology of metastatic processes driven by CTCs. Transcriptomics analysis of single CTCs can decipher tumor heterogeneity and phenotypic plasticity for exploring promising novel therapeutic targets. The integrated approach provides a perspective on the mechanisms underlying tumor development and interrogates CTCs interactions with other blood cell types, particularly those of the immune system. This review aims to comprehensively describe the current study on CTC transcriptomic analysis through scRNA-seq technology. We emphasize the workflow for scRNA-seq analysis of CTCs, including enrichment, single cell isolation, and bioinformatic tools applied for this purpose. Furthermore, we elucidated the translational knowledge from the transcriptomic profile of individual CTCs and the biology of cancer metastasis for developing effective therapeutics through targeting key pathways in CTCs.

A tetramethylpyrazine-loaded hyaluronic acid-based hydrogel modulates macrophage polarization for promoting wound recovery in diabetic mice

The failure of wound healing often causes lower limb disability and amputation of diabetic patients. Current strategies for diabetic wound management often fail to achieve the expected outcomes, and emerging alternatives are urgently needed. Recent advances in the identification of active compounds from traditional herbal medicines provide promising therapeutics for tissue repair and regeneration. In this study, the pro-healing effects of tetramethylpyrazine (TMP, a natural alkaloid found in Ligusticum chuanxiong Hort) for diabetic wounds were for the first time demonstrated. The cutaneous healing was mainly achieved by TMP-mediated macrophage polarization from pro-inflammatory to pro-healing phenotype. In addition, the topical administration of TMP was facilitated by the hyaluronic acid (HA) hydrogel for promoting the full-thickness wounds in the experimental diabetic mice. Consequently, TMP-loaded HA hydrogel (TMP-HA) profoundly accelerated the wound closure in comparison with TMP-loaded INTRASITE Gel (it is a commercial hydrogel), which was evident with the inflammation mitigation, the angiogenesis enhancement, and the collagen deposition. Our work reveals the macrophage-modulatory function of TMP for diabetic wound healing and demonstrates great potential of TMP-HA for clinical application.

Uncoding the interdependency of tumor microenvironment and macrophage polarization: insights from a continuous network approach

The balance between pro- and anti-inflammatory immune system responses is crucial to preventing complex diseases like cancer. Macrophages are essential immune cells that contribute to this balance constrained by the local signaling profile of the tumor microenvironment. To understand how pro- and anti-inflammatory unbalance emerges in cancer, we developed a theoretical analysis of macrophage differentiation that is derived from activated monocytes circulating in the blood. Once recruited to the site of inflammation, monocytes can be polarized based on the specific interleukins and chemokines in the microenvironment. To quantify this process, we used a previous regulatory network reconstructed by our group and transformed Boolean Network attractors of macrophage polarization to an ODE scheme, it enables us to quantify the activation of their genes in a continuous fashion. The transformation was developed using the interaction rules with a fuzzy logic approach. By implementing this approach, we analyzed different aspects that cannot be visualized in the Boolean setting. For example, this approach allows us to explore the dynamic behavior at different concentrations of cytokines and transcription factors in the microenvironment. One important aspect to assess is the evaluation of the transitions between phenotypes, some of them characterized by an abrupt or a gradual transition depending on specific concentrations of exogenous cytokines in the tumor microenvironment. For instance, IL-10 can induce a hybrid state that transits between an M2c and an M2b macrophage. Interferon- γ can induce a hybrid between M1 and M1a macrophage. We further demonstrated the plasticity of macrophages based on a combination of cytokines and the existence of hybrid phenotypes or partial polarization. This mathematical model allows us to unravel the patterns of macrophage differentiation based on the competition of expression of transcriptional factors. Finally, we survey how macrophages may respond to a continuously changing immunological response in a tumor microenvironment.

A systemically administered detoxified TLR4 agonist displays potent antitumor activity and an acceptable tolerance profile in preclinical models

Bacterial lipopolysaccharides (LPS) are potent innate immunostimulants targeting the Toll-like receptor 4 (TLR4), an attractive and validated target for immunostimulation in cancer therapy. Although LPS possess anti-tumor activity, toxicity issues prevent their systemic administration at effective doses in humans. We first demonstrated that LPS formulated in liposomes preserved a potent antitumor activity per se upon systemic administration in syngeneic models, and significantly enhance the antitumor activity of the anti-CD20 antibody rituximab in mice xenografted with the human RL lymphoma model. Liposomal encapsulation also allowed a 2-fold reduction in the induction of pro-inflammatory cytokines by LPS. Mice receiving an intravenous administration demonstrated a significant increase of neutrophils, monocytes and macrophages at the tumor site as well as an increase of macrophages in spleen. Further, we chemically detoxified LPS to obtain MP-LPS that was associated with a 200-fold decrease in the induction of proinflammatory cytokines. When encapsulated in a clinically approved liposomal formulation, toxicity, notably pyrogenicity (10-fold), was limited while the antitumor activity and immunoadjuvant effect were maintained. This improved tolerance profile of liposomal MP-LPS was associated with the preferential activation of the TLR4-TRIF pathway. Finally, in vitro studies demonstrated that stimulation with encapsulated MP-LPS reversed the polarization of M2 macrophages towards an M1 phenotype, and a phase 1 trial in healthy dogs validated its tolerance upon systemic administration up to very high doses (10µg/kg). Altogether, our results demonstrate the strong therapeutic potential of MPLPS formulated in liposomes as a systemically active anticancer agent, supporting its evaluation in patients with cancer.

Osteoimmune regulation underlies oral implant osseointegration and its perturbation

In the field of biomaterials, an endosseous implant is now recognized as an osteoimmunomodulatory but not bioinert biomaterial. Scientific advances in bone cell biology and in immunology have revealed a close relationship between the bone and immune systems resulting in a field of science called osteoimmunology. These discoveries have allowed for a novel interpretation of osseointegration as representing an osteoimmune reaction rather than a classic bone healing response, in which the activation state of macrophages ((M1-M2 polarization) appears to play a critical role. Through this viewpoint, the immune system is responsible for isolating the implant biomaterial foreign body by forming bone around the oral implant effectively shielding off the implant from the host bone system, i.e. osseointegration becomes a continuous and dynamic host defense reaction. At the same time, this has led to the proposal of a new model of osseointegration, the foreign body equilibrium (FBE). In addition, as an oral wound, the soft tissues are involved with all their innate immune characteristics. When implant integration is viewed as an osteoimmune reaction, this has implications for how marginal bone is regulated. For example, while bacteria are constitutive components of the soft tissue sulcus, if the inflammatory front and immune reaction is at some distance from the marginal bone, an equilibrium is established. If however, this inflammation approaches the marginal bone, an immune osteoclastic reaction occurs and marginal bone is removed. A number of clinical scenarios can be envisioned whereby the osteoimmune equilibrium is disturbed and marginal bone loss occurs, such as complications of aseptic nature and the synergistic activation of pro-inflammatory pathways (implant/wear debris, DAMPs, and PAMPs). Understanding that an implant is a foreign body and that the host reacts osteoimmunologically to shield off the implant allows for a distinction to be drawn between osteoimmunological conditions and peri-implant bone loss. This review will examine dental implant placement as an osteoimmune reaction and its implications for marginal bone loss.

Epigenetic Regulation of Macrophage Polarization in Cardiovascular Diseases

Cardiovascular diseases (CVDs) are the leading cause of hospitalization and death worldwide, especially in developing countries. The increased prevalence rate and mortality due to CVDs, despite the development of several approaches for prevention and treatment, are alarming trends in global health. Chronic inflammation and macrophage infiltration are key regulators of the initiation and progression of CVDs. Recent data suggest that epigenetic modifications, such as DNA methylation, posttranslational histone modifications, and RNA modifications, regulate cell development, DNA damage repair, apoptosis, immunity, calcium signaling, and aging in cardiomyocytes; and are involved in macrophage polarization and contribute significantly to cardiac disease development. Cardiac macrophages not only trigger damaging inflammatory responses during atherosclerotic plaque formation, myocardial injury, and heart failure but are also involved in tissue repair, remodeling, and regeneration. In this review, we summarize the key epigenetic modifications that influence macrophage polarization and contribute to the pathophysiology of CVDs, and highlight their potential for the development of advanced epigenetic therapies.

Galectin-4 increases the ability of M2 macrophages to enhance antiviral CD4+ T-cell responses

Galectin-4 (Gal-4) is a β-galactoside-binding protein belonging to the galectin family. Although Gal-4 is known to be involved in several physiologic processes of the gastrointestinal tract, its immunomodulatory roles remain unclear. In this study, we investigated whether Gal-4 influences the function of M1 and M2 macrophages. Gal-4 treatment drove more robust changes in the gene expression of M2 macrophages compared to M1 macrophages. Antiviral immune response-related genes were significantly upregulated in Gal-4-treated M2 macrophages. Gal-4 significantly enhanced the immunostimulatory activity of M2 macrophages upon Toll-like receptor 7 stimulation or infection with lymphocytic choriomeningitis virus (LCMV). Moreover, the antibody production against LCMV infection and the antiviral CD4+ T-cell responses, but not the antiviral CD8+ T-cell responses, were greatly increased by Gal-4-treated M2 macrophages in vivo. The present results indicate that Gal-4 enhances the ability of M2 macrophages to promote antiviral CD4+ T-cell responses. Thus, Gal-4 could be used to boost antiviral immune responses.

Macrophage inflammatory and regenerative response periodicity is programmed by cell cycle and chromatin state

Cell cycle (CC) facilitates cell division via robust, cyclical gene expression. Protective immunity requires the expansion of pathogen-responsive cell types, but whether CC confers unique gene expression programs that direct the subsequent immunological response remains unclear. Here, we demonstrate that single macrophages (MFs) adopt different plasticity states in CC, which leads to heterogeneous cytokine-induced polarization, priming, and repolarization programs. Specifically, MF plasticity to interferon gamma (IFNG) is substantially reduced during S-G2/M, whereas interleukin 4 (IL-4) induces S-G2/M-biased gene expression, mediated by CC-biased enhancers. Additionally, IL-4 polarization shifts the CC-phase distribution of MFs toward the G2/M phase, providing a subpopulation-specific mechanism for IL-4-induced, dampened IFNG responsiveness. Finally, we demonstrate CC-dependent MF responses in murine and human disease settings in vivo, including Th2-driven airway inflammation and pulmonary fibrosis, where MFs express an S-G2/M-biased tissue remodeling gene program. Therefore, MF inflammatory and regenerative responses are gated by CC in a cyclical, phase-dependent manner.

Density dependent regulation of inflammatory responses in macrophages

Macrophage distribution density is tightly regulated within the body, yet the importance of macrophage crowding during in vitro culture is largely unstudied. Using a human induced pluripotent stem cell (iPSC)-derived macrophage model of tissue resident macrophages, we characterize how increasing macrophage culture density changes their morphology and phenotype before and after inflammatory stimulation. In particular, density drives changes in macrophage inflammatory cytokine and chemokine secretion in both resting and activated states. This density regulated inflammatory state is also evident in blood monocyte derived-macrophages, the human monocytic THP-1 immortalized cell line, and iPSC-derived microglia. Density-dependent changes appear to be driven by a transferable soluble factor, yet the precise mechanism remains unknown. Our findings highlight cell plating density as an important but frequently overlooked consideration of in vitro macrophage research relevant to a variety of fields ranging from basic macrophage cell biology to disease studies.

A novel strategy to dissect multifaceted macrophage function in human diseases

Macrophages are widely distributed immune cells that play central roles in a variety of physiologic and pathologic processes, including obesity and cardiovascular disease (CVD). They are highly plastic cells that execute diverse functions according to a combination of signaling and environmental cues. While macrophages have traditionally been understood to polarize to either proinflammatory M1-like or anti-inflammatory M2-like states, evidence has shown that they exist in a spectrum of states between those 2 phenotypic extremes. In obesity-related disease, M1-like macrophages exacerbate inflammation and promote insulin resistance, while M2-like macrophages reduce inflammation, promoting insulin sensitivity. However, polarization markers are expressed inconsistently in adipose tissue macrophages, and they additionally exhibit phenotypes differing from the M1/M2 paradigm. In atherosclerotic CVD, activated plaque macrophages can also exist in a range of proinflammatory or anti-inflammatory states. Some of these macrophages scavenge lipids, developing into heterogeneous foam cell populations. To better characterize the many actions of macrophages in human disease, we have designed a novel set of computational tools: MacSpectrum and AtheroSpectrum. These tools provide information on the inflammatory polarization status, differentiation, and foaming of macrophages in both human and mouse samples, allowing for better characterization of macrophage subpopulations based on their function. Using these tools, we identified disease-relevant cell states in obesity and CVD, including the novel concept that macrophage-derived foam cell formation can follow homeostatic noninflammatory or pathogenic inflammatory foaming programs.

The Phylogeny, Ontogeny, and Organ-specific Differentiation of Macrophages in the Developing Intestine

Macrophages are large highly motile phagocytic leukocytes that appear early during embryonic development and have been conserved during evolution. The developmental roles of macrophages were first described nearly a century ago, at about the time these cells were being identified as central effectors in phagocytosis and elimination of microbes. Since then, we have made considerable progress in understanding the development of various subsets of macrophages and the diverse roles these cells play in both physiology and disease. This article reviews the phylogeny and the ontogeny of macrophages with a particular focus on the gastrointestinal tract, and the role of these mucosal macrophages in immune surveillance, innate immunity, homeostasis, tissue remodeling, angiogenesis, and repair of damaged tissues. We also discuss the importance of these macrophages in the inflammatory changes in neonatal necrotizing enterocolitis (NEC). This article presents a combination of our own peer-reviewed clinical and preclinical studies, with an extensive review of the literature using the databases PubMed, EMBASE, and Scopus.

Ferroptosis: A potential opportunity for intervention of pre-metastatic niche

It is widely thought that the tumor microenvironment (TME) provides the "soil" for malignant tumors to survive. Prior to metastasis, the interaction at the host site between factors secreted by primary tumors, bone-marrow-derived cells, with stromal components initiates and establishes a pre-metastatic niche (PMN) characterized by immunosuppression, inflammation, angiogenesis and vascular permeability, as well as lymphangiogenesis, reprogramming and organotropism. Ferroptosis is a non-apoptotic cell death characterized by iron-dependent lipid peroxidation and metabolic constraints. Ferroptotic cancer cells release various signal molecules into the TME to either suppress or promote tumor progression. This review highlights the important role played by ferroptosis in PMN, focusing on the relationship between ferroptosis and PMN characteristics, and discusses future research directions.

Leishmania infection-derived extracellular vesicles drive transcription of genes involved in M2 polarization

Although it is known that the composition of extracellular vesicles (EVs) is determined by the characteristics of the cell and its environment, the effects of intracellular infection on EV composition and functions are not well understood. We had previously shown that cultured macrophages infected with Leishmania parasites release EVs (LiEVs) containing parasite-derived molecules. In this study we show that LdVash, a molecule previously identified in LiEVs from L. donovani infected RAW264.7 macrophages, is widely distributed in the liver of L. donovani infected mice. This result shows for the first time that parasite molecules are released in EVs and distributed in infected tissues where they can be endocytosed by cells in the liver, including macrophages that significantly increase numbers as the infection progresses. To evaluate the potential impact of LiEVs on macrophage functions, we show that primary peritoneal exudate macrophages (PECs) express transcripts of signature molecules of M2 macrophages such as arginase 1, IL-10, and IL-4R when incubated with LiEVs. In comparative studies that illustrate how intracellular pathogens control the composition and functions of EVs released from macrophages, we show that EVs from RAW264.7 macrophages infected with Salmonella Typhimurium activate PECs to express transcripts of signature molecules of M1 macrophages such as iNOS, TNF alpha, and IFN-gamma and not M2 signature molecules. Finally, in contrast to the polarized responses observed in in vitro studies of macrophages, both M1 and M2 signature molecules are detected in L. donovani infected livers, although they exhibit differences in their spatial distribution in infected tissues. In conclusion, EVs produced by macrophages during Leishmania infection lead to the gene expression consistent with M2 polarization. In contrast, the EVs produced during S. Typhimurium infection stimulated the transcription of genes associated with M1 polarization.

In vitro assessment of the probiotic properties of an industrial preparation containing Lacticaseibacillus paracasei in the context of athlete health

Intense physical activity is often associated with undesirable physiological changes, including increased inflammation, transient immunodepression, increased susceptibility to infections, altered intestinal barrier integrity, and increased oxidative stress. Several trials suggested that probiotics supplementation may have beneficial effects on sport-associated gastro-intestinal and immune disorders. Recently, in a placebo-controlled human trial, the AminoAlta™ probiotic formulation (AApf) was demonstrated to increase the absorption of amino acids from pea protein, suggesting that the administration of AApf could overcome the compositional limitations of plant proteins. In this study, human cell line models were used to assess in vitro the potential capacity of AApf to protect from the physiological damages that an intense physical activity may cause. The obtained results revealed that the bacteria in the AApf have the ability to adhere to differentiated Caco-2 epithelial cell layer. In addition, the AApf was shown to reduce the activation of NF-κB in Caco-2 cells under inflammatory stimulation. Notably, this anti-inflammatory activity was enhanced in the presence of partially hydrolyzed plant proteins. The AApf also triggered the expression of cytokines by the THP-1 macrophage model in a dose-dependent manner. In particular, the expression of cytokines IL-1β, IL-6, and TNF-α was higher than that of the regulatory cytokine IL-10, resembling a cytokine profile characteristic of M1 phenotype, which typically intervene in counteracting bacterial and viral infections. Finally, AApf was shown to reduce transepithelial permeability and increase superoxide dismutase activity in the Caco-2 cell model. In conclusion, this study suggests that the AApf may potentially provide a spectrum of benefits useful to dampen the gastro-intestinal and immune detrimental consequences of an intense physical activity.

Tumor-associated macrophages (TAMs) modulate response to HER2-targeted agents in a humanized mouse model of breast cancer

PURPOSE

Tumor-associated macrophages (TAM) may participate to antitumor activity of anti-HER2-targeted therapies (Pertuzumab, Trastuzumab) in breast cancers harbouring HER-2 overexpression through antibody-dependent phagocytosis. Additive antitumor effect of concurrent cytotoxic chemotherapies, including Paclitaxel, may be counterbalanced by alteration in TAM infiltrate. The aim of this study is to evaluate the role of TAM in tumor response to anti-HER2-targeted therapies and chemotherapy in an experimental model of HER2-amplified breast cancer.

METHODS

A xenograft mouse model was built by subcutaneous injection of the SKBR-3 human HER2-amplified breast cancer cell line in Hu-CD34+ mice. Animals were randomized to receive weekly administration of Cremophor (control), Trastuzumab+Pertuzumab (TP), and Paclitaxel+Trastuzumab+Pertuzumab (PTP) with or without macrophage depletion with clodronate (C). At week 4, mice were euthanised and tumors were harvested for immunohistochemical analysis of TAM infiltration (RBP-J CD163 and CD68 for M1, M2, and overall TAM, respectively).

RESULTS

Tumor size was significantly lower in mice treated with TP, PTP, and PTP+C as compared to control, while no meaningful difference was observed in the TP+C arm. Analysis of TAM infiltrate showed significantly lower CD68 and CD163 expression in PTP, TP+C, and PTP+C as compared to TP and control arm. RBP-J expression was significantly decreased in mice treated with clodronate depletion.

CONCLUSIONS

Activity of TP is modulated by TAM infiltrate, that is inhibited by concurrent administration of Paclitaxel. To enhance the effect of anti-HER2-targeted therapies and minimize chemotherapy-related side effects, modulation of TAM should be considered in novel therapeutic combinations.

Epigenetic paradigms/exemplars of the macrophage: inflammasome axis in Leishmaniasis

The infectious paradigms have recently led to the recognition interplay of complex phenomenon underpinning disease diagnosis and prognosis. Evidently, parasitic infection studies are depicting converging trends of the epigenetic, environmental, and microbiome contributions, assisting pathogen-directed modulations of host biological system. The molecular details of epigenetic variations and memory, along with the multi-omics data at the interface of the host-pathogen level becomes strong indicator of immune cell plasticity, differentiation, and pathogen survival. Despite being one of the most important aspects of the disease's etiopathology, the epigenetic regulation of host-pathogen interactions and evolutionary epigenetics have received little attention thus far. Recent evidence has focused on the growing need to link epigenetic and microbiome modulations on parasite phenotypic plasticity and pathogen-induced host phenotypic plasticity for designing futuristic therapeutic regimes. Leishmaniasis is a neglected tropical illness with varying degrees of disease severity that is linked to a trans-species and epigenetic heredity process, including the pathogen-induced host and strain-specific modulations. The review configures research findings aligning to the epigenetic epidemiology niche, involving co-evolutionary epigenetic inheritance and plasticity disease models. The epigenetic exemplars focus on the host-pathogen interactome expanse at the macrophage-inflammasome axis.

Itaconate and leptin affecting PPARγ in M2 macrophages: A potential link to early-onset colorectal cancer

BACKGROUND

Along with the rising incidence of obesity, there has been an increase in patients diagnosed with early-onset colorectal cancer (<50 years old). In colorectal cancer, worse patient survival is associated with certain cytokine expression and downregulation of peroxisome proliferator activated receptor gamma expression. The effects of the obesity hormone leptin and macrophage-specific metabolite itaconate on these mechanisms are poorly understood. We investigated their impact on peroxisome proliferator activated receptor gamma and macrophage cytokine expression in vitro.

METHODS

M2-like macrophages were treated with either leptin, 4-octyl itaconate, or dimethyl itaconate in a dose- and time-dependent manner. Gene expression after treatment with 4 doses (D1-4) of each compound was analyzed at 4 time points (3, 6, 18, and 24 hours).

RESULTS

Peroxisome proliferator activated receptor gamma was downregulated after 4-octyl itaconate treatment at 18 hours (FC -32.67, P ≤ .001). Interleukin-8 was upregulated after leptin and dimethyl itaconate treatment at 6 hours (FC 26.35 at D4, P ≤ .001, and FC 23.26 at D3, P = .006). Dimethyl itaconate upregulated IL-1β at 24 hours (FC 18.00 at D4, P ≤ .001). Tumor necrosis factor-α showed maximum downregulation after 4-octyl itaconate at 18 hours (FC -103.25 at D4, P ≤ .001).

CONCLUSIONS

Itaconate downregulates peroxisome proliferator activated receptor gamma as a tumor-suppressing factor and upregulates anti-inflammatory cytokines in M2-like macrophages. Itaconate provides a link between obesity and colorectal cancer and may be a key regulator in early-onset colorectal cancer.

Single-Cell RNA Sequencing of Human Pluripotent Stem Cell-Derived Macrophages for Quality Control of The Cell Therapy Product

Macrophages exhibit high plasticity to achieve their roles in maintaining tissue homeostasis, innate immunity, tissue repair and regeneration. Therefore, macrophages are being evaluated for cell-based therapeutics against inflammatory disorders and cancer. To overcome the limitation related to expansion of primary macrophages and cell numbers, human pluripotent stem cell (hPSC)-derived macrophages are considered as an alternative source of primary macrophages for clinical application. However, the quality of hPSC-derived macrophages with respect to the biological homogeneity remains still unclear. We previously reported a technique to produce hPSC-derived macrophages referred to as iMACs, which is amenable for scale-up. In this study, we have evaluated the biological homogeneity of the iMACs using a transcriptome dataset of 6,230 iMACs obtained by single-cell RNA sequencing. The dataset provides a valuable genomic profile for understanding the molecular characteristics of hPSC-derived macrophage cells and provide a measurement of transcriptomic homogeneity. Our study highlights the usefulness of single cell RNA-seq data in quality control of the cell-based therapy products.

Remodeling immune microenvironment in periodontitis using resveratrol liposomes as an antibiotic-free therapeutic strategy

BACKGROUND

Periodontitis is a complicated inflammatory disease that damages the tooth-supporting tissues, with limited pharmacotherapy available. Macrophage-targeting therapy is promising for inflammatory diseases. Resveratrol (RSV), a nonflavonoid polyphenol, is known for its anti-inflammatory and immunomodulatory effects. However, its medical application is limited by its poor stability and water-solubility, as well as its low bioavailability.

RESULT

A therapeutic resveratrol-loaded liposomal system (Lipo-RSV) was developed to treat periodontitis. The physical properties of Lipo-RSV and its ability to regulate macrophages were investigated. The results showed that Lipo-RSV had good biocompatibility and could re-educate the inflammatory macrophages from M1- to M2-like phenotype through activating p-STAT3 and downregulating p-STAT1. Besides, the Lipo-RSV could scavenge ROS and inhibit the NF-κB signal and inflammasomes, thereby reducing the pro-inflammatory cytokines IL-1β, IL-6, and TNF-α.

CONCLUSION

These results revealed that Lipo-RSV could be a potential therapeutic system for the antibiotic-free treatment for periodontal diseases.

Paclitaxel Induces Micronucleation and Activates Pro-Inflammatory cGAS-STING Signaling in Triple-Negative Breast Cancer

Taxanes remain one of the most effective medical treatments for breast cancer. Clinical trials have coupled taxanes with immune checkpoint inhibitors in patients with triple-negative breast cancer (TNBC) with promising results. However, the mechanism linking taxanes to immune activation is unclear. To determine if paclitaxel could elicit an antitumoral immune response, we sampled tumor tissues from patients with TNBC receiving weekly paclitaxel (80 mg/m2) and found increased stromal tumor-infiltrating lymphocytes and micronucleation over baseline in three of six samples. At clinically relevant concentrations, paclitaxel can induce chromosome missegregation on multipolar spindles during mitosis. Consequently, post-mitotic cells are multinucleated and contain micronuclei, which often activate cyclic GMP-AMP synthase (cGAS) and may induce a type I IFN response reliant on the stimulator of IFN genes (STING) pathway. Other microtubule-targeting agents, eribulin and vinorelbine, recapitulate this cGAS/STING response and increased the expression of immune checkpoint molecule, PD-L1, in TNBC cell lines. To test the possibility that microtubule-targeting agents sensitize tumors that express cGAS to immune checkpoint inhibitors, we identified 10 patients with TNBC treated with PD-L1 or PD-1, seven of whom also received microtubule-targeting agents. Elevated baseline cGAS expression significantly correlated with treatment response in patients receiving microtubule-targeting agents in combination with immune checkpoint inhibitors. Our study identifies a mechanism by which microtubule-targeting agents can potentiate an immune response in TNBC. Further, baseline cGAS expression may predict patient treatment response to therapies combining microtubule-targeting agents and immune checkpoint inhibitors.

Alphavirus-Driven Interferon Gamma (IFNg) Expression Inhibits Tumor Growth in Orthotopic 4T1 Breast Cancer Model

Interferon gamma (IFNg) is a pleiotropic cytokine that can potentially reprogram the tumor microenvironment; however, the antitumor immunomodulatory properties of IFNg still need to be validated due to variable therapeutic outcomes in preclinical and clinical studies. We developed a replication-deficient Semliki Forest virus vector expressing IFNg (SFV/IFNg) and evaluated its immunomodulatory antitumor potential in vitro in a model of 3D spheroids and in vivo in an immunocompetent 4T1 mouse breast cancer model. We demonstrated that SFV-derived, IFN-g-stimulated bone marrow macrophages can be used to acquire the tumoricidal M1 phenotype in 3D nonattached conditions. Coculturing SFV/IFNg-infected 4T1 spheroids with BMDMs inhibited spheroid growth. In the orthotopic 4T1 mouse model, intratumoral administration of SFV/IFNg virus particles alone or in combination with the Pam3CSK4 TLR2/1 ligand led to significant inhibition of tumor growth compared to the administration of the control SFV/Luc virus particles. Analysis of the composition of intratumoral lymphoid cells isolated from tumors after SFV/IFNg treatment revealed increased CD4⁺ and CD8⁺ and decreased T-reg (CD4⁺/CD25⁺/FoxP3⁺) cell populations. Furthermore, a significant decrease in the populations of cells bearing myeloid cell markers CD11b, CD38, and CD206 was observed. In conclusion, the SFV/IFNg vector induces a therapeutic antitumor T-cell response and inhibits myeloid cell infiltration in treated tumors.

Going ballistic: Leishmania nuclear subversion of host cell plasticity

Intracellular parasites have evolved intricate strategies to subvert host cell functions for their own survival. These strategies are particularly damaging to the host if the infection involves immune cells, as illustrated by protozoan parasites of the genus Leishmania that thrive inside mononuclear phagocytic cells, causing devastating immunopathologies. While the impact of Leishmania infection on host cell phenotype and functions has been well documented, the regulatory mechanisms underlying host cell subversion were only recently investigated. Here we summarize the current knowledge on how Leishmania infection affects host nuclear activities and propose thought-provoking new concepts on the reciprocal relationship between epigenetic and transcriptional regulation in host cell phenotypic plasticity, its potential subversion by the intracellular parasite, and its relevance for host-directed therapy.

Epithelial-Macrophage Crosstalk Initiates Sterile Inflammation in Embryonic Skin

Macrophages are highly responsive to the environmental cues and are the primary responders to tissue stress and damage. While much is known about the role of macrophages during inflammatory disease progression; the initial series of events that set up the inflammation remains less understood. In this study, we use next generation sequencing (NGS) of embryonic skin macrophages and the niche cells - skin epithelia and stroma in the epidermis specific knockout of integrin beta 1 (Itgβ1) model to uncover specific roles of each cell type and identify how these cell types communicate to initiate the sterile inflammatory response. We demonstrate that while the embryonic skin fibroblasts in the Itgβ1 knockout skin are relatively inactive, the keratinocytes and macrophages are the critical responders to the sterile inflammatory cues. The epidermis expresses damage associated molecular patterns (DAMPs), stress response genes, pro-inflammatory cytokines, and chemokines that aid in eliciting the inflammatory response. The macrophages, in-turn, respond by acquiring enhanced M2-like characteristics expressing ECM remodeling and matrisome signatures that exacerbate the basement membrane disruption. Depletion of macrophages by blocking the CSF1 receptor (CSF1R) results in improved basement membrane integrity and reduced ECM remodeling activity in the KO skin. Further, blocking the skin inflammation with celecoxib reveals that the acquired fate of macrophages in the KO skin is dependent on its interaction with the epidermal compartment through COX2 dependent cytokine production. Taken together, our study highlights a critical crosstalk between the epithelia and the dermal macrophages that shapes macrophage fate and initiates sterile inflammation in the skin. The insights gained from our study can be extrapolated to other inflammatory disorders to understand the early events that set up the disease.

Early changes in the immune microenvironment of oral potentially malignant disorders reveal an unexpected association of M2 macrophages with oral cancer free survival

Understanding the dynamics of the immune microenvironment is critical to the development of immuno-based strategies for the prevention of oral potentially malignant disorders transformation to oral squamous cell carcinoma (OSCC). We used laser capture microdissection and RNA-sequencing to profile the expression of 13 matched pairs of epithelial versus stromal compartments from normal mucosa, hyperplasia, dysplasia, and invasive tumors in the 4-nitroquinolein (4-NQO) murine model of oral carcinogenesis. Genes differentially expressed at each step of transformation were defined. Immune cell deconvolution and enrichment scores of various biological processes including immune-related ones were computed. Immunohistochemistry was also performed to characterize the immune infiltrates by T-cells (T-cells CD3+, helper CD4+, cytotoxic CD8+, regulatory FoxP3+), B-cells (B220+), and macrophages (M1 iNOS+, M2 CD163+) at each histological step. Enrichment of three independent M2 macrophages signatures were computed in 86 oral leukoplakia with available clinical outcome. Most gene expression changes were observed in the stromal compartment and related to immune biological processes. Immune cell deconvolution identified infiltration by the macrophage population as the most important quantitatively especially at the stage of dysplasia. In 86 patients with oral leukoplakia, three M2 macrophages signatures were independently associated with improved oral cancer-free survival. This study provides a better understanding of the dynamics of the immune microenvironment during oral carcinogenesis and highlights an unexpected association of M2 macrophages gene expression signatures with oral cancer free survival in patients with oral leukoplakia.

Time-Programmed Delivery of Sorafenib and Anti-CD47 Antibody via a Double-Layer-Gel Matrix for Postsurgical Treatment of Breast Cancer

The highly immunosuppressive microenvironment after surgery has a crucial impact on the recurrence and metastasis in breast cancer patients. Programmable delivery of immunotherapy-involving combinations through a single drug delivery system is highly promising, yet greatly challenging, to reverse postoperative immunosuppression. Here, an injectable hierarchical gel matrix, composed of dual lipid gel (DLG) layers with different soybean phosphatidylcholine/glycerol dioleate mass ratios, was developed to achieve the time-programmed sequential delivery of combined cancer immunotherapy. The outer layer of the DLG matrix was thermally responsive and loaded with sorafenib-adsorbed graphene oxide (GO) nanoparticles. GO under manually controlled near-infrared irradiation generated mild heat and provoked the release of sorafenib first to reeducate tumor-associated macrophages (TAMs) and promote an immunogenic tumor microenvironment. The inner layer, loaded with anti-CD47 antibody (aCD47), could maintain the gel state for a much longer time, enabling the sustained release of aCD47 afterward to block the CD47-signal regulatory protein α (SIRPα) pathway for a long-term antitumor effect. In vivo studies on 4T1 tumor-bearing mouse model demonstrated that the DLG-based strategy efficiently prevented tumor recurrence and metastasis by locally reversing the immunosuppression and synergistically blocking the CD47-dependent immune escape, thereby boosting the systemic immune responses.

Macrophage Polarization in Cardiac Tissue Repair Following Myocardial Infarction

Cardiovascular disease is the leading cause of mortality and morbidity around the globe, creating a substantial socio-economic burden as a result. Myocardial infarction is a significant contributor to the detrimental impact of cardiovascular disease. The death of cardiomyocytes following myocardial infarction causes an immune response which leads to further destruction of tissue, and subsequently, results in the formation of non-contractile scar tissue. Macrophages have been recognized as important regulators and participants of inflammation and fibrosis following myocardial infarction. Macrophages are generally classified into two distinct groups, namely, classically activated, or M1 macrophages, and alternatively activated, or M2 macrophages. The phenotypic profile of cardiac macrophages, however, is much more diverse and should not be reduced to these two subsets. In this review, we describe the phenotypes and functions of macrophages which are present in the healthy, as well as the infarcted heart, and analyze them with respect to M1 and M2 polarization states. Furthermore, we discuss therapeutic strategies which utilize macrophage polarization towards an anti-inflammatory or reparative phenotype for the treatment of myocardial infarction.

Function of Macrophages in Disease: Current Understanding on Molecular Mechanisms

Tissue-resident macrophages (TRMs) are heterogeneous populations originating either from monocytes or embryonic progenitors, and distribute in lymphoid and non-lymphoid tissues. TRMs play diverse roles in many physiological processes, including metabolic function, clearance of cellular debris, and tissue remodeling and defense. Macrophages can be polarized to different functional phenotypes depending on their origin and tissue microenvironment. Specific macrophage subpopulations are associated with disease progression. In studies of fate-mapping and single-cell RNA sequencing methodologies, several critical molecules have been identified to induce the change of macrophage function. These molecules are potential markers for diagnosis and selective targets for novel macrophage-mediated treatment. In this review, we discuss some of the recent findings regarding less-known molecules and new functions of well-known molecules. Understanding the mechanisms of these molecules in macrophages has the potential to yield new macrophage-mediated treatments or diagnostic approaches to disease.

Iron Metabolism in the Tumor Microenvironment-Implications for Anti-Cancer Immune Response

New insights into the field of iron metabolism within the tumor microenvironment have been uncovered in recent years. Iron promotes the production of reactive oxygen species, which may either trigger ferroptosis cell death or contribute to malignant transformation. Once transformed, cancer cells divert tumor-infiltrating immune cells to satisfy their iron demand, thus affecting the tumor immunosurveillance. In this review, we highlight how the bioavailability of this metal shapes complex metabolic pathways within the tumor microenvironment and how this affects both tumor-associated macrophages and tumor-infiltrating lymphocytes functions. Furthermore, we discuss the potentials as well as the current clinical controversies surrounding the use of iron metabolism as a target for new anticancer treatments in two opposed conditions: i) the "hot" tumors, which are usually enriched in immune cells infiltration and are extremely rich in iron availability within the microenvironment, and ii) the "cold" tumors, which are often very poor in immune cells, mainly due to immune exclusion.

Regulation of extracellular matrix assembly and structure by hybrid M1/M2 macrophages

Aberrant extracellular matrix (ECM) assembly surrounding implanted biomaterials is the hallmark of the foreign body response, in which implants become encapsulated in thick fibrous tissue that prevents their proper function. While macrophages are known regulators of fibroblast behavior, how their phenotype influences ECM assembly and the progression of the foreign body response is poorly understood. In this study, we used in vitro models with physiologically relevant macrophage phenotypes, as well as controlled release of macrophage-modulating cytokines from gelatin hydrogels implanted subcutaneously in vivo to investigate the role of macrophages in ECM assembly. Primary human macrophages were polarized to four distinct phenotypes, which have each been associated with fibrosis, including pro-inflammatory M1, pro-healing M2, and a hybrid M1/M2, generated by exposing macrophages to M1-and M2-promoting stimuli simultaneously. Additionally, macrophages were first polarized to M1 and then to M2 (M1→M2) to generate a phenotype typically observed during normal wound healing. Human dermal fibroblasts that were cultured in macrophage-conditioned media upregulated numerous genes involved in regulation of ECM assembly, especially in M2-conditioned media. Hybrid M1/M2 macrophage-conditioned media caused fibroblasts to produce a matrix with thicker and less aligned fibers, while M2 macrophage-conditioned media caused the formation of a more aligned matrix with thinner fibers. Gelatin methacrylate hydrogels containing interleukin-4 (IL4) and IL13-loaded poly(lactic-co-glycolic acid) (PLGA) microparticles were designed to promote the M2 phenotype in a murine subcutaneous in vivo model. NanoString multiplex gene expression analysis of hydrogel explants showed that hydrogels without cytokines caused mostly M1 phenotype markers to be highly expressed at an early time point (3 days), but the release of IL4+IL13 promoted upregulation of M2 markers and genes associated with regulation of ECM assembly, such as Col5a1 and Col6a1. Biochemical analysis and second harmonic generation microscopy showed that the release of IL4+IL13 increased total sulfated glycosaminoglycan content and decreased fibril alignment, which is typically associated with less fibrotic tissue. Together, these results show that hybrid M1/M2 macrophages regulate ECM assembly, and that shifting the balance towards M2 may promote architectural and compositional changes in ECM with enhanced potential for downstream remodeling.