Biophysical regulation of macrophages in health and disease

Dichroa febrifuga Lour.: A review of its botany, traditional use, phytochemistry, pharmacological activities, toxicology, and progress in reducing toxicity

ETHNOPHARMACOLOGICAL RELEVANCE

Dichroa febrifuga Lour., a toxic but extensively used traditional Chinese medicine with a remarkable effect, is commonly called "Changshan" in China. It has been used to treat malaria and many other parasitic diseases.

AIM OF THE REVIEW

The study aims to provide a current overview of the progress in the research on traditional use, phytochemistry, pharmacological activities, toxicology, and methods of toxicity reduction of D. febrifuga. Additionally, further research directions and development prospects for the plant were put forward.

MATERIALS AND METHODS

The article uses "Dichroa febrifuga Lour." "D. febrifuga" as the keyword and all relevant information on D. febrifuga was collected from electronic searches (Elsevier, PubMed, ACS, CNKI, Google Scholar, and Baidu Scholar), doctoral and master's dissertations and classic books about Chinese herbs.

RESULTS

30 chemical compounds, including alkaloids, terpenoids, flavonoids and other kinds, were isolated and identified from D. febrifuga. Modern pharmacological studies have shown that these components have a variety of pharmacological activities, including anti-malarial activities, anti-inflammatory activities, anti-tumor activities, anti-parasitic activities and anti-oomycete activities. Meanwhile, alkaloids, as the material basis of its efficacy, are also the source of its toxicity. It can cause multiple organ damage, including liver, kidney and heart, and cause adverse reactions such as nausea and vomiting, abdominal pain and diarrhea. In the current study, the toxicity can be reduced by modifying the structure of the compound, processing and changing the dosage forms.

CONCLUSIONS

There are few studies on the chemical constituents of D. febrifuga, so the components and their structure characterization contained in it can become the focus of future research. In view of the toxicity of D. febrifuga, there are many methods to reduce it, but the safety and rationality of these methods need further study.

Modulation of Stiffness-Dependent Macrophage Inflammatory Responses by Collagen Deposition

Macrophages are innate immune cells that interact with complex extracellular matrix environments, which have varied stiffness, composition, and structure, and such interactions can lead to the modulation of cellular activity. Collagen is often used in the culture of immune cells, but the effects of substrate functionalization conditions are not typically considered. Here, we show that the solvent system used to attach collagen onto a hydrogel surface affects its surface distribution and organization, and this can modulate the responses of macrophages subsequently cultured on these surfaces in terms of their inflammatory activation and expression of adhesion and mechanosensitive molecules. Collagen was solubilized in either acetic acid (Col-AA) or N-(2-hydroxyethyl)piperazine-N'-ethanesulfonic acid (HEPES) (Col-HEP) solutions and conjugated onto soft and stiff polyacrylamide (PA) hydrogel surfaces. Bone marrow-derived macrophages cultured under standard conditions (pH 7.4) on the Col-HEP-derived surfaces exhibited stiffness-dependent inflammatory activation; in contrast, the macrophages cultured on Col-AA-derived surfaces expressed high levels of inflammatory cytokines and genes, irrespective of the hydrogel stiffness. Among the collagen receptors that were examined, leukocyte-associated immunoglobulin-like receptor-1 (LAIR-1) was the most highly expressed, and knockdown of the Lair-1 gene enhanced the secretion of inflammatory cytokines. We found that the collagen distribution was more homogeneous on Col-AA surfaces but formed aggregates on Col-HEP surfaces. The macrophages cultured on Col-AA PA hydrogels were more evenly spread, expressed higher levels of vinculin, and exerted higher traction forces compared to those of cells on Col-HEP. These macrophages on Col-AA also had higher nuclear-to-cytoplasmic ratios of yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ), key molecules that control inflammation and sense substrate stiffness. Our results highlight that seemingly slight variations in substrate deposition for immunobiology studies can alter critical immune responses, and this is important to elucidate in the broader context of immunomodulatory biomaterial design.

Modeling mechanical activation of macrophages during pulmonary fibrogenesis for targeted anti-fibrosis therapy

Pulmonary fibrosis is an often fatal lung disease. Immune cells such as macrophages were shown to accumulate in the fibrotic lung, but their contribution to the fibrosis development is unclear. To recapitulate the involvement of macrophages in the development of pulmonary fibrosis, we developed a fibrotic microtissue model with cocultured human macrophages and fibroblasts. We show that profibrotic macrophages seeded on topographically controlled stromal tissues became mechanically activated. The resulting co-alignment of macrophages, collagen fibers, and fibroblasts promoted widespread fibrogenesis in micro-engineered lung tissues. Anti-fibrosis treatment using pirfenidone disrupts the polarization and mechanical activation of profibrotic macrophages, leading to fibrosis inhibition. Pirfenidone inhibits the mechanical activation of macrophages by suppressing integrin αMβ2 and Rho-associated kinase 2. These results demonstrate a potential pulmonary fibrogenesis mechanism at the tissue level contributed by macrophages. The cocultured microtissue model is a powerful tool to study the immune-stromal cell interactions and the anti-fibrosis drug mechanism.

Novel 3-D macrophage spheroid model reveals reciprocal regulation of immunomechanical stress and mechano-immunological response

Purpose

In many diseases, an overabundance of macrophages contributes to adverse outcomes. While numerous studies have compared macrophage phenotype after mechanical stimulation or with varying local stiffness, it is unclear if and how macrophages themselves contribute to mechanical forces in their microenvironment.

Methods

Raw 264.7 murine macrophages were embedded in a confining agarose gel, where they proliferated to form spheroids over time. Gels were synthesized at various concentrations to tune the stiffness and treated with various growth supplements to promote macrophage polarization. The spheroids were then analyzed by immunofluorescent staining and qPCR for markers of proliferation, mechanosensory channels, and polarization. Finally, spheroid geometries were used to computationally model the strain generated in the agarose by macrophage spheroid growth.

Results

Macrophages form spheroids and generate growth-induced mechanical forces (i.e., solid stress) within confining agarose gels, which can be maintained for at least 16 days in culture. Increasing agarose concentration restricts spheroid expansion, promotes discoid geometries, limits gel deformation, and induces an increase in iNOS expression. LPS stimulation increases spheroid growth, though this effect is reversed with the addition of IFN-γ. Ki67 expression decreases with increasing agarose concentration, in line with the growth measurements.

Conclusions

Macrophages alone both respond to and generate solid stress. Understanding how macrophage generation of growth-induced solid stress responds to different environmental conditions will help to inform treatment strategies for the plethora of diseases that involve macrophage accumulation.

Transcription factor c-Maf drives macrophages to promote hypertrophic scar formation

BACKGROUND

Hypertrophic scar (HS) is caused by the abnormal proliferation of fibroblasts and excessive deposition of extracellular matrix (ECM). Emerging evidence demonstrates that c-Maf positive M2 macrophages were mainly located in the hypertrophic scar tissues of proliferative phase. But whether c-Maf positive M2 macrophages can promote hypertrophic scar formation through modulating hypertrophic scar fibroblasts remains elusive.

AIMS

The aim of this study is to investigate the effects of c-Maf positive M2 macrophages on the biological behaviors and functions of hypertrophic scar fibroblasts and the potential mechanism.

METHODS

HE and Masson trichrome staining were used to examine the histological features of human hypertrophic scar. Immunofluorescence staining was employed to label and quantify the c-Maf+ /CD68+ M2 macrophages. CCK8, wound healing, and transwell assays were utilized to test the effects of c-Maf overexpressed M2 macrophages or the cell culture supernatants on the proliferation and migration of hypertrophic scar derived fibroblasts (HFBs) and normal skin derived fibroblasts (NFBs). Western blot and qPCR were harnessed to test the expressions of COL1, COL3, and α-SMA in the co-cultivated fibroblasts and TGF-β1 in the c-Maf overexpressed M2 macrophages.

RESULTS

Increased number of c-Maf+ /CD68+ M2 macrophages were found in HS in contrast to the normal skin (NS). Elevated proliferation and migration were observed in the HFBs or NFBs co-cultured with c-Maf overexpressed macrophages or the cell culture supernatants. A higher mRNA and protein expressions of COL1, COL3, and α-SMA were recorded in the HFBs co-cultured with c-Maf overexpressed macrophages or treated with its culture supernatants. In addition, augmented mRNA and protein expressions of TGF-β1 were also investigated in the c-Maf overexpressed macrophages.

CONCLUSION

c-Maf positive macrophages promote hypertrophic scar formation through regulating HFBs proliferation, migration, and ECM deposition via the secreted TGF-β1.

Inflammasomes as regulators of mechano-immunity

Mechano-immunity, the intersection between cellular or tissue mechanics and immune cell function, is emerging as an important factor in many inflammatory diseases. Mechano-sensing defines how cells detect mechanical changes in their environment. Mechano-response defines how cells adapt to such changes, e.g. form synapses, signal or migrate. Inflammasomes are intracellular immune sensors that detect changes in tissue and cell homoeostasis during infection or injury. We and others recently found that mechano-sensing of tissue topology (swollen tissue), topography (presence and distribution of foreign solid implant) or biomechanics (stiffness), alters inflammasome activity. Once activated, inflammasomes induce the secretion of inflammatory cytokines, but also change cellular mechanical properties, which influence how cells move, change their shape, and interact with other cells. When overactive, inflammasomes lead to chronic inflammation. This clearly places inflammasomes as important players in mechano-immunity. Here, we discuss a model whereby inflammasomes integrate pathogen- and tissue-injury signals, with changes in tissue mechanics, to shape the downstream inflammatory responses and allow cell and tissue mechano-adaptation. We will review the emerging evidence that supports this model.

Increased H3K9me3 and F-Actin Reorganization in the Rapid Adaptive Response to Hypergravity in Human T Lymphocytes

Our study explored the impact of hypergravity on human T cells, which experience additional acceleration forces beyond Earth's gravity due to various factors, such as pulsatile blood flow, and technology, such as high-performance aircraft flights or spaceflights. We investigated the histone modifications Histone 3 lysine 4 and 9 trimethylation (H3K4me3 and H3K9me3, respectively), as well as the structural and cytoskeletal organization of Jurkat T cells in response to hypergravity. Histone modifications play a crucial role in gene regulation, chromatin organization and DNA repair. In response to hypergravity, we found only minimal changes of H3K4me3 and a rapid increase in H3K9me3, which was sustained for up to 15 min and then returned to control levels after 1 h. Furthermore, rapid changes in F-actin fluorescence were observed within seconds of hypergravity exposure, indicating filament depolymerization and cytoskeletal restructuring, which subsequently recovered after 1 h of hypergravity. Our study demonstrated the rapid, dynamic and adaptive cellular response to hypergravity, particularly in terms of histone modifications and cytoskeletal changes. These responses are likely necessary for maintaining genome stability and structural integrity under hypergravity conditions as they are constantly occurring in the human body during blood cell circulation.

Overlooked Candida glabrata petites are echinocandin tolerant, induce host inflammatory responses, and display poor in vivo fitness

IMPORTANCE

Candida glabrata is a major fungal pathogen, which is able to lose mitochondria and form small and slow-growing colonies, called "petite." This attenuated growth rate has created controversies and questioned the clinical importance of petiteness. Herein, we have employed multiple omics technologies and in vivo mouse models to critically assess the clinical importance of petite phenotype. Our WGS identifies multiple genes potentially underpinning petite phenotype. Interestingly, petite C. glabrata cells engulfed by macrophages are dormant and, therefore, are not killed by the frontline antifungal drugs. Interestingly, macrophages infected with petite cells mount distinct transcriptomic responses. Consistent with our ex vivo observations, mitochondrial-proficient parental strains outcompete petites during systemic and gut colonization. Retrospective examination of C. glabrata isolates identified petite prevalence a rare entity, which can significantly vary from country to country. Collectively, our study overcomes the existing controversies and provides novel insights regarding the clinical relevance of petite C. glabrata isolates.

PCLLA-nanoHA Bone Substitute Promotes M2 Macrophage Polarization and Improves Alveolar Bone Repair in Diabetic Environments

The utilization of bioresorbable synthetic bone substitutes with immunomodulatory properties has gained significant attention in dental clinical applications for the absorption of alveolar bone induced by orthodontic treatment. In this study, we developed two distinct materials: a conventional hydroxyapatite (HA) bone powder comprised of hydroxyapatite particles and nanoHA embedded within a poly(caprolactone-co-lactide) (PCLLA) elastomeric matrix. We assessed the physicochemical characteristics of the bone substitute, specifically focusing on its composition and the controlled release of ions. Our findings show that PCLLA-nanoHA has deformable properties under 40 N, and a significant release of Ca and P elements was noted after 7 days in aqueous settings. Moreover, at the protein and gene expression levels, PCLLA-nanoHA enhances the capacity of macrophages to polarize towards an M2 phenotype in vitro. In vivo, PCLLA-nanoHA exhibits comparable effects to standard HA bone powder in terms of promoting alveolar bone regeneration. Extensive investigations reveal that PCLLA-nanoHA surpasses the commonly employed HA bone powder in stimulating bone tissue repair in diabetic mice. We have identified that PCLLA-nanoHA regulates macrophage M2 polarization by activating the PI3K/AKT and peroxisome proliferator-activated receptor gamma (PPAR) signaling pathways, thereby facilitating a favorable local immune microenvironment conducive to bone repair and regeneration. Our findings suggest that PCLLA-nanoHA presents itself as a promising bioresorbable bone substitute with properties that promote macrophage M2 polarization, particularly in the context of regulating the local microenvironment of alveolar bone in diabetic mice, potentially facilitating bone tissue regeneration.

Immunomodulatory Effects of Microcin C7 in Cyclophosphamide-Induced Immunosuppressed Mice

Microcin C7 (McC) as a viable immunomodulator peptide can be a potential solution for pathogenic microbial infection in the post-antibiotic era and has gained substantial attention. This study was designed to evaluate the immunomodulatory activity of Microcin C7 in a cyclophosphamide (CTX)-induced immunodeficient mouse model. We show that Microcin C7 treatment significantly alleviated the CTX-caused body weight loss, improved the feed and water consumption to improve the state of the mice, and elevated the absolute number and proportion of peripheral blood lymphocytes as well as the level of hemoglobulin. We further aim to characterize the phenotypes of the immune function and intestinal health profiles. The results demonstrate that Microcin C7 treatment increased serum levels of immunoglobulin A (IgA), IgG, interleukin 6, and hemolysin, promoted splenic lymphocyte proliferation induced by concanavalin A and LPS, and enhanced the phagocytosis of peritoneal macrophages immunized by sheep red blood cells. Additionally, Microcin C7 treatment decreased levels of diamine oxidase and d-lactate, ameliorated CTX-induced intestinal morphological damage, and increased the levels of zonula occluden 1, occludin, claudin-1, mucin 2, and secretary IgA in the jejunum and colon. Moreover, Microcin C7 administration is sufficient to reverse CTX-induced intestinal microbiota dysbiosis by increasing the number of Lactobacillus and Bifidobacterium, decreasing the number of Escherichia coli in colonic contents. Collectively, our results demonstrate that Microcin C7 may have protective and immunomodulatory functions and could be a potential candidate used in animal feed, functional foods, and immunological regimens..

The role of macrophages in rosacea: implications for targeted therapies

Introduction

Rosacea, a widespread chronic skin condition, may be influenced by macrophages, key immune cells in the skin, although their exact role is not yet fully understood. This review delves into the function of macrophages, their potential contribution to rosacea pathogenesis, current treatments, and promising macrophage-targeted therapies. It concludes by identifying knowledge gaps and potential areas for future rosacea research.

Method

Leveraging systematic and narrative literature review techniques, we conducted a comprehensive search of databases such as PubMed, Embase, and Web of Science. Utilizing keywords like "rosacea" and "macrophages", we targeted English articles from the last 5 years (2018-2023). We manually checked reference lists of relevant articles for additional studies. We included only articles emphasizing macrophages' role in rosacea and/or the development of related therapies and published within the specified timeframe.

Results

The systematic search of electronic databases yielded a total of 4,263 articles. After applying the inclusion and exclusion criteria, 156 articles were selected for inclusion in this review. These articles included original research studies, review articles, and clinical trials that focused on the role of macrophages in rosacea and/or the development of macrophage-targeted therapies for the disease. The selected articles provided a comprehensive and up-to-date overview of the current state of research on macrophages in rosacea, including their function in the skin, the potential mechanisms through which they may contribute to rosacea pathogenesis, and the current treatments and therapies available for the disease. Additionally, the articles identified gaps in knowledge regarding the role of macrophages in rosacea and suggested potential areas for future research.

Conclusion

This literature review emphasizes the important role that macrophages, vital immune cells in the skin, may play in the pathogenesis of rosacea, a common chronic inflammatory skin disorder. The selected studies suggest potential mechanisms by which these cells might contribute to rosacea progression, although these mechanisms are not yet fully understood. The studies also spotlight current rosacea treatments and illuminate the promising potential of new macrophage-focused therapies. Despite these insights, significant gaps persist in our understanding of the precise role of macrophages in rosacea. Future research in this area could provide further insights into the pathogenesis of rosacea and contribute to the development of more effective, targeted therapeutic strategies.

Modulation of macrophages by biophysical cues in health and beyond

Macrophages play a key role in tissue development and homeostasis, innate immune defence against microbes or tumours, and restoring homeostasis through tissue regeneration following infection or injury. The ability to adopt such diverse functions is due to their heterogeneous nature, which is driven largely by their developmental origin and their response to signals they encounter from the microenvironment. The most well-characterized signals driving macrophage phenotype and function are biochemical and metabolic. However, the way macrophages sense and respond to their extracellular biophysical environment is becoming increasingly recognized in the field of mechano-immunology. These biophysical cues can be signals from tissue components, such as the composition and charge of extracellular matrix or topography, elasticity, and stiffness of the tissue surrounding cells; and mechanical forces such as shear stress or stretch. Macrophages are important in determining whether a disease resolves or becomes chronic. Ageing and diseases such as cancer or fibrotic disorders are associated with significant changes in the tissue biophysical environment, and this provides signals that integrate with those from biochemical and metabolic stimuli to ultimately dictate the overall function of macrophages. This review provides a brief overview of macrophage polarization, followed by a selection of commonly recognized physiological and applied biophysical stimuli impacting macrophage activity, and the potential signalling mechanisms driving downstream responses. The effects of biophysical cues on macrophages' function in homeostasis and disease and the associated clinical implications are also highlighted.

Modeling Mechanical Activation of Macrophages During Pulmonary Fibrogenesis for Targeted Anti-Fibrosis Therapy

Pulmonary fibrosis, as seen in idiopathic pulmonary fibrosis (IPF) and COVID-induced pulmonary fibrosis, is an often-fatal lung disease. Increased numbers of immune cells such as macrophages were shown to accumulate in the fibrotic lung, but it is unclear how they contribute to the development of fibrosis. To recapitulate the macrophage mechanical activation in the fibrotic lung tissue microenvironment, we developed a fibrotic microtissue model with cocultured human macrophages and fibroblasts. We show that profibrotic macrophages seeded on topographically controlled stromal tissue constructs become mechanically activated. The resulting co-alignment of macrophages, collagen fibers and fibroblasts promote widespread fibrogenesis in micro-engineered lung tissues. Anti-fibrosis treatment using pirfenidone disrupts the polarization and mechanical activation of profibrotic macrophages, leading to fibrosis inhibition. Pirfenidone inhibits the mechanical activation of macrophages by suppressing integrin αMβ2 (CD11b/CD18) and Rho-associated kinase 2, which is a previously unknown mechanism of action of the drug. Together, these results demonstrate a potential pulmonary fibrogenesis mechanism at the tissue level contributed by mechanically activated macrophages. We propose the coculture, force-sensing microtissue model as a powerful tool to study the complex immune-stromal cell interactions and the mechanism of action of anti-fibrosis drugs.

Coupled mechanical mapping and interference contrast microscopy reveal viscoelastic and adhesion hallmarks of monocyte differentiation into macrophages

Monocytes activated by pro-inflammatory signals adhere to the vascular endothelium and migrate from the bloodstream to the tissue ultimately differentiating into macrophages. Cell mechanics and adhesion play a crucial role in macrophage functions during this inflammatory process. However, how monocytes change their adhesion and mechanical properties upon differentiation into macrophages is still not well understood. In this work, we used various tools to quantify the morphology, adhesion, and viscoelasticity of monocytes and differentiatted macrophages. Combination of atomic force microscopy (AFM) high resolution viscoelastic mapping with interference contrast microscopy (ICM) at the single-cell level revealed viscoelasticity and adhesion hallmarks during monocyte differentiation into macrophages. Quantitative holographic tomography imaging revealed a dramatic increase in cell volume and surface area during monocyte differentiation and the emergence of round and spread macrophage subpopulations. AFM viscoelastic mapping showed important stiffening (increase of the apparent Young's modulus, E₀) and solidification (decrease of cell fluidity, β) on differentiated cells that correlated with increased adhesion area. These changes were enhanced in macrophages with a spread phenotype. Remarkably, when adhesion was perturbed, differentiated macrophages remained stiffer and more solid-like than monocytes, suggesting a permanent reorganization of the cytoskeleton. We speculate that the stiffer and more solid-like microvilli and lamellipodia might help macrophages to minimize energy dissipation during mechanosensitive activities. Thus, our results revealed viscoelastic and adhesion hallmarks of monocyte differentiation that may be important for biological function.

Overlooked Candida glabrata petites are echinocandin tolerant, induce host inflammatory responses, and display poor in vivo fitness

Small colony variants (SCVs) are relatively common among some bacterial species and are associated with poor prognosis and recalcitrant infections. Similarly, Candida glabrata - a major intracellular fungal pathogen - produces small and slow-growing respiratory-deficient colonies, termed "petite." Despite reports of clinical petite C . glabrata strains, our understanding of petite behavior in the host remains obscure. Moreover, controversies exist regarding in-host petite fitness and its clinical relevance. Herein, we employed whole-genome sequencing (WGS), dual-RNAseq, and extensive ex vivo and in vivo studies to fill this knowledge gap. WGS identified multiple petite-specific mutations in nuclear and mitochondrially-encoded genes. Consistent with dual-RNAseq data, petite C . glabrata cells did not replicate inside host macrophages and were outcompeted by their non-petite parents in macrophages and in gut colonization and systemic infection mouse models. The intracellular petites showed hallmarks of drug tolerance and were relatively insensitive to the fungicidal activity of echinocandin drugs. Petite-infected macrophages exhibited a pro-inflammatory and type I IFN-skewed transcriptional program. Interrogation of international C . glabrata blood isolates ( n =1000) showed that petite prevalence varies by country, albeit at an overall low prevalence (0-3.5%). Collectively, our study sheds new light on the genetic basis, drug susceptibility, clinical prevalence, and host-pathogen responses of a clinically overlooked phenotype in a major fungal pathogen.

Importance

Candida glabrata is a major fungal pathogen, which is able to lose mitochondria and form small and slow-growing colonies, called "petite". This attenuated growth rate has created controversies and questioned the clinical importance of petiteness. Herein, we have employed multiple omicstechnologies and in vivo mouse models to critically assess the clinical importance of petite phenotype. Our WGS identifies multiple genes potentially underpinning petite phenotype. Interestingly, petite C. glabrata cells engulfed by macrophages are dormant and therefore are not killed by the frontline antifungal drugs. Interestingly, macrophages infected with petite cells mount distinct transcriptomic responses. Consistent with our ex-vivo observations, mitochondrial-proficient parental strains outcompete petites during systemic and gut colonization. Retrospective examination of C. glabrata isolates identified petite prevalence a rare entity, can significantly vary from country to country. Collectively, our study overcomes the existing controversies and provides novel insights regarding the clinical relevance of petite C. glabrata isolates.

Macrophages in immunoregulation and therapeutics

Macrophages exist in various tissues, several body cavities, and around mucosal surfaces and are a vital part of the innate immune system for host defense against many pathogens and cancers. Macrophages possess binary M1/M2 macrophage polarization settings, which perform a central role in an array of immune tasks via intrinsic signal cascades and, therefore, must be precisely regulated. Many crucial questions about macrophage signaling and immune modulation are yet to be uncovered. In addition, the clinical importance of tumor-associated macrophages is becoming more widely recognized as significant progress has been made in understanding their biology. Moreover, they are an integral part of the tumor microenvironment, playing a part in the regulation of a wide variety of processes including angiogenesis, extracellular matrix transformation, cancer cell proliferation, metastasis, immunosuppression, and resistance to chemotherapeutic and checkpoint blockade immunotherapies. Herein, we discuss immune regulation in macrophage polarization and signaling, mechanical stresses and modulation, metabolic signaling pathways, mitochondrial and transcriptional, and epigenetic regulation. Furthermore, we have broadly extended the understanding of macrophages in extracellular traps and the essential roles of autophagy and aging in regulating macrophage functions. Moreover, we discussed recent advances in macrophages-mediated immune regulation of autoimmune diseases and tumorigenesis. Lastly, we discussed targeted macrophage therapy to portray prospective targets for therapeutic strategies in health and diseases.

Mechanosensation to inflammation: Roles for YAP/TAZ in innate immune cells

Innate immune cells are responsible for eliminating foreign infectious agents and cellular debris, and their ability to perceive, respond to, and integrate biochemical and mechanical cues from their microenvironment eventually determines their behavior. In response to tissue injury, pathogen invasion, or a biomaterial implant, immune cells activate many pathways to initiate inflammation in the tissue. In addition to common inflammatory pathways, studies have demonstrated the role of the mechanosensitive proteins and transcriptional coactivators YAP and TAZ (YAP/TAZ) in inflammation and immunity. We review our knowledge of YAP/TAZ in controlling inflammation and immunity in innate immune cells. Furthermore, we discuss the roles of YAP/TAZ in inflammatory diseases, wound healing, and tissue regeneration and how they integrate mechanical cues with biochemical signaling during disease progression. Last, we comment on possible approaches that can be exploited to harness the therapeutic potential of YAP/TAZ in inflammatory diseases.

Mobile mechanical signal generator for macrophage polarization

The importance of mechanical signals in regulating the fate of macrophages is gaining increased attention recently. However, the recently used mechanical signals normally rely on the physical characteristics of matrix with non-specificity and instability or mechanical loading devices with uncontrollability and complexity. Herein, we demonstrate the successful fabrication of self-assembled microrobots (SMRs) based on magnetic nanoparticles as local mechanical signal generators for precise macrophage polarization. Under a rotating magnetic field (RMF), the propulsion of SMRs occurs due to the elastic deformation via magnetic force and hydrodynamics. SMRs perform wireless navigation toward the targeted macrophage in a controllable manner and subsequently rotate around the cell for mechanical signal generation. Macrophages are eventually polarized from M0 to anti-inflammatory related M2 phenotypes by blocking the Piezo1-activating protein-1 (AP-1）-CCL2 signaling pathway. The as-developed microrobot system provides a new platform of mechanical signal loading for macrophage polarization, which holds great potential for precise regulation of cell fate.

Neutrophil extracellular traps primed intercellular communication in cancer progression as a promising therapeutic target

In addition to the anti-infection response, neutrophils are linked to tumor progression through the secretion of inflammation components and neutrophil extracellular traps (NETs) formation. NET is a web-like structure constituted by a chromatin scaffold coated with specific nuclear and cytoplasmic proteins, such as histone and granule peptides. Increasing evidence has demonstrated that NETs are favorable factors to promote tumor growth, invasion, migration, and immunosuppression. However, the cell-cell interaction between NETs and other cells (tumor cells and immune cells) is complicated and poorly studied. This work is the first review to focus on the intercellular communication mediated by NETs in cancer. We summarized the complex cell-cell interaction between NETs and other cells in the tumor microenvironment. We also address the significance of NETs as both prognostic/predictive biomarkers and molecular targets for cancer therapy. Moreover, we presented a comprehensive landscape of cancer immunity, improving the therapeutic efficacy for advanced cancer in the future.

The extracellular matrix and the immune system: A mutually dependent relationship

For decades, immunologists have studied the role of circulating immune cells in host protection, with a more recent appreciation of immune cells resident within the tissue microenvironment and the intercommunication between nonhematopoietic cells and immune cells. However, the extracellular matrix (ECM), which comprises at least a third of tissue structures, remains relatively underexplored in immunology. Similarly, matrix biologists often overlook regulation of complex structural matrices by the immune system. We are only beginning to understand the scale at which ECM structures determine immune cell localization and function. Additionally, we need to better understand how immune cells dictate ECM complexity. This review aims to highlight the potential for biological discovery at the interface of immunology and matrix biology.

Tuning immunity through tissue mechanotransduction

Immune responses are governed by signals from the tissue microenvironment, and in addition to biochemical signals, mechanical cues and forces arising from the tissue, its extracellular matrix and its constituent cells shape immune cell function. Indeed, changes in biophysical properties of tissue alter the mechanical signals experienced by cells in many disease conditions, in inflammatory states and in the context of ageing. These mechanical cues are converted into biochemical signals through the process of mechanotransduction, and multiple pathways of mechanotransduction have been identified in immune cells. Such pathways impact important cellular functions including cell activation, cytokine production, metabolism, proliferation and trafficking. Changes in tissue mechanics may also represent a new form of 'danger signal' that alerts the innate and adaptive immune systems to the possibility of injury or infection. Tissue mechanics can change temporally during an infection or inflammatory response, offering a novel layer of dynamic immune regulation. Here, we review the emerging field of mechanoimmunology, focusing on how mechanical cues at the scale of the tissue environment regulate immune cell behaviours to initiate, propagate and resolve the immune response.

A study of macrophage mechanical properties and functional modulation based on the Young's modulus of PLGA-PEG fibers

The immune response of macrophages plays an important role in defending against viral infection, tumor deterioration and repairing of contused tissue. Macrophage functional differentiation induced by nanodrugs is the leading edge of current research, but nanodrugs have toxic side effects, and the influence of their physical properties on macrophages is not clear. Here we create an alternative way to modulate macrophage function through PLGA-PEG fibers' Young's modulus. Previously, we revealed that by controlling the Young's modulus of the fibers from kPa to MPa, all the fibers entered murine macrophage cells (RWA 264.7) in a similar manner, and based on that, we found that macrophages' mechanical properties were affected by the fibers' Young's modulus, that is, hard fibers with a Young's modulus of ∼1 MPa increased the cell average Young's modulus, but did not affect the cell shape, while soft fibers with a Young's modulus of ∼100 kPa decreased the cell average Young's modulus and modulated the cell shape to a more spherical one. On the other hand, only the soft fibers induced proinflammatory cytokine secretion, indicating an M1 macrophage functional modulation by low Young's modulus fibers. This study explored the mechanical properties of the interactions between PLGA-PEG fibers and cells, in particular, when guiding the direction of the modulation of macrophage function, which is of great significance for the applications of material biology in the biomedical field.

Phosphatidylserine liposome multilayers mediate the M1-to-M2 macrophage polarization to enhance bone tissue regeneration

An appropriate immune microenvironment, governed by macrophages, is essential for rapid tissue regeneration after biomaterial implantation. The macrophage phenotypes, M1 (inflammatory) and M2 (anti-inflammatory/healing), exert opposing effects on the repair of various tissues. In this study, a new strategy to promote tissue repair and tissue-to-biomaterial integration by M1-to-M2 macrophage transition using artificial apoptotic cell mimetics (phosphatidylserine liposomes; PSLs) was developed using bone as a model tissue. Titanium was also selected as a model substrate material because it is widely used for dental and orthopedic implants. Titanium implants were functionalized with multilayers via layer-by-layer assembly of cationic protamine and negatively charged PSLs that were chemically stabilized to prevent disruption of lipid bilayers. Samples carrying PSL multilayers could drive M1-type macrophages into M2-biased phenotypes, resulting in a dramatic change in macrophage secretion for tissue regeneration. In a rat femur implantation model, the PSL-multilayer-coated implant displayed augmented de novo bone formation and bone-to-implant integration, associated with an increased M1-to-M2-like phenotypic transition. This triggered the proper generation and activation of bone-forming osteoblasts and bone-resorbing osteoclasts relative to their uncoated counterparts. This study demonstrates the benefit of local M1-to-M2 macrophage polarization induced by PSL-multilayers constructed on implants for potent bone regeneration and bone-to-implant integration. The results of this study may help in the design of new immunomodulatory biomaterials. STATEMENT OF SIGNIFICANCE: Effective strategies for tissue regeneration are essential in the clinical practice. The macrophage phenotypes, M1 (inflammatory) and M2 (anti-inflammatory/healing), exert opposing effects on the repair of various tissues. Artificially produced phosphatidylserine-containing liposomes (PSLs) can induce M2 macrophage polarization by mimicking the inverted plasma membranes of apoptotic cells. This study demonstrates the advantages of local M1-to-M2 macrophage polarization induced by PSL-multilayers constructed on implants for effective bone regeneration and osseointegration (bone-to-implant integration). Mechanistically, M2 macrophages promote osteogenesis but inhibit osteoclastogenesis, and M1 macrophages vice versa. We believe that our study makes a significant contribution to the design of new immunomodulatory biomaterials for regenerative medicine because it is the first to validate the benefit of PSLs for tissue regeneration.

The intracellular signaling pathways governing macrophage activation and function in human atherosclerosis

Atherosclerosis is a chronic inflammatory disease characterized by lipid accumulation and plaque formation in arterial vessel walls. Atherosclerotic plaques narrow the arterial lumen to increase the risk of heart attacks, ischemic stroke and peripheral vascular disease, which are major and worldwide health and economic burdens. Macrophage accumulation within plaques is characteristic of all stages of atherosclerosis and their presence is a potential marker of disease activity and plaque stability. Macrophages engulf lipids and modified lipoproteins to form foam cells that express pro-inflammatory and chemotactic effector molecules, stress inducing factors and reactive oxygen species. They control plaque stability and rupture through secretion of metalloproteinases and extracellular matrix degradation. Although macrophages can worsen disease by propagating inflammation, they can stabilize atherosclerotic plaques through tissue remodeling, promoting the formation of a fibrous cap, clearing apoptotic cells to prevent necrotic core formation and through vascular repair. In atherosclerosis, macrophages respond to dyslipidaemia, cytokines, dying cells, metabolic factors, lipids, physical stimuli and epigenetic factors and exhibit heterogeneity in their activation depending on the stimuli they receive. Understanding these signals and the pathways driving macrophage function within developing and established plaques and how they can be pharmacologically modulated, represents a strategy for the prevention and treatment of atherosclerosis. This review focusses on the current understanding of factors controlling macrophage heterogeneity and function in atherosclerosis. Particular attention is given to the macrophage intracellular signaling pathways and transcription factors activated by biochemical and biophysical stimuli within plaques, and how they are integrated to regulate plaque formation and stability.

Mechanosensing in macrophages and dendritic cells in steady-state and disease

Macrophages and dendritic cells are myeloid cells that play critical roles in immune responses. Macrophages help to maintain homeostasis through tissue regeneration and the clearance of dead cells, but also mediate inflammatory processes against invading pathogens. As the most potent antigen-presenting cells, dendritic cells are important in connecting innate to adaptive immune responses via activation of T cells, and inducing tolerance under physiological conditions. While it is known that macrophages and dendritic cells respond to biochemical cues in the microenvironment, the role of extracellular mechanical stimuli is becoming increasingly apparent. Immune cell mechanotransduction is an emerging field, where accumulating evidence suggests a role for extracellular physical cues coming from tissue stiffness in promoting immune cell recruitment, activation, metabolism and inflammatory function. Additionally, many diseases such as pulmonary fibrosis, cardiovascular disease, cancer, and cirrhosis are associated with changes to the tissue biophysical environment. This review will discuss current knowledge about the effects of biophysical cues including matrix stiffness, topography, and mechanical forces on macrophage and dendritic cell behavior under steady-state and pathophysiological conditions. In addition, we will also provide insight on molecular mediators and signaling pathways important in macrophage and dendritic cell mechanotransduction.

Methyl Gallate Alleviates Acute Ulcerative Colitis by Modulating Gut Microbiota and Inhibiting TLR4/NF-κB Pathway

Ulcerative colitis (UC) is a complex immune-mediated inflammatory disease. In recent years, the incidence of UC has increased rapidly, however, its exact etiology and mechanism are still unclear. Based on the definite anti-inflammatory and antibacterial activities of Sanguisorba officinalis L., we studied its monomer, methyl gallate (MG). In this study, we employed flow cytometry and detected nitric oxide production, finding MG regulated macrophage polarization and inhibited the expression of proinflammatory cytokines in vitro. MG also exhibited anti-inflammatory activity accompanying with ameliorating body weight loss, improving colon length and histological damage in dextran sulfate sodium-induced UC mice. Meanwhile, transcription sequencing and 16S rRNA sequencing analyzed the key signaling pathways and changes in the gut microbiota of MG for UC treatment, proving that MG could alleviate inflammation by regulating the TLR4/NF-κB pathway in vivo and in vitro. Additionally, MG altered the diversity and composition of the gut microbiota and changed the abundance of metabolic products. In conclusion, our results are the first to demonstrate that MG has obvious therapeutic effects against acute UC, which is related to macrophage polarization, improved intestinal flora dysbiosis and inhibition of TLR4/NF-κB signaling pathway, and MG may be a promising therapeutic agent for UC treatment.

N6-methyladenosine of Socs1 modulates macrophage inflammatory response in different stiffness environments

Macrophages exhibit diverse functions within various tissues during the inflammatory response, and the physical properties of tissues also modulate the characteristics of macrophages. However, the underlying N6-methyladenosine (m⁶A)-associated molecular mechanisms remain unclear. Accordingly, we examined the potential role of m⁶A in macrophage activation and stiffness sensing. Intriguingly, we found that the macrophage inflammatory response and global levels of m⁶A were stiffness-dependent and that this was due to mechanically loosening the chromatin and epigenetic modification (H3K36me2 and HDAC3). In addition, we targeted suppressor of cytokine signalling 1 (Socs1) m⁶A methylation in a stiffness-dependent manner by screening the sequencing data and found that a higher stiffness hydrogel activated Jak-STAT and NFκB signalling and suppressed Fto gene expression. Next, by using the CRISPR/Cas9 system to knockout the FTO gene in macrophages, we demonstrated that FTO affects the stiffness-controlled macrophage inflammatory response by sustaining the negative feedback generated by SOCS1. Finally, we determined that the m⁶A reader YTHDF1 binds Socs1 mRNA and thereby maintains expression of SOCS1. Our results suggest that the FTO/Socs1/YTHDF1 regulatory axis is vital to the stiffness-controlled macrophage inflammatory response and that the deletion of FTO affects the negative feedback control exerted by SOCS1. Our findings increase understanding of the regulatory mechanisms involved in macrophage activation and the control of inflammation.

Ion channel Piezo1 activation promotes aerobic glycolysis in macrophages

Altered microenvironmental stiffness is a hallmark of inflammation. It is sensed by the mechanically activated cation channel Piezo1 in macrophages to induce subsequent immune responses. However, the mechanism by which the mechanosensitive signals shape the metabolic status of macrophages and tune immune responses remains unclear. We revealed that Piezo1-deficient macrophages exhibit reduced aerobic glycolysis in resting or liposaccharide (LPS)-stimulated macrophages with impaired LPS-induced secretion of inflammatory cytokines in vitro. Additionally, pretreatment with the Piezo1 agonist, Yoda1, or cyclical hydrostatic pressure (CHP) upregulated glycolytic activity and enhanced LPS-induced secretion of inflammatory cytokines. Piezo1-deficient mice were less susceptible to dextran sulfate sodium (DSS)-induced colitis, whereas Yoda1 treatment aggravated colitis. Mechanistically, we found that Piezo1 activation promotes aerobic glycolysis through the Ca²⁺-induced CaMKII-HIF1α axis. Therefore, our study revealed that Piezo1-mediated mechanosensitive signals Piezo1 can enhance aerobic glycolysis and promote the LPS-induced immune response in macrophages.

Can't handle the stress? Mechanobiology and disease

Mechanobiology is a rapidly growing research area focused on how mechanical forces and properties influence biological systems at the cell, molecular, and tissue level, and how those biological systems, in turn, control mechanical parameters. Recently, it has become apparent that disrupted mechanobiology has a significant role in many diseases, from cardiovascular disease to muscular dystrophy and cancer. An improved understanding of this intricate process could be harnessed toward developing alternative and more targeted treatment strategies, and to advance the fields of regenerative and personalized medicine. Modulating the mechanical properties of the cellular microenvironment has already been used successfully to boost antitumor immune responses and to induce cardiac and spinal regeneration, providing inspiration for further research in this area.

Mechanoimmunology: Are inflammatory epigenetic states of macrophages tuned by biophysical factors?

Many inflammatory diseases that are responsible for a majority of deaths are still uncurable, in part as the underpinning pathomechanisms and how to combat them is still poorly understood. Tissue-resident macrophages play pivotal roles in the maintenance of tissue homeostasis, but if they gradually convert to proinflammatory phenotypes, or if blood-born proinflammatory macrophages persist long-term after activation, they contribute to chronic inflammation and fibrosis. While biochemical factors and how they regulate the inflammatory transcriptional response of macrophages have been at the forefront of research to identify targets for therapeutic interventions, evidence is increasing that physical factors also tune the macrophage phenotype. Recently, several mechanisms have emerged as to how physical factors impact the mechanobiology of macrophages, from the nuclear translocation of transcription factors to epigenetic modifications, perhaps even DNA methylation. Insight into the mechanobiology of macrophages and associated epigenetic modifications will deliver novel therapeutic options going forward, particularly in the context of increased inflammation with advancing age and age-related diseases. We review here how biophysical factors can co-regulate pro-inflammatory gene expression and epigenetic modifications and identify knowledge gaps that require urgent attention if this therapeutic potential is to be realized.

Extracellular matrix of early pulmonary fibrosis modifies the polarization of alveolar macrophage

Macrophage polarization is modulated by many different stimuli. However, the effect of fibrotic extracellular matrix (ECM) on macrophage polarization remains unclear. In this study, a mouse model of radiation induced pulmonary fibrosis (RIPF) was established. Alveolar macrophages (AMs) were seeded on separated decellularized ECM respectively derived from early RIPF lung tissue (dECM-RIPF) and normal lung tissue (dECM-Nor), on which the polarization of AMs was examined. By way of bio-AFM analysis, a significant difference in surface roughness, but no difference in stiffness, was found between dECM-RIPF and dECM-Nor. Compared with dECM-Nor, dECM-RIPF induced a higher M1 activation and increased the levels of TNF-α, IL-6 and IL-1β, while it showed no significant effect M2 density. Nevertheless, such effects induced by dECM-RIPF could be abrogated by the integrin pan-inhibitor. Furthermore, dECM-RIPF caused integrin-dependent activation of NFκB, and NFκB inhibitor was capable of inhibiting dECM-RIPF-induced AMs proliferation and M1 activation. Animal experiments showed that NFκB inhibitor alleviated RIPF mainly through inhibiting M1 activation and down-regulating the levels of inflammatory cytokines. Our results showed that differential biophysical signaling from the fibrotic ECM of early RIPF promoted AMs polarization towards a M1 phenotype via integrin-NFκB. Inhibition of M1 activation may be an attractive approach for treating RIPF.

Titania nanospikes activate macrophage phagocytosis by ligand-independent contact stimulation

Macrophage phagocytosis is an important research target to combat various inflammatory or autoimmune diseases; however, the phenomenon has never been controlled by artificial means. Titania nanospikes created by alkaline etching treatment can tune macrophage polarization toward a M1-like type and might regulate macrophage phagocytosis. This in vitro study aimed to determine whether the two-dimensional titania nanosurfaces created by alkaline etching treatment activated the macrophage phagocytosis by nanospike-mediated contact stimulation. On two-dimensional pure titanium sheets, alkaline etching treatments with different protocols created superhydrophilic nanosurfaces with hydroxyl function groups and moderate or dense nanospikes. Both types of titania nanosurfaces promoted the phagocytic activity of the mouse macrophage-like cell line, J774A.1, through upregulation of M1 polarization markers and phagocytosis-related receptors, such as toll-like receptors (TLR2 and 4). In contrast, the hydrophobic smooth or micro-roughened titanium surfaces did not activate macrophage phagocytosis or the expression of related receptors. These phenomena remained unchanged even under the antibody blockade of macrophage TLR2 but were either suppressed or augmented for each surface excited by ultraviolet irradiation. Titania nanospikes induced paxillin expression and provided physical stimuli to macrophages, the extent of which was positively correlated with TLR expression levels. Ligand stimulation with lipopolysaccharide did not upregulate macrophage TLR expression but further enhanced M1 marker expression by titania nanosurfaces. These results showed that the two-dimensional titania nanosurfaces activated macrophage phagocytosis by enhancing expression of phagocytosis-related receptors through nanospike-mediated contact stimulation, in assistance with physical surface properties, in a ligand-independent manner.

Data driven and biophysical insights into the regulation of trafficking vesicles by extracellular matrix stiffness

Biomechanical signals from remodeled extracellular matrix (ECM) promote tumor progression. Here, we show that cell-matrix and cell-cell communication may be inherently linked and tuned through mechanisms of mechanosensitive biogenesis of trafficking vesicles. Pan-cancer analysis of cancer cells' mechanical properties (focusing primarily on cell stiffness) on substrates of varied stiffness and composition elucidated a heterogeneous cellular response to mechanical stimuli. Through machine learning, we identified a fingerprint of cytoskeleton-related proteins that accurately characterize cell stiffness in different ECM conditions. Expression of their respective genes correlates with patient prognosis across different tumor types. The levels of selected cytoskeleton proteins indicated that cortical tension mirrors the increase (or decrease) in cell stiffness with a change in ECM stiffness. A mechanistic biophysical model shows that the tendency for curvature generation by curvature-inducing proteins has an ultrasensitive dependence on cortical tension. This study thus highlights the effect of ECM stiffness, mediated by cortical tension, in modulating vesicle biogenesis.

A myogenic niche with a proper mechanical stress environment improves abdominal wall muscle repair by modulating immunity and preventing fibrosis

Volumetric muscle loss (VML) healing is often complicated by fibrosis, which impairs muscle regeneration and function. Adjusting mechanical stress in the repair environment may modulate immunity and reduce fibrosis. In this study, we aimed to create a biomaterial with suitable tension conditions and bidirectional tissue-inducing abilities to prevent fibrosis thus promote muscle regeneration and induce aponeurosis-like structures to restore muscle force transmission. A protocol was developed to manufacture decellularized muscle aponeurosis (D-MA) patches with an intact extracellular matrix (ECM) and low cytotoxicity. D-MA optimized the mechanical stress distribution in muscle injury sites and decreased the number of proinflammatory macrophages and myofibroblasts, thereby attenuating muscle fibrosis. Muscle and aponeurosis ECM environments had different microstructures and mechanical properties, which specifically enhanced stem cell differentiation into muscle-like cells on muscle ECM and tenocyte-like cells on aponeurosis ECM in vitro. Four weeks after orthotopic implantation, the biphasic muscle-aponeurosis-like tissue was successfully regenerated by the D-MA scaffold. The regenerated muscle fibers in D-MA were more abundant than those in the fibrotic decellularized muscle (D-M) scaffold. D-MA can be used to repair abdominal defects, which significantly improves the repair outcomes. Our results suggest D-MA as a promising material for VML repair.

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.

Stiffness- and Bioactive Factor-Mediated Protection of Self-Assembled Cartilage against Macrophage Challenge in a Novel Co-Culture System

OBJECTIVE

Tissue-engineered cartilage implants must withstand the potential inflammatory and joint loading environment for successful long-term repair of defects. The work's objectives were to develop a novel, direct cartilage-macrophage co-culture system and to characterize interactions between self-assembled neocartilage and differentially stimulated macrophages.

DESIGN

In study 1, it was hypothesized that the proinflammatory response of macrophages would intensify with increasing construct stiffness; it was expected that the neocartilage would display a decrease in mechanical properties after co-culture. In study 2, it was hypothesized that bioactive factors would protect neocartilage properties during macrophage co-culture. Also, it was hypothesized that interleukin 10 (IL-10)-stimulated macrophages would improve neocartilage mechanical properties compared to lipopolysaccharide (LPS)-stimulated macrophages.

RESULTS

As hypothesized, stiffer neocartilage elicited a heightened proinflammatory macrophage response, increasing tumor necrosis factor alpha (TNF-α) secretion by 5.47 times when LPS-stimulated compared to construct-only controls. Interestingly, this response did not adversely affect construct properties for the stiffest neocartilage but did correspond to a significant decrease in aggregate modulus for soft and medium stiffness constructs. In addition, bioactive factor-treated constructs were protected from macrophage challenge compared to chondrogenic medium-treated constructs, but IL-10 did not improve neocartilage properties, although stiff constructs appeared to bolster the anti-inflammatory nature of IL-10-stimulated macrophages. However, co-culture of bioactive factor-treated constructs with LPS-treated macrophages reduced TNF-α secretion by over 4 times compared to macrophage-only controls.

CONCLUSIONS

In conclusion, neocartilage stiffness can mediate macrophage behavior, but stiffness and bioactive factors prevent macrophage-induced degradation. Ultimately, this co-culture system could be utilized for additional studies to develop the burgeoning field of cartilage mechano-immunology.

Characterization of Macrophage and Cytokine Interactions with Biomaterials Used in Negative-Pressure Wound Therapy

Macrophages are innate immune cells that help wounds heal. Here, we study the potential immunomodulatory effects of negative-pressure wound therapy (NPWT) materials on the macrophage inflammatory response. We compared the effects of two materials, Granufoam™ (GF) and Veraflo Cleanse™ (VC), on macrophage function in vitro. We find that both materials cause reduced expression of inflammatory genes, such as TNF and IL1B, in human macrophages stimulated with bacterial lipopolysaccharide (LPS) and interferon-gamma (IFNγ). Relative to adherent glass control surfaces, VC discourages macrophage adhesion and spreading, and may potentially sequester LPS/IFNγ and cytokines that the cells produce. GF, on the other hand, was less suppressive of inflammation, supported macrophage adhesion and spreading better than VC, and sequestered lesser quantities of LPS/IFNγ in comparison to VC. The control dressing material cotton gauze (CT) was also immunosuppressive, capable of TNF-α retention and LPS/IFNγ sequestration. Our findings suggest that NPWT material interactions with cells, as well as soluble factors including cytokines and LPS, can modulate the immune response, independent of vacuum application. We have also established methodological strategies for studying NPWT materials and reveal the potential utility of cell-based in vitro studies for elucidating biological effects of NPWT materials.

Anti-Cancer Activity Profiling of Chemotherapeutic Agents in 3D Co-Cultures of Pancreatic Tumor Spheroids with Cancer-Associated Fibroblasts and Macrophages

Activated pancreatic stellate cells (aPSCs) and M2 macrophages modulate tumor progression and therapeutic efficacy in pancreatic ductal adenocarcinoma (PDAC) via epithelial-mesenchymal transition (EMT). Here, our aim was to analyze the anti-invasion effects of anti-cancer agents where EMT-inducing cancer-stroma interaction occurs under three-dimensional (3D) culture conditions. We used microfluidic channel chips to co-culture pancreatic tumor spheroids (TSs) with aPSCs and THP-1-derived M2 macrophages (M2 THP-1 cells) embedded in type I collagen. Under stromal cell co-culture conditions, PANC-1 TSs displayed elevated expression of EMT-related proteins and increased invasion and migration. When PANC-1 TSs were exposed to gemcitabine, 5-fluorouracil, oxaliplatin, or paclitaxel, 30-50% cells were found unaffected, with no significant changes in the dose-response profiles under stromal cell co-culture conditions. This indicated intrinsic resistance to these drugs and no further induction of drug resistance by stromal cells. Paclitaxel had a significant anti-invasion effect; in contrast, oxaliplatin did not show such effect despite its specific cytotoxicity in M2 THP-1 cells. Overall, our findings demonstrate that the TS-stroma co-culture model of PDAC is useful for activity profiling of anti-cancer agents against cancer and stromal cells, and analyzing the relationship between anti-stromal activity and anti-invasion effects.

Stretching the Function of Innate Immune Cells

The importance of innate immune cells to sense and respond to their physical environment is becoming increasingly recognized. Innate immune cells (e.g. macrophages and neutrophils) are able to receive mechanical signals through several mechanisms. In this review, we discuss the role of mechanosensitive ion channels, such as Piezo1 and transient receptor potential vanilloid 4 (TRPV4), and cell adhesion molecules, such as integrins, selectins, and cadherins in biology and human disease. Furthermore, we explain that these mechanical stimuli activate intracellular signaling pathways, such as MAPK (p38, JNK), YAP/TAZ, EDN1, NF-kB, and HIF-1α, to induce protein conformation changes and modulate gene expression to drive cellular function. Understanding the mechanisms by which immune cells interpret mechanosensitive information presents potential targets to treat human disease. Important areas of future study in this area include autoimmune, allergic, infectious, and malignant conditions.

A Src-H3 acetylation signaling axis integrates macrophage mechanosensation with inflammatory response

Macrophages are mechanosensitive cells that can exquisitely fine-tune their function in response to their microenvironment. While macrophage polarization results in concomitant changes in cell morphology and epigenetic reprogramming, how biophysically-induced signaling cascades contribute to gene regulatory programs that drive polarization remains unknown. We reveal a cytoskeleton-dependent Src-H3 acetylation (H3Ac) axis responsible for inflammation-associated histone hyperacetylation. Inflammatory stimuli caused increases in traction forces, Src activity and H3Ac marks in macrophages, accompanied by reduced cell elongation and motility. These effects were curtailed following disruption of H3Ac-signaling through either micropattern-induced cell elongation or inhibition of H3Ac readers (BRD proteins) directly. Src activation relieves the suppression of p300 histone acetyltransferase (HAT) activity by PKCδ. Furthermore, while inhibition of Src reduced p300 HAT activity and H3Ac marks globally, local H3Ac levels within the Src promoter were increased, suggesting H3Ac regulates Src levels through feedback. Together, our study reveals an adhesome-to-epigenome regulatory nexus underlying macrophage mechanosensation, where Src modulates H3Ac-associated epigenetic signaling as a means of tuning inflammatory gene activity and macrophage fate decisions in response to microenvironmental cues.

Treating Autoimmune Inflammatory Diseases with an siERN1-Nanoprodrug That Mediates Macrophage Polarization and Blocks Toll-like Receptor Signaling

The clinical application of small interfering RNA (siRNA) drugs provides promising opportunities to develop treatment strategies for autoimmune inflammatory diseases. In this study, siRNAs targeting the endoplasmic reticulum to nucleus signaling 1 (ERN1) gene (siERN1) were screened. Two cationic polymers, polyethylenimine (PEI) and poly(β-amino amine) (PBAA), which can improve the efficiency of the siRNA transfection, were used as siERN1 delivery carriers. They were implemented to construct a nanodrug delivery system with macrophage-targeting ability and dual responsiveness for the treatment of autoimmune inflammatory diseases. In terms of the mechanism, siERN1 can regulate the intracellular calcium ion concentration by interfering with the function of inositol 1,4,5-trisphosphate receptor 1/3 (IP3R1/3) and thus inducing M2 polarization of macrophages. Furthermore, siERN1-nanoprodrug [FA (folic acid)-PEG-R(RKKRRQRRR)-NPs(ss-PBAA-PEI)@siERN1] acts as a conductor of macrophage polarization by controlling the calcium ion concentration and is an inhibitor of MyD88-dependent Toll-like receptor signaling. The results revealed that the FA-PEG-R-NPs@siERN1 has universal biocompatibility, long-term drug release responsiveness, superior targeting properties, and therapeutic effects in mouse collagen-induced arthritis and inflammatory bowel disease models. In conclusion, this study reveals a potential strategy to treat autoimmune inflammatory disorders.

Hippo/yes-associated protein signaling functions as a mechanotransducer in regulating vascular homeostasis

Cells are constantly exposed to various mechanical forces, including hydrostatic pressure, cyclic stretch, fluid shear stress, and extracellular matrix stiffness. Mechanical cues can be translated into the cell-specific transcriptional process by a cellular mechanic-transducer. Evidence suggests that mechanical signals assist activated intracellular signal transduction pathways and the relative phenotypic adaptation to coordinate cell behavior and disease appropriately. The Hippo/yes-associated protein (YAP) signaling pathway is regulated in response to numerous mechanical stimuli. It plays an important role in the mechanotransduction mechanism, which converts mechanical forces to cascades of molecular signaling to modulate gene expression. This review summarizes the recent findings relevant to the Hippo/YAP pathway-based mechanotransduction in cell behavior and maintaining blood vessels, as well as cardiovascular disease.

Isolation and characterization of porcine macrophages and their inflammatory and fusion responses in different stiffness environments

Evaluating the host immune response to biomaterials is an essential step in the development of medical devices and tissue engineering strategies. To aid in this process, in vitro studies, whereby immune cells such as macrophages are cultured on biomaterials, can often expedite high throughput testing of many materials prior to implantation. While most studies to date utilize murine or human cells, the use of porcine macrophages has been less well described, despite the prevalent use of porcine models in medical device and tissue engineering development. In this study, we describe the isolation and characterization of porcine bone marrow- and peripheral blood-derived macrophages, and their interactions with biomaterials. We confirmed the expression of the macrophage surface markers CD68 and F4/80 and characterized the porcine macrophage response to the inflammatory stimulus, bacterial lipopolysaccharide. Finally, we investigated the inflammatory and fusion response of porcine macrophages cultured on different stiffness hydrogels, and we found that stiffer hydrogels enhanced inflammatory activation by more than two-fold and promoted fusion to form foreign body giant cells. Together, this study establishes the use of porcine macrophages in biomaterial testing and reveals a stiffness-dependent effect on biomaterial-induced giant cell formation.

Translation of Collagen Ultrastructure to Biomaterial Fabrication for Material-Independent but Highly Efficient Topographic Immunomodulation

Supplement-free induction of cellular differentiation and polarization solely through the topography of materials is an auspicious strategy but has so far significantly lagged behind the efficiency and intensity of media-supplementation-based protocols. Consistent with the idea that 3D structural motifs in the extracellular matrix possess immunomodulatory capacity as part of the natural healing process, it is found in this study that human-monocyte-derived macrophages show a strong M2a-like prohealing polarization when cultured on type I rat-tail collagen fibers but not on collagen I films. Therefore, it is hypothesized that highly aligned nanofibrils also of synthetic polymers, if packed into larger bundles in 3D topographical biomimetic similarity to native collagen I, would induce a localized macrophage polarization. For the automated fabrication of such bundles in a 3D printing manner, the strategy of "melt electrofibrillation" is pioneered by the integration of flow-directed polymer phase separation into melt electrowriting and subsequent selective dissolution of the matrix polymer postprocessing. This process yields nanofiber bundles with a remarkable structural similarity to native collagen I fibers, particularly for medical-grade poly(ε-caprolactone). These biomimetic fibrillar structures indeed induce a pronounced elongation of human-monocyte-derived macrophages and unprecedentedly trigger their M2-like polarization similar in efficacy as interleukin-4 treatment.

Biomedical Implants with Charge-Transfer Monitoring and Regulating Abilities

Transmembrane charge (ion/electron) transfer is essential for maintaining cellular homeostasis and is involved in many biological processes, from protein synthesis to embryonic development in organisms. Designing implant devices that can detect or regulate cellular transmembrane charge transfer is expected to sense and modulate the behaviors of host cells and tissues. Thus, charge transfer can be regarded as a bridge connecting living systems and human-made implantable devices. This review describes the mode and mechanism of charge transfer between organisms and nonliving materials, and summarizes the strategies to endow implants with charge-transfer regulating or monitoring abilities. Furthermore, three major charge-transfer controlling systems, including wired, self-activated, and stimuli-responsive biomedical implants, as well as the design principles and pivotal materials are systematically elaborated. The clinical challenges and the prospects for future development of these implant devices are also discussed.