The role of CSF1R-dependent macrophages in control of the intestinal stem-cell niche

The intestinal barrier: a pivotal role in health, inflammation, and cancer

The intestinal barrier serves as a boundary between the mucosal immune system in the lamina propria and the external environment of the intestinal lumen, which contains a diverse array of microorganisms and ingested environmental factors, including pathogens, food antigens, toxins, and other foreign substances. This barrier has a central role in regulating the controlled interaction between luminal factors and the intestinal immune system. Disruptions of intestinal epithelial cells, which serve as a physical barrier, or the antimicrobial peptides and mucins they produce, which act as a chemical barrier, can lead to a leaky gut. In this state, the intestinal wall is unable to efficiently separate the intestinal flora and luminal contents from the intestinal immune system. The subsequent activation of the immune system has an important role in the pathogenesis of inflammatory bowel disease, as well as in metabolic dysfunction-associated steatohepatitis, primary sclerosing cholangitis, and colorectal cancer. Dysregulated intestinal barrier integrity has also been described in patients with chronic inflammatory diseases outside the gastrointestinal tract, including rheumatoid arthritis and neurodegenerative disorders. Mechanistic studies of barrier dysfunction have revealed that the subsequent local activation and systemic circulation of activated immune cells and the cytokines they secrete, as well as extracellular vesicles, promote proinflammatory processes within and outside the gastrointestinal tract. In this Review, we summarise these findings and highlight several new therapeutic concepts currently being developed that attempt to control inflammatory processes via direct or indirect modulation of intestinal barrier function.

The Intestinal Macrophage-Intestinal Stem Cell Axis in Inflammatory Bowel Diseases: From Pathogenesis to Therapy

The gut plays a crucial role in digestion and immunity, so its balance is essential to overall health. This balance relies on dynamic interactions between intestinal epithelial cells, immune cells, and crypt stem cells. Inflammatory bowel disease (IBD), which consists of ulcerative colitis and Crohn's disease, is a chronic relapsing inflammatory disease of the gastrointestinal tract closely related to immune dysfunction. Stem cells, known for their ability to self-renew and differentiate, play an important role in repairing damaged intestinal epithelium and maintaining homeostasis in vivo. Macrophages are key gatekeepers of intestinal immune homeostasis and have a significant impact on IBD. Current research has focused on the link between epithelial cells and stem cells, but interactions with macrophages, which have been recognized as attractive targets for the development of new therapeutic approaches to disease, have been less explored. Recently, the developing field of immunometabolism has reinforced that metabolic reprogramming is a key determinant of macrophage function and subsequent disease progression. The aim of this review is to explore the role of the macrophage-stem cell axis in the maintenance of intestinal homeostasis and to summarize potential approaches to treating IBD by manipulating the cellular metabolism of macrophages, as well as the main opportunities and challenges faced. In summary, our overview provides a framework for understanding the critical role of macrophage immunometabolism in maintaining gut health and potential therapeutic targets.

A review of gut failure as a cause and consequence of critical illness

In critical illness, all elements of gut function are perturbed. Dysbiosis develops as the gut microbial community loses taxonomic diversity and new virulence factors appear. Intestinal permeability increases, allowing for translocation of bacteria and/or bacterial products. Epithelial function is altered at a cellular level and homeostasis of the epithelial monolayer is compromised by increased intestinal epithelial cell death and decreased proliferation. Gut immunity is impaired with simultaneous activation of maladaptive pro- and anti-inflammatory signals leading to both tissue damage and susceptibility to infections. Additionally, splanchnic vasoconstriction leads to decreased blood flow with local ischemic changes. Together, these interrelated elements of gastrointestinal dysfunction drive and then perpetuate multi-organ dysfunction syndrome. Despite the clear importance of maintaining gut homeostasis, there are very few reliable measures of gut function in critical illness. Further, while multiple therapeutic strategies have been proposed, most have not been shown to conclusively demonstrate benefit, and care is still largely supportive. The key role of the gut in critical illness was the subject of the tenth Perioperative Quality Initiative meeting, a conference to summarize the current state of the literature and identify key knowledge gaps for future study. This review is the product of that conference.

Single-cell transcriptomics identify a novel macrophage population associated with bone invasion in pituitary neuroendocrine tumors

BACKGROUND

Bone-invasive Pituitary Neuroendocrine Tumors (BI PitNETs) epitomize an aggressive subtype of pituitary tumors characterized by bone invasion, culminating in extensive skull base bone destruction and fragmentation. This infiltration poses a significant surgical risk due to potential damage to vital nerves and arteries. However, the mechanisms underlying bone invasion caused by PitNETs remain elusive, and effective interventions for PitNET-induced bone invasion are lacking in clinical practice.

METHODS

In this study, we performed single-cell (n = 87,287) RNA sequencing on 10 cases of bone-invasive PitNETs and 5 cases of non-bone-invasion PitNETs (Non-BI PitNETs). We identified various cell types and determined their interactions through cell-cell communication analysis, which was further validated experimentally.

RESULTS

We identified a novel TNF-α+ TAM macrophage subset. BI PitNETs showed increased IL-34 secretion, impacting TNF-α+ TAMs via the IL34/CSF1R axis, leading to TNF-α production. TNF-α+ TAMs, in turn, communicate with CD14+ monocytes to promote their differentiation into osteoclasts and leading to bone invasion. In addition, we defined a gene signature for TNF-α+ TAM to guide the clinical prognosis prediction of BI PitNETs.

CONCLUSIONS

Our study elucidates the tumor microenvironment changes in bone invasion and identifies the critical role of TNF-α+ TAMs in promoting bone invasion of PitNETs, laying a foundation for developing new molecular markers or therapeutic agents targeting BI PitNETs.

Ribosome profiling and single-cell RNA sequencing identify the unfolded protein response as a key regulator of pigeon lactation

Pigeons and certain other avian species produce a milk-like secretion in their crop sacs to nourish offspring, yet the detailed processes involved are not fully elucidated. This study investigated the crop sacs of 225-day-old unpaired non-lactating male pigeons (MN) and males initiating lactation on the first day after incubation (ML). Using RNA sequencing, ribosome profiling, and single-cell transcriptome sequencing (scRNA-seq), we identified a significant up-regulation of genes associated with ribosome assembly and protein synthesis in ML compared to MN. Results from scRNA-seq analysis identified 12 distinct cell types and 22 clusters, with secretory epithelial cells (SECs) exhibiting marked expression of plasma cell markers, including IGLL1 and MZB1. RNA fluorescence in situ hybridization (RNA FISH) and IgY quantification confirmed the critical role of SECs in producing endogenous IgY during lactation. We propose that fibroblast-derived BAFF signals activate SECs, mimicking B cell transformation and enhancing protein production through the unfolded protein response (UPR). These findings shed light on the cellular dynamics of pigeon milk production and contribute to a broader understanding of avian biology.

Akkermansia muciniphila exacerbates acute radiation-induced intestinal injury by depleting mucin and enhancing inflammation

Dysbiosis of gut microbiota plays a crucial role in acute radiation-induced intestinal injury. However, studies on the influence of gut microbiota on acute radiation-induced intestinal injury are inconsistent. In this study, we established an acute radiation-induced intestinal injury mouse model and performed fecal microbiota transplantation to explore the role of the gut microbiota in acute radiation-induced intestinal injury. We observed a significant increase in Akkermansia muciniphila following irradiation, whereas fecal microbiota transplantation effectively reduced A. muciniphila levels. Contrary to expectations, A. muciniphila supplementation increased acute radiation-induced intestinal injury and mortality. Mechanistically, postradiation A. muciniphila upregulates mucin metabolism genes and consumes mucin, thinning the mucosal barrier and promoting the adhesion and translocation of potential pathogens to epithelial cells, thus exacerbating acute radiation-induced intestinal injury. This enables A. muciniphila to use mucin as an energy source. Additionally, A. muciniphila increases the inflammatory macrophage changes and secretion of inflammatory cytokines, leading to a decrease in epithelial stem cell density and inhibition of goblet cell differentiation, further exacerbating acute radiation-induced intestinal injury. Our findings suggest that in certain intestinal environments, the addition of A. muciniphila may worsen radiation-induced intestinal damage; thus, alternative approaches to reverse the dysbiosis associated with radiotherapy should be explored.

The effect of ionizing radiation on testicular interstitial stromal cells

Purpose

Testis is one of the most radiosensitive tissues. Interstitial stromal cells play a supportive role in male fertility, but radiation-induced damage to those cells has not yet been well understood. We aimed to investigate radiation-induced changes in interstitial stromal cells in the testis.

Methods

Adult male C57BL/6N mice (8 weeks) received a single pelvic exposure to a relatively high dose (1 Gy) or a very high dose (8 Gy) X-ray. We collected the testicular tissues for evaluation at 1, 9, and 60 days after irradiation.

Results

We detected a recoverable moderate degeneration of seminiferous tubules after 1 Gy exposure but an irreversible severe damage to the testis after 8 Gy exposure. Immunostaining results revealed that 1 Gy exposure induced DNA damage at day 1, upregulated intratubular GDNF at days 1 and 9, upregulated FGF at all time points, and upregulated CSF-1R at day 9. In contrast, 8 Gy exposure induced DNA damage at days 1 and 9, upregulated intratubular GDNF at days 1 and 9, downregulated CD105 at day 60, and upregulated FGF at all time points.

Conclusion

Radiation-induced dynamic changes to interstitial stromal cells in the testis. Upregulated interstitial CSF-1R and FGF2 may support spermatogenesis recovery after high-dose radiation.

Wild-type bone marrow cells repopulate tissue resident macrophages and reverse the impacts of homozygous CSF1R mutation

Adaptation to existence outside the womb is a key event in the life of a mammal. The absence of macrophages in rats with a homozygous mutation in the colony-stimulating factor 1 receptor (Csf1r) gene (Csf1rko) severely compromises pre-weaning somatic growth and maturation of organ function. Transfer of wild-type bone marrow cells (BMT) at weaning rescues tissue macrophage populations permitting normal development and long-term survival. To dissect the phenotype and function of macrophages in postnatal development, we generated transcriptomic profiles of all major organs of wild-type and Csf1rko rats at weaning and in selected organs following rescue by BMT. The transcriptomic profiles revealed subtle effects of macrophage deficiency on development of all major organs. Network analysis revealed a common signature of CSF1R-dependent resident tissue macrophages that includes the components of complement C1Q (C1qa/b/c genes). Circulating C1Q was almost undetectable in Csf1rko rats and rapidly restored to normal levels following BMT. Tissue-specific macrophage signatures were also identified, notably including sinus macrophage populations in the lymph nodes. Their loss in Csf1rko rats was confirmed by immunohistochemical localisation of CD209B (SIGNR1). By 6-12 weeks, Csf1rko rats succumb to emphysema-like pathology associated with the selective loss of interstitial macrophages and granulocytosis. This pathology was reversed by BMT. Along with physiological rescue, BMT precisely regenerated the abundance and expression profiles of resident macrophages. The exception was the brain, where BM-derived microglia-like cells had a distinct expression profile compared to resident microglia. In addition, the transferred BM failed to restore blood monocyte or CSF1R-positive bone marrow progenitors. These studies provide a model for the pathology and treatment of CSF1R mutations in humans and the innate immune deficiency associated with prematurity.

Effects of Intestinal M Cells on Intestinal Barrier and Neuropathological Properties in an AD Mouse Model

Intestinal microfold cells (M cells) play a critical role in the immune response of the intestinal mucosa by actively taking up antigens, facilitating antigen presentation to immune cells, and promoting the production of secretory immunoglobulin A by B cells. Despite their known important functions in the gut, the effect of M cells on the central nervous system remains unclear. We investigated the expression of M cell-related factor genes and protein levels in Peyer's patches (PPs) of 3-month-old and 9-month-old APP/PS1 mice, as well as the expression of intestinal barrier proteins in the ileum and colon of these mice. Furthermore, we employed intestinal M cell conditional ablation mice (i.e., RankΔIEC mice) to assess the influence of M cells on the intestinal barrier and Alzheimer's disease (AD)-like behavioral and pathological features. Our findings revealed that compared to wild-type mice, APP/PS1 mice showed altered M cell-related genes and disrupted intestinal barriers. In addition, there is a significant decrease in glycoprotein 2 (GP2) mRNA levels in the PPs of 3-month-old APP/PS1 mice, with the relative expression of GP2 mRNA tending to zero. Parameters related to the intestinal barrier (IgA, MUC2, Claudin-5, ZO-1) were significantly downregulated in both 3-month-old and 9-month-old APP/PS1 mice compared to wild-type controls, and the differences were more pronounced in the 9-month-old mice. Moreover, M cell ablation in APP/PS1 mice (i.e., APP/PS1ΔMC mice) resulted in more severe intestinal barrier destruction. Notably, we observed through water maze experiments that APP/PS1ΔMC mice at 6 months of age exhibited significantly poorer spatial learning memory compared to APP/PS1 mice. And the neuropathological alterations were also observed in APP/PS1ΔMC mice at 6 months of age that when intestinal M cells are damaged in APP/PS1 mice, brain microglia are activated, Tau phosphorylation is exacerbated, and the number of neurons is reduced. Our results suggest for the first time that the absence of intestinal M cells might further aggravate intestinal leakage, lead to neuropathological damage, and subsequently cause the impairment of learning memory ability in AD mice. Our research highlights the impact of intestinal M cells on the intestinal barrier and AD neuropathogenesis in AD mouse model.

Impact of T-2 toxin on intestinal inflammation and transcriptional regulation of inflammatory response in mouse macrophages

T-2 toxin, a fungal secondary metabolite produced by toxigenic Fusarium species, poses a significant threat to grain food and feed due to its potential to cause intestinal inflammation in livestock and poultry. Macrophages play a crucial role as integral components of the body's immune system during intestinal inflammation. This study aimed to elucidate the mechanism behind the inflammatory response triggered by T-2 toxin in macrophages. Compared to the control group, gavage administration of T-2 toxin (0.33, 1, and 4 mg kg-1) led to a decrease in body weight and feed intake, along with histopathological alterations in the colon of mice. In addition, T-2 toxin induced the upregulation of macrophage-derived cytokines like IL-1β, IL-6, and TNF-α, as well as a rise in the population of F4/80+ macrophages in the colon. T-2 toxin also led to the upregulation of IL-1β, IL-6, and TNF-α in mouse bone marrow-derived macrophages (BMDMs). Furthermore, the transcriptomic analysis of BMDMs exposed to T-2 toxin (10 nM) identified the "TNF signaling pathway," "Lipid and atherosclerosis," "Epstein-Barr virus infection," "MAPK signaling pathway," and the "NF-kappa B signaling pathway" as the top five significantly enriched pathways. Subsequently, twelve inflammation-related genes were randomly chosen for validation through quantitative reverse transcription PCR (RT-qPCR), with the results corroborating those from the transcriptomic analysis. The comprehensive analysis of transcriptome data highlights the activation of several signaling pathways associated with the inflammatory response following T-2 toxin-induced BMDMs, offering potential therapeutic targets for the prevention and treatment of T-2 toxin-induced intestinal inflammation.

Wall of Resilience: How the Intestinal Epithelium Prevents Inflammatory Onslaught in the Gut

The intestinal epithelium forms the boundary between the intestinal immune system in the lamina propria and the outside world, the intestinal lumen, which contains a diverse array of microbial and environmental antigens. Composed of specialized cells, this epithelial monolayer has an exceptional turnover rate. Differentiated epithelial cells are released into the intestinal lumen within a few days, at the villus tip, a process that requires strict regulation. Dysfunction of the epithelial barrier increases the intestinal permeability and paves the way for luminal antigens to pass into the intestinal serosa. Stem cells at the bottom of Lieberkühn crypts provide a constant supply of mature epithelial cells. Differentiated intestinal epithelial cells exhibit a diverse array of mechanisms that enable communication with surrounding cells, fortification against microorganisms, and orchestration of nutrient absorption and hormonal balance. Furthermore, tight junctions regulate paracellular permeability properties, and their disruption can lead to an impairment of the intestinal barrier, allowing inflammation to develop or further progress. Intestinal epithelial cells provide a communication platform through which they maintain homeostasis with a spectrum of entities including immune cells, neuronal cells, and connective tissue cells. This homeostasis can be disrupted in disease, such as inflammatory bowel disease. Patients suffering from inflammatory bowel disease show an impaired gut barrier, dysregulated cellular communication, and aberrant proliferation and demise of cells. This review summarizes the individual cellular and molecular mechanisms pivotal for upholding the integrity of the intestinal epithelial barrier and shows how these can be disrupted in diseases, such as inflammatory bowel disease.

Insights into CSF-1R Expression in the Tumor Microenvironment

The colony-stimulating factor 1 receptor (CSF-1R) plays a pivotal role in orchestrating cellular interactions within the tumor microenvironment (TME). Although the CSF-1R has been extensively studied in myeloid cells, the expression of this receptor and its emerging role in other cell types in the TME need to be further analyzed. This review explores the multifaceted functions of the CSF-1R across various TME cellular populations, including tumor-associated macrophages (TAMs), myeloid-derived suppressor cells (MDSCs), dendritic cells (DCs), cancer-associated fibroblasts (CAFs), endothelial cells (ECs), and cancer stem cells (CSCs). The activation of the CSF-1R by its ligands, colony-stimulating factor 1 (CSF-1) and Interleukin-34 (IL-34), regulates TAM polarization towards an immunosuppressive M2 phenotype, promoting tumor progression and immune evasion. Similarly, CSF-1R signaling influences MDSCs to exert immunosuppressive functions, hindering anti-tumor immunity. In DCs, the CSF-1R alters antigen-presenting capabilities, compromising immune surveillance against cancer cells. CSF-1R expression in CAFs and ECs regulates immune modulation, angiogenesis, and immune cell trafficking within the TME, fostering a pro-tumorigenic milieu. Notably, the CSF-1R in CSCs contributes to tumor aggressiveness and therapeutic resistance through interactions with TAMs and the modulation of stemness features. Understanding the diverse roles of the CSF-1R in the TME underscores its potential as a therapeutic target for cancer treatment, aiming at disrupting pro-tumorigenic cellular crosstalk and enhancing anti-tumor immune responses.

CSF1 is expressed by the intestinal epithelial cells to regulate Mφ macrophages and maintain epithelial homeostasis and is downregulated in neonates with necrotizing enterocolitis

BACKGROUND

Colony stimulating factor 1 (CSF1) is generally expressed by immune cells in response to pro-inflammatory stimuli. The CSF1 receptor (CSFR) is activated by CSF1, and plays a key role in macrophage homeostasis. Furthermore, the CSF1R+ macrophages maintain homeostasis in the intestinal epithelium. The aim of this study was to explore the functions of CSF1-expressing and CSF1R+ macrophages in necrotizing enterocolitis (NEC), which commonly affects the ileum of neonates.

METHODS

In-situ CSF1 expression in the intestines of neonates with NEC or intestinal atresia (n = 4 each) was detected by immunofluorescence staining. The CSF1 levels in the intestinal crypt-derived organoid cultures were measured by ELISA. Peripheral blood monocyte-derived Mφ macrophages were co-cultured with the organoids and stimulated with lipopolysaccharide (LPS) to mimic the inflamed state of the ileum in NEC patients.

RESULTS

CSF1 was expressed in the intestinal epithelial cells of the fetal and neonatal samples, but suppressed in the NEC samples. Furthermore, CSF1 expression was downregulated in the intestinal crypt-derived organoids by LPS. CSF1R+ macrophages were detected near the intestinal crypts in the non-inflamed intestines but were absent in tissues obtained from pediatric NEC patients. Peripheral blood monocyte-derived macrophages promoted intestinal organoid proliferation in vitro following CSF1 stimulation. Finally, low concentrations of LPS slightly enhanced the proliferation of organoids co-cultured with the macrophages, whereas higher doses had a significant inhibitory effect.

CONCLUSIONS

Intestinal epithelial cells express CSF1 to regulate the resident macrophages, maintain epithelial homeostasis, and resist infection. The abundant CSF1R+ macrophages in the fetal intestine may overexpress TNF-α upon activation of the TLR4/NF-κB pathway, resulting in epithelial damage and NEC induction.

Huang Lian Jie Du decoction attenuated colitis via suppressing the macrophage Csf1r/Src pathway and modulating gut microbiota

Introduction

Ulcerative colitis, a subtype of chronic inflammatory bowel disease (IBD), is characterized by relapsing colonic inflammation and ulcers. The traditional Chinese herbal formulation Huang Lian Jie Du (HLJD) decoction is used clinically to treat diarrhea and colitis. However, the mechanisms associated with the effects of treatment remain unclear. This study aims to elucidate the molecular mechanistic effects of HLJD formulation on colitis.

Methods

Chronic colitis in mice was induced by adding 1% dextran sulfate sodium (DSS) to their drinking water continuously for 8 weeks, and HLJD decoction at the doses of 2 and 4 g/kg was administered orally to mice daily from the second week until experimental endpoint. Stool consistency scores, blood stool scores, and body weights were recorded weekly. Disease activity index (DAI) was determined before necropsy, where colon tissues were collected for biochemical analyses. In addition, the fecal microbiome of treated mice was characterized using 16S rRNA amplicon sequencing.

Results

HLJD decoction at doses of 2 and 4 g/kg relieved DSS-induced chronic colitis in mice by suppressing inflammation through compromised macrophage activity in colonic tissues associated with the colony-stimulating factor 1 receptor (Csf1r)/Src pathway. Furthermore, the HLJD formula could modify the gut microbiota profile by decreasing the abundance of Bacteroides, Odoribacter, Clostridium_sensu_stricto_1, and Parasutterella. In addition, close correlations between DAI, colon length, spleen weight, and gut microbiota were identified.

Discussion

Our findings revealed that the HLJD formula attenuated DSS-induced chronic colitis by reducing inflammation via Csf1r/Src-mediated macrophage infiltration, as well as modulating the gut microbiota profile.

Neuroimmune Crossroads: The Interplay of the Enteric Nervous System and Intestinal Macrophages in Gut Homeostasis and Disease

A defining unique characteristic of the gut immune system is its ability to respond effectively to foreign pathogens while mitigating unnecessary inflammation. Intestinal macrophages serve as the cornerstone of this balancing act, acting uniquely as both the sword and shield in the gut microenvironment. The GI tract is densely innervated by the enteric nervous system (ENS), the intrinsic nervous system of the gut. Recent advances in sequencing technology have increasingly suggested neuroimmune crosstalk as a critical component for homeostasis both within the gut and in other tissues. Here, we systematically review the ENS-macrophage axis. We focus on the pertinent molecules produced by the ENS, spotlight the mechanistic contributions of intestinal macrophages to gut homeostasis and inflammation, and discuss both existing and potential strategies that intestinal macrophages use to integrate signals from the ENS. This review aims to elucidate the complex molecular basis governing ENS-macrophage signaling, highlighting their cooperative roles in sustaining intestinal health and immune equilibrium.

Tyrosine kinases: multifaceted receptors at the intersection of several neurodegenerative disease-associated processes

Tyrosine kinases (TKs) are catalytic enzymes activated by auto-phosphorylation that function by phosphorylating tyrosine residues on downstream substrates. Tyrosine kinase inhibitors (TKIs) have been heavily exploited as cancer therapeutics, primarily due to their role in autophagy, blood vessel remodeling and inflammation. This suggests tyrosine kinase inhibition as an appealing therapeutic target for exploiting convergent mechanisms across several neurodegenerative disease (NDD) pathologies. The overlapping mechanisms of action between neurodegeneration and cancer suggest that TKIs may play a pivotal role in attenuating neurodegenerative processes, including degradation of misfolded or toxic proteins, reduction of inflammation and prevention of fibrotic events of blood vessels in the brain. In this review, we will discuss the distinct roles that select TKs have been shown to play in various disease-associated processes, as well as identify TKs that have been explored as targets for therapeutic intervention and associated pharmacological agents being investigated as treatments for NDDs.

Identification of crosstalk genes and immune characteristics between Alzheimer's disease and atherosclerosis

Background

Advancements in modern medicine have extended human lifespan, but they have also led to an increase in age-related diseases such as Alzheimer's disease (AD) and atherosclerosis (AS). Growing research evidence indicates a close connection between these two conditions.

Methods

We downloaded four gene expression datasets related to AD and AS from the Gene Expression Omnibus (GEO) database (GSE33000, GSE100927, GSE44770, and GSE43292) and performed differential gene expression (DEGs) analysis using the R package "limma". Through Weighted gene correlation network analysis (WGCNA), we selected the gene modules most relevant to the diseases and intersected them with the DEGs to identify crosstalk genes (CGs) between AD and AS. Subsequently, we conducted functional enrichment analysis of the CGs using DAVID. To screen for potential diagnostic genes, we applied the least absolute shrinkage and selection operator (LASSO) regression and constructed a logistic regression model for disease prediction. We established a protein-protein interaction (PPI) network using STRING (https://cn.string-db.org/) and Cytoscape and analyzed immune cell infiltration using the CIBERSORT algorithm. Additionally, NetworkAnalyst (http://www.networkanalyst.ca) was utilized for gene regulation and interaction analysis, and consensus clustering was employed to determine disease subtypes. All statistical analyses and visualizations were performed using various R packages, with a significance level set at p<0.05.

Results

Through intersection analysis of disease-associated gene modules identified by DEGs and WGCNA, we identified a total of 31 CGs co-existing between AD and AS, with their biological functions primarily associated with immune pathways. LASSO analysis helped us identify three genes (C1QA, MT1M, and RAMP1) as optimal diagnostic CGs for AD and AS. Based on this, we constructed predictive models for both diseases, whose accuracy was validated by external databases. By establishing a PPI network and employing four topological algorithms, we identified four hub genes (C1QB, CSF1R, TYROBP, and FCER1G) within the CGs, closely related to immune cell infiltration. NetworkAnalyst further revealed the regulatory networks of these hub genes. Finally, defining C1 and C2 subtypes for AD and AS respectively based on the expression profiles of CGs, we found the C2 subtype exhibited immune overactivation.

Conclusion

This study utilized gene expression matrices and various algorithms to explore the potential links between AD and AS. The identification of CGs revealed interactions between these two diseases, with immune and inflammatory imbalances playing crucial roles in their onset and progression. We hope these findings will provide valuable insights for future research on AD and AS.

L-Wnk1 Deletion in Smooth Muscle Cells Causes Aortitis and Inflammatory Shift

BACKGROUND

The long isoform of the Wnk1 (with-no-lysine [K] kinase 1) is a ubiquitous serine/threonine kinase, but its role in vascular smooth muscle cells (VSMCs) pathophysiology remains unknown.

METHODS

AngII (angiotensin II) was infused in Apoe-/- to induce experimental aortic aneurysm. Mice carrying an Sm22-Cre allele were cross-bred with mice carrying a floxed Wnk1 allele to specifically investigate the functional role of Wnk1 in VSMCs.

RESULTS

Single-cell RNA-sequencing of the aneurysmal abdominal aorta from AngII-infused Apoe-/- mice revealed that VSMCs that did not express Wnk1 showed lower expression of contractile phenotype markers and increased inflammatory activity. Interestingly, WNK1 gene expression in VSMCs was decreased in human abdominal aortic aneurysm. Wnk1-deficient VSMCs lost their contractile function and exhibited a proinflammatory phenotype, characterized by the production of matrix metalloproteases, as well as cytokines and chemokines, which contributed to local accumulation of inflammatory macrophages, Ly6Chi monocytes, and γδ T cells. Sm22Cre+Wnk1lox/lox mice spontaneously developed aortitis in the infrarenal abdominal aorta, which extended to the thoracic area over time without any negative effect on long-term survival. AngII infusion in Sm22Cre+Wnk1lox/lox mice aggravated the aortic disease, with the formation of lethal abdominal aortic aneurysms. Pharmacological blockade of γδ T-cell recruitment using neutralizing anti-CXCL9 (anti-CXC motif chemokine ligand 9) antibody treatment, or of monocyte/macrophage using Ki20227, a selective inhibitor of CSF1 receptor, attenuated aortitis. Wnk1 deletion in VSMCs led to aortic wall remodeling with destruction of elastin layers, increased collagen content, and enhanced local TGF-β (transforming growth factor-beta) 1 expression. Finally, in vivo TGF-β blockade using neutralizing anti-TGF-β antibody promoted saccular aneurysm formation and aorta rupture in Sm22 Cre+ Wnk1lox/lox mice but not in control animals.

CONCLUSION

Wnk1 is a key regulator of VSMC function. Wnk1 deletion promotes VSMC phenotype switch toward a pathogenic proinflammatory phenotype, orchestrating deleterious vascular remodeling and spontaneous severe aortitis in mice.

Monocyte-macrophages modulate intestinal homeostasis in inflammatory bowel disease

BACKGROUND

Monocytes and macrophages play an indispensable role in maintaining intestinal homeostasis and modulating mucosal immune responses in inflammatory bowel disease (IBD). Although numerous studies have described macrophage properties in IBD, the underlying mechanisms whereby the monocyte-macrophage lineage modulates intestinal homeostasis during gut inflammation remain elusive.

MAIN BODY

In this review, we decipher the cellular and molecular mechanisms governing the generation of intestinal mucosal macrophages and fill the knowledge gap in understanding the origin, maturation, classification, and functions of mucosal macrophages in intestinal niches, particularly the phagocytosis and bactericidal effects involved in the elimination of cell debris and pathogens. We delineate macrophage-mediated immunoregulation in the context of producing pro-inflammatory and anti-inflammatory cytokines, chemokines, toxic mediators, and macrophage extracellular traps (METs), and participating in the modulation of epithelial cell proliferation, angiogenesis, and fibrosis in the intestine and its accessory tissues. Moreover, we emphasize that the maturation of intestinal macrophages is arrested at immature stage during IBD, and the deficiency of MCPIP1 involves in the process via ATF3-AP1S2 signature. In addition, we confirmed the origin potential of IL-1B+ macrophages and defined C1QB+ macrophages as mature macrophages. The interaction crosstalk between the intestine and the mesentery has been described in this review, and the expression of mesentery-derived SAA2 is upregulated during IBD, which contributes to immunoregulation of macrophage. Moreover, we also highlight IBD-related susceptibility genes (e.g., RUNX3, IL21R, GTF2I, and LILRB3) associated with the maturation and functions of macrophage, which provide promising therapeutic opportunities for treating human IBD.

CONCLUSION

In summary, this review provides a comprehensive, comprehensive, in-depth and novel description of the characteristics and functions of macrophages in IBD, and highlights the important role of macrophages in the molecular and cellular process during IBD.

Nur77 as a novel regulator of Paneth cell differentiation and function

Serving as a part of intestinal innate immunity, Paneth cells play an important role in intestinal homeostasis maintenance via their multiple functions. However, the regulation of Paneth cells has been proven to be complex and diverse. Here, we identified nuclear receptor Nur77 as a novel regulator of Paneth cell differentiation and function. Nur77 deficiency led to the loss of Paneth cells in murine ileal crypts. Intestinal tissues or organoids with Nur77 deficiency exhibited the impaired intestinal stem cell niche and failed to enhance antimicrobial peptide expression after Paneth cell degranulation. The defects in Paneth cells and antimicrobial peptides in Nur7-/- mice led to intestinal microbiota disorders. Nur77 deficiency rendered postnatal mice susceptible to necrotizing enterocolitis. Mechanistically, Nur77 transcriptionally inhibited Dact1 expression to activate Wnt signaling activity, thus promoting Paneth cell differentiation and function. Taken together, our data suggest the regulatory role of Nur77 in Paneth cell differentiation and function and reveal a novel Dact1-mediated Wnt inhibition mechanism in Paneth cell development.

Keratinocytes drive the epithelial hyperplasia key to sea lice resistance in coho salmon

BACKGROUND

Salmonid species have followed markedly divergent evolutionary trajectories in their interactions with sea lice. While sea lice parasitism poses significant economic, environmental, and animal welfare challenges for Atlantic salmon (Salmo salar) aquaculture, coho salmon (Oncorhynchus kisutch) exhibit near-complete resistance to sea lice, achieved through a potent epithelial hyperplasia response leading to rapid louse detachment. The molecular mechanisms underlying these divergent responses to sea lice are unknown.

RESULTS

We characterized the cellular and molecular responses of Atlantic salmon and coho salmon to sea lice using single-nuclei RNA sequencing. Juvenile fish were exposed to copepodid sea lice (Lepeophtheirus salmonis), and lice-attached pelvic fin and skin samples were collected 12 h, 24 h, 36 h, 48 h, and 60 h after exposure, along with control samples. Comparative analysis of control and treatment samples revealed an immune and wound-healing response that was common to both species, but attenuated in Atlantic salmon, potentially reflecting greater sea louse immunomodulation. Our results revealed unique but complementary roles of three layers of keratinocytes in the epithelial hyperplasia response leading to rapid sea lice rejection in coho salmon. Our results suggest that basal keratinocytes direct the expansion and mobility of intermediate and, especially, superficial keratinocytes, which eventually encapsulate the parasite.

CONCLUSIONS

Our results highlight the key role of keratinocytes in coho salmon's sea lice resistance and the diverged biological response of the two salmonid host species when interacting with this parasite. This study has identified key pathways and candidate genes that could be manipulated using various biotechnological solutions to improve Atlantic salmon sea lice resistance.

Cell competition in primary and metastatic colorectal cancer

Adult tissues set the scene for a continuous battle between cells, where a comparison of cellular fitness results in the elimination of weaker "loser" cells. This phenomenon, named cell competition, is beneficial for tissue integrity and homeostasis. In fact, cell competition plays a crucial role in tumor suppression, through elimination of early malignant cells, as part of Epithelial Defense Against Cancer. However, it is increasingly apparent that cell competition doubles as a tumor-promoting mechanism. The comparative nature of cell competition means that mutational background, proliferation rate and polarity all factor in to determine the outcome of these processes. In this review, we explore the intricate and context-dependent involvement of cell competition in homeostasis and regeneration, as well as during initiation and progression of primary and metastasized colorectal cancer. We provide a comprehensive overview of molecular and cellular mechanisms governing cell competition and its parallels with regeneration.

M1 and M2 Macrophages Differentially Regulate Colonic Crypt Renewal

BACKGROUND

The colonic epithelium is the most rapidly renewing tissue in the body and is organized into a single cell layer of invaginations called crypts. Crypt renewal occurs through Lgr5 + gut stem cells situated at the crypt base, which divide, produce daughter cells that proliferate, migrate, differentiate into all the cells required for normal gut function, and are finally shed into the crypt lumen. In health, this rapid renewal helps maintain barrier function next to the hostile gut microbial luminal environment. Inflammation results in an influx of immune cells including inflammatory M1 macrophages into the gut mucosa next to the crypt epithelium, but the direct effect of macrophages on crypt regeneration and renewal are poorly understood.

METHODS

Using an in vitro macrophage-crypt coculture model, we show that homeostatic M2 macrophages and inflammatory M1 macrophages confer different effects on the crypt epithelium.

RESULTS

Both M1 and M2 increase crypt cell proliferation, with M2 macrophages requiring physical contact with the crypt epithelium, whereas M1 macrophages exert their effect through a secreted factor. Only M1 macrophages reduce goblet and Tuft cell numbers and increase Lgr5 + crypt stem cell numbers, all dependent on physical contact with the crypt epithelium. Further studies showed that M1 macrophages increase the Wnt signaling pathways cyclin D1 and LEF1 through physical contact rather than a secreted factor.

CONCLUSIONS

These findings highlight the importance of understanding distinct cellular interactions and direct dialogue between cells and increase our understanding of the contribution of different immune cell subtypes on crypt cell biology during inflammation.

Efficacy of mesenchymal stem cells in treating tracheoesophageal fistula via the TLR4/NF-κb pathway in beagle macrophages

Background

Tracheoesophageal fistula (TEF) remains a rare but significant clinical challenge, mainly due to the absence of established, effective treatment approaches. The current focus of therapeutic strategy is mainly on fistula closure. However, this approach often misses important factors, such as accelerating fistula contraction and fostering healing processes, which significantly increases the risk of disease recurrence.

Methods

In order to investigate if Mesenchymal Stem Cells (MSCs) can enhance fistula repair, developed a TEF model in beagles. Dynamic changes in fistula diameter were monitored by endoscopy. Concurrently, we created a model of LPS-induced macrophage to replicate the inflammatory milieu typical in TEF. In addition, the effect of MSC supernatant on inflammation mitigation was evaluated. Furthermore, we looked at the role of TLR4/NF-κB pathway plays in the healing process.

Results

Our research revealed that the local administration of MSCs significantly accelerated the fistula's healing process. This was demonstrated by a decline in TEF apoptosis and decrease in the production of pro-inflammatory cytokines. Furthermore, in vivo experiments demonstrated that the MSC supernatant was effective in suppressing pro-inflammatory cytokine expression and alleviating apoptosis in LPS-induced macrophages. These therapeutic effects were mainly caused by the suppression of TLR4/NF-κB pathway.

Conclusion

According to this study, MSCs can significantly improve TEF recovery. They achieve this via modulating apoptosis and inflammatory responses, mainly by selectively inhibiting the TLR4/NF-κB pathway.

Advancements of Macrophages Involvement in Pathological Progression of Colitis-Associated Colorectal Cancer and Associated Pharmacological Interventions

Intestinal macrophages play crucial roles in both intestinal inflammation and immune homeostasis. They can adopt two distinct phenotypes, primarily determined by environmental cues. These phenotypes encompass the classically activated pro-inflammatory M1 phenotype, as well as the alternatively activated anti-inflammatory M2 phenotype. In regular conditions, intestinal macrophages serve to shield the gut from inflammatory harm. However, when a combination of genetic and environmental elements influences the polarization of these macrophages, it can result in an M1/M2 macrophage activation imbalance, subsequently leading to a loss of control over intestinal inflammation. This shift transforms normal inflammatory responses into pathological damage within the intestines. In patients with ulcerative colitis-associated colorectal cancer (UC-CRC), disorders related to intestinal inflammation are closely correlated with an imbalance in the polarization of intestinal M1/M2 macrophages. Therefore, reinstating the equilibrium in M1/M2 macrophage polarization could potentially serve as an effective approach to the prevention and treatment of UC-CRC. This paper aims to scrutinize the clinical evidence regarding Chinese medicine (CM) in the treatment of UC-CRC, the pivotal role of macrophage polarization in UC-CRC pathogenesis, and the potential mechanisms through which CM regulates macrophage polarization to address UC-CRC. Our objective is to offer fresh perspectives for clinical application, fundamental research, and pharmaceutical advancement in UC-CRC.

Epithelial-immune cell crosstalk for intestinal barrier homeostasis

The intestinal barrier is mainly formed by a monolayer of epithelial cells, which forms a physical barrier to protect the gut tissues from external insults and provides a microenvironment for commensal bacteria to colonize while ensuring immune tolerance. Moreover, various immune cells are known to significantly contribute to intestinal barrier function by either directly interacting with epithelial cells or by producing immune mediators. Fulfilling this function of the gut barrier for mucosal homeostasis requires not only the intrinsic regulation of intestinal epithelial cells (IECs) but also constant communication with immune cells and gut microbes. The reciprocal interactions between IECs and immune cells modulate mucosal barrier integrity. Dysregulation of barrier function could lead to dysbiosis, inflammation, and tumorigenesis. In this overview, we provide an update on the characteristics and functions of IECs, and how they integrate their functions with tissue immune cells and gut microbiota to establish gut homeostasis.

The intestinal epithelial-macrophage-crypt stem cell axis plays a crucial role in regulating and maintaining intestinal homeostasis

The intestinal tract plays a vital role in both digestion and immunity, making its equilibrium crucial for overall health. This equilibrium relies on the dynamic interplay among intestinal epithelial cells, macrophages, and crypt stem cells. Intestinal epithelial cells play a pivotal role in protecting and regulating the gut. They form vital barriers, modulate immune responses, and engage in pathogen defense and cytokine secretion. Moreover, they supervise the regulation of intestinal stem cells. Macrophages, serving as immune cells, actively influence the immune response through the phagocytosis of pathogens and the release of cytokines. They also contribute to regulating intestinal stem cells. Stem cells, known for their self-renewal and differentiation abilities, play a vital role in repairing damaged intestinal epithelium and maintaining homeostasis. Although research has primarily concentrated on the connections between epithelial and stem cells, interactions with macrophages have been less explored. This review aims to fill this gap by exploring the roles of the intestinal epithelial-macrophage-crypt stem cell axis in maintaining intestinal balance. It seeks to unravel the intricate dynamics and regulatory mechanisms among these essential players. A comprehensive understanding of these cell types' functions and interactions promises insights into intestinal homeostasis regulation. Moreover, it holds potential for innovative approaches to manage conditions like radiation-induced intestinal injury, inflammatory bowel disease, and related diseases.

Macrophage niche imprinting as a determinant of macrophage identity and function

Macrophage niches are the anatomical locations within organs or tissues consisting of various cells, intercellular and extracellular matrix, transcription factors, and signaling molecules that interact to influence macrophage self-maintenance, phenotype, and behavior. The niche, besides physically supporting macrophages, imposes a tissue- and organ-specific identity on the residing and infiltrating monocytes and macrophages. In this review, we give examples of macrophage niches and the modes of communication between macrophages and surrounding cells. We also describe how macrophages, acting against their immune defensive nature, can create a hospitable niche for pathogens and cancer cells.

Regional differences in the ultrastructure of mucosal macrophages in the rat large intestine

We previously clarified the histological characteristics of macrophages in the rat small intestine using serial block-face scanning electron microscopy (SBF-SEM). However, the regional differences in the characteristics of macrophages throughout the large intestine remain unknown. Here, we performed a pilot study to explore the regional differences in the ultrastructure of mucosal macrophages in the large intestine by using SBF-SEM analysis. SBF-SEM analysis conducted on the luminal side of the cecum and descending colon revealed macrophages as amorphous cells possessing abundant lysosomes and vacuoles. Macrophages in the cecum exhibited a higher abundance of lysosomes and a lower abundance of vacuoles than those in the descending colon. Macrophages with many intraepithelial cellular processes were observed beneath the intestinal superficial epithelium in the descending colon. Moreover, macrophages in contact with nerve fibers were more prevalent in the cecum than in the descending colon, and a subset of them surrounded a nerve bundle only in the cecum. In conclusion, the present pilot study suggested that the quantity of some organelles (lysosomes and vacuoles) in macrophages differed between the cecum and the descending colon and that there were some region-specific subsets of macrophages like nerve-associated macrophages in the cecum.

Discrimination of distinct chicken M cell subsets based on CSF1R expression

In mammals, a subset of follicle-associated epithelial (FAE) cells, known as M cells, conduct the transcytosis of antigens across the epithelium into the underlying lymphoid tissues. We previously revealed that M cells in the FAE of the chicken lung, bursa of Fabricius (bursa), and caecum based on the expression of CSF1R. Here, we applied RNA-seq analysis on highly enriched CSF1R-expressing bursal M cells to investigate their transcriptome and identify novel chicken M cell-associated genes. Our data show that, like mammalian M cells, those in the FAE of the chicken bursa also express SOX8, MARCKSL1, TNFAIP2 and PRNP. Immunohistochemical analysis also confirmed the expression of SOX8 in CSF1R-expressing cells in the lung, bursa, and caecum. However, we found that many other mammalian M cell-associated genes such as SPIB and GP2 were not expressed by chicken M cells or represented in the chicken genome. Instead, we show bursal M cells express high levels of related genes such as SPI1. Whereas our data show that bursal M cells expressed CSF1R-highly, the M cells in the small intestine lacked CSF1R and both expressed SOX8. This study offers insights into the transcriptome of chicken M cells, revealing the expression of CSF1R in M cells is tissue-specific.

Intraepithelial lymphocytes promote intestinal regeneration through CD160/HVEM signaling

Chemotherapy and radiotherapy frequently lead to intestinal damage. The mechanisms governing the repair or regeneration of intestinal damage are still not fully elucidated. Intraepithelial lymphocytes (IELs) are the primary immune cells residing in the intestinal epithelial layer. However, whether IELs are involved in intestinal epithelial injury repair remains unclear. Here, we found that IELs rapidly infiltrated the intestinal crypt region and are crucial for the recovery of the intestinal epithelium post-chemotherapy. Interestingly, IELs predominantly promoted intestinal regeneration by modulating the proliferation of transit-amplifying (TA) cells. Mechanistically, the expression of CD160 on IELs allows for interaction with herpes virus entry mediator (HVEM) on the intestinal epithelium, thereby activating downstream nuclear factor kappa (NF-κB) signaling and further promoting intestinal regeneration. Deficiency in either CD160 or HVEM resulted in reduced proliferation of intestinal progenitor cells, impaired intestinal damage repair, and increased mortality following chemotherapy. Remarkably, the adoptive transfer of CD160-sufficient IELs rescued the Rag1 deficient mice from chemotherapy-induced intestinal inflammation. Overall, our study underscores the critical role of IELs in intestinal regeneration and highlights the potential applications of targeting the CD160-HVEM axis for managing intestinal adverse events post-chemotherapy and radiotherapy.

Immune cell-derived signals governing epithelial phenotypes in homeostasis and inflammation

The intestinal epithelium fulfills important physiological functions and forms a physical barrier to the intestinal lumen. Barrier function is regulated by several pathways, and its impairment contributes to the pathogenesis of inflammatory bowel disease (IBD), a chronic inflammatory condition affecting more than seven million people worldwide. Current treatment options specifically target inflammatory mediators and have led to improvement of clinical outcomes; however, a significant proportion of patients experience treatment failure. Pro-repair effects of inflammatory mediators on the epithelium are emerging. In this review we summarize current knowledge on involved epithelial pathways, identify open questions, and put recent findings into clinical perspective, and pro-repair effects. A detailed understanding of epithelial pathways integrating mucosal stimuli in homeostasis and inflammation is crucial for the development of novel, more targeted therapies.

Adaptor molecules mediate negative regulation of macrophage inflammatory pathways: a closer look

Macrophages play a central role in initiating, maintaining, and terminating inflammation. For that, macrophages respond to various external stimuli in changing environments through signaling pathways that are tightly regulated and interconnected. This process involves, among others, autoregulatory loops that activate and deactivate macrophages through various cytokines, stimulants, and other chemical mediators. Adaptor proteins play an indispensable role in facilitating various inflammatory signals. These proteins are dynamic and flexible modulators of immune cell signaling and act as molecular bridges between cell surface receptors and intracellular effector molecules. They are involved in regulating physiological inflammation and also contribute significantly to the development of chronic inflammatory processes. This is at least partly due to their involvement in the activation and deactivation of macrophages, leading to changes in the macrophages' activation/phenotype. This review provides a comprehensive overview of the 20 adaptor molecules and proteins that act as negative regulators of inflammation in macrophages and effectively suppress inflammatory signaling pathways. We emphasize the functional role of adaptors in signal transduction in macrophages and their influence on the phenotypic transition of macrophages from pro-inflammatory M1-like states to anti-inflammatory M2-like phenotypes. This endeavor mainly aims at highlighting and orchestrating the intricate dynamics of adaptor molecules by elucidating the associated key roles along with respective domains and opening avenues for therapeutic and investigative purposes in clinical practice.

Deficiency of inflammation-sensing protein neuropilin-2 in myeloid-derived macrophages exacerbates colitis via NF-κB activation

Neuropilin-2 (NRP2) is a multifunctional protein engaged in the regulation of angiogenesis, lymphangiogenesis, axon guidance, and tumor metastasis, but its function in colitis remains unclear. Here, we found that NRP2 was an inflammation-sensing protein rapidly and dramatically induced in myeloid cells, especially in macrophages, under inflammatory contexts. NRP2 deficiency in myeloid cells exacerbated dextran sulfate sodium salt-induced experimental colitis by promoting polarization of M1 macrophages and colon injury. Mechanistically, NRP2 could be induced via NF-κB activation by TNF-α in macrophages, but exerted an inhibitory effect on NF-κB signaling, forming a negative feedback loop with NF-κB to sense and alleviate inflammation. Deletion of NRP2 in macrophages broke this negative feedback circuit, leading to NF-κB overactivation, inflammatory exacerbation, and more severe colitis. Collectively, these findings reveal inflammation restriction as a role for NRP2 in macrophages under inflammation contexts and suggest that NRP2 in macrophages may relieve inflammation in inflammatory bowel disease. © 2023 The Pathological Society of Great Britain and Ireland.

Role reversals: non-canonical roles for immune and non-immune cells in the gut

The intestine is home to an intertwined network of epithelial, immune, and neuronal cells as well as the microbiome, with implications for immunity, systemic metabolism, and behavior. While the complexity of this microenvironment has long since been acknowledged, recent technological advances have propelled our understanding to an unprecedented level. Notably, the microbiota and non-immune or structural cells have emerged as important conductors of intestinal immunity, and by contrast, cells of both the innate and adaptive immune systems have demonstrated non-canonical roles in tissue repair and metabolism. This review highlights recent works in the following two streams: non-immune cells of the intestine performing immunological functions; and traditional immune cells exhibiting non-immune functions in the gut.

Developmental role of macrophages modeled in human pluripotent stem cell-derived intestinal tissue

Macrophages populate the embryo early in gestation, but their role in development is not well defined. In particular, specification and function of macrophages in intestinal development remain little explored. To study this event in the human developmental context, we derived and combined human intestinal organoid and macrophages from pluripotent stem cells. Macrophages migrate into the organoid, proliferate, and occupy the emerging microanatomical niches of epithelial crypts and ganglia. They also acquire a transcriptomic profile similar to that of fetal intestinal macrophages and display tissue macrophage behaviors, such as recruitment to tissue injury. Using this model, we show that macrophages reduce glycolysis in mesenchymal cells and limit tissue growth without affecting tissue architecture, in contrast to the pro-growth effect of enteric neurons. In short, we engineered an intestinal tissue model populated with macrophages, and we suggest that resident macrophages contribute to the regulation of metabolism and growth of the developing intestine.

Farnesoid X receptor mediates macrophage-intrinsic responses to suppress colitis-induced colon cancer progression

Bile acids (BAs) affect the intestinal environment by ensuring barrier integrity, maintaining microbiota balance, regulating epithelium turnover, and modulating the immune system. As a master regulator of BA homeostasis, farnesoid X receptor (FXR) is severely compromised in patients with inflammatory bowel disease (IBD) and colitis-associated colorectal cancer (CAC). At the front line, gut macrophages react to the microbiota and metabolites that breach the epithelium. We aim to study the role of the BA/FXR axis in macrophages. This study demonstrates that inflammation-induced epithelial abnormalities compromised FXR signaling and altered BAs' profile in a mouse CAC model. Further, gut macrophage-intrinsic FXR sensed aberrant BAs, leading to pro-inflammatory cytokines' secretion, which promoted intestinal stem cell proliferation. Mechanistically, activation of FXR ameliorated intestinal inflammation and inhibited colitis-associated tumor growth, by regulating gut macrophages' recruitment, polarization, and crosstalk with Th17 cells. However, deletion of FXR in bone marrow or gut macrophages escalated the intestinal inflammation. In summary, our study reveals a distinctive regulatory role of FXR in gut macrophages, suggesting its potential as a therapeutic target for addressing IBD and CAC.

The roles of tissue resident macrophages in health and cancer

As integral components of the immune microenvironment, tissue resident macrophages (TRMs) represent a self-renewing and long-lived cell population that plays crucial roles in maintaining homeostasis, promoting tissue remodeling after damage, defending against inflammation and even orchestrating cancer progression. However, the exact functions and roles of TRMs in cancer are not yet well understood. TRMs exhibit either pro-tumorigenic or anti-tumorigenic effects by engaging in phagocytosis and secreting diverse cytokines, chemokines, and growth factors to modulate the adaptive immune system. The life-span, turnover kinetics and monocyte replenishment of TRMs vary among different organs, adding to the complexity and controversial findings in TRMs studies. Considering the complexity of tissue associated macrophage origin, macrophages targeting strategy of each ontogeny should be carefully evaluated. Consequently, acquiring a comprehensive understanding of TRMs' origin, function, homeostasis, characteristics, and their roles in cancer for each specific organ holds significant research value. In this review, we aim to provide an outline of homeostasis and characteristics of resident macrophages in the lung, liver, brain, skin and intestinal, as well as their roles in modulating primary and metastatic cancer, which may inform and serve the future design of targeted therapies.

Cellular and transcriptome signatures unveiled by single-cell RNA-Seq following ex vivo infection of murine splenocytes with Borrelia burgdorferi

Introduction

Lyme disease, the most common tick-borne infectious disease in the US, is caused by a spirochetal pathogen Borrelia burgdorferi (Bb). Distinct host responses are observed in susceptible and resistant strains of inbred of mice following infection with Bb reflecting a subset of inflammatory responses observed in human Lyme disease. The advent of post-genomic methodologies and genomic data sets enables dissecting the host responses to advance therapeutic options for limiting the pathogen transmission and/or treatment of Lyme disease.

Methods

In this study, we used single-cell RNA-Seq analysis in conjunction with mouse genomics exploiting GFP-expressing Bb to sort GFP+ splenocytes and GFP- bystander cells to uncover novel molecular and cellular signatures that contribute to early stages of immune responses against Bb.

Results

These data decoded the heterogeneity of splenic neutrophils, macrophages, NK cells, B cells, and T cells in C3H/HeN mice in response to Bb infection. Increased mRNA abundance of apoptosis-related genes was observed in neutrophils and macrophages clustered from GFP+ splenocytes. Moreover, complement-mediated phagocytosis-related genes such as C1q and Ficolin were elevated in an inflammatory macrophage subset, suggesting upregulation of these genes during the interaction of macrophages with Bb-infected neutrophils. In addition, the role of DUSP1 in regulating the expression of Casp3 and pro-inflammatory cytokines Cxcl1, Cxcl2, Il1b, and Ccl5 in Bb-infected neutrophils were identified.

Discussion

These findings serve as a growing catalog of cell phenotypes/biomarkers among murine splenocytes that can be exploited for limiting spirochetal burden to limit the transmission of the agent of Lyme disease to humans via reservoir hosts.

A novel role of TGFBI in macrophage polarization and macrophage-induced pancreatic cancer growth and therapeutic resistance

Tumor-associated macrophages (TAMs), as a major and essential component of tumor microenvironment (TME), play a critical role in orchestrating pancreatic cancer (PaC) tumorigenesis from initiation to angiogenesis, growth, and systemic dissemination, as well as immunosuppression and resistance to chemotherapy and immunotherapy; however, the critical intrinsic factors responsible for TAMs reprograming and function remain to be identified. By performing single-cell RNA sequencing, transforming growth factor-beta-induced protein (TGFBI) was identified as TAM-producing factor in murine PaC tumors. TAMs express TGFBI in human PaC and TGFBI expression is positively related with human PaC growth. By inducing TGFBI loss-of-function in macrophage (MΦs) in vitro with siRNA and in vivo with Cre-Lox strategy in our developed TGFBI-floxed mice, we demonstrated disruption of TGFBI not only inhibited MΦ polarization to M2 phenotype and MΦ-mediated stimulation on PaC growth, but also significantly improved anti-tumor immunity, sensitizing PaC to chemotherapy in association with regulation of fibronectin 1, Cxcl10, and Ccl5. Our studies suggest that targeting TGFBI in MΦ can develop an effective therapeutic intervention for highly lethal PaC.

Crosstalk between gut microbiota and gut resident macrophages in inflammatory bowel disease

Macrophages residing in the gut maintain gut homeostasis by orchestrating patho-gens and innocuous antigens. A disturbance in macrophages leads to gut inflamma-tion, causing conditions such as inflammatory bowel disease (IBD). Macrophages ex-hibit remarkable plasticity, as they are sensitive to various signals in the tissue micro-environment. During the recent decades, gut microbiota has been highlighted refer-ring to their critical roles in immunity response. Microbiome-derived metabolites and products can interact with macrophages to participate in the progression of IBD. In this review, we describe recent findings in this field and provide an overview of the current understanding of microbiota-macrophages interactions in IBD, which may lead to the development of new targets and treatment options for patients with IBD.

The multivalency game ruling the biology of immunity

Macrophages play a crucial role in our immune system, preserving tissue health and defending against harmful pathogens. This article examines the diversity of macrophages influenced by tissue-specific functions and developmental origins, both in normal and disease conditions. Understanding the spectrum of macrophage activation states, especially in pathological situations where they contribute significantly to disease progression, is essential to develop targeted therapies effectively. These states are characterized by unique receptor compositions and phenotypes, but they share commonalities. Traditional drugs that target individual entities are often insufficient. A promising approach involves using multivalent systems adorned with multiple ligands to selectively target specific macrophage populations based on their phenotype. Achieving this requires constructing supramolecular structures, typically at the nanoscale. This review explores the theoretical foundation of engineered multivalent nanosystems, dissecting the key parameters governing specific interactions. The goal is to design targeting systems based on distinct cell phenotypes, providing a pragmatic approach to navigating macrophage heterogeneity's complexities for more effective therapeutic interventions.

Anti-inflammatory effect of dental pulp stem cells

Dental pulp stem cells (DPSCs) have received a lot of attention as a regenerative medicine tool with strong immunomodulatory capabilities. The excessive inflammatory response involves a variety of immune cells, cytokines, and has a considerable impact on tissue regeneration. The use of DPSCs for controlling inflammation for the purpose of treating inflammation-related diseases and autoimmune disorders such as supraspinal nerve inflammation, inflammation of the pulmonary airways, systemic lupus erythematosus, and diabetes mellitus is likely to be safer and more regenerative than traditional medicines. The mechanism of the anti-inflammatory and immunomodulatory effects of DPSCs is relatively complex, and it may be that they themselves or some of the substances they secrete regulate a variety of immune cells through inflammatory immune-related signaling pathways. Most of the current studies are still at the laboratory cellular level and animal model level, and it is believed that through the efforts of more researchers, DPSCs/SHED are expected to be transformed into excellent drugs for the clinical treatment of related diseases.

Systemically delivered adipose stromal vascular fraction mitigates radiation-induced gastrointestinal syndrome by immunomodulating the inflammatory response through a CD11b+ cell-dependent mechanism

BACKGROUND

Stromal vascular fraction (SVF) treatment promoted the regeneration of the intestinal epithelium, limiting lethality in a mouse model of radiation-induced gastrointestinal syndrome (GIS). The SVF has a heterogeneous cell composition; the effects between SVF and the host intestinal immunity are still unknown. The specific role of the different cells contained in the SVF needs to be clarified. Monocytes-macrophages have a crucial role in repair and monocyte recruitment and activation are orchestrated by the chemokine receptors CX3CR1 and CCR2.

METHODS

Mice exposed to abdominal radiation (18 Gy) received a single intravenous injection of SVF (2.5 × 106 cells), obtained by enzymatic digestion of inguinal fat tissue, on the day of irradiation. Intestinal immunity and regeneration were evaluated by flow cytometry, RT-PCR and histological analyses.

RESULTS

Using flow cytometry, we showed that SVF treatment modulated intestinal monocyte differentiation at 7 days post-irradiation by very early increasing the CD11b+Ly6C+CCR2+ population in the intestine ileal mucosa and accelerating the phenotype modification to acquire CX3CR1 in order to finally restore the F4/80+CX3CR1+ macrophage population. In CX3CR1-depleted mice, SVF treatment fails to mature the Ly6C-MCHII+CX3CR1+ population, leading to a macrophage population deficit associated with proinflammatory environment maintenance and defective intestinal repair; this impaired SVF efficiency on survival. Consistent with a CD11b+ being involved in SVF-induced intestinal repair, we showed that SVF-depleted CD11b+ treatment impaired F4/80+CX3CR1+macrophage pool restoration and caused loss of anti-inflammatory properties, abrogating stem cell compartment repair and survival.

CONCLUSIONS

These data showed that SVF treatment mitigates the GIS-involving immunomodulatory effect. Cooperation between the monocyte in SVF and the host monocyte defining the therapeutic properties of the SVF is necessary to guarantee the effective action of the SVF on the GIS.

Metabolic support by macrophages sustains colonic epithelial homeostasis

The intestinal epithelium has a high turnover rate and constantly renews itself through proliferation of intestinal crypt cells, which depends on insufficiently characterized signals from the microenvironment. Here, we showed that colonic macrophages were located directly adjacent to epithelial crypt cells in mice, where they metabolically supported epithelial cell proliferation in an mTORC1-dependent manner. Specifically, deletion of tuberous sclerosis complex 2 (Tsc2) in macrophages activated mTORC1 signaling that protected against colitis-induced intestinal damage and induced the synthesis of the polyamines spermidine and spermine. Epithelial cells ingested these polyamines and rewired their cellular metabolism to optimize proliferation and defense. Notably, spermine directly stimulated proliferation of colon epithelial cells and colon organoids. Genetic interference with polyamine production in macrophages altered global polyamine levels in the colon and modified epithelial cell proliferation. Our results suggest that macrophages act as "commensals" that provide metabolic support to promote efficient self-renewal of the colon epithelium.

Interleukin-6 in Traumatic Brain Injury: A Janus-Faced Player in Damage and Repair

Traumatic brain injury (TBI) is a common and often devastating illness, with wide-ranging public health implications. In addition to the primary injury, victims of TBI are at risk for secondary neurological injury by numerous mechanisms. Current treatments are limited and do not target the profound immune response associated with injury. This immune response reflects a convergence of peripheral and central nervous system-resident immune cells whose interaction is mediated in part by a disruption in the blood-brain barrier (BBB). The diverse family of cytokines helps to govern this communication and among these, Interleukin (IL)-6 is a notable player in the immune response to acute neurological injury. It is also a well-established pharmacological target in a variety of other disease contexts. In TBI, elevated IL-6 levels are associated with worse outcomes, but the role of IL-6 in response to injury is double-edged. IL-6 promotes neurogenesis and wound healing in animal models of TBI, but it may also contribute to disruptions in the BBB and the progression of cerebral edema. Here, we review IL-6 biology in the context of TBI, with an eye to clarifying its controversial role and understanding its potential as a target for modulating the immune response in this disease.

Macrophage heterogeneity in the single-cell era: facts and artifacts

In this spotlight, we review technical issues that compromise single-cell analysis of tissue macrophages, including limited and unrepresentative yields, fragmentation and generation of remnants, and activation during tissue disaggregation. These issues may lead to a misleading definition of subpopulations of macrophages and the expression of macrophage-specific transcripts by unrelated cells. Recognition of the technical limitations of single-cell approaches is required in order to map the full spectrum of tissue-resident macrophage heterogeneity and assess its biological significance.

New insights into intestinal macrophages in necrotizing enterocolitis: the multi-functional role and promising therapeutic application

Necrotizing enterocolitis (NEC) is an inflammatory intestinal disease that profoundly affects preterm infants. Currently, the pathogenesis of NEC remains controversial, resulting in limited treatment strategies. The preterm infants are thought to be susceptible to gut inflammatory disorders because of their immature immune system. In early life, intestinal macrophages (IMφs), crucial components of innate immunity, demonstrate functional plasticity and diversity in intestinal development, resistance to pathogens, maintenance of the intestinal barrier, and regulation of gut microbiota. When the stimulations of environmental, dietary, and bacterial factors interrupt the homeostatic processes of IMφs, they will lead to intestinal disease, such as NEC. This review focuses on the IMφs related pathogenesis in NEC, discusses the multi-functional roles and relevant molecular mechanisms of IMφs in preterm infants, and explores promising therapeutic application for NEC.

Microbial energy metabolism fuels an intestinal macrophage niche in solitary isolated lymphoid tissues through purinergic signaling

Maintaining macrophage (MΦ) heterogeneity is critical to ensure intestinal tissue homeostasis and host defense. The gut microbiota and host factors are thought to synergistically guide intestinal MΦ development, although the exact nature, regulation, and location of such collaboration remain unclear. Here, we report that microbial biochemical energy metabolism promotes colony-stimulating factor 2 (CSF2) production by group 3 innate lymphoid cells (ILC3s) within solitary isolated lymphoid tissues (SILTs) in a cell-extrinsic, NLRP3/P2X7R-dependent fashion in the steady state. Tissue-infiltrating monocytes accumulating around SILTs followed a spatially constrained, distinct developmental trajectory into SILT-associated MΦs (SAMs). CSF2 regulated the mitochondrial membrane potential and reactive oxygen species production of SAMs and contributed to the antimicrobial defense against enteric bacterial infections. Collectively, these findings identify SILTs and CSF2-producing ILC3s as a microanatomic niche for intestinal MΦ development and functional programming fueled by the integration of commensal microbial energy metabolism.