Macrophages from the synovium of active rheumatoid arthritis exhibit an activin A-dependent pro-inflammatory profile

Ubiquitin specific peptidase 13 protects against inflammation-associated joint injury in collagen-induced rheumatoid arthritis mice by targeting TRAF6

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease with complex pathogenesis. Ubiquitin-specific protease 13 (USP13), a member of the deubiquitinating enzyme (DUB) superfamily, plays diverse roles in cellular events. This study investigates the role of USP13 in RA, revealing its significant downregulation in peripheral blood mononuclear cells (PBMCs) from RA patients compared to healthy individuals. USP13 expression negatively correlates with RA characteristics, including erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and rheumatoid factor (RF). Consistent with these findings, USP13 levels were reduced in knee joint synovial tissues of collagen-induced arthritis (CIA) mice and lipopolysaccharide (LPS)-stimulated bone marrow-derived macrophages (BMDMs). Mechanistically, USP13 directly interacts with tumor necrosis factor receptor-associated factor 6 (TRAF6), reducing its K63-linked polyubiquitination and thereby inhibiting TRAF6 expression. This interaction restrains nuclear factor κB (NF-κB) signaling, leading to a marked attenuation of LPS-induced inflammatory responses in BMDMs. Importantly, the anti-inflammatory effects of USP13 over-expression are largely dependent on TRAF6 suppression. In vitro, USP13 over-expression in BMDMs inhibits the proliferation of fibroblast-like synoviocytes (FLS) and osteoclastogenesis. In addition, USP13-overexpressing BMDMs in CIA mice significantly alleviates RA development, as evidenced by reduced synovial hyperplasia, inflammatory cell infiltration, cartilage destruction, and bone loss. These findings highlight the essential role of USP13 in macrophages during RA progression and reveal its therapeutic potential by targeting TRAF6 signaling.

Reprogramming of GM-CSF-dependent alveolar macrophages through GSK3 activity modulation

Monocyte-derived macrophages recruited into inflamed tissues can acquire an array of functional states depending on the extracellular environment. Since the anti-inflammatory/pro-fibrotic macrophage profile is determined by MAFB, whose activity/protein levels are regulated by GSK3, we addressed the macrophage reprogramming potential of GSK3 modulation. GM-CSF-dependent (GM-MØ) and M-CSF-dependent monocyte-derived macrophages (M-MØ) exhibited distinct levels of inactive GSK3, and inhibiting GSK3 in GM-MØ led to the acquisition of transcriptional, phenotypic, and functional properties characteristic of M-MØ (enhanced expression of IL-10 and monocyte-recruiting factors, and higher efferocytosis). These reprogramming effects were also observed upon GSK3α/β knockdown and through GSK3 inhibition in ex vivo isolated human alveolar macrophages (AMØ). Notably, GSK3 downmodulation potentiated the transcriptional signature of interstitial macrophages (IMØ) while suppressing the AMØ-specific gene profile. Indeed, heightened levels of inactive GSK3 and MAFB-dependent proteins were observed in severe COVID-19 patients' lung macrophages, highlighting the GSK3-MAFB axis as a therapeutic target for macrophage reprogramming.

Reprogramming and targeting of cholesterol metabolism in tumor-associated macrophages

Cholesterol, as a major component of cell membranes, is closely related to the metabolic regulation of cells and organisms; tumor-associated macrophages play an important push role in tumor progression. We know that tumor-associated macrophages are polarized from macrophages, and the abnormalities of cholesterol metabolism that may be induced during their polarization are worth discussing. This manuscript focuses on metabolic abnormalities in tumor-associated macrophages, and first provides a basic summary of the regulatory mechanisms of abnormal macrophage polarization. Subsequently, it comprehensively describes the features of abnormal glucose, lipid and cholesterol metabolism in TAMs as well as the different regulatory pathways. Then, the paper also discusses the link between abnormal cholesterol metabolism in TAMs and tumors, chronic diseases and aging. Finally, the paper summarizes cancer therapeutic strategies targeting cholesterol metabolism that are already in clinical trials, as well as nanomaterials capable of targeting cholesterol metabolism that are in the research stage, in the hope of providing value for the design of targeting materials. Overall, elucidating metabolic abnormalities in tumor-associated macrophages, particularly cholesterol metabolism, could provide assistance in tumor therapy and the design of targeted drugs.

Investigating endogenous immune-mediated monocyte memory in rheumatoid arthritis

OBJECTIVES

Inflammation triggered by endogenous stimuli that signal cellular stress or tissue injury must be tightly controlled to balance robust protection from intrinsic danger while avoiding catastrophic destruction of healthy tissues. Here, we assess the contribution of innate memory to this balance.

METHODS

Memory evoked by the extracellular matrix protein tenascin-C, a damage-associated, toll-like receptor 4 (TLR4) agonist, was compared to that induced by the pathogenic TLR4 agonist lipopolysaccharide (LPS) by transcriptomic and epigenetic profiling of monocytes from healthy individuals or people wirh rheumatoid arthritis (RA), and tissue macrophages from the RA synovium.

RESULTS

Tenascin-C reprograms monocyte response to subsequent threats, inducing concomitantly suppressed and enhanced responses to rechallenge. Comparative analysis of tenascin-C and LPS revealed common and distinct gene expression signatures, effects controlled transcriptionally and associated with stimulus-specific epigenetic mediators. Altered responses following rechallenge after priming with tenascin-C were not limited to subsequent TLR4 activation but were evident in response to various pathogenic and endogenous stimuli detected by different receptors. In healthy monocytes primed with tenascin-C, rechallenge with stimuli found at high levels in the joints of people with RA resulted in trained responses that were not induced by LPS, including genes associated with chronic inflammation, tissue destruction, altered metabolism, and poor treatment response in RA. The expression of a large subset of these genes was elevated in monocytes from people with RA in the absence of any stimulation and in RA synovial macrophage populations associated with disease flare. Moreover, higher levels of permissive complexes within key epigenetic nodes and increased bivalent modification creating poised loci within endogenously trained genes were observed in RA cells.

CONCLUSIONS

These data highlight how innate reprogramming during 'sterile' inflammatory diseases contributes to chronicity, uncovering pathways unique to endogenous immune triggers that could provide disease-specific points of intervention without engendering global immune suppression.

P2Y6 promoted pruning of FSTL1 nerves by cutaneous macrophages to reset pain threshold and cardiac function

Hyperactivation of cutaneous macrophages promotes the development of chronic pain. Stimulation of nociceptive regions promotes neuroplasticity, which affects pain perception and related physiological responses. However, the specific mechanisms by which cutaneous macrophages sense and elicit nociceptive responses are unknown. Here, we exacerbated the reduction of systemic pain threshold after chronic heart failure (CHF) by silencing follistatin-like 1 (FSTL1), especially the abnormal cutaneous nociceptive sensation at PC6 acupoint, the site associated with cardiac involvement pain. The upregulation of P2Y6 and interleukin-27 expression is intimately linked to the activation of skin macrophages. Hyperactivation of P2Y6 receptor (P2Y6R) may be associated with MHC II M1+ macrophage polarization in PC6. Thus, P2Y6 is one of the key factors that modulate the functional polarization of skin macrophages, which may subsequently influence the expansion of the pain field. The supportive effect of CD206 M2+ macrophages on the cutaneous FSTL1+ nerves was significantly reduced. Meanwhile, FSTL1+ nerves in PC6 functionally interacted with calcitonin gene-related peptide (CGRP)+ nerves, and the overactivation of nerve growth factor (NGF) secreted by cutaneous macrophages induced CGRP+ neuropathological remodeling, which supported the enlargement of the pain sensory area. The activation of CGRP and P2X3 receptor (P2X3R), Na+/K+ ATPase (NKA), and P2X3R in the C8 DRG may be one of the molecular bases mediating cutaneous nociceptive transmission and affecting the function of the heart. Hyperactivation of NKA was consistent with decreased pain threshold and changes in cardiac dysfunction, and PC6 injection of an NKA inhibitor (digilanid C) was effective in ameliorating nociception and cardiac impairment. The beneficial effects of digilanid C were counteracted by FSTL1 silencing. These results indicated that P2Y6 mediates the remodeling of pain perception by skin macrophages via the action of FSTL1, while NKA inhibitors synergistically exert their therapeutic effects.

Immunoregulatory iPSC-derived non-lymphoid progeny in autoimmunity and GVHD alloimmunity

Non-lymphoid immunoregulatory cells, including mesenchymal stem cells (MSCs), myeloid-derived suppressor cells (MDSCs), regulatory macrophages (Mregs), and tolerogenic dendritic cells (Tol-DCs), play critical roles in maintaining immune homeostasis. However, their therapeutic application in autoimmune diseases and graft-versus-host disease (GVHD) has received comparatively less attention. Induced pluripotent stem cells (iPSCs) offer a promising platform for cell engineering, enabling superior quality control, scalable production, and large-scale in vitro expansion of iPSC-derived non-lymphoid immunoregulatory cells. These advances pave the way for their broader application in autoimmune disease and GVHD therapy. Recent innovations in iPSC differentiation protocols have facilitated the generation of these cell types with functional characteristics akin to their primary counterparts. This review explores the unique features and generation processes of iPSC-derived non-lymphoid immunoregulatory cells, their therapeutic potential in GVHD and autoimmune disease, and their progress toward clinical translation. It emphasizes the phenotypic and functional diversity within each cell type and their distinct effects on disease modulation. Despite these advancements, challenges persist in optimizing differentiation efficiency, ensuring functional stability, and bridging the gap to clinical application. By synthesizing current methodologies, preclinical findings, and translational efforts, this review underscores the transformative potential of iPSC-derived non-lymphoid immunoregulatory cells in advancing cell-based therapies for alloimmune and autoimmune diseases.

Unraveling the Complex Nexus of Macrophage Metabolism, Periodontitis, and Associated Comorbidities

BACKGROUND

Periodontitis is recognized as one of the most prevalent oral dysbiotic inflammatory diseases, ultimately leading to the irreversible destruction of periodontal tissues. Macrophages play a pivotal role in the development and progression of periodontitis, and the feasibility of targeting them therapeutically has been established. Since metabolic switching significantly contributes to macrophage regulation, conducting an in-depth review of macrophage metabolism in periodontitis may serve as the foundation for developing innovative treatments.

SUMMARY

This paper has been carefully reviewed to provide a comprehensive overview of the roles played by macrophages in periodontitis and associated comorbidities. Initially, detailed presentations on the metabolic reprogramming of macrophages, including glucose, lipid, and amino acid metabolism, were provided. Subsequently, dominating macrophage phenotype and metabolism under lipopolysaccharide (LPS) stimulation or during periodontitis were presented with emphasize on critical molecules involved. Furthermore, in recognition of the close association between periodontitis and several comorbidities, the interaction among macrophage metabolism, periodontitis, and related metabolic diseases, was thoroughly discussed.

KEY MESSAGES

Through the examination of current research on macrophage metabolic reprogramming induced by periodontitis, this review provides potential immunometabolic therapeutic targets for the future and raises many important, yet unstudied, subjects for follow-up.

BACKGROUND

Periodontitis is recognized as one of the most prevalent oral dysbiotic inflammatory diseases, ultimately leading to the irreversible destruction of periodontal tissues. Macrophages play a pivotal role in the development and progression of periodontitis, and the feasibility of targeting them therapeutically has been established. Since metabolic switching significantly contributes to macrophage regulation, conducting an in-depth review of macrophage metabolism in periodontitis may serve as the foundation for developing innovative treatments.

SUMMARY

This paper has been carefully reviewed to provide a comprehensive overview of the roles played by macrophages in periodontitis and associated comorbidities. Initially, detailed presentations on the metabolic reprogramming of macrophages, including glucose, lipid, and amino acid metabolism, were provided. Subsequently, dominating macrophage phenotype and metabolism under lipopolysaccharide (LPS) stimulation or during periodontitis were presented with emphasize on critical molecules involved. Furthermore, in recognition of the close association between periodontitis and several comorbidities, the interaction among macrophage metabolism, periodontitis, and related metabolic diseases, was thoroughly discussed.

KEY MESSAGES

Through the examination of current research on macrophage metabolic reprogramming induced by periodontitis, this review provides potential immunometabolic therapeutic targets for the future and raises many important, yet unstudied, subjects for follow-up.

The activin-follistatin system: Key regulator of kidney development, regeneration, inflammation, and fibrosis

Activins, multifunctional cytokines of the transforming growth factor-beta superfamily, play critical roles in the regulation of growth and differentiation in multiple biological systems. Activin activity is finely regulated by the endogenous antagonist follistatin. Early studies reported that activins are involved in renal organogenesis, but subsequent research demonstrated that activins also play a significant role in kidney regeneration following injury. The results of more recent studies suggest activins play roles in both inflammatory kidney diseases and renal fibrosis, conditions that often culminate in end-stage renal disease. Given these findings, the inhibition of activin activity represents a promising therapeutic approach for treating a range of kidney disorders. This review discusses the latest discoveries concerning the role of the activin-follistatin system in renal development and pathophysiology and explores the potential therapeutic implications of targeting this system in the management of kidney diseases.

Follistatin drives neuropathic pain in mice through IGF1R signaling in nociceptive neurons

Neuropathic pain is a debilitating chronic condition that lacks effective treatment. The role of cytokine- and chemokine-mediated neuroinflammation in its pathogenesis has been well documented. Follistatin (FST) is a secreted protein known to antagonize the biological activity of cytokines in the transforming growth factor-β (TGF-β) superfamily. The involvement of FST in neuropathic pain and the underlying mechanism remain largely unknown. Here, we report that FST was up-regulated in A-fiber sensory neurons after spinal nerve ligation (SNL) in mice. Inhibition or deletion of FST alleviated neuropathic pain and reduced the nociceptive neuron hyperexcitability induced by SNL. Conversely, intrathecal or intraplantar injection of recombinant FST, or overexpression of FST in the dorsal root ganglion (DRG) neurons, induced pain hypersensitivity. Furthermore, exogenous FST increased neuronal excitability in nociceptive neurons. The biolayer interferometry (BLI) assay and coimmunoprecipitation (co-IP) demonstrated direct binding of FST to the insulin-like growth factor-1 receptor (IGF1R), and IGF1R inhibition reduced FST-induced activation of extracellular signal-regulated kinase (ERK) and protein kinase B (AKT), as well as neuronal hyperexcitability. Further co-IP analysis revealed that the N-terminal domain of FST exhibits the highest affinity for IGF1R, and blocking this interaction with a peptide derived from FST attenuated Nav1.7-mediated neuronal hyperexcitability and neuropathic pain after SNL. In addition, FST enhanced neuronal excitability in human DRG neurons through IGF1R. Collectively, our findings suggest that FST, released from A-fiber neurons, enhances Nav1.7-mediated hyperexcitability of nociceptive neurons by binding to IGF1R, making it a potential target for neuropathic pain treatment.

Loss of synovial tissue macrophage homeostasis precedes rheumatoid arthritis clinical onset

This study performed an in-depth investigation into the myeloid cellular landscape in the synovium of patients with rheumatoid arthritis (RA), "individuals at risk" of RA, and healthy controls (HC). Flow cytometric analysis demonstrated the presence of a CD40-expressing CD206+CD163+ macrophage population dominating the inflamed RA synovium, associated with disease activity and treatment response. In-depth RNA sequencing and metabolic analysis demonstrated that this macrophage population is transcriptionally distinct, displaying unique inflammatory and tissue-resident gene signatures, has a stable bioenergetic profile, and regulates stromal cell responses. Single-cell RNA sequencing profiling of 67,908 RA and HC synovial tissue cells identified nine transcriptionally distinct macrophage clusters. IL-1B+CCL20+ and SPP1+MT2A+ are the principal macrophage clusters in RA synovium, displaying heightened CD40 gene expression, capable of shaping stromal cell responses, and are importantly enriched before disease onset. Combined, these findings identify the presence of an early pathogenic myeloid signature that shapes the RA joint microenvironment and represents a unique opportunity for early diagnosis and therapeutic intervention.

Redox regulation of macrophages

Redox signaling, a mode of signal transduction that involves the transfer of electrons from a nucleophilic to electrophilic molecule, has emerged as an essential regulator of inflammatory macrophages. Redox reactions are driven by reactive oxygen/nitrogen species (ROS and RNS) and redox-sensitive metabolites such as fumarate and itaconate, which can post-translationally modify specific cysteine residues in target proteins. In the past decade our understanding of how ROS, RNS, and redox-sensitive metabolites control macrophage function has expanded dramatically. In this review, we discuss the latest evidence of how ROS, RNS, and metabolites regulate macrophage function and how this is dysregulated with disease. We highlight the key tools to assess redox signaling and important questions that remain.

Macrophage re-programming by JAK inhibitors relies on MAFB

Monocyte-derived macrophages play a key pathogenic role in inflammatory diseases. In the case of rheumatoid arthritis (RA), the presence of specific synovial tissue-infiltrating macrophage subsets is associated with either active disease or inflammation resolution. JAK inhibitors (JAKi) are the first targeted synthetic disease-modifying antirheumatic drugs (tsDMARD) approved for treatment of RA with comparable efficacy to biologics. However, the effects of JAKi on macrophage specification and differentiation are currently unknown. We have analyzed the transcriptional and functional effects of JAKi on human peripheral blood monocyte subsets from RA patients and on the differentiation of monocyte-derived macrophages promoted by granulocyte-macrophage colony-stimulating factor (GM-CSF), a factor that drives the development and pathogenesis of RA. We now report that JAKi Upadacitinib restores the balance of peripheral blood monocyte subsets in RA patients and skewed macrophages towards the acquisition of an anti-inflammatory transcriptional and functional profile in a dose-dependent manner. Upadacitinib-treated macrophages showed a strong positive enrichment of the genes that define synovial macrophages associated to homeostasis/inflammation resolution. Specifically, Upadacitinib-treated macrophages exhibited significantly elevated expression of MAFB and MAFB-regulated genes, elevated inhibitory phosphorylation of GSK3β, and higher phagocytic activity and showed an anti-inflammatory cytokine profile upon activation by pathogenic stimuli. These outcomes were also shared by macrophages exposed to other JAKi (baricitinib, tofacitinib), but not in the presence of the TYK2 inhibitor deucravacitinib. As a whole, our results indicate that JAKi promote macrophage re-programming towards the acquisition of a more anti-inflammatory/pro-resolution profile, an effect that correlates with the ability of JAKi to enhance MAFB expression.

CD36 regulates macrophage and endothelial cell activation and multinucleate giant cell formation in anti neutrophil cytoplasm antibody vasculitis

OBJECTIVE

To investigate CD36 in ANCA-associated vasculitis (AAV), a condition characterized by monocyte/macrophage activation and vascular damage.

METHODS

CD36 expression was assessed in AAV patients and healthy controls (HC). The impact of palmitic acid (PA) stimulation on multinucleate giant cell (MNGC) formation, macrophage, and endothelial cell activation, with or without CD36 knockdown, was examined.

RESULTS

CD36 was overexpressed on AAV patients' monocytes compared to HC, regardless of disease activity. AAV patients exhibited elevated soluble CD36 levels in serum and plasma and PR3-ANCA patients' monocytes demonstrated increased MNGC formation following PA stimulation compared to HC. PA stimulation of macrophages or endothelial cells resulted in heightened CD36 expression, cell activation, increased macrophage migration inhibitory factor (MIF) production, and c-Myc expression, with attenuation upon CD36 knockdown.

CONCLUSION

CD36 participates in macrophage and endothelial cell activation and MNGC formation, features of AAV pathogenesis. AAV treatment may involve targeting CD36 or MIF.

A multifunctional nanoaggregate‐based system for detection of rheumatoid arthritis via Optoacoustic/NIR‐II fluorescent imaging and therapy via inhibiting JAK‐STAT/NF‐κB/NLRP3 pathways

Rheumatoid arthritis (RA) is a debilitating autoimmune disease that causes chronic pain and serious complications, presenting a significant challenge to treat. Promising approaches for treating RA involve signaling pathways modulation and targeted therapy. To this end, a multifunctional nanosystem, TPC‐U@HAT, has been designed for RA therapy, featuring multitargeting, dual‐stimuli response, and on‐demand drug release capabilities. TPC‐U@HAT is composed of a probe/prodrug TPC, a JAK1 kinase inhibitor upadacitinib, and the drug carrier HAT. TPC is composed of an aggregation‐induced emission (AIE)‐active NIR‐II chromophore TPY and an NF‐κB/NLRP3 inhibitor caffeic acid phenethyl ester (CAPE), connected via boronic ester bond which serves as the reactive‐oxygen‐species‐responsive linker. The carrier, HAT, is created by grafting bone‐targeting alendronate and hydrophobic tocopheryl succinate onto hyaluronic acid chains, which can encapsulate TPC and upadacitinib to form TPC‐U@HAT. Upon intravenous injection into mice, TPC‐U@HAT accumulates at inflamed lesions of RA through both active and passive targeting, and the overexpressed hyaluronidase and H2O2 therein cleave the hyaluronic acid polymer chains and boronate bonds, respectively. This generates an AIE‐active chromophore for detection and therapeutic evaluation of RA via both optoacoustic imaging and NIR‐II fluorescent imaging and concomitantly releases CAPE and upadacitinib to exert efficacious therapy by inhibiting NF‐κB/NLRP3 and JAK‐STAT pathways.

MAFB shapes human monocyte-derived macrophage response to SARS-CoV-2 and controls severe COVID-19 biomarker expression

Monocyte-derived macrophages, the major source of pathogenic macrophages in COVID-19, are oppositely instructed by macrophage CSF (M-CSF) or granulocyte macrophage CSF (GM-CSF), which promote the generation of antiinflammatory/immunosuppressive MAFB+ (M-MØ) or proinflammatory macrophages (GM-MØ), respectively. The transcriptional profile of prevailing macrophage subsets in severe COVID-19 led us to hypothesize that MAFB shapes the transcriptome of pulmonary macrophages driving severe COVID-19 pathogenesis. We have now assessed the role of MAFB in the response of monocyte-derived macrophages to SARS-CoV-2 through genetic and pharmacological approaches, and we demonstrate that MAFB regulated the expression of the genes that define pulmonary pathogenic macrophages in severe COVID-19. Indeed, SARS-CoV-2 potentiated the expression of MAFB and MAFB-regulated genes in M-MØ and GM-MØ, where MAFB upregulated the expression of profibrotic and neutrophil-attracting factors. Thus, MAFB determines the transcriptome and functions of the monocyte-derived macrophage subsets that underlie pulmonary pathogenesis in severe COVID-19 and controls the expression of potentially useful biomarkers for COVID-19 severity.

A Nanomedicine-Enabled Ion-Exchange Strategy for Enhancing Curcumin-Based Rheumatoid Arthritis Therapy

Curcumin (Cur) has been clinically used for rheumatoid arthritis treatment by the means of reactive oxygen species (ROS) scavenging and immune microenvironment regulation. However, this compound has a poor water solubility and moderate antioxidative activity, favoring no further broadened application. Metal complexes of curcumin such as zinc-curcumin (Zn-Cur) features enhanced water solubilities, while copper-curcumin (Cu-Cur) shows a higher antioxidant activity but lower solubility than Zn-Cur. Based on their inherent biological properties, this work proposes a nanomedicine-based ion-exchange strategy to enhance the efficacy of Cur for rheumatoid arthritis treatment. Copper silicate nanoparticles with hollow mesoporous structure were prepared to load water-soluble Zn-Cur for constructing a composite nanomedicine, which can degrade in acidic microenvironment of arthritic region, releasing Cu2+ and Zn-Cur. Cu2+ then substitute for Zn2+ in Zn-Cur to form Cu-Cur with a significantly enhanced antioxidative effect, capable of efficiently scavenging ROS in M1 macrophages, promoting their transition to an anti-inflammatory M2 phenotype. In addition, the silicate released after nanocarrier degradation and the Zn2+ released after ion exchange reaction synergistically promote the biomineralization of osteoblasts. This work provides a new approach for enhancing the antiarthritic effect of Cur via an ion-exchange strategy.

Innate immune memory in inflammatory arthritis

The concept of immunological memory was demonstrated in antiquity when protection against re-exposure to pathogens was observed during the plague of Athens. Immunological memory has been linked with the adaptive features of T and B cells; however, in the past decade, evidence has demonstrated that innate immune cells can exhibit memory, a phenomenon called 'innate immune memory' or 'trained immunity'. Innate immune memory is currently being defined and is transforming our understanding of chronic inflammation and autoimmunity. In this Review, we provide an up-to-date overview of the memory-like features of innate immune cells in inflammatory arthritis and the crosstalk between chronic inflammatory milieu and cell reprogramming. Aberrant pro-inflammatory signalling, including cytokines, regulates the metabolic and epigenetic reprogramming of haematopoietic progenitors, leading to exacerbated inflammatory responses and osteoclast differentiation, in turn leading to bone destruction. Moreover, imprinted memory on mature cells including terminally differentiated osteoclasts alters responsiveness to therapies and modifies disease outcomes, commonly manifested by persistent inflammatory flares and relapse following medication withdrawal.

Single-cell transcriptional profiling reveals immunomodulatory properties of stromal and epithelial cells in periodontal immune milieu with diabetes in rats

Periodontitis is the sixth major complication of diabetes. Gingiva, as an important component of periodontal tissues, serves as the first defense barrier against infectious stimuli. However, relatively little is known about cellular heterogeneity and cell-specific changes in gingiva in response to diabetes-associated periodontitis. To characterize molecular changes linking diabetes with periodontitis, we profiled single-cell transcriptome analyses of a total of 45,259 cells from rat gingiva with periodontitis under normoglycemic and diabetic condition. The single-cell profiling revealed that stromal and epithelial cells of gingiva contained inflammation-related subclusters enriched in functions of immune cell recruitment. Compared to normoglycemic condition, diabetes led to a reduction in epithelial basal cells, fibroblasts and smooth muscle cells in gingiva with periodontitis. Analysis of differentially expressed genes indicated that stromal and epithelial populations were reprogrammed towards pro-inflammatory phenotypes promoting immune cell recruitment in diabetes-related periodontitis. In aspect of immune cells, diabetes prominently enhanced neutrophil and M1 macrophage infiltration in periodontitis lesions. Cell-cell communications revealed enhanced crosstalk between stromal/epithelial cells and immune cells mediating by chemokine/chemokine receptor interplay in diabetes-associated periodontitis. Our findings deconvolved cellular heterogeneity of rat gingiva associated with periodontitis and diabetes, uncovered altered immune milieu caused by the disease, and revealed immunomodulatory functions of stromal and epithelial cells in gingival immune niche. The present study improves the understanding of the link between the diabetes and periodontitis and helps in formulating precise therapeutic strategies for diabetes-enhanced periodontitis.

Global scientific trends update on macrophage polarization in rheumatoid arthritis: A bibliometric and visualized analysis from 2000 to 2022

The goal of this work was to use bibliometric analysis to help guide future research on macrophage polarization in RA. We looked for studies on macrophage polarization in RA published between January 1, 2000, and December 31, 2022, in the WoSCC database. Research trends and hotspots were shown and assessed using VOSviewer and CiteSpace. A total of 181 articles were gathered. Belgium was among the early adopters of the field. Chinese institutes have produced the most research. Researchers such as Angel Luis Corb, Amaya Puig-Kröger, and Lizbeth Estrada-Capetillo have made major contributions to the field. Frontiers in Immunology has published the most study findings. According to VOSviewer, the most investigated immune cells, biomarkers, and signaling pathways in the previous three years have been "T cells", "gm-csf", and "nf-κb" in that order. We discovered that the most often used terms in the previous three years were "pathway", "oxidative stress", "extracellular capsule" and "nlrp3 inflammasome" using Citespace. We emphasize these concepts in our findings, presenting the exact mechanisms of pathophysiology related to macrophage polarization in RA, as well as current breakthroughs in therapy strategies.

Transcriptome analysis of multiple tissues reveals the potential mechanism of death under acute heat stress in chicken

BACKGROUND

Acute heat stress could induce high mortality and cause huge economic losses in the poultry industry. Although many studies have revealed heat stress-induced injuries of multiple tissues, the main target tissue and molecular mechanism of death under acute heat stress was largely unknown. This study systematically compared the transcriptome data of five main visceral tissues in chickens to reveal the response of multiple tissues to acute heat stress and determine the main target tissue of acute heat stress, further revealing the injuries of main target tissue and their potential mechanism by combing pathological section and qRT-PCR technologies.

RESULTS

The transcriptome data of five visceral tissues revealed that acute heat stress broadly caused inflammatory response and damaged tissues metabolic homeostasis. Among the five tested visceral tissues, the number of differentially expressed genes in the lung was the highest, and their fold changes were the greatest, indicating that the lung was the main target tissue of acute heat stress. The results of pathological section revealed severe inflammation, emphysema and pulmonary hemorrhage in the lung under acute heat stress. Our study found that some pro-inflammatory genes, including CNTFR, FURIN, CCR6, LIFR and IL20RA, were significantly up-regulated both in the heat-stress and heat-death groups, and their fold changes in the heat-death group were significantly greater than that in the heat-stress group. We also found an anti-inflammatory gene, AvBD9, exhibiting an extremely high expression in the heat-stress group but a low expression in the heat-death group.

CONCLUSIONS

Our study found that acute heat stress caused multiple tissue injuries broadly and the lung was the main target tissue of acute heat stress in chicken. Acute heat stress caused a severe inflammatory response, emphysema, and pulmonary haemorrhage, The severe inflammatory response in the heat-death group was related to the up-regulation of pro-inflammatory genes and down-regulation of anti-inflammatory genes.

Single-cell transcriptomics of human cholesteatoma identifies an activin A-producing osteoclastogenic fibroblast subset inducing bone destruction

Cholesteatoma, which potentially results from tympanic membrane retraction, is characterized by intractable local bone erosion and subsequent hearing loss and brain abscess formation. However, the pathophysiological mechanisms underlying bone destruction remain elusive. Here, we performed a single-cell RNA sequencing analysis on human cholesteatoma samples and identify a pathogenic fibroblast subset characterized by abundant expression of inhibin βA. We demonstrate that activin A, a homodimer of inhibin βA, promotes osteoclast differentiation. Furthermore, the deletion of inhibin βA /activin A in these fibroblasts results in decreased osteoclast differentiation in a murine model of cholesteatoma. Moreover, follistatin, an antagonist of activin A, reduces osteoclastogenesis and resultant bone erosion in cholesteatoma. Collectively, these findings indicate that unique activin A-producing fibroblasts present in human cholesteatoma tissues are accountable for bone destruction via the induction of local osteoclastogenesis, suggesting a potential therapeutic target.

Rheumatoid arthritis macrophages are primed for inflammation and display bioenergetic and functional alterations

OBJECTIVES

Myeloid cells with a monocyte/macrophage phenotype are present in large numbers in the RA joint, significantly contributing to disease; however, distinct macrophage functions have yet to be elucidated. This study investigates the metabolic activity of infiltrating polarized macrophages and their impact on pro-inflammatory responses in RA.

METHODS

CD14+ monocytes from RA and healthy control (HC) bloods were isolated and examined ex vivo or following differentiation into 'M1/M2' macrophages. Inflammatory responses and metabolic analysis ± specific inhibitors were quantified by RT-PCR, western blot, Seahorse XFe technology, phagocytosis assays and transmission electron microscopy along with RNA-sequencing (RNA-seq) transcriptomic analysis.

RESULTS

Circulating RA monocytes are hyper-inflammatory upon stimulation, with significantly higher expression of key cytokines compared with HC (P < 0.05) a phenotype which is maintained upon differentiation into mature ex vivo polarized macrophages. This induction in pro-inflammatory mechanisms is paralleled by cellular bioenergetic changes. RA macrophages are highly metabolic, with a robust boost in both oxidative phosphorylation and glycolysis in RA along with altered mitochondrial morphology compared with HC. RNA-seq analysis revealed divergent transcriptional variance between pro- and anti-inflammatory RA macrophages, revealing a role for STAT3 and NAMPT in driving macrophage activation states. STAT3 and NAMPT inhibition results in significant decrease in pro-inflammatory gene expression observed in RA macrophages. Interestingly, NAMPT inhibition specifically restores macrophage phagocytic function and results in reciprocal STAT3 inhibition, linking these two signalling pathways.

CONCLUSION

This study demonstrates a unique inflammatory and metabolic phenotype of RA monocyte-derived macrophages and identifies a key role for NAMPT and STAT3 signalling in regulating this phenotype.

Methotrexate Provokes Disparate Folate Metabolism Gene Expression and Alternative Splicing in Ex Vivo Monocytes and GM-CSF- and M-CSF-Polarized Macrophages

Macrophages constitute important immune cell targets of the antifolate methotrexate (MTX) in autoimmune diseases, including rheumatoid arthritis. Regulation of folate/MTX metabolism remains poorly understood upon pro-inflammatory (M1-type/GM-CSF-polarized) and anti-inflammatory (M2-type/M-CSF-polarized) macrophages. MTX activity strictly relies on the folylpolyglutamate synthetase (FPGS) dependent intracellular conversion and hence retention to MTX-polyglutamate (MTX-PG) forms. Here, we determined FPGS pre-mRNA splicing, FPGS enzyme activity and MTX-polyglutamylation in human monocyte-derived M1- and M2-macrophages exposed to 50 nmol/L MTX ex vivo. Moreover, RNA-sequencing analysis was used to investigate global splicing profiles and differential gene expression in monocytic and MTX-exposed macrophages. Monocytes displayed six-eight-fold higher ratios of alternatively-spliced/wild type FPGS transcripts than M1- and M2-macrophages. These ratios were inversely associated with a six-ten-fold increase in FPGS activity in M1- and M2-macrophages versus monocytes. Total MTX-PG accumulation was four-fold higher in M1- versus M2-macrophages. Differential splicing after MTX-exposure was particularly apparent in M2-macrophages for histone methylation/modification genes. MTX predominantly induced differential gene expression in M1-macrophages, involving folate metabolic pathway genes, signaling pathways, chemokines/cytokines and energy metabolism. Collectively, macrophage polarization-related differences in folate/MTX metabolism and downstream pathways at the level of pre-mRNA splicing and gene expression may account for variable accumulation of MTX-PGs, hence possibly impacting MTX treatment efficacy.

Inhibition of LXR controls the polarization of human inflammatory macrophages through upregulation of MAFB

Monocyte-derived macrophages contribute to pathogenesis in inflammatory diseases and their effector functions greatly depend on the prevailing extracellular milieu. Whereas M-CSF primes macrophages for acquisition of an anti-inflammatory profile, GM-CSF drives the generation of T cell-stimulatory and pro-inflammatory macrophages. Liver X Receptors (LXRα and LXRβ) are nuclear receptors that control cholesterol metabolism and regulate differentiation of tissue-resident macrophages. Macrophages from rheumatoid arthritis and other inflammatory pathologies exhibit an enriched LXR pathway, and recent reports have shown that LXR activation raises pro-inflammatory effects and impairs the acquisition of the anti-Inflammatory profile of M-CSF-dependent monocyte-derived macrophages (M-MØ). We now report that LXR inhibition prompts the acquisition of an anti-inflammatory gene and functional profile of macrophages generated within a pathological environment (synovial fluid from Rheumatoid Arthritis patients) as well as during the GM-CSF-dependent differentiation of human monocyte-derived macrophages (GM-MØ). Mechanistically, inhibition of LXR results in macrophages with higher expression of the v-Maf Avian Musculoaponeurotic Fibrosarcoma Oncogene Homolog B (MAFB) transcription factor, which governs the macrophage anti-inflammatory profile, as well as over-expression of MAFB-regulated genes. Indeed, gene silencing experiments on human macrophages evidenced that MAFB is required for the LXR inhibitor to enhance the anti-inflammatory nature of human macrophages. As a whole, our results demonstrate that LXR inhibition prompts the acquisition of an anti-inflammatory transcriptional and functional profile of human macrophages in a MAFB-dependent manner, and propose the use of LXR antagonists as potential therapeutic alternatives in macrophage re-programming strategies during inflammatory responses.

Reversing inflammatory microenvironment by a single intra-articular injection of multi-stimulus responsive lipogel to relieve rheumatoid arthritis and promote joint repair

Rheumatoid arthritis (RA) is a common chronic disease dominated by inflammatory synovitis, which is characterized with hyperplastic synovium, up-regulated matrix metalloproteinase (MMP) expression, hypoxic joint cavity and excessive reactive oxygen species (ROS) accumulation. Such local adverse microenvironment in RA joints further exacerbates the infiltration of synovial inflammatory cells, especially M1-type macrophages. Regulating intra-articular pathological conditions, eliminating excess M1 macrophages or converting them to an anti-inflammatory M2 phenotype may break the vicious progression circle. Herein, we develop a multi-stimulus responsive lipogel as effective platform to relieve RA symptoms and promote articular cartilage recovery via reversing its inflammatory microenvironment. The injectable lipogel is fabricated by loading polydopamine nanoparticles and methotrexate into a thermosensitive gel, and intra-articularly injected to form the therapeutic depot (PDA/MTX@TSG) in situ. The gel degrades slowly under esterase hydrolysis, and maintains sustained drug release in physiological conditions. Meanwhile, it can 1) induce a reversible gel-sol phase transition upon mild photothermal treatment (external NIR light control), and 2) specifically respond to MMP-rich RA microenvironment (internal enzymatic hydrolysis effect). Such stimulus-responsive system can deliver therapeutic components in a controllable manner, and significantly reverse adverse inflammatory microenvironment of RA joints through ROS eliminating, hypoxia alleviating, and M1-M2 macrophage polarization effects. Animal experiments indicate that observable RA relief and joint repair are realized after a single lipogel injection combined with NIR irradiation. Our study highlights the importance of altering local RA microenvironment via anti-inflammatory macrophage polarization, and therefore presents a potent therapeutic strategy for RA treatment in clinical intervention.

Role of chemokine receptor 2 in rheumatoid arthritis: A research update

Rheumatoid arthritis (RA) is a multisystemic and inflammatory autoimmune disease characterized by joint destruction. The C-C motif chemokine receptor 2 (CCR2) is mainly expressed in monocytes and T cells, initiating their migration to sites of inflammation, ultimately leading to cartilage damage and bone destruction. CCR2 has long been considered a prospective target for treating autoimmune diseases. However, clinical studies on inhibitors or neutralizing antibodies against CCR2 in RA have exhibited limited efficacy. Recent evidence indicates that CCR2 may play different roles in RA. Hence, a comprehensive understanding regarding the role of CCR2 may facilitate the development of targeted drugs and provide novel insights for improving CCL2-mediated inflammatory diseases. This review summarizes the biological characteristics of CCR2, the related signaling pathways, and recent developments in CCR2-targeting therapeutics.

The imbalance of liver resident macrophages polarization promotes chronic autoimmune hepatitis development in mice

Background

Autoimmune hepatitis (AIH) is a chronic immune-mediated inflammatory liver disease. At present, it is largely unknown how the innate immune cells influence AIH development.

Objective

To inquiry about mechanism of liver resident macrophages in AIH development, thus offering a new direction for AIH targeted treatment.

Methods

The liver resident macrophages were eliminated by clodronate liposomes in AIH liver tissues, followed by HE and Picrosirius assay to detect liver fibrosis and lymphocyte infiltration. The liver resident macrophages polarization was detected by Immunohistochemistry and qPCR. The collagenase digestion was used to isolate Kupffer cells from AIH mice liver tissues and pro-/anti-inflammatory cytokines were determined by qPCR.

Results

M2 macrophages were the dominant phenotype at early immune response stage and hepatic inflammation was progressively aggravated after depletion of liver resident macrophages. M2 macrophages could effectively delay the development of AIH and could be polarized to M1 macrophages at the disease progresses. TLR2 ligands could promote M2 macrophages producing anti-inflammatory cytokines, whereas TLR4 ligands could promote M1 macrophages producing proinflammatory cytokines. The change of TLR2 and TLR4 ligands could lead to continuous high expression of TLR4 and decreased expression of TLR2 in macrophages to further affect liver resident macrophages polarization state.

Conclusion

TLR2 and TLR4 ligands mediated liver resident macrophages polarization to favor chronic autoimmune hepatitis development.

Macrophage: Key player in the pathogenesis of autoimmune diseases

The macrophage is an essential part of the innate immune system and also serves as the bridge between innate immunity and adaptive immune response. As the initiator and executor of the adaptive immune response, macrophage plays an important role in various physiological processes such as immune tolerance, fibrosis, inflammatory response, angiogenesis and phagocytosis of apoptotic cells. Consequently, macrophage dysfunction is a vital cause of the occurrence and development of autoimmune diseases. In this review, we mainly discuss the functions of macrophages in autoimmune diseases, especially in systemic lupus erythematosus (SLE), rheumatic arthritis (RA), systemic sclerosis (SSc) and type 1 diabetes (T1D), providing references for the treatment and prevention of autoimmune diseases.

Longitudinal 18F-VUIIS1008 PET imaging in a rat model of rheumatoid arthritis

Macrophages have crucial roles in the pathogenesis of rheumatoid arthritis (RA). We aimed to elucidate the temporal profile of macrophage infiltration in synovitis in RA rat models using PET (positron emission tomography) imaging based a new generation of TSPO (Translocator protein, 18 kDa)-PET ligand, ¹⁸F-VUIIS1008 {2-[5,7-Diethyl-2-{4-[2-(¹⁸F)fluoroethoxy]phenyl}pyrazolo(1,5-a)pyri-midin-3-yl]-N, N-diethylacetamide}. In vitro and in vivo studies were conducted using RAW264.7 macrophage cells and a rat model of RA induced by Complete Freund's Adjuvant (CFA). Our results showed ¹⁸F-VUIIS1008 showed excellent stability in vitro and binding specificity to RAW264.7 cells, and rapid accumulation in the left inflammatory ankles. PET studies revealed that ¹⁸F-VUIIS1008 could clearly identify the left inflammatory ankles with good contrast at 30-120 min post-injection. The uptake of ¹⁸F-VUIIS1008 of left inflammatory ankles was a wiggle trace with two peaks on day 7 and 29, and then, the highest peak uptake was seen on day 29 (3.00% ± 0.08%ID/g) at 60 min after injection. Tracer uptakes could be inhibited by PK11195 or VUIIS1008. Immunohistochemistry and immunofluorescence tests showed that elevated TSPO expression and infiltrated macrophages were found in the left inflammation ankles. ¹⁸F-VUIIS1008 as a novel PET imaging agent showed great potential to identify temporal profile of macrophage infiltration in synovitis in RA, and deliver accurate non-invasive diagnosis and real-time monitoring of RA development.

Effect of Er Miao San on peritoneal macrophage polarisation through the miRNA-33/NLRP3 signalling pathway in a rat model of adjuvant arthritis

CONTEXT

Er Miao San (EMS) is a formulation that contains Atractylodis Rhizoma and Phellodendri Cortex in 1:1 ratio, and is commonly used to treat rheumatoid arthritis (RA) and other inflammatory diseases.

OBJECTIVE

We investigated the mechanism of action and effects of EMS on peritoneal macrophage differentiation in a rat model of adjuvant arthritis (AA).

MATERIALS AND METHODS

EMS (3, 1.5 and 0.75 g/kg; once daily) and methotrexate (0.5 mg/kg; once every 3 days) were administered orally from days 21 to 35 after immunisation. Paw swelling and arthritis index were measured; pathological changes in the ankle joint were observed using x-ray and haematoxylin eosin staining. The ratio of CD86/CD206 in macrophages was detected by flow cytometry. Examination of the miRNA-33/NLRP3 signalling pathway was examined by RT-qPCR and western blotting. The levels of cytokines in the serum and cell supernatants were tested by ELISA.

RESULTS

EMS significantly reduced the AA index in rats (from 11.0 to 9.3) and pathological changes in the ankle joint (from 3.8 to 1.4). The ratio of CD86/CD206 was reduced, and polarisation to M1 improved (from 0.9 to 0.6) in macrophages of EMS-treated rats. EMS downregulated the miRNA-33/NLRP3 pathway. Furthermore, EMS treatment increased IL-10 and TGF-β levels in the serum and supernatant of macrophages of AA rats and simultaneously decreased the levels of IL-1β and TNF-α.

DISCUSSION AND CONCLUSIONS

Our results suggest that EMS may reduce macrophage polarisation to the M1 inflammatory phenotype by downregulating the miRNA-33/NLRP3 pathway in AA rats. These findings may provide new insights into the treatment of RA.

Activin A and CCR2 regulate macrophage function in testicular fibrosis caused by experimental autoimmune orchitis

Experimental autoimmune-orchitis (EAO), a rodent model of chronic testicular inflammation and fibrosis, replicates pathogenic changes seen in some cases of human spermatogenic disturbances. During EAO, increased levels of pro-inflammatory and pro-fibrotic mediators such as TNF, CCL2, and activin A are accompanied by infiltration of leukocytes into the testicular parenchyma. Activin A levels correlate with EAO severity, while elevated CCL2 acting through its receptor CCR2 mediates leukocyte trafficking and recruits macrophages. CCR2 + CXCR4 + macrophages producing extracellular matrix proteins contribute widely to fibrogenesis. Furthermore, testicular macrophages (TMs) play a critical role in organ homeostasis. Therefore, we aimed to investigate the role of the activin A/CCL2-CCR2/macrophage axis in the development of testicular fibrosis. Following EAO induction, we observed lower levels of organ damage, collagen deposition, and leukocyte infiltration (including fibronectin+, collagen I+ and CXCR4+ TMs) in Ccr2-/- mice than in WT mice. Furthermore, levels of Il-10, Ccl2, and the activin A subunit Inhba mRNAs were lower in Ccr2-/- EAO testes. Notably, fibronectin+ TMs were also present in biopsies from patients with impaired spermatogenesis and fibrotic alterations. Overexpression of the activin A antagonist follistatin reduced tissue damage and collagen I+ TM accumulation in WT EAO testes, while treating macrophages with activin A in vitro increased the expression of Ccr2, Fn1, Cxcr4, and Mmp2 and enhanced migration along a CCL2 gradient; these effects were abolished by follistatin. Taken together, our data indicate that CCR2 and activin A promote fibrosis during testicular inflammation by regulating macrophage function. Inhibition of CCR2 or activin A protects against damage progression, offering a promising avenue for therapeutic intervention.

NLRC4-mediated activation of CD1c+ DC contributes to perpetuation of synovitis in rheumatoid arthritis

The individual contribution of specific myeloid subsets such as CD1c+ conventional DC (cDC) to perpetuation of rheumatoid arthritis (RA) pathology remains unclear. In addition, the specific innate sensors driving pathogenic activation of CD1c+ cDC in patients with RA and their functional implications have not been characterized. Here, we assessed phenotypical, transcriptional, and functional characteristics of CD1c+ and CD141+ cDC and monocytes from the blood and synovial fluid of patients with RA. Increased levels of CCR2 and the IgG receptor CD64 on circulating CD1c+ cDC was associated with the presence of this DC subset in the synovial membrane in patients with RA. Moreover, synovial CD1c+ cDC are characterized by increased expression of proinflammatory cytokines and high abilities to induce pathogenic IFN-γ+IL-17+CD4+ T cells in vitro. Finally, we identified the crosstalk between Fcγ receptors and NLRC4 as a potential molecular mechanism mediating pathogenic activation, CD64 upregulation, and functional specialization of CD1c+ cDC in response to dsDNA-IgG in patients with RA.

Regulation of differentiation and generation of osteoclasts in rheumatoid arthritis

INTRODUCTION

Rheumatoid arthritis (RA), which affects nearly 1% of the world's population, is a debilitating autoimmune disease. Bone erosion caused by periarticular osteopenia and synovial pannus formation is the most destructive pathological changes of RA, also leads to joint deformity and loss of function,and ultimately affects the quality of life of patients. Osteoclasts (OCs) are the only known bone resorption cells and their abnormal differentiation and production play an important role in the occurrence and development of RA bone destruction; this remains the main culprit behind RA.

METHOD

Based on the latest published literature and research progress at home and abroad, this paper reviews the abnormal regulation mechanism of OC generation and differentiation in RA and the possible targeted therapy.

RESULT

OC-mediated bone destruction is achieved through the regulation of a variety of cytokines and cell-to-cell interactions, including gene transcription, epigenetics and environmental factors. At present, most methods for the treatment of RA are based on the regulation of inflammation, the inhibition of bone injury and joint deformities remains unexplored.

DISCUSSION

This article will review the mechanism of abnormal differentiation of OC in RA, and summarise the current treatment oftargeting cytokines in the process of OC generation and differentiation to reduce bone destruction in patients with RA, which isexpected to become a valuable treatment choice to inhibit bone destruction in RA.

Xanthones from Securidaca inappendiculata Hassk. attenuate collagen-induced arthritis in rats by inhibiting the nicotinamide phosphoribosyltransferase/glycolysis pathway and macrophage polarization

Securidaca inappendiculata (SI) Hassk. is a traditional medicine used to treat rheumatoid arthritis. Recent studies have reported that macrophages are the primary regulators of joint homeostasis and their polarization is closely related to their metabolic mode. Here, we aimed to investigate the relationship between the joint protective effect of SI's xanthone-rich fraction (XRF) on collagen-induced arthritis (CIA) in rats and the nicotinamide phosphoribosyltransferase (NAMPT)-glycolysis-polarization axis of macrophages. CIA model rats were treated with oral XRF and therapeutic efficacy was assessed based on arthritis score, degree of paw swelling, histological examination, and immunohistochemical analysis. Serum levels of cytokines, cellular metabolite concentrations, and protein and mRNA expression were determined by enzyme-linked immunosorbent assay (ELISA), western blotting (WB), and quantitative real-time PCR (RT-qPCR), respectively. The effects of dihydroxy-3,4-dimethoxyxanthone (XAN), a representative SI-derived compound, on RAW264.7 macrophages was analyzed in vitro using confocal laser scanning and flow cytometry. We found that XRF treatment significantly alleviated disease severity in CIA model rats. Levels of pro-inflammatory cytokines in the serum and M1 markers in synovium were reduced after XRF treatment, accompanied by an increase in the levels of anti-inflammatory cytokines and M2 markers. Further, XRF significantly suppressed synovial glycolysis by regulating NAMPT. In vitro studies further showed that XAN induced repolarization of lipopolysaccharide (LPS)-induced RAW264.7 macrophages with M1-M2 phenotype. Moreover, XAN negatively regulated glycolysis in the LPS-induced RAW264.7 macrophages in correlation with changes in NAMPT expression. Overall, the findings of this study suggest that the joint protective effects of XRF are achieved by inhibiting the NAMPT/glycolysis pathway and thereby regulating macrophage polarization.

Semaphorin 3G exacerbates joint inflammation through the accumulation and proliferation of macrophages in the synovium

Objectives

Methotrexate (MTX) is an anchor drug for the treatment of rheumatoid arthritis (RA). However, the precise mechanisms by which MTX stalls RA progression and alleviates the ensuing disease effects remain unknown. The aim of the present study was to identify novel therapeutic target molecules, the expression patterns of which are affected by MTX in patients with RA.

Methods

CD4⁺ T cells from 28 treatment-naïve patients with RA before and 3 months after the initiation of MTX treatment were subjected to DNA microarray analyses. The expression levels of semaphorin 3G, a differentially expressed gene, and its receptor, neuropilin-2, were evaluated in the RA synovium and collagen-induced arthritis synovium. Collagen-induced arthritis and collagen antibody-induced arthritis were induced in semaphorin3G-deficient mice and control mice, and the clinical score, histological score, and serum cytokines were assessed. The migration and proliferation of semaphorin 3G-stimulated bone marrow-derived macrophages were analyzed in vitro. The effect of local semaphorin 3G administration on the clinical score and number of infiltrating macrophages during collagen antibody-induced arthritis was evaluated.

Results

Semaphorin 3G expression in CD4⁺ T cells was downregulated by MTX treatment in RA patients. It was determined that semaphorin 3G is expressed in RA but not in the osteoarthritis synovium; its receptor neuropilin-2 is primarily expressed on activated macrophages. Semaphorin3G deficiency ameliorated collagen-induced arthritis and collagen antibody-induced arthritis. Semaphorin 3G stimulation enhanced the migration and proliferation of bone marrow-derived macrophages. Local administration of semaphorin 3G deteriorated collagen antibody-induced arthritis and increased the number of infiltrating macrophages.

Conclusions

Upregulation of semaphorin 3G in the RA synovium is a novel mechanism that exacerbates joint inflammation, leading to further deterioration, through macrophage accumulation.

Metabolic Reprogramming of Innate Immune Cells as a Possible Source of New Therapeutic Approaches in Autoimmunity

Immune cells undergo different metabolic pathways or immunometabolisms to interact with various antigens. Immunometabolism links immunological and metabolic processes and is critical for innate and adaptive immunity. Although metabolic reprogramming is necessary for cell differentiation and proliferation, it may mediate the imbalance of immune homeostasis, leading to the pathogenesis and development of some diseases, such as autoimmune diseases. Here, we discuss the effects of metabolic changes in autoimmune diseases, exerted by the leading actors of innate immunity, and their role in autoimmunity pathogenesis, suggesting many immunotherapeutic approaches.

Identification of Diagnostic Biomarkers, Immune Infiltration Characteristics, and Potential Compounds in Rheumatoid Arthritis

Aims

This study is aimed at investigating the pathogenesis of rheumatoid arthritis (RA) by identifying key biomarkers, associated immune infiltration, and small-molecule compounds using bioinformatic analysis.

Methods

Six datasets were obtained from the Gene Expression Omnibus database, and the batch effect was adjusted. Functional enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) were used to analyse differentially expressed genes (DEGs). Furthermore, candidate small-molecule drugs associated with RA were selected from the Connectivity Map (CMap) database. The least absolute shrinkage and selection operator regression, support vector machine recursive feature elimination, and multivariate logistic regression analyses were performed on DEGs to screen for RA diagnostic markers. The receiver operating characteristic curve, concordance index, and GiViTi calibration band were the metrics used to assess the diagnostic markers of RA identified in this analysis. The single-sample gene set enrichment analysis was performed to calculate the scores of infiltrating immune cells and evaluate the activities of immune-related pathways. Finally, the correlation between screening markers and RA diagnosis was determined.

Results

A total of 227 DEGs were identified. Functional enrichment analysis and KEGG revealed that DEGs were enriched by the immune response. CMap analysis identified 11 small-molecule compounds with therapeutic potential for RA. In gene expression, the activities of 13 immune cells and 12 immune-related pathways significantly differed between patients with RA and healthy controls. DPYSL3 and SPP1 had the potential to diagnose RA. SPP1 expression was positively correlated with DPYSL3 in 11 immune cells and 10 immune-related pathways.

Conclusion

This study comprehensively analysed DEGs and immune infiltration and screened for potential diagnostic markers and small-molecule compounds of RA.

Activation of LXR Nuclear Receptors Impairs the Anti-Inflammatory Gene and Functional Profile of M-CSF-Dependent Human Monocyte-Derived Macrophages

Liver X Receptors (LXR) control cholesterol metabolism and exert anti-inflammatory actions but their contribution to human macrophage polarization remains unclear. The LXR pathway is enriched in pro-inflammatory macrophages from rheumatoid arthritis as well as in tumors-associated macrophages from human tumors. We now report that LXR activation inhibits the anti-inflammatory gene and functional profile of M-CSF-dependent human macrophages, and prompts the acquisition of a pro-inflammatory gene signature, with both effects being blocked by an LXR inverse agonist. Mechanistically, the LXR-stimulated macrophage polarization shift correlates with diminished expression of MAFB and MAF, which govern the macrophage anti-inflammatory profile, and with enhanced release of activin A. Indeed, LXR activation impaired macrophage polarization in response to tumor-derived ascitic fluids, as well as the expression of MAF- and MAFB-dependent genes. Our results demonstrate that LXR activation limits the anti-inflammatory human macrophage polarization and prompts the acquisition of an inflammatory transcriptional and functional profile.

IL-21 impairs pro-inflammatory activity of M1-like macrophages exerting anti-inflammatory effects on rheumatoid arthritis

Objective：Macrophages are the main source of inflammatory mediators and play important roles in the pathogenesis of rheumatoid arthritis (RA). Interleukin-21 (IL-21) regulates both innate and adaptive immune responses and exerts major effects on inflammatory responses that promote the development of RA. However, its effect on macrophage polarisation remains unclear.Methods：CD14⁺ monocytes of the peripheral blood of Human healthy donors (HD) and RA, and macrophages of RA synovial fluid (RA-SF MΦs) were isolated. IL-21 receptor (IL-21R) was detected by flow cytometry. Cytokine production by MΦs from different sources pre-treated with IL-21 and/or LPS was measured by real-time polymerase chain reaction (RT-PCR) and ELISA. CD14⁺ monocytes were differentiated into M1-like and M2-like macrophages via stimulation with GM-CSF, interferon-γ (IFN-γ), and LPS or M-CSF, IL-4, and IL-13, respectively. To determine the effect of IL-21 on macrophage polarisation, macrophage phenotypes, gene expression, and cytokine secretion were detected by flow cytometry, RT-PCR, and ELISA. TLR4 and ERK1/2 were determined by western blotting.Results：IL-21 exerted different effects on LPS-mediated inflammatory responses in various derived MΦs, and inhibited macrophages polarisation to M1-like macrophages and promote their polarisation to M2-like macrophages in HD and RA. Moreover, IL-21 inhibited LPS-mediated secretion of inflammatory cytokines, probably by downregulating the ERK1/2, in RA-SF MΦs.Conclusion：For the first time, we indicated that IL-21 inhibits LPS-mediated cytokine production in RA-SF MΦs, and impairs pro-inflammatory activity of M1-like macrophages, hereby exerting anti-inflammatory effects on RA. Thus, IL-21 might not be an appropriate therapeutic target for RA.

Molecular and Cellular Heterogeneity in Rheumatoid Arthritis: Mechanisms and Clinical Implications

Rheumatoid arthritis is an autoimmune disease that exhibits significant clinical heterogeneity. There are various treatments for rheumatoid arthritis, including disease-modifying anti-rheumatic drugs (DMARDs), glucocorticoids, non-steroidal anti-inflammatory drugs (NSAIDs), and inflammatory cytokine inhibitors (ICI), typically associated with differentiated clinical effects and characteristics. Personalized responsiveness is observed to the standard treatment due to the pathophysiological heterogeneity in rheumatoid arthritis, resulting in an overall poor prognosis. Understanding the role of individual variation in cellular and molecular mechanisms related to rheumatoid arthritis will considerably improve clinical care and patient outcomes. In this review, we discuss the source of pathophysiological heterogeneity derived from genetic, molecular, and cellular heterogeneity and their possible impact on precision medicine and personalized treatment of rheumatoid arthritis. We provide emphasized description of the heterogeneity derived from mast cells, monocyte cell, macrophage fibroblast-like synoviocytes and, interactions within immune cells and with inflammatory cytokines, as well as the potential as a new therapeutic target to develop a novel treatment approach. Finally, we summarize the latest clinical trials of treatment options for rheumatoid arthritis and provide a suggestive framework for implementing preclinical and clinical experimental results into clinical practice.

The Macrophage Reprogramming Ability of Antifolates Reveals Soluble CD14 as a Potential Biomarker for Methotrexate Response in Rheumatoid Arthritis

The identification of “trained immunity/tolerance” in myeloid cells has changed our perception of the performance of monocytes and macrophages during inflammatory and immune responses. Pemetrexed (PMX) and methotrexate (MTX) are blockers of the one-carbon metabolism (OCM) and commonly used therapeutic agents in cancer and rheumatoid arthritis (RA). We have previously showed that MTX promotes trained immunity in human macrophages. In the present manuscript, we have assessed the anti-inflammatory effects of PMX and MTX and found that OCM blockers alter the functional and gene expression profile of human macrophages and that OCM blockade reprograms macrophages towards a state of lipopolysaccharide (LPS) tolerance at the signaling and functional levels. Moreover, OCM blockade reduced macrophage LPS responsiveness by impairing the expression of membrane-bound and soluble CD14 (sCD14). The therapeutic relevance of these results was later confirmed in early RA patients, as MTX-responder RA patients exhibit lower sCD14 serum levels, with baseline sCD14 levels predicting MTX response. As a whole, our results demonstrate that OCM is a metabolic circuit that critically mediates the acquisition of innate immune tolerance and positions sCD14 as a valuable tool to predict MTX response in RA patients.

Identification of Candidate Genes Related to Synovial Macrophages in Rheumatoid Arthritis by Bioinformatics Analysis

Objective

Rheumatoid arthritis (RA) is one of the most prevalent inflammatory arthritis worldwide. However, the genes and pathways associated with macrophages from synovial fluids in RA patients still remain unclear. This study aims to screen and verify differentially expressed genes (DEGs) related to identifying candidate genes related to synovial macrophages in rheumatoid arthritis by bioinformatics analysis.

Methods

We searched the Gene Expression Omnibus (GEO) database, and GSE97779 and GSE10500 with synovial macrophages expression profiling from multiple RA microarray dataset were selected to conduct a systematic analysis. GSE97779 included nine macrophage samples from synovial fluids of RA patients and five macrophage samples from primary human blood of HC. GSE10500 included five macrophage samples from synovial fluids of RA patients and three macrophage samples from primary human blood of HC. Functional annotation of DEGs was performed, including Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. Protein–protein interaction (PPI) network of DEGs was established using the STRING database. CytoHubba was used to identify hub genes. MCODE was used to determine gene clusters in the interactive network.

Results

There were 2638 DEGs (1425 upregulated genes and 1213 downregulated ones) and 889 DEGs (438 upregulated genes and 451 downregulated ones) selected from GSE97779 and GSE10500, respectively. Venn diagrams showed that 173 genes were upregulated and 106 downregulated in both two datasets. The top 10 hub genes, including FN1, VEGFA, HGF, SERPINA1, MMP9, PPBP, CD44, FPR2, IGF1, and ITGAM, were identified using the PPI network.

Conclusion

This study provides new insights for the potential biomarkers and the relevant molecular mechanisms in RA patients. Our findings suggest that the 10 candidate genes might be used in diagnosis, prognosis, and therapy of RA in the future. However, further studies are required to confirm the expression of these genes in synovial macrophages in RA and control specimen.

Significance of Interleukin (IL)-4 and IL-13 in Inflammatory Arthritis

Interleukin (IL)-4 and IL-13 belong to the T helper 2 (Th2) cytokine family, along with IL-3, IL-5, and IL-9. These cytokines are key mediators of allergic inflammation. They have important immunomodulatory activities and exert influence on a wide variety of immune cells, such as B cells, eosinophils, basophils, monocytes, fibroblasts, endothelial cells, airway epithelial cells, smooth muscle cells, and keratinocytes. Recent studies have implicated IL-4 and IL-13 in the development of various autoimmune diseases. Additionally, these cytokines have emerged as potential players in pathogenesis of inflammatory arthritis. Recent findings suggest that the IL-4 and IL-13 might play a significant role in the downregulation of inflammatory processes underlying RA pathology, and beneficially modulate the course of the disease. This review summarizes the biological features of the IL-4 and IL-13 and provides current knowledge regarding the role of these cytokines in inflammatory arthritis.

Cronkhite-Canada syndrome: An investigation in clinical features and pathogenesis

OBJECTIVE

This study aimed to investigate the clinical features and potential pathogenesis of a rare nonhereditary polyposis syndrome, Cronkhite-Canada syndrome (CCS).

METHODS

Medical records of eight patients with CCS who were admitted to our hospital from January 2005 to November 2019 were reviewed. Transcriptome profiling was performed in one patient to investigate its difference between gastric polyp tissue and normal mucosa. Differentially expressed genes (DEGs) were determined for functional analysis. The expression of inhibin beta A (INHBA) was further assessed by using immunohistochemistry.

RESULTS

All patients presented with gastrointestinal polyposis, accompanied by diarrhea, skin hyperpigmentation, hair loss and nail dystrophy. Hyperplastic polyps were observed in seven patients, tubular adenoma in two, inflammatory polyps in one and hamartomatous polyps in one, respectively. All patients underwent comprehensive treatment and five achieved clinical remission. A total of 2107 DEGs, including 1265 upregulated and 842 downregulated, were found in the gastric polyp. Gene ontology analysis showed that upregulated genes were significantly enriched in the positive regulation of cell proliferation, epithelium development and angiogenesis. A protein-protein interaction analysis suggested that INHBA was at the center of the interaction network and might play an important role in CCS. Immunohistochemistry confirmed that INHBA expression was upregulated in CCS gastric polyps.

CONCLUSIONS

CCS is a rare disease and its diagnosis mainly depends on typical clinical manifestations, endoscopic findings and histological features. INHBA upregulation may contribute to its pathogenesis.

Glaucocalyxin B inhibits cartilage inflammatory injury in rheumatoid arthritis by regulating M1 polarization of synovial macrophages through NF-κB pathway

Background: Glaucocalyxin B (Gla B) is a type of sesquiterpenoids. At present, there are rare studies on the pharmacological effects and targets of sesquiterpenoids, while multiple sesquiterpenoids have good anti-inflammatory properties. Therefore, in this study, we aimed to investigate the mechanism of Gla B on macrophages and rheumatoid arthritis.

Methods: LPS/IFN-γ was used to induce M1 polarization of synovial macrophage (SMG) in vitro, followed by Gla B pretreatment (5 μM and 15 μM). Afterwards, flow cytometry was performed to detect the proportion of M1 cells (F4/80+CD86+), enzyme-linked immunosorbent assay (ELISA) was used to determine the expression levels of M1 cell markers (TNF-α, IL-1β, IL-6, iNOS and IL-12) as well as M2 cell markers (IL-10 and TGF- β1), immunofluorescence (IF) staining was utilized to measure the expression of CD86, the level of ROS was assessed by probe and Western blot was conducted to detect the expression of P65 and p-P65. M1 polarization was detected in SMG cells with P65 silencing after 15 μM Gla B intervention. The culture medium from M1 cell was used to culture cartilage cells in vitro, followed by detection of cartilage cell injury. In animal models, collagen antibodies and LPS were combined to induce RA mouse model. Afterwards, H and E staining was performed to detect pathological changes in mouse joint synovium, safranin O-fast green staining was used to determine cartilage injury, and immunohistochemistry was utilized to detect CD86 and P65 expression. Small molecule-protein docking and co-immunoprecipitation (Co-IP) were used to verify the targeted binding relationship between Gal B and P65.

Results: LPS and IFN-γ could induce M1 polarization in SMG. Gal B could inhibit M1 polarization, decrease the levels of TNF-α, IL-1β, IL-6, iNOS and IL-12, inhibit the expression of P65 and p-P65 while did not affect the expression of IL-10 or TGF-β1. Gal B had no significant effect in SMG cells with P65 silencing. The small molecule-protein docking and Co-IP both showed that Gal B had a targeted binding relationship with P65, and Gal B could inhibit joint injury and inflammation in mice.

Conclusion: Gal B could target the P65 protein. Moreover, Gal B could inhibit the inflammatory injury of articular cartilage in RA by regulating M1 polarization of SMG through inhibiting the NF-κB signaling.

Macrophages: The Good, the Bad, and the Gluttony

Macrophages are dynamic cells that play critical roles in the induction and resolution of sterile inflammation. In this review, we will compile and interpret recent findings on the plasticity of macrophages and how these cells contribute to the development of non-infectious inflammatory diseases, with a particular focus on allergic and autoimmune disorders. The critical roles of macrophages in the resolution of inflammation will then be examined, emphasizing the ability of macrophages to clear apoptotic immune cells. Rheumatoid arthritis (RA) is a chronic autoimmune-driven spectrum of diseases where persistent inflammation results in synovial hyperplasia and excessive immune cell accumulation, leading to remodeling and reduced function in affected joints. Macrophages are central to the pathophysiology of RA, driving episodic cycles of chronic inflammation and tissue destruction. RA patients have increased numbers of active M1 polarized pro-inflammatory macrophages and few or inactive M2 type cells. This imbalance in macrophage homeostasis is a main contributor to pro-inflammatory mediators in RA, resulting in continual activation of immune and stromal populations and accelerated tissue remodeling. Modulation of macrophage phenotype and function remains a key therapeutic goal for the treatment of this disease. Intriguingly, therapeutic intervention with glucocorticoids or other DMARDs promotes the re-polarization of M1 macrophages to an anti-inflammatory M2 phenotype; this reprogramming is dependent on metabolic changes to promote phenotypic switching. Allergic asthma is associated with Th2-polarised airway inflammation, structural remodeling of the large airways, and airway hyperresponsiveness. Macrophage polarization has a profound impact on asthma pathogenesis, as the response to allergen exposure is regulated by an intricate interplay between local immune factors including cytokines, chemokines and danger signals from neighboring cells. In the Th2-polarized environment characteristic of allergic asthma, high levels of IL-4 produced by locally infiltrating innate lymphoid cells and helper T cells promote the acquisition of an alternatively activated M2a phenotype in macrophages, with myriad effects on the local immune response and airway structure. Targeting regulators of macrophage plasticity is currently being pursued in the treatment of allergic asthma and other allergic diseases. Macrophages promote the re-balancing of pro-inflammatory responses towards pro-resolution responses and are thus central to the success of an inflammatory response. It has long been established that apoptosis supports monocyte and macrophage recruitment to sites of inflammation, facilitating subsequent corpse clearance. This drives resolution responses and mediates a phenotypic switch in the polarity of macrophages. However, the role of apoptotic cell-derived extracellular vesicles (ACdEV) in the recruitment and control of macrophage phenotype has received remarkably little attention. ACdEV are powerful mediators of intercellular communication, carrying a wealth of lipid and protein mediators that may modulate macrophage phenotype, including a cargo of active immune-modulating enzymes. The impact of such interactions may result in repair or disease in different contexts. In this review, we will discuss the origin, characterization, and activity of macrophages in sterile inflammatory diseases and the underlying mechanisms of macrophage polarization via ACdEV and apoptotic cell clearance, in order to provide new insights into therapeutic strategies that could exploit the capabilities of these agile and responsive cells.

Polarization of rheumatoid macrophages is regulated by the CDKN2B-AS1/ MIR497/TXNIP axis

The polarization of macrophages plays a critical role in the pathophysiology of rheumatoid arthritis. The macrophages can have pro-inflammatory M1 polarization and various types of alternative anti-inflammatory M2 polarization. Our preliminary results showed that the CDKN2B-AS1/MIR497/TXNIP axis might regulate macrophages of rheumatoid arthritis patients. Therefore, we hypothesized that this axis regulated the polarization of rheumatoid macrophages. Flow cytometry was used to determine the surface polarization markers in M1 or M2 macrophages from healthy donors and rheumatoid arthritis patients. The QPCR and Western Blotting were used to compare the expression of the CDKN2B-AS1/MIR497/TXNIP axis in these macrophages. We Knocked down and overexpressed the axis in the macrophage cell line MD to test its roles in macrophage polarization. Compared to cells from healthy donors, cells from rheumatoid arthritis patients expressed higher levels of CD40 and CD80 and lower levels of CD16, CD163, CD206, and CD200R after polarization, they also expressed higher CDKN2B-AS1, lower MIR497, and higher TXNIP. In macrophages from healthy donors, there was no correlation among CDKN2B-AS1, MIR497, and TXNIP. But in macrophages from patients, there were significant correlations. The CDKN2B-AS1 knockdown, MIR497 mimics suppressed the M1 polarization but promoted the M2 polarization in MD cells, while the MIR497 knockdown and the TXNIP overexpression did the opposite. This study demonstrated that elevated CDKN2B-AS1 in macrophages promotes the M1 polarization and inhibited the M2 polarization of macrophages by the CDKN2B-AS1/ MIR497/TXNIP axis.

Signals and Mechanisms Regulating Monocyte and Macrophage Activation in the Pathogenesis of Juvenile Idiopathic Arthritis

Monocytes (Mos) and macrophages (Mφs) are key players in the innate immune system and are critical in coordinating the initiation, expansion, and regression of many autoimmune diseases. In addition, they display immunoregulatory effects that impact inflammation and are essential in tissue repair and regeneration. Juvenile idiopathic arthritis (JIA) is an umbrella term describing inflammatory joint diseases in children. Accumulated evidence suggests a link between Mo and Mφ activation and JIA pathogenesis. Accordingly, topics regarding the signals and mechanisms regulating Mo and Mφ activation leading to pathologies in patients with JIA are of great interest. In this review, we critically summarize recent advances in the understanding of how Mo and Mφ activation is involved in JIA pathogenesis and focus on the signaling pathways and mechanisms participating in the related cell activation processes.

Liver X receptors conserve the therapeutic target potential for the treatment of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic multi-system autoimmune disease with extremely complex pathogenesis. Significantly altered lipid paradox related to the inflammatory burden is reported in RA patients, inducing 50% higher cardiovascular risks. Recent studies have also demonstrated that lipid metabolism can regulate many functions of immune cells in which metabolic pathways have altered. The nuclear liver X receptors (LXRs), including LXRα and LXRβ, play a central role in regulating lipid homeostasis and inflammatory responses. Undoubtedly, LXRs have been considered as an attractive therapeutic target for the treatment of RA. However, there are some contradictory effects of LXRs agonists observed in previous animal studies where both pro-inflammatory role and anti-inflammatory role were revealed for LXRs activation in RA. Therefore, in addition to updating the knowledge of LXRs as the prominent regulators of lipid homeostasis, the purpose of this review is to summarize the effects of LXRs agonists in RA-associated immune cells, to explore the underlying reasons for the contradictory therapeutic effects of LXRs agonists observed in RA animal models, and to discuss future strategy for the treatment of RA with LXRs modulators.

Dissecting the microenvironment around biosynthetic scaffolds in murine skin wound healing

The structural properties of biomaterials play crucial roles in guiding cell behavior and influencing immune responses against the material. We fabricated electrospun membranes with three types of surface topography (random, aligned, and latticed), introduced them to dorsal skin excisional wounds in mice and rats, and evaluated their effects on wound healing and immunomodulatory properties. An overview of different immune cells in the microenvironment with the help of single-cell RNA sequencing revealed diverse cellular heterogeneity in vivo. The time course of immune response was advanced toward an adaptive immunity–dominant stage by the aligned scaffold. In mice without mature T lymphocytes, lack of wound-induced hair neogenesis indicated a regulatory role of T cells on hair follicle regeneration. The microenvironment around scaffolds involved an intricate interplay of immune and cutaneous cells.