Differential expression of CD11c defines two types of tissue-resident macrophages with different origins in steady-state salivary glands

Impaired autophagy-mediated macrophage polarization contributes to age-related hyposalivation

Age-related dysfunction of salivary glands (SGs) leading to xerostomia or dry mouth is typically associated with increased dental caries and difficulties in mastication, deglutition or speech. Inflammaging-induced hyposalivation plays a significant role in aged SGs; however, the mechanisms by which ageing shapes the inflammatory microenvironment of SGs remain unclear. Here, we show that reduced salivary secretion flow rate in aged human and mice SGs is associated with impaired autophagy and increased M1 polarization of macrophages. Our study reveals the crucial roles of SIRT6 in regulating macrophage autophagy and polarization through the PI3K/AKT/mTOR pathway, as demonstrated by generating two conditional knock out mice. Furthermore, triptolide (TP) effectively rejuvenates macrophage autophagy and polarization via targeting this pathway. We also design a local delivery of TP-loaded apoptotic extracellular vesicles (ApoEVs) to improve age-related SGs dysfunction therapeutically. Collectively, our findings uncover a previously unknown link between SIRT6-regulated autophagy and macrophage polarization in age-mediated hyposalivation, while our locally therapeutic strategy exhibits potential preventive effects for age-related hyposalivation.

Immune cell composition and inflammatory profile of human peri-implantitis and periodontitis lesions

Peri-implantitis (PI) and periodontitis (PD) are common oral inflammatory diseases, which seem to exhibit critical differences in some of their molecular features. Thus, we assessed the immune cell composition of PI and PD lesions and the corresponding inflammatory profile in soft tissues and crevicular fluid. PI, PD, and control patients were recruited (n = 62), and soft tissue biopsies were collected during surgery. Crevicular fluid around implant or tooth was collected. The proportions of major immune cell populations in tissues were analyzed by flow cytometry, and the inflammatory profile in tissue and crevicular fluid by a multiplex immunoassay. No significant difference was seen between PI and PD lesions in the proportions of immune cells. PI tissues showed an increased frequency of B cells in comparison with control tissues, along with higher levels of IL-1β, TNF-α, IL-4, and BAFF in tissue and crevicular fluid. Moreover, TNF-α, IL-17A, and BAFF were higher in PI tissues, but not in PD, than in control tissues. The immune cell composition did not differ significantly between PI and PD, but an enhanced inflammatory profile was seen in PI tissue. PI lesions were enriched in B cells, and displayed increased levels of IL-1β, TNF-α, IL-4, and BAFF in both tissue and crevicular fluid.

Targeting dendritic cell-specific TNFR2 improves skin and joint inflammation by inhibiting IL-12/ IFN-γ pathways in a mouse model of psoriatic arthritis

Psoriasis (PsO) and Psoriatic arthritis (PsA) are immune-mediated inflammatory diseases affecting the skin and joints. Approximately, 30% of patients with PsO develop PsA over time with both conditions being associated with elevated tumor necrosis factor-alpha (TNF-α) expression. TNF-α mediates its effect through two membrane receptors, TNFR1 and TNFR2. While current TNF-α-neutralizing agents, targeting both TNFR1 and TNFR2 receptors, constitute the primary treatment for psoriatic diseases, their long-term use is limited due to an increase in opportunistic infections, tuberculosis reactivation and malignancies likely attributed to TNFR1 inactivation. Recent findings suggest a pivotal role of TNFR2 in psoriatic disease, as evidenced by its amelioration in global TNFR2-knockout (TNFR2KO) mice, but not in TNFR1KO mice. The diminished disease phenotype in TNFR2KO mice is accompanied by a decrease in DC populations. However, the specific contribution of TNFR2 in dendritic cells (DCs) remains unclear. Here, utilizing a mannan-oligosaccharide (MOS)-induced PsA model, we demonstrate a significant reduction in PsA-like skin scaling and joint inflammation in dendritic cell-specific TNFR2 knockout mice (DC-TNFR2KO). Notably, MOS treatment in control mice (TNFR2 fl/fl) led to an increase in conventional type 1 dendritic cells (cDC1) population in the spleen, a response inhibited in DC-TNFR2KO mice. Furthermore, DC-TNFR2KO mice exhibited reduced levels of interleukin-12 (IL-12), a Th1 cell activator, as well as diminished Th1 cells, and interferon-gamma (IFN-γ) levels in the serum compared to controls following MOS stimulation. In summary, our study provides compelling evidence supporting the role of TNFR2 in promoting PsA-like inflammation through cDC1/Th1 activation pathways.

Enhancing Infected Diabetic Wound Healing through Multifunctional Nanocomposite-Loaded Microneedle Patch: Inducing Multiple Regenerative Sites

Infected diabetic wound (DW) presents a prolonged and challenging healing process within the field of regenerative medicine. The effectiveness of conventional drug therapies is hindered by their limited ability to reach deep tissues and promote adequate wound healing rates. Therefore, there is an imperative to develop drug delivery systems that can penetrate deep tissues while exhibiting multifunctional properties to expedite wound healing. In this study, w e devised a soluble microneedle (MN) patch made of γ-PGA, featuring multiple arrays, which w as loaded with core-shell structured nanoparticles (NPs) known as Ag@MSN@CeO2, to enhance the healing of infected DWs. The NP comprises a cerium dioxide (CeO2) core with anti-inflammatory and antioxidant properties, a mesoporous silica NP (MSN) shell with angiogenic characteristics, and an outermost layer doped with Ag to combat bacterial infections. W e demonstrated that the MN platform loaded with Ag@MSN@CeO2 successfully penetrated deep tissues for effective drug delivery. These MN tips induced the formation of multiple regenerative sites at various points, leading to antibacterial, reactive oxygen species-lowering, macrophage ecological niche-regulating, vascular regeneration-promoting, and collagen deposition-promoting effects, thus significantly expediting the healing process of infected DWs. Considering these findings, the multifunctional MN@Ag@MSN@CeO2 patch exhibits substantial potential for clinical applications in the treatment of infected DW.

Advanced insights on tumor-associated macrophages revealed by single-cell RNA sequencing: The intratumor heterogeneity, functional phenotypes, and cellular interactions

Single-cell RNA sequencing (scRNA-seq) is an emerging technology used for cellular transcriptome analysis. The application of scRNA-seq has led to profoundly advanced oncology research, continuously optimizing novel therapeutic strategies. Intratumor heterogeneity extensively consists of all tumor components, contributing to different tumor behaviors and treatment responses. Tumor-associated macrophages (TAMs), the core immune cells linking innate and adaptive immunity, play significant roles in tumor progression and resistance to therapies. Moreover, dynamic changes occur in TAM phenotypes and functions subject to the regulation of the tumor microenvironment. The heterogeneity of TAMs corresponding to the state of the tumor microenvironment has been comprehensively recognized using scRNA-seq. Herein, we reviewed recent research and summarized variations in TAM phenotypes and functions from a developmental perspective to better understand the significance of TAMs in the tumor microenvironment.

CSF1R-dependent macrophages in the salivary gland are essential for epithelial regeneration after radiation-induced injury

The salivary glands often become damaged in individuals receiving radiotherapy for head and neck cancer, resulting in chronic dry mouth. This leads to detrimental effects on their health and quality of life, for which there is no regenerative therapy. Macrophages are the predominant immune cell in the salivary glands and are attractive therapeutic targets due to their unrivaled capacity to drive tissue repair. Yet, the nature and role of macrophages in salivary gland homeostasis and how they may contribute to tissue repair after injury are not well understood. Here, we show that at least two phenotypically and transcriptionally distinct CX3CR1+ macrophage populations are present in the adult salivary gland, which occupy anatomically distinct niches. CD11c+CD206-CD163- macrophages typically associate with gland epithelium, whereas CD11c-CD206+CD163+ macrophages associate with blood vessels and nerves. Using a suite of complementary fate mapping systems, we show that there are highly dynamic changes in the ontogeny and composition of salivary gland macrophages with age. Using an in vivo model of radiation-induced salivary gland injury combined with genetic or antibody-mediated depletion of macrophages, we demonstrate an essential role for macrophages in clearance of cells with DNA damage. Furthermore, we show that epithelial-associated macrophages are indispensable for effective tissue repair and gland function after radiation-induced injury, with their depletion resulting in reduced saliva production. Our data, therefore, provide a strong case for exploring the therapeutic potential of manipulating macrophages to promote tissue repair and thus minimize salivary gland dysfunction after radiotherapy.

Immune responses in the uterine mucosa: clues for vaccine development in pigs

The immune system in the upper reproductive tract (URT) protects against sexually transmitted pathogens, while at the same time providing immune tolerance responses against allogenic sperm and the developing fetus. The uterine environment is also responsive to hormonal variations during the estrus cycle, although the most likely timing of exposure to pathogens is during estrus and breeding when the cervix is semi-permissive. The goal for intrauterine immunization would be to induce local or systemic immunity and/or to promote colostral/lactogenic immunity that will passively protect suckling offspring. The developing fetus is not the vaccine target. This minireview article focuses on the immune response induced in the pig uterus (uterine body and uterine horns) with some comparative references to other livestock species, mice, and humans.

CX3CR1 modulates SLE-associated glomerulonephritis and cardiovascular disease in MRL/lpr mice

OBJECTIVE

Patients with systemic lupus erythematosus (SLE) often develop multi-organ damages including heart and kidney complications. We sought to better define the underlying mechanisms with a focus on the chemokine receptor CX3CR1.

METHODS

We generated Cx3cr1-deficient MRL/lpr lupus-prone mice through backcrossing. We then employed heterozygous intercross to generate MRL/lpr littermates that were either sufficient or deficient of CX3CR1. The mice were also treated with either Lactobacillus spp. or a high-fat diet (HFD) followed by assessments of the kidney and heart, respectively.

RESULTS

Cx3cr1-/- MRL/lpr mice exhibited a distinct phenotype of exacerbated glomerulonephritis compared to Cx3cr1+/+ littermates, which was associated with a decrease of spleen tolerogenic marginal zone macrophages and an increase of double-negative T cells. Interestingly, upon correction of the gut microbiota with Lactobacillus administration, the phenotype of exacerbated glomerulonephritis was reversed, suggesting that CX3CR1 controls glomerulonephritis in MRL/lpr mice through a gut microbiota-dependent mechanism. Upon treatment with HFD, Cx3cr1-/- MRL/lpr mice developed significantly more atherosclerotic plaques that were promoted by Ly6C+ monocytes. Activated monocytes expressed ICOS-L that interacted with ICOS-expressing follicular T-helper cells, which in turn facilitated a germinal center reaction to produce more autoantibodies. Through a positive feedback mechanism, the increased circulatory autoantibodies further promoted the activation of Ly6C+ monocytes and their display of ICOS-L.

CONCLUSIONS

We uncovered novel, Cx3cr1 deficiency-mediated pathogenic mechanisms contributing to SLE-associated glomerulonephritis and cardiovascular disease.

A Salivary Gland Resident Macrophage Subset Regulating Radiation Responses

Radiotherapy of head and neck cancers frequently leads to irreversible hypofunction of salivary glands, which severely compromises the quality of life and is extremely difficult to treat. We found recently that salivary gland resident macrophages are sensitive to radiation and interact with epithelial progenitors and endothelial cells through homeostatic paracrine factors. Heterogeneous subpopulations of resident macrophages are present in other organs with distinct functions, whereas subpopulations of salivary gland resident macrophages with distinct functions or transcriptional profiles have not been reported yet. Using single-cell RNA sequencing, we found that mouse submandibular glands (SMGs) contain 2 distinct self-renewing resident macrophage subsets, an MHC-IIhi subset present in many other organs and an uncommon Csf2r+ subset. The main source of Csf2 in SMGs are innate lymphoid cells (ILCs) that rely on IL15 for maintenance, while the main source of IL15 protein is Csf2r+ resident macrophages, indicating a homeostatic paracrine interaction between these cells. Csf2r+ resident macrophages are the major source of hepatocyte growth factor (Hgf) that regulates homeostasis of SMG epithelial progenitors. Meanwhile, Csf2r+ resident macrophages are responsive to Hedgehog signaling that can rescue salivary function impaired by radiation. Consistently, irradiation persistently decreased numbers of ILCs and levels of IL15 and Csf2 in SMGs, which were all recovered by transient activation of Hedgehog signaling after radiation. Csf2r+ resident macrophages and MHC-IIhi resident macrophages share transcriptome profiles of perivascular macrophages and macrophages associated with nerves and/or epithelial cells in other organs, respectively, and such niche preferences were supported by lineage tracing and immunofluorescent staining. These findings reveal an uncommon resident macrophage subset that regulates the homeostasis of the salivary gland and is promising as the target to restore salivary gland function impaired by radiation.

Microbiota-dependent and -independent postnatal development of salivary immunity

While saliva regulates the interplay between the microbiota and the oral immune system, the mechanisms establishing postnatal salivary immunity are ill-defined. Here, we show that high levels of neutrophils and neonatal Fc receptor (FcRn)-transferred maternal IgG are temporarily present in the neonatal murine salivary glands in a microbiota-independent manner. During weaning, neutrophils, FcRn, and IgG decrease in the salivary glands, while the polymeric immunoglobulin receptor (pIgR) is upregulated in a growth arrest-specific 6 (GAS6)-dependent manner independent of the microbiota. Production of salivary IgA begins following weaning and relies on CD4-help, IL-17, and the microbiota. The weaning phase is characterized by a transient accumulation of dendritic cells capable of migrating from the oral mucosa to the salivary glands upon exposure to microbial challenges and activating T cells. This study reveals the postnatal mechanisms developed in the salivary glands to induce immunity and proposes the salivary glands as an immune inductive site.

Cationic Polyethyleneimine (PEI)–Gold Nanocomposites Modulate Macrophage Activation and Reprogram Mouse Breast Triple-Negative MET-1 Tumor Immunological Microenvironment

Nanomedicines based on inorganic nanoparticles have grown in the last decades due to the nanosystems’ versatility in the coating, tuneability, and physical and chemical properties. Nonetheless, concerns have been raised regarding the immunotropic profile of nanoparticles and how metallic nanoparticles affect the immune system. Cationic polymer nanoparticles are widely used for cell transfection and proved to exert an adjuvant immunomodulatory effect that improves the efficiency of conventional vaccines against infection or cancer. Likewise, gold nanoparticles (AuNPs) also exhibit diverse effects on immune response depending on size or coatings. Photothermal or photodynamic therapy, radiosensitization, and drug or gene delivery systems take advantage of the unique properties of AuNPs to deeply modify the tumoral ecosystem. However, the collective effects that AuNPs combined with cationic polymers might exert on their own in the tumor immunological microenvironment remain elusive. The purpose of this study was to analyze the triple-negative breast tumor immunological microenvironment upon intratumoral injection of polyethyleneimine (PEI)–AuNP nanocomposites (named AuPEI) and elucidate how it might affect future immunotherapeutic approaches based on this nanosystem. AuPEI nanocomposites were synthesized through a one-pot synthesis method with PEI as both a reducing and capping agent, resulting in fractal assemblies of about 10 nm AuNPs. AuPEI induced an inflammatory profile in vitro in the mouse macrophage-like cells RAW264.7 as determined by the secretion of TNF-α and CCL5 while the immunosuppressor IL-10 was not increased. However, in vivo in the mouse breast MET-1 tumor model, AuPEI nanocomposites shifted the immunological tumor microenvironment toward an M2 phenotype with an immunosuppressive profile as determined by the infiltration of PD-1-positive lymphocytes. This dichotomy in AuPEI nanocomposites in vitro and in vivo might be attributed to the highly complex tumor microenvironment and highlights the importance of testing the immunogenicity of nanomaterials in vitro and more importantly in vivo in relevant immunocompetent mouse tumor models to better elucidate any adverse or unexpected effect.