DHRS9 Is a Stable Marker of Human Regulatory Macrophages

Cellular interactions within the immune microenvironment underpins resistance to cell cycle inhibition in breast cancers

Immune evasion by cancer cells involves reshaping the tumor microenvironment (TME) via communication with non-malignant cells. However, resistance-promoting interactions during treatment remain lesser known. Here we examine the composition, communication, and phenotypes of tumor-associated cells in serial biopsies from stage II and III high-risk estrogen receptor positive (ER+ ) breast cancers of patients receiving endocrine therapy (letrozole) as single agent or in combination with ribociclib, a CDK4/6-targeting cell cycle inhibitor. Single-cell RNA sequencing analyses on longitudinally collected samples show that in tumors overcoming the growth suppressive effects of ribociclib, first cancer cells upregulate cytokines and growth factors that stimulate immune-suppressive myeloid differentiation, resulting in reduced myeloid cell- CD8 + T-cell crosstalk via IL-15/18 signaling. Subsequently, tumors growing during treatment show diminished T-cell activation and recruitment. In vitro, ribociclib does not only inhibit cancer cell growth but also T cell proliferation and activation upon co-culturing. Exogenous IL-15 improves CDK4/6 inhibitor efficacy by augmenting T-cell proliferation and cancer cell killing by T cells. In summary, response to ribociclib in stage II and III high-risk ER +  breast cancer depends on the composition, activation phenotypes and communication network of immune cells.

Deconvolution of cell-type-associated markers predictive of response to neoadjuvant radiotherapy

Tumor microenvironent contains prognostic molecular markers and therapeutic targets from different cellular sources, which are still not fully revealed in the resistance and recurrence after radiotherapy for rectal cancer. By integrating the scRNA-seq data, we deconvoluted the bulk transcriptomics of rectal cancer collected before preoperative neoadjuvant radiotherapy (nRT) into fractions and gene expression of the six cell types. The inferred cell-type-associated DEGs, abbreviated as caDEGs, of myeloid and stromal cells were enriched for overlapping yet unique biological processes including immunity, angiogenesis, and metabolism, respectively. Ecotyper analysis indicates that the caDEGs reflects cell states and ecotypes in association with nRT response. By mapping the caDEGs onto the context-free and newly built ligand-receptor and collagen-integrin lists from scRNA-Seq data, respectively, we inferred 297 cell-type-specific trans- and/or cis-collagen-integrin and 219 heterotypic ligand-receptor interactions potentially associated with nRT response, including interactions between stromal-associated COL1A2/COL6A1/COL6A2 and stromal or CMS1-associated ITGA1/B1, between epithelial-associated JAG1 and stromal-associated NOTCHs, between CMS2 epithelial-associated CCL15 and proliferating myeloid-associated CCR1, between myeloid-associated CCL4/CD86 and lymphatic endothelial-associated ACKR2, and between myeloid-associated TNFS13B and B cell-associated TNFRSF13B/C, etc. Intriguingly, results suggest a greater number of down-regulated cell-type-related markers in resistant cancers to nRT. Favorable myeloid-associated CD14, epithelial-associated DYM, stromal-associated COL1A2 and COL3A1, and unfavorable epithelial-associated CELSR3 and KCNH8 markers were inferred at least from two independent nCRT datasets of GSE119409, GSE35452, and GSE45404. The results provide insights into roles of the stromal and immune cells beside epithelial cells in resistance to radiotherapy for rectal cancers. The proposed approach can be applicable to other diseases as well. Codes and additional data are available at https://github.com/Xueling21/rectalNRT_deconv.

Embryonic macrophages support endocrine commitment during human pancreatic differentiation

Organogenesis is a complex process that relies on a dynamic interplay between extrinsic factors originating from the microenvironment and tissue-specific intrinsic factors. For pancreatic endocrine cells, the local niche consists of acinar and ductal cells as well as neuronal, immune, endothelial, and stromal cells. Hematopoietic cells have been detected in human pancreas as early as 6 post-conception weeks, but whether they play a role during human endocrinogenesis remains unknown. To investigate this, we performed single-nucleus RNA sequencing (snRNA-seq) of the second-trimester human pancreas and identified a wide range of hematopoietic cells, including two distinct subsets of tissue-resident macrophages. Leveraging this discovery, we developed a co-culture system of human embryonic stem cell-derived endocrine-macrophage organoids to model their interaction in vitro. Here, we show that macrophages support the differentiation and viability of endocrine cells in vitro and enhance tissue engraftment, highlighting their potential role in tissue engineering strategies for diabetes.

Identification of prognostic biomarkers related to retinoic acid metabolism in gliomas and analysis of their impact on the immune microenvironment

Glioma is a primary tumor of the central nervous system. Numerous investigations have demonstrated that retinoic acid (RA) signaling plays an important role in glioblastoma. This research aimed to develop a RA metabolism-related gene signature associated with glioma. The RA metabolism-related differentially expressed genes were obtained through differential analysis of RA metabolism-related genes in GSE4290. The univariate Cox and least absolute shrinkage and selection operator regression analysis were adopted to build a RA metabolism-related glioma prognostic signature. We further conducted immune feature estimation and functional enrichment analysis between 2 risk subgroups. Finally, the potential drug-targeting prognostic genes were predicted through the DrugBank database. A sum of 10 RA metabolism-related differentially expressed genes between normal and tumor groups were identified. Then, a RA metabolism-related prognostic signature was built based on the 7 prognostic genes (ADH4, DHRS3, DHRS9, LRAT, RDH10, RDH12, and RDH5). Glioma patients were separated into 2 risk subgroups (low-risk vs high-risk) based on the median value of the risk score. We found that monocytes were negatively correlated with DHRS9, while activated naive CD4+T cell was positively correlated with RDH10. These prognostic genes participated in some immune-related processes, such as "B cell-mediated immunity." Finally, 4 drugs targeting DHRS3, LRAT, and RDH12 were predicted, including vitamin A, nicotinamide adenine dinucleotide, ethanol, and cyclohexylformamide. The prognostic signature comprised of ADH4, DHRS3, DHRS9, LRAT, RDH10, RDH12, and RDH5 based on RA metabolism was established, which provided a theoretical basis and reference value for the research of glioma.

The role and research progress of macrophages after heart transplantation

Since the 60s of the 20th century, heart transplantation has been the best treatment for patients with end-stage heart failure. Due to the increasing number of patients, how to expand the number of donor organs and enhance immune compatibility has become an urgent problem to be solved at this stage. Although current immunosuppression is effective, its side effects are also quite obvious, such as opportunistic infections and malignant tumors. In this review, we focus on the important role in macrophages after heart transplantation and their potential targets for achieving allogeneic graft tolerance, in order to improve effective graft survival and reduce infection and the occurrence of malignant tumors.

The Role of Hyaluronan/Receptor for Hyaluronan-Mediated Motility Interactions in the Modulation of Macrophage Polarization and Cartilage Repair

Hyaluronan (HA), a negatively charged linear glycosaminoglycan, is a key macromolecular component of the articular cartilage extracellular matrix. The differential effects of HA are determined by a spatially/temporally regulated display of HA receptors, such as CD44 and receptor for hyaluronan-mediated motility (RHAMM). HA signaling through CD44 with RHAMM has been shown to stimulate inflammation and fibrotic processes. This study shows an increased expression of RHAMM in proinflammatory macrophages. Interfering with HA/RHAMM interactions using a 15-mer RHAMM-mimetic, HA-binding peptide, together with high-molecular-weight (HMW) HA reduced the expression and release of inflammatory markers and increased the expression of anti-inflammatory markers in proinflammatory macrophages. HA/RHAMM interactions were interfered in vivo during the regeneration of a full-thickness cartilage defect after microfracture surgery in rabbits using three intra-articular injections of 15-mer RHAMM-mimetic. HA-binding peptide together with HMWHA reduced the number of proinflammatory macrophages and increased the number of anti-inflammatory macrophages in the injured knee joint and greatly improved the repair of the cartilage defect compared with intra-articular injections of HMWHA alone. These findings suggest that HA/RHAMM interactions play a key role in cartilage repair/regeneration via stimulating inflammatory and fibrotic events, including increasing the ratio of proinflammatory/anti-inflammatory macrophages. Interfering with these interactions reduced inflammation and greatly improved cartilage repair.

Insights into the effect of benzotriazoles in liver using integrated metabolomic and transcriptomic analysis

Benzotriazoles (BTRs) are a class of benzoheterocyclic chemicals that are frequently used as metal-corrosive inhibitors, both in industry and daily use. However, the exposure effect information on BTRs remains relatively limited. In this study, an integrated metabolomic and transcriptomic approach was utilized to evaluate the effect of three BTRs, benzotriazole, 6-chloro-1-hydroxi-benzotriazole, and 1-hydroxy-benzotriazole, in the mouse liver with results showing disrupted basal metabolic processes and vitamin and cofactor metabolism after 28 days. The expression of several genes that are related to the inflammatory response and aryl hydrocarbon receptor pathways, such as Gstt2 and Arntl, was altered by the exposure to BTRs. Exposure to BTRs also affected metabolites and genes that are involved in the immune system and xenobiotic responses. The altered expression of several cytochrome P450 family genes reveal a potential detoxification mechanism in the mouse liver. Taken together, our findings provide new insights into the multilayer response of the mouse liver to BTRs exposure as well as a resource for further exploration of the molecular mechanisms by which the response occurs.

Regulatory macrophages in solid organ xenotransplantation

Due to a critical organ shortage, pig organs are being explored for use in transplantation. Differences between species, particularly in cell surface glycans, can trigger elevated immune responses in xenotransplantation. To mitigate the risk of hyperacute rejection, genetically modified pigs have been developed that lack certain glycans and express human complement inhibitors. Nevertheless, organs from these pigs may still provoke stronger inflammatory and innate immune reactions than allotransplants. Dysregulation of coagulation and persistent inflammation remain obstacles in the transplantation of pig organs into primates. Regulatory macrophages (Mregs), known for their anti-inflammatory properties, could offer a potential solution. Mregs secrete interleukin 10 and transforming growth factor beta, thereby suppressing immune responses and promoting the development of regulatory T cells. These Mregs are typically induced via the stimulation of monocytes or macrophages with macrophage colony-stimulating factor and interferon gamma, and they conspicuously express the stable marker dehydrogenase/reductase 9. Consequently, understanding the precise mechanisms governing Mreg generation, stability, and immunomodulation could pave the way for the therapeutic use of Mregs generated in vitro. This approach has the potential to reduce the required dosages and durations of anti-inflammatory and immunosuppressive medications in preclinical and clinical settings.

Human Regulatory Macrophages Derived from THP-1 Cells Using Arginylglycylaspartic Acid and Vitamin D3

Regulatory macrophages (Mregs) are unique in that they have anti-inflammatory and immunosuppressive properties. Thus, treating inflammatory diseases using Mregs is an area of active research. Human Mregs are usually generated by culturing peripheral blood monocytes stimulated using a macrophage colony-stimulating factor with interferon (IFN)-γ. Herein, we generated Mregs with an elongated cell morphology from THP-1 cells that were stimulated with phorbol 12-myristate 13-acetate and cultured with both arginylglycylaspartic acid and vitamin D3. These Mregs regulated macrophage function, and respectively downregulated and upregulated the expression of pro-inflammatory and immunosuppressive mediators. They also expressed Mregs-specific markers, such as dehydrogenase/reductase 9, even when exposed to such inflammatory stimulants as IFN-γ, lipopolysaccharide, purified xenogeneic antigen, and xenogeneic cells. The Mregs also exerted anti-inflammatory and anticoagulatory actions in response to xenogeneic cells, as well as exerting immunosuppressive effects on mitogen-induced Jurkat T-cell proliferation. Our method of generating functional Mregs in vitro without cytokines is simple and cost-effective.

Multiple Shades of Gray-Macrophages in Acute Allograft Rejection

Long-term results following solid organ transplantation do not mirror the excellent short-term results achieved in recent decades. It is therefore clear that current immunosuppressive maintenance protocols primarily addressing the adaptive immune system no longer meet the required clinical need. Identification of novel targets addressing this shortcoming is urgently needed. There is a growing interest in better understanding the role of the innate immune system in this context. In this review, we focus on macrophages, which are known to prominently infiltrate allografts and, during allograft rejection, to be involved in the surge of the adaptive immune response by expression of pro-inflammatory cytokines and direct cytotoxicity. However, this active participation is janus-faced and unspecific targeting of macrophages may not consider the different subtypes involved. Under this premise, we give an overview on macrophages, including their origins, plasticity, and important markers. We then briefly describe their role in acute allograft rejection, which ranges from sustaining injury to promoting tolerance, as well as the impact of maintenance immunosuppressants on macrophages. Finally, we discuss the observed immunosuppressive role of the vitamin-like compound tetrahydrobiopterin and the recent findings that suggest the innate immune system, particularly macrophages, as its target.

Immune cell dynamics deconvoluted by single-cell RNA sequencing in normothermic machine perfusion of the liver

Normothermic machine perfusion (NMP) has emerged as an innovative organ preservation technique. Developing an understanding for the donor organ immune cell composition and its dynamic changes during NMP is essential. We aimed for a comprehensive characterization of immune cell (sub)populations, cell trafficking and cytokine release during liver NMP. Single-cell transcriptome profiling of human donor livers prior to, during NMP and after transplantation shows an abundance of CXC chemokine receptor 1⁺/2⁺ (CXCR1⁺/CXCR2⁺) neutrophils, which significantly decreased during NMP. This is paralleled by a large efflux of passenger leukocytes with neutrophil predominance in the perfusate. During NMP, neutrophils shift from a pro-inflammatory state towards an aged/chronically activated/exhausted phenotype, while anti-inflammatory/tolerogenic monocytes/macrophages are increased. We herein describe the dynamics of the immune cell repertoire, phenotypic immune cell shifts and a dominance of neutrophils during liver NMP, which potentially contribute to the inflammatory response. Our findings may serve as resource to initiate future immune-interventional studies.

Functional characterization of interleukin 4 and retinoic acid signaling crosstalk during alternative macrophage activation

Retinoic acid possesses potent immunomodulatory properties in various cell types, including macrophages. In this study, we first investigated the effects at the transcriptional and functional levels of exogenous retinoic acid in murine bone marrow-derived macrophages (BMDMs) in the presence or absence of interleukin 4 (IL4), a cytokine with potent anti-inflammatory properties. We examined the effect of IL4 on vitamin A homeostasis in macrophages by quantifying retinoid synthesis and secretion. Our RNAseq data show that exogenous retinoic acid synergizes with IL4 to regulate anti-inflammatory pathways such as oxidative phosphorylation and phagocytosis. Efferocytosis and lysosomal degradation assays validated gene expression changes at the functional level. IL4 treatment altered the expression of several genes involved in vitamin A transport and conversion to retinoic acid. Radiolabeling experiments and mass spectrometry assays revealed that IL4 stimulates retinoic acid production and secretion in a signal transducer and activator of transcription 6 (STAT6)-dependent manner. In summary, our studies highlight the key role of exogenous and endogenous retinoic acid in shaping the anti-inflammatory response of macrophages.

PDMS Micropatterns Coated with PDA and RGD Induce a Regulatory Macrophage-like Phenotype

Regulatory macrophages (Mreg) are a special cell type that present a potential therapeutic strategy for various inflammatory diseases. In vitro, Mreg generation mainly takes 7-10 days of treatment with chemicals, including cytokines. In the present study, we established a new approach for Mreg generation using a three-dimensional (3D) micropatterned polydimethylsiloxane (PDMS) surface coated with a natural biopolymer adhesive polydopamine (PDA) and the common cell adhesion peptide motif arginylglycylaspartic acid (RGD). The 3D PDMS surfaces were fabricated by photolithography and soft lithography techniques and were subsequently coated with an RGD+PDA mixture to form a surface that facilitates cell adhesion. Human monocytes (THP-1 cells) were cultured on different types of 2D or 3D micropatterns for four days, and the cell morphology, elongation, and Mreg marker expression were assessed using microscopic and flow cytometric analyses. The cells grown on the PDA+RGD-coated 3D micropatterns (20-µm width/20-µm space) exhibited the most elongated morphology and strongest expression levels of Mreg markers, such as CD163, CD206, CD209, CD274, MER-TK, TREM2, and DHRS9. The present study demonstrated that PDA+RGD-coated 3D PDMS micropatterns successfully induced Mreg-like cells from THP-1 cells within four days without the use of cytokines, suggesting a time- and cost-effective method to generate Mreg-like cells in vitro.

Regulatory cells and the effect of cancer immunotherapy

Several mechanisms and cell types are involved in the regulation of the immune response. These include mostly regulatory T cells (Tregs), regulatory macrophages (Mregs), myeloid suppressor cells (MDSCs) and other regulatory cell types such as tolerogenic dendritic cells (tolDCs), regulatory B cells (Bregs), and mesenchymal stem cells (MSCs). These regulatory cells, known for their ability to suppress immune responses, can also suppress the anti-tumor immune response. The infiltration of many regulatory cells into tumor tissues is therefore associated with a poor prognosis. There is growing evidence that elimination of Tregs enhances anti-tumor immune responses. However, the systemic depletion of Treg cells can simultaneously cause deleterious autoimmunity. Furthermore, since regulatory cells are characterized by their high level of expression of immune checkpoints, it is also expected that immune checkpoint inhibitors perform part of their function by blocking these molecules and enhancing the immune response. This indicates that immunotherapy does not only act by activating specific effector T cells but can also directly or indirectly attenuate the suppressive activity of regulatory cells in tumor tissues. This review aims to draw together our current knowledge about the effect of immunotherapy on the various types of regulatory cells, and how these effects may be beneficial in the response to immunotherapy.

The Monocyte, a Maestro in the Tumor Microenvironment (TME) of Breast Cancer

Simple Summary

Breast cancer is one of the most prevalent cancers worldwide, surpassing lung cancer as the leading cause of overall cancer incidence. Available possible treatments nowadays include chemotherapy, hormonal therapy, and HER2-targeted therapy. Chemotherapy is notorious for its severe adverse effects. On the other hand, hormonal and HER2-targeted therapies only cover a narrow range of breast cancer subtypes. Accordingly, it is important to shed light on other therapy options. For this reason, immunotherapy nowadays is one of the most important research topics. It can be accomplished either by enhancing the pro-inflammatory immunity or suppressing the anti-inflammatory immunity. This review article aims to shed light on the importance of monocytes in the TME of breast cancer. The review also aims to highlight the behavior of the monocyte-derived populations, especially the anti-inflammatory populations. Thus, suppressing this anti-inflammatory activity might have a remarkable impact on future immunotherapy research.

Abstract

Breast cancer (BC) is well-known for being a leading cause of death worldwide. It is classified molecularly into luminal A, luminal B HER2−, luminal B HER2+, HER2+, and triple-negative breast cancer (TNBC). These subtypes differ in their prognosis; thus, understanding the tumor microenvironment (TME) makes new treatment strategies possible. The TME contains populations that exhibit anti-tumorigenic actions such as tumor-associated eosinophils. Moreover, it contains pro-tumorigenic populations such as tumor-associated neutrophils (TANs), or monocyte-derived populations. The monocyte-derived populations are tumor-associated macrophages (TAMs) and MDSCs. Thus, a monocyte can be considered a maestro within the TME. Moreover, the expansion of monocytes in the TME depends on many factors such as the BC stage, the presence of macrophage colony-stimulating factor (M-CSF), and the presence of some chemoattractants. After expansion, monocytes can differentiate into pro-inflammatory populations such as M1 macrophages or anti-inflammatory populations such as M2 macrophages according to the nature of cytokines present in the TME. Differentiation to TAMs depends on various factors such as the BC subtype, the presence of anti-inflammatory cytokines, and epigenetic factors. Furthermore, TAMs and MDSCs not only have a role in tumor progression but also are key players in metastasis. Thus, understanding the monocytes further can introduce new target therapies.

Identifying potential signatures for atherosclerosis in the context of predictive, preventive, and personalized medicine using integrative bioinformatics approaches and machine-learning strategies

Background

Atherosclerosis is a major contributor to morbidity and mortality worldwide. Although several molecular markers associated with atherosclerosis have been developed in recent years, the lack of robust evidence hinders their clinical applications. For these reasons, identification of novel and robust biomarkers will directly contribute to atherosclerosis management in the context of predictive, preventive, and personalized medicine (PPPM). This integrative analysis aimed to identify critical genetic markers of atherosclerosis and further explore the underlying molecular immune mechanism attributing to the altered biomarkers.

Methods

Gene Expression Omnibus (GEO) series datasets were downloaded from GEO. Firstly, differential expression analysis and functional analysis were conducted. Multiple machine-learning strategies were then employed to screen and determine key genetic markers, and receiver operating characteristic (ROC) analysis was used to assess diagnostic value. Subsequently, cell-type identification by estimating relative subsets of RNA transcript (CIBERSORT) and a single-cell RNA sequencing (scRNA-seq) data were performed to explore relationships between signatures and immune cells. Lastly, we validated the biomarkers' expression in human and mice experiments.

Results

A total of 611 overlapping differentially expressed genes (DEGs) included 361 upregulated and 250 downregulated genes. Based on the enrichment analysis, DEGs were mapped in terms related to immune cell involvements, immune activating process, and inflaming signals. After using multiple machine-learning strategies, dehydrogenase/reductase 9 (DHRS9) and protein tyrosine phosphatase receptor type J (PTPRJ) were identified as critical biomarkers and presented their high diagnostic accuracy for atherosclerosis. From CIBERSORT analysis, both DHRS9 and PTPRJ were significantly related to diverse immune cells, such as macrophages and mast cells. Further scRNA-seq analysis indicated DHRS9 was specifically upregulated in macrophages of atherosclerotic lesions, which was confirmed in atherosclerotic patients and mice.

Conclusions

Our findings are the first to report the involvement of DHRS9 in the atherogenesis, and the proatherogenic effect of DHRS9 is mediated by immune mechanism. In addition, we confirm that DHRS9 is localized in macrophages within atherosclerotic plaques. Therefore, upregulated DHRS9 could be a novel potential target for the future predictive diagnostics, targeted prevention, patient stratification, and personalization of medical services in atherosclerosis.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13167-022-00289-y.

Effects of chronic hypoxia on the gene expression profile in the embryonic heart in three Chinese indigenous chicken breeds (Gallus gallus)

Hypoxia exposure (HE) has adverse impacts on the embryonic development of chicken, whereas the mechanism underlying the response of the heart to HE during embryo development in birds is still unclear. Therefore, our study was designed to reveal the hub genes and the signaling pathways linked to chronic hypoxia stress. Thus, the gene expression microarray GSE12675, downloaded from the GEO database, included 12 embryonic heart samples in hypoxia and normoxia of three Chinese indigenous chicken breeds [Shouguang (SG), Tibetan (TB), and Dwarf Recessive White (DRW) chickens]. A total of 653 to 714 breed-specific differentially expressed genes (DEGs) were detected in each pairwise comparison. Gene ontology (GO) showed that the DEGs were mainly involved in biological processes, including vasoconstriction, cell differentiation, and the positive regulation of vasoconstriction. KEGG enrichment revealed that the DEGs were mainly enriched in MAPK, PPAR, insulin, adrenergic signaling in cardiomyocytes, etc. Moreover, 48 genes (e.g., SGCD, DHRS9, HELQ, MCMDC2, and ESCO2) might contribute to the response of the heart to HE. Taken together, the current study provides important clues for understanding the molecular mechanism of the heart's response to HE during the embryonic period of chicken.

All trans retinoic acid as a host-directed immunotherapy for tuberculosis

Tuberculosis (TB) is the top bacterial infectious disease killer and one of the top ten causes of death worldwide. The emergence of strains of multiple drug-resistant tuberculosis (MDR-TB) has pushed our available stock of anti-TB agents to the limit of effectiveness. This has increased the urgent need to develop novel treatment strategies using currently available resources. An adjunctive, host-directed therapy (HDT) designed to act on the host, instead of the bacteria, by boosting the host immune response through activation of intracellular pathways could be the answer. The integration of multidisciplinary approaches of repurposing currently FDA-approved drugs, with a targeted drug-delivery platform is a very promising option to reduce the long timeline associated with the approval of new drugs - time that cannot be afforded given the current levels of morbidity and mortality associated with TB infection. The deficiency of vitamin A has been reported to be highly associated with the increased susceptibility of TB. All trans retinoic acid (ATRA), the active metabolite of vitamin A, has proven to be very efficacious against TB both in vitro and in vivo. In this review, we discuss and summarise the importance of vitamin A metabolites in the fight against TB and what is known regarding the molecular mechanisms of ATRA as a host-directed therapy for TB including its effect on macrophages cytokine profile and cellular pathways. Furthermore, we focus on the issues behind why previous clinical trials with vitamin A supplementation have failed, and how these issues might be overcome.

Identification of Potential Key Biomarkers of Atrial Fibrillation and Their Correlation with Immune Infiltration in Atrial Tissue

Objective

To identify potential key biomarkers and characterize immune infiltration in atrial tissue of patients with atrial fibrillation (AF) through bioinformatics analysis.

Methods

Differentially expressed genes (DEGs) were identified by the LIMMA package in Bioconductor, and functional and pathway enrichment analyses were undertaken using GO and KEGG. The LASSO logistic regression and BORUTA algorithm were employed to screen for potential novel key markers of AF from all DEGs. Gene set variation analysis was also performed. Single-sample gene set enrichment analysis was employed to quantify the infiltration levels for each immune cell type, and the correlation between hub genes and infiltrating immune cells was analyzed.

Results

A total of 52 DEGs were identified, including of 26 downregulated DEGs and 26 upregulated DEGs. DEGs were primarily enriched in the Major Histocompatibility Complex class II protein complex, glucose homeostasis, protein tetramerization, regulation of synapse organization, cytokine activity, heart morphogenesis, and blood circulation. Three downregulated genes and three upregulated genes were screened by LASSO logistic regression and the BORUTA algorithm. Finally, immune infiltration analysis indicated that the atrial tissue of AF patients contained significant infiltration of APC_co_inhibition, Mast_cell, neutrophils, pDCs, T_cell_costimulation, and Th1_cells compared with paired sinus rhythm (SR) atrial tissue, and the three downregulated genes were negatively correlated with the six kinds of immune cells mentioned above.

Conclusion

The hub genes identified in this study and the differences in immune infiltration of atrial tissue observed between AF and SR tissue might help to characterize the occurrence and progression of AF.

Macrophages in Transplantation: A Matter of Plasticity, Polarization, and Diversity

Macrophages have emerged at the forefront of research in immunology and transplantation because of recent advances in basic science. New findings have illuminated macrophage populations not identified previously, expanded upon traditional macrophage phenotypes, and overhauled macrophage ontogeny. These advances have major implications for the field of transplant immunology. Macrophages are known to prime adaptive immune responses, perpetuate T-cell-mediated rejection and antibody-mediated rejection, and promote allograft fibrosis. In this review, macrophage phenotypes and their role in allograft injury of solid organ transplants will be discussed with an emphasis on kidney transplantation. Additionally, consideration will be given to the prospect of manipulating macrophage phenotypes as cell-based therapy. Innate immunity and macrophages represent important players in allograft injury and a promising target to improve transplant outcomes.

Dehydrogenase reductase 9 (SDR9C4) and related homologs recognize a broad spectrum of lipid mediator oxylipins as substrates

Bioactive oxylipins play multiple roles during inflammation and in the immune response, with termination of their actions partly dependent on the activity of yet-to-be characterized dehydrogenases. Here, we report that human microsomal dehydrogenase reductase 9 (DHRS9, also known as SDR9C4 of the short-chain dehydrogenase/reductase (SDR) superfamily) exhibits a robust oxidative activity toward oxylipins with hydroxyl groups located at carbons C9 and C13 of octadecanoids, C12 and C15 carbons of eicosanoids, and C14 carbon of docosanoids. DHRS9/SDR9C4 is also active toward lipid inflammatory mediator dihydroxylated Leukotriene B₄ and proresolving mediators such as tri-hydroxylated Resolvin D1 and Lipoxin A₄, although notably, with lack of activity on the 15-hydroxyl of prostaglandins. We also found that the SDR enzymes phylogenetically related to DHRS9, i.e., human SDR9C8 (or retinol dehydrogenase 16), the rat SDR9C family member known as retinol dehydrogenase 7, and the mouse ortholog of human DHRS9 display similar activity toward oxylipin substrates. Mice deficient in DHRS9 protein are viable, fertile, and display no apparent phenotype under normal conditions. However, the oxidative activity of microsomal membranes from the skin, lung, and trachea of Dhrs9^−/− mice toward 1 μM Leukotriene B₄ is 1.7- to 6-fold lower than that of microsomes from wild-type littermates. In addition, the oxidative activity toward 1 μM Resolvin D1 is reduced by about 2.5-fold with DHRS9-null microsomes from the skin and trachea. These results strongly suggest that DHRS9 might play an important role in the metabolism of a wide range of bioactive oxylipins in vivo.

Transitions in lineage specification and gene regulatory networks in hematopoietic stem/progenitor cells over human development

Human hematopoiesis is a dynamic process that starts in utero 18-21 days post-conception. Understanding the site- and stage-specific variation in hematopoiesis is important if we are to understand the origin of hematological disorders, many of which occur at specific points in the human lifespan. To unravel how the hematopoietic stem/progenitor cell (HSPC) compartment changes during human ontogeny and the underlying gene regulatory mechanisms, we compare 57,489 HSPCs from 5 different tissues spanning 4 developmental stages through the human lifetime. Single-cell transcriptomic analysis identifies significant site- and developmental stage-specific transitions in cellular architecture and gene regulatory networks. Hematopoietic stem cells show progression from cycling to quiescence and increased inflammatory signaling during ontogeny. We demonstrate the utility of this dataset for understanding aberrant hematopoiesis through comparison to two cancers that present at distinct time points in postnatal life-juvenile myelomonocytic leukemia, a childhood cancer, and myelofibrosis, which classically presents in older adults.

Immune characterization and profiles of SARS-CoV-2 infected patients reveals potential host therapeutic targets and SARS-CoV-2 oncogenesis mechanism

The spread of SARS-CoV-2 and the increasing mortality rates of COVID-19 create an urgent need for treatments, which are currently lacking. Although vaccines have been approved by the FDA for emergency use in the U.S., patients will continue to require pharmacologic intervention to reduce morbidity and mortality as vaccine availability remains limited. The rise of new variants makes the development of therapeutic strategies even more crucial to combat the current pandemic and future outbreaks. Evidence from several studies suggests the host immune response to SARS-CoV-2 infection plays a critical role in disease pathogenesis. Consequently, host immune factors are becoming more recognized as potential biomarkers and therapeutic targets for COVID-19. To develop therapeutic strategies to combat current and future coronavirus outbreaks, understanding how the coronavirus hijacks the host immune system during and after the infection is crucial. In this study, we investigated immunological patterns or characteristics of the host immune response to SARS-CoV-2 infection that may contribute to the disease severity of COVID-19 patients. We analyzed large bulk RNASeq and single cell RNAseq data from COVID-19 patient samples to immunoprofile differentially expressed gene sets and analyzed pathways to identify human host protein targets. We observed an immunological profile of severe COVID-19 patients characterized by upregulated cytokines, interferon-induced proteins, and pronounced T cell lymphopenia, supporting findings by previous studies. We identified a number of host immune targets including PERK, PKR, TNF, NF-kB, and other key genes that modulate the significant pathways and genes identified in COVID-19 patients. Finally, we identified genes modulated by COVID-19 infection that are implicated in oncogenesis, including E2F transcription factors and RB1, suggesting a mechanism by which SARS-CoV-2 infection may contribute to oncogenesis. Further clinical investigation of these targets may lead to bonafide therapeutic strategies to treat the current COVID-19 pandemic and protect against future outbreaks and viral escape variants.

Regulatory Macrophages and Tolerogenic Dendritic Cells in Myeloid Regulatory Cell-Based Therapies

Myeloid regulatory cell-based therapy has been shown to be a promising cell-based medicinal approach in organ transplantation and for the treatment of autoimmune diseases, such as type 1 diabetes, rheumatoid arthritis, Crohn's disease and multiple sclerosis. Dendritic cells (DCs) are the most efficient antigen-presenting cells and can naturally acquire tolerogenic properties through a variety of differentiation signals and stimuli. Several subtypes of DCs have been generated using additional agents, including vitamin D3, rapamycin and dexamethasone, or immunosuppressive cytokines, such as interleukin-10 (IL-10) and transforming growth factor-beta (TGF-β). These cells have been extensively studied in animals and humans to develop clinical-grade tolerogenic (tol)DCs. Regulatory macrophages (Mregs) are another type of protective myeloid cell that provide a tolerogenic environment, and have mainly been studied within the context of research on organ transplantation. This review aims to thoroughly describe the ex vivo generation of tolDCs and Mregs, their mechanism of action, as well as their therapeutic application and assessment in human clinical trials.

Revealing immune responses in the Mycobacterium avium subsp. paratuberculosis-infected THP-1 cells using single cell RNA-sequencing

Mycobacterium avium subsp. paratuberculosis (MAP) is a causative agent of Johne’s disease, which is a chronic and debilitating disease in ruminants. MAP is also considered to be a possible cause of Crohn’s disease in humans. However, few studies have focused on the interactions between MAP and human macrophages to elucidate the pathogenesis of Crohn’s disease. We sought to determine the initial responses of human THP-1 cells against MAP infection using single-cell RNA-seq analysis. Clustering analysis showed that THP-1 cells were divided into seven different clusters in response to phorbol-12-myristate-13-acetate (PMA) treatment. The characteristics of each cluster were investigated by identifying cluster-specific marker genes. From the results, we found that classically differentiated cells express CD14, CD36, and TLR2, and that this cell type showed the most active responses against MAP infection. The responses included the expression of proinflammatory cytokines and chemokines such as CCL4, CCL3, IL1B, IL8, and CCL20. In addition, the Mreg cell type, a novel cell type differentiated from THP-1 cells, was discovered. Thus, it is suggested that different cell types arise even when the same cell line is treated under the same conditions. Overall, analyzing gene expression patterns via scRNA-seq classification allows a more detailed observation of the response to infection by each cell type.

Immune characterization and profiles of SARS-CoV-2 infected patients reveals potential host therapeutic targets and SARS-CoV-2 oncogenesis mechanism

The spread of SARS-CoV-2 and the increasing mortality rates of COVID-19 create an urgent need for treatments, which are currently lacking. Although vaccines have been approved by the FDA for emergency use in the U.S., patients will continue to require pharmacologic intervention to reduce morbidity and mortality as vaccine availability remains limited. The rise of new variants makes the development of therapeutic strategies even more crucial to combat the current pandemic and future outbreaks. Evidence from several studies suggests the host immune response to SARS-CoV-2 infection plays a critical role in disease pathogenesis. Consequently, host immune factors are becoming more recognized as potential biomarkers and therapeutic targets for COVID-19. To develop therapeutic strategies to combat current and future coronavirus outbreaks, understanding how the coronavirus hijacks the host immune system during and after the infection is crucial. In this study, we investigated immunological patterns or characteristics of the host immune response to SARS-CoV-2 infection that may contribute to the disease severity of COVID-19 patients. We analyzed large bulk RNASeq and single cell RNAseq data from COVID-19 patient samples to immunoprofile differentially expressed gene sets and analyzed pathways to identify human host protein targets. We observed an immunological profile of severe COVID-19 patients characterized by upregulated cytokines, interferon-induced proteins, and pronounced T cell lymphopenia, supporting findings by previous studies. We identified a number of host immune targets including PERK, PKR, TNF, NF-kB, and other key genes that modulate the significant pathways and genes identified in COVID-19 patients. Finally, we identified genes modulated by COVID-19 infection that are implicated in oncogenesis, including E2F transcription factors and RB1, suggesting a mechanism by which SARS-CoV-2 infection may contribute to oncogenesis. Further clinical investigation of these targets may lead to bonafide therapeutic strategies to treat the current COVID-19 pandemic and protect against future outbreaks and viral escape variants.

The characteristics of regulatory macrophages and their roles in transplantation

Regulatory macrophages (Mregs) are a subtype of macrophages that are involved in regulating immune responses and inhibiting activated T lymphocyte proliferation. With advances in our basic understanding of Mregs and the revelation of their biological characteristics, Mregs have become a focus of research. In addition to promoting malignant tumor progression, Mregs also play an immunosuppressive role in inflammatory diseases and transplantation. Recent studies have shown that Mregs are closely associated with the induction of transplantation immune tolerance. Immune regulatory cell treatment as an adjunct immunosuppressive therapy offers new insights into the mechanism by which transplantation immune tolerance is established. The application of Mreg-based cellular immunotherapy has shown promise in clinical solid organ transplantation. Here, we provide a comprehensive overview of Mreg morphology, phenotype, induction and negative immunoregulatory function and discuss the role of Mregs in different transplantation models as well as their potential application value in clinical organ transplantation.

Human Mesenchymal Stromal Cell Secretome Promotes the Immunoregulatory Phenotype and Phagocytosis Activity in Human Macrophages

Human mesenchymal stromal/stem cells (hMSCs) show great promise in cell therapy due to their immunomodulatory properties. The overall immunomodulatory response of hMSCs resembles the resolution of inflammation, in which lipid mediators and regulatory macrophages (Mregs) play key roles. We investigated the effect of hMSC cell-cell contact and secretome on macrophages polarized and activated toward Mreg phenotype. Moreover, we studied the effect of supplemented polyunsaturated fatty acids (PUFAs): docosahexaenoic acid (DHA) and arachidonic acid, the precursors of lipid mediators, on hMSC immunomodulation. Our results show that unlike hMSC cell-cell contact, the hMSC secretome markedly increased the CD206 expression in both Mreg-polarized and Mreg-activated macrophages. Moreover, the secretome enhanced the expression of programmed death-ligand 1 on Mreg-polarized macrophages and Mer receptor tyrosine kinase on Mreg-activated macrophages. Remarkably, these changes were translated into improved Candida albicans phagocytosis activity of macrophages. Taken together, these results demonstrate that the hMSC secretome promotes the immunoregulatory and proresolving phenotype of Mregs. Intriguingly, DHA supplementation to hMSCs resulted in a more potentiated immunomodulation with increased CD163 expression and decreased gene expression of matrix metalloproteinase 2 in Mreg-polarized macrophages. These findings highlight the potential of PUFA supplementations as an easy and safe method to improve the hMSC therapeutic potential.

Transcriptomics uncovers substantial variability associated with alterations in manufacturing processes of macrophage cell therapy products

Gene expression plasticity is central for macrophages' timely responses to cues from the microenvironment permitting phenotypic adaptation from pro-inflammatory (M1) to wound healing and tissue-regenerative (M2, with several subclasses). Regulatory macrophages are a distinct macrophage type, possessing immunoregulatory, anti-inflammatory, and angiogenic properties. Due to these features, regulatory macrophages are considered as a potential cell therapy product to treat clinical conditions, e.g., non-healing diabetic foot ulcers. In this study we characterized two differently manufactured clinically relevant regulatory macrophages, programmable cells of monocytic origin and comparator macrophages (M1, M2a and M0) using flow-cytometry, RT-qPCR, phagocytosis and secretome measurements, and RNA-Seq. We demonstrate that conventional phenotyping had a limited potential to discriminate different types of macrophages which was ameliorated when global transcriptome characterization by RNA-Seq was employed. Using this approach we confirmed that macrophage manufacturing processes can result in a highly reproducible cell phenotype. At the same time, minor changes introduced in manufacturing resulted in phenotypically and functionally distinct regulatory macrophage types. Additionally, we have identified a novel constellation of process specific biomarkers, which will support further clinical product development.

Prognostic Impact of DHRS9 Overexpression in Pancreatic Cancer

Purpose

Pancreatic cancer (PC) has poor prognosis despite systemic treatment. Dehydrogenase/reductase member 9 (DHRS9) has been reported to be involved in many events of tumorigenesis, but its prognostic impact in PC remains undetermined. Thus, this study aimed to explore the association between DHRS9 expression and the prognosis of PC and investigate the possible mechanism by which DHRS9 is involved in PC progression.

Patients and Methods

The study used data: from Gene Expression Omnibus (GEO) and our institution to compare the DHRS9 expression between PC and adjacent normal tissues; from The Cancer Genome Atlas (TCGA) and our institution to assess the clinicopathological characteristics and prognosis of PC patients in high and low DHRS9 expression groups; and from TCGA to predict the potential mechanism of DHRS9 in PC. Western blot assay was used to identify DHRS9 expression in specimens collected from five patients who underwent surgery in our institute. Furthermore, immunohistochemistry (IHC) was then used to identify DHRS9 expression in the specimens of 109 patients who underwent surgery at our institute. Kaplan–Meier and Cox regression analyses were used to assess the prognostic significance of DHRS9 expression among PC patients.

Results

All the IHC, Western blot, and GEO datasets indicated that compared to normal tissues, DHRS9 was significantly overexpressed in PC tissues. IHC results demonstrated that the strong intensity of DHRS9 expression was significantly correlated with vascular infiltration (P < 0.05). Further, high DHRS9 expression was identified as a prognostic risk factor for overall survival. Functional analysis of DHRS9 co-expressed genes indicated that DHRS9 was involved in mitogen-activated protein kinases/extracellular signal-regulated kinase (MAPK/ERK) signaling pathway.

Conclusion

DHRS9 is upregulated in PC tissue, and high DHRS9 expression is correlated with poor prognosis in PC. DHRS9 may affect the oncological process of PC through MAPK/ERK pathway.

Identification of Differentially Expressed lncRNAs and mRNAs in Children with Acquired Aplastic Anemia by RNA Sequencing

Background

The effects of long noncoding RNAs (lncRNAs) and their related messenger RNAs (mRNAs) remain unknown in children with acquired aplastic anemia (AA). The aim of this study is to screen key lncRNAs and mRNAs and investigate their potential roles in the pathology of acquired AA in children.

Methods

RNA sequencing was performed to identify differentially expressed lncRNAs (DElncRNAs) and mRNAs (DEmRNAs) between blood samples of acquired AA children and healthy controls. cis-regulation, trans-regulation, competing endogenous (Ce) regulation networks of DElncRNAs and DEmRNAs were constructed. A literature search was performed to identify immune- or hematopoietic-related DElncRNA-DEmRNA pairs, and qPCR was conducted to validate the expression of the immune- or hematopoietic-related DElncRNA and DEmRNA.

Results

60 DElncRNAs and 364 DEmRNAs were identified. 13 DElncRNAs were predicted to have 15 cis-regulated target DEmRNAs, 16 DElncRNAs might have 28 trans-regulated DEmRNAs, and 2 DElncRNAs might have 9 Ce-regulated DEmRNAs. After literature screen and qPCR validation, 6 immune- or hematopoietic-related DElncRNA-DEmRNA pairs in the networks above were identified as key RNAs in the pathology of acquired AA.

Conclusion

This study revealed key lncRNAs in children with acquired AA and proposed their potential functions by predicting their target mRNAs, which lay the foundation for future study of potential effects of lncRNAs in children with acquired AA.

Chimerism, Transplant Tolerance, and Beyond

The present review discusses current developments in tolerance induction for solid organ transplantation with a particular emphasis on chimerism-based approaches. It explains the basic mechanisms of chimerism-based tolerance and provides an update on ongoing clinical tolerance trials. The concept of "delayed tolerance" is presented, and ongoing preclinical studies in the nonhuman primate setting-including current limitations and hurdles regarding this approach-are illustrated. In addition, a brief overview and update on cell-based tolerogenic clinical trials is provided. In a critical approach, advantages, limitations, and potential implications for the future of these different regimens are discussed.

Myeloid-Derived Suppressor Cells in Kidney Transplant Recipients and the Effect of Maintenance Immunotherapy

Myeloid-derived suppressor cells (MDSC) represent a heterogeneous group of myeloid regulatory cells that were originally described in cancer. Several studies in animal models point to MDSC as important players in the induction of allograft tolerance due to their immune modulatory function. Most of the published studies have been performed in animal models, and the data addressing MDSCs in human organ transplantation are scarce. We evaluated the phenotype and function of different MDSCs subsets in 38 kidney transplant recipients (KTRs) at different time points. Our data indicate that monocytic MDSCs (Mo-MDSC) increase in KTR at 6 and 12 months posttransplantation. On the contrary, the percentages of polymorphonuclear MDSC (PMN-MDSC) and early-stage MDSC (e-MDSC) are not significantly increased. We evaluated the immunosuppressive activity of Mo-MDSC in KTR and confirmed their ability to increase regulatory T cells (Treg) in vitro. Interestingly, when we compared the ability of Mo-MDSC to suppress T cell proliferation, we observed that tacrolimus, but not rapamycin-treated KTR, was able to inhibit CD4⁺ T cell proliferation in vitro. This indicates that, although mTOR inhibitors are widely regarded as supportive of regulatory responses, rapamycin may impair Mo-MDSC function, and suggests that the choice of immunosuppressive therapy may determine the tolerogenic pathway and participating immune cells that promote organ transplant acceptance in KTR.

Innate immunity in ischemia-reperfusion injury and graft rejection

PURPOSE OF REVIEW

Although organ transplantation has become the standard life-saving strategy for patients with end-stage organ failure and those with malignancies, effective and safe therapeutic strategies to combat allograft loss remain to be established. With the emerging evidence suggesting the critical role of innate immunity in the mechanism of allograft injury, we summarize the latest understanding of macrophage-neutrophil cross-communication and discuss therapeutic prospects of their targeting in transplant recipients.

RECENT FINDINGS

Macrophages and neutrophils contribute to the pathogenesis of early peritransplant ischemia-reperfusion injury and subsequent allograft rejection immune cascade, primarily by exacerbating inflammatory response and tissue damage. Noteworthy, recent advances enabled to elucidate multifaceted functions of innate immune cells, which are not only deleterious but may also prove graft-protective. Indeed, the efficacy of macrophage polarizing regimens or macrophage-targeted migration have been recognized to create graft-protective local environment. Moreover, novel molecular mechanisms in the neutrophil function have been identified, such as neutrophil extracellular traps, tissue-repairing capability, crosstalk with macrophages and T cells as well as reverse migration into the circulation.

SUMMARY

As efficient strategies to manage allograft rejection and improve transplant outcomes are lacking, newly discovered, and therapeutically attractive innate immune cell functions warrant comprehensive preclinical and clinical attention.

Post-natal all-trans-retinoic acid biosynthesis

Generation of the autacoid all-trans-retinoic acid (ATRA) from retinol (vitamin A) relies on a complex metabolon that includes retinol binding-proteins and enzymes from the short-chain dehydrogenase/reductase and aldehyde dehydrogenase gene families. Serum retinol binding-protein delivers all-trans-retinol (vitamin A) from blood to cells through two membrane receptors, Stra6 and Rbpr2. Stra6 and Rbpr2 convey retinol to cellular retinol binding-protein type 1 (Crbp1). Holo-Crbp1 delivers retinol to lecithin: retinol acyl transferase (Lrat) for esterification and storage. Lrat channels retinol directly into its active site from holo-Crbp1 by protein-protein interaction. The ratio apo-Crbp1/holo-Crbp1 directs flux of retinol into and out of retinyl esters, through regulating esterification vs ester hydrolysis. Multiple retinol dehydrogenases (Rdh1, Rdh10, Dhrs9, Rdhe2, Rdhe2s) channel retinol from holo-Crbp1 to generate retinal for ATRA biosynthesis. β-Carotene oxidase type 1 generates retinal from carotenoids, delivered by the scavenger receptor-B1. Retinal reductases (Dhrs3, Dhrs4, Rdh11) reduce retinal into retinol, thereby restraining ATRA biosynthesis. Retinal dehydrogenases (Raldh1, 2, 3) dehydrogenate retinal irreversibly into ATRA. ATRA regulates its own concentrations by inducing Lrat and ATRA degradative enzymes. ATRA exhibits hormesis. Its effects relate to its concentration as an inverted J-shaped curve, transitioning from beneficial in the "goldilocks" zone to toxicity, as concentrations increase. Hormesis has distorted understanding physiological effects of ATRA post-nataly using chow-diet fed, ATRA-dosed animal models. Cancer, immune deficiency and metabolic abnormalities result from mutations and/or insufficiency in Crbp1 and retinoid metabolizing enzymes.

Activation of immunosuppressive network in the aging process

Chronic low-grade inflammation has a key role in the aging process, a state called inflammaging. It is known that the chronic inflammatory condition generates counteracting immunosuppressive state in many diseases. Inflammaging is also associated with an immune deficiency; generally termed as immunosenescence, although it is not known whether it represents the senescence of immune cells or the active remodeling of immune system. Evidence has accumulated since the 1970's indicating that immunosenescence might be caused by an increased activity of immunosuppressive cells rather than cellular senescence. Immune cells display remarkable plasticity; many of these cells can express both proinflammatory and immunosuppressive phenotypes in a context-dependent manner. The immunosuppressive network involves the regulatory subtypes of T (Treg) and B (Breg) cells as well as regulatory phenotypes of macrophages (Mreg), dendritic (DCreg), natural killer (NKreg), and type II natural killer T (NKT) cells. The immunosuppressive network also includes monocytic (M-MDSC) and polymorphonuclear (PMN-MDSC) myeloid-derived suppressor cells which are immature myeloid cells induced by inflammatory mediators. This co-operative network is stimulated in chronic inflammatory conditions preventing excessive inflammatory responses but at the same time they exert harmful effects on the immune system and tissue homeostasis. Recent studies have revealed that the aging process is associated with the activation of immunosuppressive network, especially the functions of MDSCs, Tregs, and Mregs are increased. I will briefly review the properties of the regulatory phenotypes of immune cells and examine in detail the evidences for an activation of immunosuppressive network with aging.

Novel molecules mediate specialized functions of human regulatory macrophages

PURPOSE OF REVIEW

Now that adoptive transfer of regulatory macrophages (Mregs) is clinically practicable, we ask whether this approach could be used to achieve self-sustaining peripheral regulation and what mechanisms may be involved.

RECENT FINDINGS

Dehydrogenase/reductase 9 (DHRS9)-expressing Mregs are a specialized subset of monocyte-derived macrophages that are currently being investigated as a tolerogenic cell-based therapy. Human Mregs are defined by their capacity to convert naïve CD4 T cells to IL-10-secreting FoxP3 regulatory T cells (Tregs) through an activation-dependent process involving signals mediated by TGF-β, retinoic acid, indoleamine 2,3-dioxygenase activity, notch and progestagen associated endometrial protein (PAEP). Mreg-induced iTregs (miTregs) are a phenotypically distinct type of in-vitro-derived human iTreg that expresses butyrophilin-like protein 8 (BTNL8) and T cell immunoreceptor with Ig and ITIM domains (TIGIT). miTregs are nonspecifically suppressive of mitogen-stimulated bystander T cell proliferation and inhibit TNFα-induced maturation of monocyte-derived dendritic cells. Preclinical and clinical studies find that intravenous infusion of allogeneic Mregs leads to enrichment of circulating TIGIT Tregs.

SUMMARY

These results suggest a feed-forward mechanism by which Mreg treatment could promote solid organ transplant acceptance through rapid induction of direct pathway Tregs.

Functional aspects, phenotypic heterogeneity, and tissue immune response of macrophages in infectious diseases

Macrophages are a functionally heterogeneous group of cells with specialized functions depending not only on their subgroup but also on the function of the organ or tissue in which the cells are located. The concept of macrophage phenotypic heterogeneity has been investigated since the 1980s, and more recent studies have identified a diverse spectrum of phenotypic subpopulations. Several types of macrophages play a central role in the response to infectious agents and, along with other components of the immune system, determine the clinical outcome of major infectious diseases. Here, we review the functions of various macrophage phenotypic subpopulations, the concept of macrophage polarization, and the influence of these cells on the evolution of infections. In addition, we emphasize their role in the immune response in vivo and in situ, as well as the molecular effectors and signaling mechanisms used by these cells. Furthermore, we highlight the mechanisms of immune evasion triggered by infectious agents to counter the actions of macrophages and their consequences. Our aim here is to provide an overview of the role of macrophages in the pathogenesis of critical transmissible diseases and discuss how elucidation of this relationship could enhance our understanding of the host-pathogen association in organ-specific immune responses.

MAP7 and MUCL1 Are Biomarkers of Vitamin D3-Induced Tolerogenic Dendritic Cells in Multiple Sclerosis Patients

The administration of autologous tolerogenic dendritic cells (tolDC) has become a promising alternative for the treatment of autoimmune diseases, such as multiple sclerosis (MS). Specifically, the use of vitamin D3 for the generation of tolDC (vitD3-tolDC) constitutes one of the most widely studied approaches, as it has evidenced significant immune regulatory properties, both in vitro and in vivo. In this article, we generated human vitD3-tolDC from monocytes from healthy donors and MS patients, characterized in both cases by a semi-mature phenotype, secretion of IL-10 and inhibition of allogeneic lymphocyte proliferation. Additionally, we studied their transcriptomic profile and selected a number of differentially expressed genes compared to control mature and immature dendritic cells for their analysis. Among them, qPCR results validated CYP24A1, MAP7 and MUCL1 genes as biomarkers of vitD3-tolDC in both healthy donors and MS patients. Furthermore, we constructed a network of protein interactions based on the literature, which manifested that MAP7 and MUCL1 genes are both closely connected between them and involved in immune-related functions. In conclusion, this study evidences that MAP7 and MUCL1 constitute robust and potentially functional biomarkers of the generation of vitD3-tolDC, opening the window for their use as quality controls in clinical trials for MS.

Androgen deprivation therapy promotes an obesity-like microenvironment in periprostatic fat

Prostate cancer is a leading cause of morbidity and cancer-related death worldwide. Androgen deprivation therapy (ADT) is the cornerstone of management for advanced disease. The use of these therapies is associated with multiple side effects, including metabolic syndrome and truncal obesity. At the same time, obesity has been associated with both prostate cancer development and disease progression, linked to its effects on chronic inflammation at a tissue level. The connection between ADT, obesity, inflammation and prostate cancer progression is well established in clinical settings; however, an understanding of the changes in adipose tissue at the molecular level induced by castration therapies is missing. Here, we investigated the transcriptional changes in periprostatic fat tissue induced by profound ADT in a group of patients with high-risk tumours compared to a matching untreated cohort. We find that the deprivation of androgen is associated with a pro-inflammatory and obesity-like adipose tissue microenvironment. This study suggests that the beneficial effect of therapies based on androgen deprivation may be partially counteracted by metabolic and inflammatory side effects in the adipose tissue surrounding the prostate.

The Evolving Roles of Macrophages in Organ Transplantation

Organ transplantation is a life-saving strategy for patients with end-stage organ failure. Over the past few decades, organ transplantation has achieved an excellent success in short-term survival but only a marginal improvement in long-term graft outcomes. The pathophysiology of graft loss is multifactorial and remains incompletely defined. However, emerging evidence suggests macrophages as crucial mediators of acute and chronic allograft immunopathology. In this process, macrophage-mediated mobilization of first-line defenses, particularly phagocytosis and the release of acute inflammatory mediators, is important, but macrophages also launch adaptive alloimmune reactions against grafts through antigen processing and presentation, as well as providing costimulation. Additionally, crosstalk with other immune cells and graft endothelial cells causes tissue damage or fibrosis in transplanted organs, contributing to graft loss or tolerance resistance. However, some macrophages function as regulatory cells that are capable of suppressing allogeneic T cells, inhibiting DC maturation, inducing the differentiation of Tregs, and subsequently promoting transplant tolerance. This functional diversity of macrophages in organ transplantation is consistent with their heterogeneity. Although our knowledge of the detrimental or beneficial effects of macrophages on transplants has exponentially increased, the exact mechanisms controlling macrophage functions are not yet completely understood. Here, we review recent advances in our understanding of the multifaceted nature of macrophages, focusing on their evolving roles in organ transplantation and the mechanisms involved in their activation and function in allograft transplantation. We also discuss potential therapeutic options and opportunities to target macrophage to improve the outcomes of transplant recipients.

In Case you Missed It-Basic Science Advances in Transplantation 2017

Developments in organ preservation techniques, novel immunosuppressants and improved diagnostics have made organ transplantation the success it is today. That does not mean that we are not still striving to perfect techniques, or that there are no more problems to solve. New strategies to address the donor organ shortage, prevent and manage antibody-mediated rejection, lower long-term allograft failure rates and reduce the toxicity of lifelong immunosuppressive medication are urgently needed, and are being widely researched. Both fundamental research and preclinical studies aim to solve these problems, and ultimately, benefit organ transplant recipients. This article highlights the latest technical developments and trends in xenotransplantation, tissue injury and regeneration, immunosuppression, and transplantation immunology described in the most viewed and cited articles published in the Basic Sciences section of the Transplantation journal during the year 2017.

Searching for the Transcriptomic Signature of Immune Tolerance Induction-Biomarkers of Safety and Functionality for Tolerogenic Dendritic Cells and Regulatory Macrophages

The last years have witnessed a breakthrough in the development of cell-based tolerance-inducing cell therapies for the treatment of autoimmune diseases and solid-organ transplantation. Indeed, the use of tolerogenic dendritic cells (tolDC) and regulatory macrophages (Mreg) is currently being tested in Phase I and Phase II clinical trials worldwide, with the aim of finding an effective therapy able to abrogate the inflammatory processes causing these pathologies without compromising the protective immunity of the patients. However, there exists a wide variety of different protocols to generate human tolDC and Mreg and, consequently, the characteristics of each product are heterogeneous. For this reason, the identification of biomarkers able to define their functionality (tolerogenicity) is of great relevance, on the one hand, to guarantee the safety of tolDC and Mreg before administration and, on the other hand, to compare the results between different cell products and laboratories. In this article, we perform an exhaustive review of protocols generating human tolDC and Mreg in the literature, aiming to elucidate if there are any common transcriptomic signature or potential biomarkers of tolerogenicity among the different approaches. However, and although several effectors seem to be induced in common in some of the most reported protocols to generate both tolDC or Mreg, the transcriptomic profile of these cellular products strongly varies depending on the approach used to generate them.

TIGIT+ iTregs elicited by human regulatory macrophages control T cell immunity

Human regulatory macrophages (Mreg) have shown early clinical promise as a cell-based adjunct immunosuppressive therapy in solid organ transplantation. It is hypothesised that recipient CD4⁺ T cell responses are actively regulated through direct allorecognition of donor-derived Mregs. Here we show that human Mregs convert allogeneic CD4⁺ T cells to IL-10-producing, TIGIT⁺ FoxP3⁺-induced regulatory T cells that non-specifically suppress bystander T cells and inhibit dendritic cell maturation. Differentiation of Mreg-induced Tregs relies on multiple non-redundant mechanisms that are not exclusive to interaction of Mregs and T cells, including signals mediated by indoleamine 2,3-dioxygenase, TGF-β, retinoic acid, Notch and progestagen-associated endometrial protein. Preoperative administration of donor-derived Mregs to living-donor kidney transplant recipients results in an acute increase in circulating TIGIT⁺ Tregs. These results suggest a feed-forward mechanism by which Mreg treatment promotes allograft acceptance through rapid induction of direct-pathway Tregs.

Regulatory macrophages (Mreg) can directly suppress T effector cell responses. Here the authors show that human Mreg also elicit TIGIT⁺ regulatory T cells by integrating multiple differentiation signals, and that donor Mreg-induced recipient Tregs may promote kidney transplant acceptance in patients.