Regulatory T cell induction by mesenchymal stem cells depends on the expression of TNFR2 by T cells

The implications of the TNFα-TNFR2 immune checkpoint signaling pathway in cancer treatment: From immunoregulation to angiogenesis

Despite the tremendous advances that have been made in biomedical research, cancer remains one of the leading causes of death worldwide. Several therapeutic approaches have been suggested and applied to treat cancer with impressive results. Immunotherapy based on targeting immune checkpoint signaling pathways proved to be one of the most efficient. In this review article, we will focus on the recently discovered TNFα-TNFR2 signaling pathway, which controls the immunological and pro-angiogenic properties of many immunoregulatory and pro-angiogenic cells such as endothelial progenitor cells (EPCs), mesenchymal stem cells (MSCs), and regulatory T cells (Tregs). Due to their biological properties, these cells can play a major role in cancer progression and metastasis. Therefore, we will discuss the advantages and disadvantages of an anti-TNFR2 treatment that could carry two faces under one hood. It interrupts the immunosuppressive and pro-angiogenic behaviors of the above-mentioned cells and interferes with tumor growth and survival.

Understanding the role of TNFR2 signaling in the tumor microenvironment of breast cancer

Breast cancer (BC) is the most frequently diagnosed malignancy among women. It is characterized by a high level of heterogeneity that emerges from the interaction of several cellular and soluble components in the tumor microenvironment (TME), such as cytokines, tumor cells and tumor-associated immune cells. Tumor necrosis factor (TNF) receptor 2 (TNFR2) appears to play a significant role in microenvironmental regulation, tumor progression, immune evasion, drug resistance, and metastasis of many types of cancer, including BC. However, the significance of TNFR2 in BC biology is not fully understood. This review provides an overview of TNFR2 biology, detailing its activation and its interactions with important signaling pathways in the TME (e.g., NF-κB, MAPK, and PI3K/Akt pathways). We discuss potential therapeutic strategies targeting TNFR2, with the aim of enhancing the antitumor immune response to BC. This review provides insights into role of TNFR2 as a major immune checkpoint for the future treatment of patients with BC.

Neuroprotective effects of mesenchymal stromal cells in mouse models of Alzheimer's Disease: The Mediating role of gut microbes and their metabolites via the Microbiome-Gut-Brain axis

The intricacy and multifaceted nature of Alzheimer's disease (AD) necessitate therapies that target multiple aspects of the disease. Mesenchymal stromal cells (MSCs) emerge as potential agents to mitigate AD symptoms; however, whether their therapeutic efficacy involves modulation of gut microbiota and the microbiome-gut-brain axis (MGBA) remains unexplored. In this study, we evaluated the effects of three distinct MSCs types-derived from the umbilical cord (UCMSC), dental pulp (SHED), and adipose tissue (ADSC)-in an APP/PS1 mouse model of AD. In comparison to saline control, MSCs administration resulted in a significant reduction of behavioral disturbances, amyloid plaques, and phosphorylated tau in the hippocampus and frontal cortex, accompanied by an increase in neuronal count and Nissl body density across AD-afflicted brain regions. Through 16S rRNA gene sequencing, we identified partial restoration of gut microbial balance in AD mice post-MSCs treatment, evidenced by the elevation of neuroprotective Akkermansia and reduction of the AD-associated Sphingomonas. To examine whether gut microbiota involved in MSCs efficacy in treating AD, SHED with better anti-inflammatory and gut microbiota recovery effects among three MSCs, and another AD model 5 × FAD mice with earlier and more pathological proteins in brain than APP/PS1, were selected for further studies. Antibiotic-mediated gut microbial inactivation attenuated MSCs efficacy in 5 × FAD mice, implicating the involvement of gut microbiota in the therapeutic mechanism. Functional analysis of altered gut microbiota and targeted bile acid metabolism profiling revealed a significant enhancement in bile acid variety following MSCs therapy. A chief bile acid constituent, taurocholic acid (TCA), was orally administered to AD mice and similarly abated AD symptoms. Nonetheless, the disruption of intestinal neuronal integrity with enterotoxin abrogated the ameliorative impact of both MSCs and TCA treatments. Collectively, our findings substantiate that MSCs confer therapeutic benefits in AD within a paradigm that primarily involves regulation of gut microbiota and their metabolites through the MGBA.

Controversies regarding transplantation of mesenchymal stem cells

Mesenchymal stem cells (MSCs) have tantalized regenerative medicine with their therapeutic potential, yet a cloud of controversies looms over their clinical transplantation. This comprehensive review navigates the intricate landscape of MSC controversies, drawing upon 15 years of clinical experience and research. We delve into the fundamental properties of MSCs, exploring their unique immunomodulatory capabilities and surface markers. The heart of our inquiry lies in the controversial applications of MSC transplantation, including the perennial debate between autologous and allogeneic sources, concerns about efficacy, and lingering safety apprehensions. Moreover, we unravel the enigmatic mechanisms surrounding MSC transplantation, such as homing, integration, and the delicate balance between differentiation and paracrine effects. We also assess the current status of clinical trials and the ever-evolving regulatory landscape. As we peer into the future, we examine emerging trends, envisioning personalized medicine and innovative delivery methods. Our review provides a balanced and informed perspective on the controversies, offering readers a clear understanding of the complexities, challenges, and potential solutions in MSC transplantation.

ADSCs encapsulated in Gelatin methacrylate substrate promotes the repair of peripheral nerve injury by SIRT6/PGC-1α pathway

Peripheral nerve injury is a prevalent disease but the spontaneous recovery of nerve function is protracted and incomplete. Given the damaging of stem cells and fragile of intra-neural structures in the course of stem cell transplantation, our study tried to investigate whether encapsulating adipose derived mesenchymal stem cells (ADSCs) with GelMA could achieve better repair in peripheral nerve injury. PC-12 cells were cultured on the surface of GelMA encapsulating ADSCs and 3D co-culture system was constructed. CCK-8, Real-Time PCR, ELISA, Immunofluorescent Assay and Western Blot were used to evaluate the functionality of this system. Ultimately, nerve conduit containing the 3D co-culture system was linked between the two ends of an injured nerve. ADSCs encapsulated in 5% GeIMA had a better activity than 10% GeIMA. Furthermore, the viability of PC-12 cells was also better in this 3D co-culture system than in co-culture system with ADSCs without GeIMA. The expression of SIRT6 and PGC-1α in PC-12 cells were prominently promoted, and the entry to nuclear of PGC-1α was more obvious in this 3D co-culture system. After silencing of SIRT6, the protein expression level of PGC-1α was inhibited, and the activity of PC-12 cells was significantly reduced, suggesting that ADSCs encapsulated in GelMA upregulated the expression of SIRT6 to induce the level of PGC-1α protein, thereby achieving an impact on the activity of PC-12 cells. In vivo, nerve conduit containing the 3D co-culture system significantly promoted the repair of damaged peripheral nerves. In conclusion, our study demonstrated that 5% GelMA enhanced ADSCs activity, thereby promoting the activity of nerve cells and repair of damaged peripheral nerves by SIRT6/PGC-1α pathway.

Mesenchymal stromal cells with chimaeric antigen receptors for enhanced immunosuppression

Allogeneic mesenchymal stromal cells (MSCs) are a safe treatment option for many disorders of the immune system. However, clinical trials using MSCs have shown inconsistent therapeutic efficacy, mostly owing to MSCs providing insufficient immunosuppression in target tissues. Here we show that antigen-specific immunosuppression can be enhanced by genetically modifying MSCs with chimaeric antigen receptors (CARs), as we show for E-cadherin-targeted CAR-MSCs for the treatment of graft-versus-host disease in mice. CAR-MSCs led to superior T-cell suppression and localization to E-cadherin+ colonic cells, ameliorating the animals' symptoms and survival rates. On antigen-specific stimulation, CAR-MSCs upregulated the expression of immunosuppressive genes and receptors for T-cell inhibition as well as the production of immunosuppressive cytokines while maintaining their stem cell phenotype and safety profile in the animal models. CAR-MSCs may represent a widely applicable therapeutic technology for enhancing immunosuppression.

Therapeutic and immunomodulatory potentials of mesenchymal stromal/stem cells and immune checkpoints related molecules

Mesenchymal stromal/stem cells (MSCs) are used in many studies due to their therapeutic potential, including their differentiative ability and immunomodulatory properties. These cells perform their therapeutic functions by using various mechanisms, such as the production of anti-inflammatory cytokines, growth factors, direct cell-to-cell contact, extracellular vesicles (EVs) production, and mitochondrial transfer. However, mechanisms related to immune checkpoints (ICPs) and their effect on the immunomodulatory ability of MSCs are less discussed. The main function of ICPs is to prevent the initiation of unwanted responses and to regulate the immune system responses to maintain the homeostasis of these responses. ICPs are produced by various types of immune system regulatory cells, and defects in their expression and function may be associated with excessive responses that can ultimately lead to autoimmunity. Also, by expressing different types of ICPs and their ligands (ICPLs), tumor cells prevent the formation and durability of immune responses, which leads to tumors' immune escape. ICPs and ICPLs can be produced by MSCs and affect immune cell responses both through their secretion into the microenvironment or direct cell-to-cell interaction. Pre-treatment of MSCs in inflammatory conditions leads to an increase in their therapeutic potential. In addition to the effect that inflammatory environments have on the production of anti-inflammatory cytokines by MSCs, they can increase the expression of various types of ICPLs. In this review, we discuss different types of ICPLs and ICPs expressed by MSCs and their effect on their immunomodulatory and therapeutic potential.

The immunogenic profile and immunomodulatory function of mesenchymal stromal / stem cells in the presence of Ptychotis verticillata

Mesenchymal stromal/stem cells (MSCs) are considered to be a promising immunotherapeutic tool due to their easy accessibility, culture expansion possibilities, safety profile, and immunomodulatory properties. Although several studies have demonstrated the therapeutic effects of MSCs, their efficacy needs to be improved while also preserving their safety. It has been suggested that cell homeostasis may be particularly sensitive to plant extracts. The impact of natural compounds on immunity is thus a fascinating and growing field. Ptychotis verticillata and its bioactive molecules, carvacrol and thymol, are potential candidates for improving MSC therapeutic effects. They can be used as immunotherapeutic agents to regulate MSC functions and behavior during immunomodulation. Depending on their concentrations and incubation time, these compounds strengthened the immunomodulatory functions of MSCs while maintaining their immune-evasive profile. Incubating MSCs with carvacrol and thymol does not alter their hypoimmunogenicity, as no induction of the allogeneic immune response was observed. MSCs also showed enhanced abilities to reduce the proliferation of activated T cells. Thus, MSCs are immunologically responsive to bioactive molecules derived from PV. The bioactivity may depend on the whole phyto-complex of the oil. These findings may contribute to the development of safe and efficient immunotherapeutic MSCs by using medicinal plant-derived active molecules.

IWP-2 modulates the immunomodulatory properties of human dental pulp stem cells in vitro

AIM

To investigate the effect of IWP-2, Wnt inhibitor, on human dental pulp stem cells (hDPSCs) responses.

METHODOLOGY

hDPSCs were isolated from human dental pulp tissues. Cells were treated with 25 μM IWP-2 for 24 h, and subsequently, the gene expression profile was examined using high-throughput RNA sequencing. The mRNA expression was analysed using qPCR. The effect of IWP-2 was investigated in both normal and LPS-induced hDPSCs (inflamed hDPSCs). CD4+ T cells and CD14+ monocyte-derived macrophages were cultured with conditioned media of IWP-2 treated hDPSCs to observe the immunosuppressive property.

RESULTS

RNA sequencing indicated that IWP-2 significantly downregulated several KEGG pathways, including cytokine-cytokine receptor interaction, IL-17 signalling pathway, and TNF signalling pathway. In both normal and inflamed conditions, IWP-2 markedly upregulated TGFB1 mRNA expression while the mRNA expression of pro-inflammatory cytokines, TNFA, IL1B, IFNG, and IL6, was inhibited. In the inhibition experiment, the pretreatment with p38, MAPK, or PI3K inhibitors abolished the effects of IWP-2 in LPS-induced inflammation. In terms of immune cells, IWP-2-treated-inflamed hDPSCs conditioned media attenuated T cell proliferation and regulated regulatory T cell differentiation. In addition, the migratory property of macrophage was decreased after being exposed to IWP-2-treated inflamed hDPSCs conditioned media.

CONCLUSION

IWP-2 suppressed inflammatory cytokine expression in both normal and inflamed hDPSCs. Moreover, hDPSCs exerted the immunosuppressive property after IWP-2 treatment. These results suggest the role of Wnt in inflammatory responses and immunomodulation in dental pulp tissues.

Generic design principles for antibody-based tumour necrosis factor (TNF) receptor 2 (TNFR2) agonists with FcγR-independent agonism

Background: Selective TNFR2 activation can be used to treat immune pathologies by activating and expanding regulatory T-cells (Tregs) but may also restore anti-tumour immunity by co-stimulating CD8+ T-cells. Oligomerized TNFR2-specific TNF mutants or anti-TNFR2 antibodies can activate TNFR2 but suffer either from poor production and pharmacokinetics or in the case of anti-TNFR2 antibodies typically from the need of FcγR binding to elicit maximal agonistic activity. Methods: To identify the major factor(s) determining FcγR-independent agonism of anti-TNFR2 antibodies, we systematically investigated a comprehensive panel of anti-TNFR2 antibodies and antibody-based constructs differing in the characteristics of their TNFR2 binding domains but also in the number and positioning of the latter. Results: We identified the domain architecture of the constructs as the pivotal factor enabling FcγR-independent, thus intrinsic TNFR2-agonism. Anti-TNFR2 antibody formats with either TNFR2 binding sites on opposing sites of the antibody scaffold or six or more TNFR2 binding sites in similar orientation regularly showed strong FcγR-independent agonism. The affinity of the TNFR2 binding domain and the epitope recognized in TNFR2, however, were found to be of only secondary importance for agonistic activity. Conclusion: Generic design principles enable the generation of highly active bona fide TNFR2 agonists from nearly any TNFR2-specific antibody.

Canine amniotic membrane-derived mesenchymal stem cells ameliorate atopic dermatitis through regeneration and immunomodulation

Mesenchymal stem cells (MSCs) are a promising tool for treating immune disorders. However, the immunomodulatory effects of canine MSCs compared with other commercialized biologics for treating immune disorders have not been well studied. In this study we investigated the characteristics and immunomodulatory effects of canine amnion membrane (cAM)-MSCs. We examined gene expression of immune modulation and T lymphocytes from activated canine peripheral blood mononuclear cell (PBMC) proliferation. As a result, we confirmed that cAM-MSCs upregulated immune modulation genes (TGF-β1, IDO1 and PTGES2) and suppressed the proliferation capacity of T cells. Moreover, we confirmed the therapeutic effect of cAM-MSCs compared with oclacitinib (OCL), the most commonly used Janus kinase (JAK) inhibitor, as a treatment for canine atopic dermatitis (AD) using a mouse AD model. As a result, we confirmed that cAM-MSCs with PBS treatment groups (passage 4, 6 and 8) compared with PBS only (PBS) though scores of dermatologic signs, tissue pathologic changes and inflammatory cytokines were significantly reduced. In particular, cAM-MSCs were more effective than OCL in the recovery of wound dysfunction, regulation of mast cell activity and expression level of immune modulation protein. Interestingly, subcutaneous injection of cAM-MSCs induced weight recovery, but oral administration of oclacitinib induced weight loss as a side effect. In conclusion, this study suggests that cAM-MSCs can be developed as a safe canine treatment for atopic dermatitis without side effects through effective regeneration and immunomodulation.

Updated insight into the role of Th2-associated immunity in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease with multiple organs involvement, abundant autoantibodies, complement activation, and immune complexes depositions. By regulating inflammation and immune homeostasis, cytokines have been well documented to participate in the pathogenesis of SLE. A number of studies have shown that T helper 2 (Th2)-associated immunity plays an important role in autoimmune diseases, including SLE. Key molecules underlying Th2-related immunity are expected to serve as promising targets for the diagnosis and targeted treatment of SLE. Current progress in SLE pathogenesis and biological treatment strategies has been reviewed, focusing on the latest development in Th2-associated immunity.

Elevation of circulating TNF receptor 2 in cancer: A systematic meta-analysis for its potential as a diagnostic cancer biomarker

High Tumor Necrosis Factor Receptor 2 (TNFR2) expression is characteristic of diverse malignant cells during tumorigenesis. The protein is also expressed by many immunosuppressive cells during cancer development, allowing cancer immune escape. A growing body of evidence further suggests a correlation between the circulating form of this protein and cancer development. Here we conducted a systematic meta-analysis of cancer studies published up until 1st October 2022, in which the circulating soluble TNFR2 (sTNFR2) concentrations in patients with cancers were recorded and their association with cancer risk was assessed. Of the 14,615 identified articles, 44 studies provided data on the correlation between cancer risk and the level of circulating sTNFR2. The pooled means comparison showed a consistently significant increase in the levels of sTNFR2 in diverse cancers when compared to healthy controls. These included colorectal cancer, ovarian cancer, breast cancer, non-Hodgkin's lymphoma, Hodgkin's lymphoma, lung cancer, hepatocarcinoma, and glioblastoma. In a random-effect meta-analysis, the cancer-specific odd ratios (OR) showed significant correlations between increased circulating sTNFR2 levels and the risk of colorectal cancer, non-Hodgkin's lymphoma, and hepatocarcinoma at 1.59 (95% CI:1.20-2.11), 1.98 (95% CI:1.49-2.64) and 4.32 (95% CI:2.25-8.31) respectively. The overall result showed an association between circulating levels of sTNFR2 and the risk of developing cancer at 1.76 (95% CI:1.53-2.02). This meta-analysis supports sTNFR2 as a potential diagnostic biomarker for cancer, albeit with different predictive strengths for different cancer types. This is consistent with a potential key role for TNFR2 involvement in cancer development.

LC-MS/MS-based serum proteomics reveals a distinctive signature in a rheumatoid arthritis mouse model after treatment with mesenchymal stem cells

Mesenchymal stem cells (MSCs) are known to be able to modulate immune responses, possess tissue-protective properties, and exhibit healing capacities with therapeutic potential for various diseases. The ability of MSCs to secrete various cytokines and growth factors provides new insights into autoimmune-diseases such as rheumatoid arthritis (RA). RA is a systemic autoimmune disease that affects the lining of synovial joints, causing stiffness, pain, inflammation, and joint erosion. In recent years, MSCs-based therapies have been widely proposed as promising therapies in the treatment of RA. However, the mechanism involved in disease-specific therapeutic effects of MSCs on RA remains unclear. To clarify the mechanism involved in effects of MSCs on RA, proteomic profiling was performed using an RA mouse model before and after treatment with MSCs. In this study, treatment efficacy of human umbilical cord blood-mesenchymal stem cells (hUCB-MSCs) was confirmed using a type II collagen-induced arthritis (CIA) mouse model. Results of measuring incidence rates of arthritis and clinical arthritis index (CAI) revealed that mice administrated with hUCB-MSCs had a significant reduction in arthritis severity. Proteins that might affect disease progression and therapeutic efficacy of hUCB-MSC were identified through LC-MS/MS analysis using serum samples. In addition, L-1000 analysis was performed for hUCB-MSC culture medium. To analysis data obtained from LC–MS/MS and L-1000, tools such as ExDEGA, MEV, and DAVID GO were used. Results showed that various factors secreted from hUCB-MSCs might play roles in therapeutic effects of MSCs on RA, with platelet activation possibly playing a pivotal role. Results of this study also suggest that SERPINE1 and THBS1 among substances secreted by hUCB-MSC might be key factors that can inhibit platelet activation. This paper is expected to improve our understanding of mechanisms involved in treatment effects of stem cells on rheumatoid arthritis.

Mesenchymal stroma/stem cells: Haematologists' friend or foe?

Mesenchymal stromal cells (MSCs) are non-haematopoietic cells found in fetal and adult organs, that play important roles in tissue repair, inflammation and immune modulation. MSCs residing in the bone marrow interact closely with haematopoietic cells and comprise an important component of the microenvironment supporting haematopoiesis, in both health and disease states. Since their identification in 1970, basic scientific and preclinical research efforts have shed light on the role of MSCs in the regulation of haematopoiesis and evoked interest in their clinical application in haematopoietic stem cell transplantation (HSCT) and malignant haematology. Over the last two decades, these research efforts have led to numerous clinical trials, which have established the safety of MSC therapy; however, the optimal mode of administration and the benefit remain inconclusive. In this paper, we will review the clinical experience with use of MSCs in HSCT for enhancement of engraftment, prevention and treatment of graft-versus-host disease and haemorrhagic cystitis. Then, we will discuss the contradictory evidence regarding tumour-promoting versus tumour-suppressing effects of MSCs in haematological malignancies, which may have relevance for future clinical applications.

CD1d-independent NK1.1+ Treg cells are IL2-inducible Foxp3+ T cells co-expressing immunosuppressive and cytotoxic molecules

Regulatory T cells (Treg) play pivotal roles in maintaining self-tolerance and preventing immunological diseases such as allergy and autoimmunity through their immunosuppressive properties. Although Treg cells are heterogeneous populations with distinct suppressive functions, expression of natural killer (NK) cell receptors (NKR) by these cells remains incompletely explored. Here we identified that a small population of Foxp3+CD4+ Treg cells in mice expresses the NK1.1 NKR. Furthermore, we found that rare NK1.1+ subpopulations among CD4+ Treg cells develop normally in the spleen but not the thymus through CD1d-independent pathways. Compared with NK1.1- conventional Treg cells, these NK1.1+ Treg cells express elevated Treg cell phenotypic hallmarks, pro-inflammatory cytokines, and NK cell-related cytolytic mediators. Our results suggest that NK1.1+ Treg cells are phenotypically hybrid cells sharing functional properties of both NK and Treg cells. Interestingly, NK1.1+ Treg cells preferentially expanded in response to recombinant IL2 stimulation in vitro, consistent with their increased IL2Rαβ expression. Moreover, DO11.10 T cell receptor transgenic NK1.1+ Treg cells were expanded in an ovalbumin antigen-specific manner. In the context of lipopolysaccharide-induced systemic inflammation, NK1.1+ Treg cells downregulated immunosuppressive molecules but upregulated TNFα production, indicating their plastic adaptation towards a more pro-inflammatory rather than regulatory phenotype. Collectively, we propose that NK1.1+ Treg cells might play a unique role in controlling inflammatory immune responses such as infection and autoimmunity.

Mesenchymal stem/stromal cells in the pathogenesis and regenerative therapy of inflammatory bowel diseases

Inflammatory bowel diseases (IBDs) represent a group of chronic inflammatory disorders of the gastrointestinal (GI) tract including ulcerative colitis (UC), Crohn’s disease (CD), and unclassified IBDs. The pathogenesis of IBDs is related to genetic susceptibility, environmental factors, and dysbiosis that can lead to the dysfunction of immune responses and dysregulated homeostasis of local mucosal tissues characterized by severe inflammatory responses and tissue damage in GI tract. To date, extensive studies have indicated that IBDs cannot be completely cured and easy to relapse, thus prompting researchers to find novel and more effective therapeutics for this disease. Due to their potent multipotent differentiation and immunomodulatory capabilities, mesenchymal stem/stromal cells (MSCs) not only play an important role in regulating immune and tissue homeostasis but also display potent therapeutic effects on various inflammatory diseases, including IBDs, in both preclinical and clinical studies. In this review, we present a comprehensive overview on the pathological mechanisms, the currently available therapeutics, particularly, the potential application of MSCs-based regenerative therapy for IBDs.

Recent advances in passive immunotherapies for COVID-19: The Evidence-Based approaches and clinical trials

In late 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged, causing a global pandemic called COVID-19. Currently, there is no definitive treatment for this emerging disease. Global efforts resulted in developing multiple platforms of COVID-19 vaccines, but their efficacy in humans should be wholly investigated in the long-term clinical and epidemiological follow-ups. Despite the international efforts, COVID-19 vaccination accompanies challenges, including financial and political obstacles, serious adverse effects (AEs), the impossibility of using vaccines in certain groups of people in the community, and viral evasion due to emerging novel variants of SARS-CoV-2 in many countries. For these reasons, passive immunotherapy has been considered a complementary remedy and a promising way to manage COVID-19. These approaches arebased on reduced inflammation due to inhibiting cytokine storm phenomena, immunomodulation,preventing acute respiratory distress syndrome (ARDS), viral neutralization, anddecreased viral load. This article highlights passive immunotherapy and immunomodulation approaches in managing and treating COVID-19 patients and discusses relevant clinical trials (CTs).

Novel approaches for long-term lung transplant survival

Allograft failure remains a major barrier in the field of lung transplantation and results primarily from acute and chronic rejection. To date, standard-of-care immunosuppressive regimens have proven unsuccessful in achieving acceptable long-term graft and patient survival. Recent insights into the unique immunologic properties of lung allografts provide an opportunity to develop more effective immunosuppressive strategies. Here we describe advances in our understanding of the mechanisms driving lung allograft rejection and highlight recent progress in the development of novel, lung-specific strategies aimed at promoting long-term allograft survival, including tolerance.

Notoginsenoside R1 Promotes Migration, Adhesin, Spreading, and Osteogenic Differentiation of Human Adipose Tissue-Derived Mesenchymal Stromal Cells

Cellular activities, such as attachment, spreading, proliferation, migration, and differentiation are indispensable for the success of bone tissue engineering. Mesenchymal stromal cells (MSCs) are the key precursor cells to regenerate bone. Bioactive compounds from natural products had shown bone regenerative potential. Notoginsenoside R1 (NGR1) is a primary bioactive natural compound that regulates various biological activities, including cardiovascular protection, neuro-protection, and anti-cancer effects. However, the effect of NGR1 on migration, adhesion, spreading, and osteogenic differentiation of MSCs required for bone tissue engineering application has not been tested properly. In this study, we aimed to analyze the effect of NGR1 on the cellular activities of MSCs. Since human adipose-derived stromal cells (hASCs) are commonly used MSCs for bone tissue engineering, we used hASCs as a model of MSCs. The optimal concentration of 0.05 μg/mL NGR1 was biocompatible and promoted migration and osteogenic differentiation of hASCs. Pro-angiogenic factor VEGF expression was upregulated in NGR1-treated hASCs. NGR1 enhanced the adhesion and spreading of hASCs on the bio-inert glass surface. NGR1 robustly promoted hASCs adhesion and survival in 3D-printed TCP scaffold both in vitro and in vivo. NGR1 mitigated LPS-induced expression of inflammatory markers IL-1β, IL-6, and TNF-α in hASCs as well as inhibited the RANKL/OPG expression ratio. In conclusion, the biocompatible NGR1 promoted the migration, adhesion, spreading, osteogenic differentiation, and anti-inflammatory properties of hASCs.

Signaling pathway(s) of TNFR2 required for the immunoregulatory effect of CD4+Foxp3+ regulatory T cells

CD4⁺Foxp3⁺ regulatory T cells (Tregs), a subpopulation of CD4⁺ T cells, are engaged in maintaining the periphery tolerance and preventing autoimmunity. Recent studies showed that tumor necrosis factor receptor 2 (TNFR2) is preferentially expressed by Tregs and the expression of this receptor identifies the maximally suppressive Tregs. That is, TNFR2 is a liable phenotypic and functional surface marker of Tregs. Moreover, TNF activates and expands Tregs through TNFR2. However, it is very interesting which signaling pathway(s) of TNFR2 is required for the inhibitory effect of Tregs. Compelling evidence shows three TNFR2 signaling pathways in Tregs, including NF-κB, MAPK and PI3K-Akt pathways. Here, we summarize and discuss the latest progress in the studies on the downstream signaling pathways of TNF-TNFR2 for controlling Treg homeostasis, differentiation and proliferation.

MSC-ACE2 Ameliorates Streptococcus uberis-Induced Inflammatory Injury in Mammary Epithelial Cells by Upregulating the IL-10/STAT3/SOCS3 Pathway

In the dairy industry, Streptococcus uberis (S. uberis) is one of the most important pathogenic bacteria associated with mastitis in milk-producing cows, causing vast economic loss. To date, the only real effective method of treating and preventing streptococcal mastitis is antimicrobial therapy. In many inflammatory diseases, mesenchymal stem cells (MSCs) and angiotensin-converting enzyme 2 (ACE2) play an anti-inflammatory and anti-injurious role. Accordingly, we hypothesized that MSCs overexpressing ACE2 (MSC-ACE2) would ameliorate the inflammatory injury caused by S. uberis in mammary epithelial cells more efficiently than MSC alone. By activating the transcription 3/suppressor of cytokine signaling 3 (IL-10/STAT3/SOCS3) signaling pathway, MSC-ACE2 inhibited the NF-κB, MAPKs, apoptosis, and pyroptosis passways. Moreover, MSC-ACE2 overturned the downregulation of Occludin, Zonula occludens 1 (ZO-1), and Claudin-3 expression levels caused by S. uberis, suggesting that MSC-ACE2 promotes the repair of the blood-milk barrier. MSC-ACE2 demonstrated greater effectiveness than MSC alone, as expected. Based on these results, MSC-ACE2 effectively inhibits EpH4-Ev cell's inflammatory responses induced by S. uberis, and would be an effective therapeutic tool for treating streptococcal mastitis.

Targeting TNFR2: A Novel Breakthrough in the Treatment of Cancer

Tumor necrosis factor (TNF) receptor type II (TNFR2) is expressed in various tumor cells and some immune cells, such as regulatory T cells and myeloid-derived suppressing cells. TNFR2 contributes a lot to the tumor microenvironment. For example, it directly promotes the occurrence and growth of some tumor cells, activates immunosuppressive cells, and supports immune escape. Existing studies have proved the importance of TNFR2 in cancer treatment. Here, we reviewed the activation mechanism of TNFR2 and its role in signal transduction in the tumor microenvironment. We summarized the expression and function of TNFR2 within different immune cells and the potential opportunities and challenges of targeting TNFR2 in immunotherapy. Finally, the advantages and limitations of TNFR2 to treat tumor-related diseases are discussed, and the problems that may be encountered in the clinical development and application of targeted anti-TNFR2 agonists and inhibitors are analyzed.

Mesenchymal Stem Cells-derived Exosomes Ameliorate Lupus by Inducing M2 Macrophage Polarization and Regulatory T Cell Expansion in MRL/lpr Mice

Previous studies have implicated that the transplantation of human umbilical cord mesenchymal stem cells (hUC-MSCs) effectively alleviates systemic lupus erythematosus (SLE) primarily due to immunomodulatory effects. However, little is known about the role of hUC-MSC-derived exosomes in SLE. This study is carried out to investigate the modifying effects of hUC-MSC-exosomes on the differentiation and function of immune cells in SLE. hUC-MSC-derived exosomes were extracted from the cultural supernatant of hUC-MSCs by ultrahigh speed centrifugation. Quantitative real-time polymerase chain reaction, western blot, enzyme-linked immunosorbent assay, and flow cytometry were performed to estimate the effect of hUC-MSC-derived exosomes on macrophage and regulatory T cell (Treg) polarization. In vivo, hUC-MSC-exosomes were injected intravenously into 28-week-old MRL/lpr mice. We had found that exosomes derived from hUC-MSC restrained the proliferation and inflammation of macrophages in vitro. Besides, MSC-exosomes inhibited CD68⁺M1 and HLA-DR⁺M1 but promoted CD206⁺M2 and CD163⁺M2 in vitro. Moreover, MRL/lpr mice administrated by intravenous injection of MSC-exosomes had less infiltration of CD14⁺CD11c⁺M1 cells but more CD14⁺CD163⁺M2 cells as well as Tregs in spleens compared with those in MRL/lpr mice treated by PBS. Additionally, MSC-exosomes could alleviate nephritis, liver and lung injuries of MRL/lpr mice. The survival of lupus mice could be improved after MSC-exosome treatment. This study has suggested that MSC-derived exosomes exert anti-inflammatory and immunomodulatory effects in SLE. MSC-exosomes ameliorate nephritis and other key organ injuries by inducing M2 macrophages and Tregs polarization. As natural nanocarriers, MSC-exosomes may serve as a promising cell-free therapeutic strategy for SLE.Abbreviations: SLE: Systemic lupus erythematosus; hUC-MSCs: Human umbilical cord mesenchymal stem cells; MSCs: Mesenchymal stem cells; qRT-PCR: Quantitative real-time polymerase chain reaction; ELISA: Enzyme-linked immunosorbent assay; Tregs: Regulatory cells; TNF-α: Tumor necrosis factor alfa; IL: Interleukin; COVID-19: Coronavirus disease 2019; pTHP-1: PMA-induced THP-1 macrophages; TEM: Transmission electron microscopy; LPS: Lipopolysaccharide; EVs: Extracellular vesicles; TRAF1: Tumor necrosis factor receptor-associated factor 1; IRAK1: Interferon-α-interleukin-1 receptor-associated kinase 1; NF-κB: Nuclear factor-κB; BLyS: B lymphocyte stimulator; APRIL: A proliferation-inducing ligand.

Immunomodulatory effects of mesenchymal stem cells in peripheral nerve injury

Various immune cells and cytokines are present in the aftermath of peripheral nerve injuries (PNI), and coordination of the local inflammatory response is of great significance for the recovery of PNI. Mesenchymal stem cells (MSCs) exhibit immunosuppressive and anti-inflammatory abilities which can accelerate tissue regeneration and attenuate inflammation, but the role of MSCs in the regulation of the local inflammatory microenvironment after PNI has not been widely studied. Here, we summarize the known interactions between MSCs, immune cells, and inflammatory cytokines following PNI with a focus on the immunosuppressive role of MSCs. We also discuss the immunomodulatory potential of MSC-derived extracellular vesicles as a new cell-free treatment for PNI.

Receptor Specificity Engineering of TNF Superfamily Ligands

The tumor necrosis factor (TNF) ligand family has nine ligands that show promiscuity in binding multiple receptors. As different receptors transduce into diverse pathways, the study on the functional role of natural ligands is very complex. In this review, we discuss the TNF ligands engineering for receptor specificity and summarize the performance of the ligand variants in vivo and in vitro. Those variants have an increased binding affinity to specific receptors to enhance the cell signal conduction and have reduced side effects due to a lowered binding to untargeted receptors. Refining receptor specificity is a promising research strategy for improving the application of multi-receptor ligands. Further, the settled variants also provide experimental guidance for engineering receptor specificity on other proteins with multiple receptors.

Immunoregulatory effects of dental mesenchymal stem cells on T and B lymphocyte responses in primary Sjögren's syndrome

Background: In this article, the authors investigate the modulatory effects of dental mesenchymal stem cells (MSCs) on lymphocyte responses in primary Sjögren's syndrome (pSS), which is an autoimmune disease resulting from keratoconjunctivitis sicca and xerostomia. Methods: Mononuclear cells isolated from pSS patients cultured with or without dental MSCs and analyzed for lymphocyte responses via flow cytometry. Results: Dental-follicle (DF)- and dental-pulp (DP)-MSCs downregulated CD4⁺ T lymphocyte proliferation by increasing Fas-ligand expression on T lymphocytes and FoxP3 expressing Tregs, and decreasing intracellular IFN-γ and IL-17 secretion in pSS patients. DF-MSCs decreased the plasma B cell ratio in the favor of naive B cell population in pSS patients' mononuclear cells. Conclusion: DF- and DP-MSCs can be the new cellular therapeutic candidates for the regulation of immune responses in pSS.

Priming strategies for controlling stem cell fate: Applications and challenges in dental tissue regeneration

Mesenchymal stromal cells (MSCs) have attracted intense interest in the field of dental tissue regeneration. Dental tissue is a popular source of MSCs because MSCs can be obtained with minimally invasive procedures. MSCs possess distinct inherent properties of self-renewal, immunomodulation, proangiogenic potential, and multilineage potency, as well as being readily available and easy to culture. However, major issues, including poor engraftment and low survival rates in vivo, remain to be resolved before large-scale application is feasible in clinical treatments. Thus, some recent investigations have sought ways to optimize MSC functions in vitro and in vivo. Currently, priming culture conditions, pretreatment with mechanical and physical stimuli, preconditioning with cytokines and growth factors, and genetic modification of MSCs are considered to be the main strategies; all of which could contribute to improving MSC efficacy in dental regenerative medicine. Research in this field has made tremendous progress and continues to gather interest and stimulate innovation. In this review, we summarize the priming approaches for enhancing the intrinsic biological properties of MSCs such as migration, antiapoptotic effect, proangiogenic potential, and regenerative properties. Challenges in current approaches associated with MSC modification and possible future solutions are also indicated. We aim to outline the present understanding of priming approaches to improve the therapeutic effects of MSCs on dental tissue regeneration.

Generation and characterization of novel co-stimulatory anti-mouse TNFR2 antibodies

Tumor necrosis factor receptor 2 (TNFR2) has gained much research interest in recent years because of its potential pivotal role in autoimmune disease and cancer. However, its function in regulating different immune cells is not well understood. There is a need for well-characterized reagents to selectively modulate TNFR2 function, thereby enabling definition of TNFR2-dependent biology in human and mouse surrogate models. Here, we describe the generation, production, purification, and characterization of a panel of novel antibodies targeting mouse TNFR2. The antibodies display functional differences in binding affinity and potency to block TNFα. Furthermore, epitope binding showed that the anti-mTNFR2 antibodies target different domains on the TNFR2 protein, associated with varying capacity to enhance CD8⁺ T-cell activation and costimulation. Moreover, the anti-TNFR2 antibodies demonstrate binding to isolated splenic mouse Tregs ex vivo and activated CD8+ cells, reinforcing their potential use to establish TNFR2-dependent immune modulation in translational models of autoimmunity and cancer.

Differences and similarities between mesenchymal stem cell and endothelial progenitor cell immunoregulatory properties against T cells

Bone-marrow-derived mesenchymal stem cells and endothelial progenitor cells have some interesting biological properties that make them unique for cell therapy of degenerative and cardiovascular disorders. Although both cell populations have been already studied and used for their regenerative potentials, recently their special immunoregulatory features have brought much more attention. Mesenchymal stem cells and endothelial progenitor cells have both proangiogenic functions and have been shown to suppress the immune response, particularly T cell proliferation, activation, and cytokine production. This makes them suitable choices for allogeneic stem cell transplantation. Nevertheless, these two cells do not have equal immunoregulatory activities. Many elements including their extraction sources, age/passage, expression of different markers, secretion of bioactive mediators, and some others could change the efficiency of their immunosuppressive function. However, to our knowledge, no publication has yet compared mesenchymal stem cells and endothelial progenitor cells for their immunological interaction with T cells. This review aims to specifically compare the immunoregulatory effect of these two populations including their T cell suppression, deactivation, cytokine production, and regulatory T cells induction capacities. Moreover, it evaluates the implications of the tumor necrosis factor alpha-tumor necrosis factor receptor 2 axis as an emerging immune checkpoint signaling pathway controlling most of their immunological properties.

TNFR2: Role in Cancer Immunology and Immunotherapy

Immune checkpoint inhibitors (ICIs), including anti-CTLA-4 (cytotoxic T lymphocyte antigen-4) and anti-PD-1/PD-L1 (programmed death-1/programmed death-ligand 1), represent a turning point in the cancer immunotherapy. However, only a minor fraction of patients could derive benefit from such therapy. Therefore, new strategies targeting additional immune regulatory mechanisms are urgently needed. CD4⁺Foxp3⁺ regulatory T cells (Tregs) represent a major cellular mechanism in cancer immune evasion. There is compelling evidence that tumor necrosis factor (TNF) receptor type II (TNFR2) plays a decisive role in the activation and expansion of Tregs and other types of immunosuppressive cells such as myeloid-derived suppressor cells (MDSCs). Furthermore, TNFR2 is also expressed by some tumor cells. Emerging experimental evidence indicates that TNFR2 may be a therapeutic target to enhance naturally occurring or immunotherapeutic-triggered anti-tumor immune responses. In this article, we discuss recent advances in the understanding of the mechanistic basis underlying the Treg-boosting effect of TNFR2. The role of TNFR2-expressing highly suppressive Tregs in tumor immune evasion and their possible contribution to the non-responsiveness to checkpoint treatment are analyzed. Moreover, the role of TNFR2 expression on tumor cells and the impact of TNFR2 signaling on other types of cells that shape the immunological landscape in the tumor microenvironment, such as MDSCs, MSCs, ECs, EPCs, CD8⁺ CTLs, and NK cells, are also discussed. The reports revealing the effect of TNFR2-targeting pharmacological agents in the experimental cancer immunotherapy are summarized. We also discuss the potential opportunities and challenges for TNFR2-targeting immunotherapy.