Immunosuppressive Capabilities Research Articles

Mesenchymal stem cells for immune modulation in systemic lupus erythematosus: From bench research to clinical applications

Systemic lupus erythematosus (SLE) is a prevalent autoimmune disease affecting multiple organ systems. Disease progression is inevitable as part of its natural course, necessitating aggressive therapeutic strategies, particularly with the use of immunosuppressants. Long-term use of steroids and other immunosuppressants is associated with significant adverse effects. Mesenchymal stem cells (MSCs) have been shown to modulate the immune response, leading to immunosuppressive effects against self-antigens. MSCs have demonstrated the ability to modulate several immune cell populations, contributing to favorable outcomes in controlling immune and inflammatory conditions. Recent evidence has shown an increase in Treg and Breg cell subsets following MSC administration, along with modulation of other immune cells, including dendritic cells, B cells, and T cells. However, the balance between MSC pro-inflammatory and anti-inflammatory phenotypic activation remains a critical factor in determining therapeutic outcomes. Various covariates also influence the efficacy of MSC therapy. The aim of this study was to provide a comprehensive overview of the utilization of mesenchymal stem cells (MSCs) in SLE treatment, leveraging their immunomodulatory and immunosuppressive capabilities. Understanding the fundamental preclinical effects of MSCs and recent findings from clinical studies may enhance the potential of MSC therapy in the management of SLE patients.

Distinct Cutibacterium acnes subspecies defendens strains classified by multi-omics dissection alleviate inflammatory skin lesions of a rosacea-like mouse model

IntroductionCutibacterium acnes (C. acnes) resides in various organs such as the skin, prostate, eye, nose, stomach, and intestine, indicating the possibility of extensive crosstalk between this bacterium and the human body. C. acnes strains are classified into three subspecies based on phylogenetics and distinguishable phenotypes. Among them, C. acnes subsp. defendens strains are characterized by anti-inflammatory features, raising expectations for their potential as future microbiome therapeutics. However, the heterogeneity of C. acnes subsp. defendens and its corresponding immunological functions have not been clearly addressed.MethodsThe genetic diversity of the strains was assessed using single- and multi-locus sequence typing. Their immune-modulatory functions were evaluated in vitro using 2D and 3D assays with immune and epithelial cells. The anti-inflammatory effects were further confirmed in vivo using a rosacea-like mouse model. Comparative genomic and transcriptomic analyses were conducted to uncover mechanisms underlying the immunosuppressive activity of the strains.ResultsWe demonstrated that the newly isolated C. acnes subsp. defendens strains, exhibiting phenotypic heterogeneity, are distinctly clustered using single- and multi-locus sequence typing methods. These strains showed strong immune-regulatory functions in immune and epithelial cell-based 2D and 3D in vitro assays. Furthermore, their anti-inflammatory role was functionally confirmed in vivo using a rosacea-like mouse model, where they alleviated skin lesions characterized by hyperplasia and dermal inflammation. Comparative transcriptomics revealed that these strains may exert their immunosuppressive effects through the enhanced expression of acnecins and transcriptional variation in envelope stress regulators (specifically the two-component systems, CesSR homologs). Additionally, we propose that these C. acnes type II strains produce anti-inflammatory metabolites or peptides smaller than 3 kDa, which are associated with elevated pyrimidine and reduced L-arginine biosynthesis.DiscussionThe newly isolated C. acnes subsp. defendens strains demonstrate significant anti-inflammatory properties both in vitro and in vivo, suggesting their potential as microbiome-based therapeutics. Their unique genomic and transcriptomic profiles, including the production of small bioactive compounds and specific transcriptomic patterns, underpin their immunosuppressive capabilities. These findings provide a foundation for developing novel treatments for inflammatory skin conditions, such as rosacea.

Generation of a novel attenuated IBDV vaccine strain by mutation of critical amino acids in IBDV VP5

Infectious bursal disease virus (IBDV) is an acute and highly infectious RNA virus known for its immunosuppressive capabilities, chiefly inflicting rapid damage to the bursa of Fabricius (BF) of chickens. Current clinical control of IBDV infection relies on vaccination. However, the emergence of novel variant IBDV (nVarIBDV) has posed a threat to the poultry industry across the globe, underscoring the great demand for innovative and effective vaccines. Our previous studies have highlighted the critical role of IBDV VP5 as an apoptosis-inducer in host cells. In this study, we engineered IBDV mutants via a reverse genetic system to introduce amino acid mutations in VP5. We found that the mutant IBDV-VP5/3m strain caused reduced host cell mortality, and that strategic mutations in VP5 reduced IBDV replication early after infection, thereby delaying cell death. Furthermore, inoculation of chickens with IBDV-VP5/3m effectively reduced damage to BF and induced neutralizing antibody production comparable to that of parental IBDV WT strain. Importantly, vaccination with IBDV-VP5/3m protected chickens against challenges with nVarIBDV, an emerging IBDV variant strain in China, reducing nVarIBDV loads in BF while alleviating bursal atrophy and splenomegaly, suggesting that IBDV-VP5/3m might serve as a novel vaccine candidate that could be further developed as an effective vaccine for clinical control of IBD. This study provides a new clue to the development of novel and effective vaccines.

Enhanced immunosuppressive capability of mesenchymal stem cell-derived small extracellular vesicles with high expression of CD73 in experimental autoimmune uveitis

BackgroundAutoimmune uveitis is an inflammatory disease triggered by an aberrant immune response. Mesenchymal stem cell-derived small extracellular vesicles (MSC-sEVs) are emerging as potential therapeutic agents for this condition. CD73, an ectoenzyme present on MSC-sEVs, is involved in mitigating inflammation by converting extracellular adenosine monophosphate into adenosine. We hypothesize that the inhibitory effect of MSC-sEVs on experimental autoimmune uveitis (EAU) could be partially attributed to the surface expression of CD73.MethodsTo investigate novel therapeutic approaches for autoimmune uveitis, we performed lentiviral transduction to overexpress CD73 on the surface of MSC-sEVs, yielding CD73-enriched MSC-sEVs (sEVs-CD73). Mice with interphotoreceptor retinoid-binding protein (IRBP)-induced EAU were grouped randomly and treated with 50 µg MSC-sEVs, vector infected MSC-sEVs, sEVs-CD73 or PBS via single tail vein injection. We evaluated the clinical and histological features of the induced mice and analyzed the proportion and functional capabilities of T helper cells. Furthermore, T-cells were co-cultured with various MSC-sEVs in vitro, and we quantified the resulting inflammatory response to assess the potential therapeutic benefits of sEVs-CD73.ResultsCompared to MSC-sEVs, sEVs-CD73 significantly alleviates EAU, leading to reduced inflammation and diminished tissue damage. Treatment with sEVs-CD73 results in a decreased proportion of Th1 cells in the spleen, draining lymph nodes, and eyes, accompanied by an increased proportion of regulatory T-cells (Treg cells). In vitro assays further reveal that sEVs-CD73 inhibits T-cell proliferation, suppresses Th1 cells differentiation, and enhances Treg cells proportion.ConclusionOver-expression of CD73 on MSC-sEVs enhances their immunosuppressive effects in EAU, indicating that sEVs-CD73 has the potential as an efficient immunotherapeutic agent for autoimmune uveitis.

Regulation of Treg cells by cytokine signaling and co-stimulatory molecules.

CD4+CD25+Foxp3+ regulatory T cells (Tregs), a vital component of the immune system, are responsible for maintaining immune homeostasis and preventing excessive immune responses. This review explores the signaling pathways of the cytokines that regulate Treg cells, including transforming growth factor beta (TGF-β), interleukin (IL)-2, IL-10, and IL-35, which foster the differentiation and enhance the immunosuppressive capabilities of Tregs. It also examines how, conversely, signals mediated by IL-6 and tumor necrosis factor -alpha (TNF-α) can undermine Treg suppressive functions or even drive their reprogramming into effector T cells. The B7 family comprises indispensable co-stimulators for T cell activation. Among its members, this review focuses on the capacity of CTLA-4 and PD-1 to regulate the differentiation, function, and survival of Tregs. As Tregs play an essential role in maintaining immune homeostasis, their dysfunction contributes to the pathogenesis of autoimmune diseases. This review delves into the potential of employing Treg-based immunotherapy for the treatment of autoimmune diseases, transplant rejection, and cancer. By shedding light on these topics, this article aims to enhance our understanding of the regulation of Tregs by cytokines and their therapeutic potential for various pathological conditions.

Insights and Advancements in Periodontal Tissue Engineering and Bone Regeneration.

The regeneration of periodontal bone defects continues to be an essential therapeutic concern in dental biomaterials. Numerous biomaterials have been utilized in this sector so far. However, the immune response and vascularity in defect regions may be disregarded when evaluating the effectiveness of biomaterials for bone repair. Among several regenerative treatments, the most recent technique of in situ tissue engineering stands out for its ability to replicate endogenous restorative processes by combining scaffold with particular growth factors. Regenerative medicine solutions that combine biomaterials/scaffolds, cells, and bioactive substances have attracted significant interest, particularly for bone repair and regeneration. Dental stem cells (DSCs) share the same progenitor and immunomodulatory properties as other types of MSCs, and because they are easily isolable, they are regarded as desirable therapeutic agents in regenerative dentistry. Recent research has demonstrated that DSCs sown on newly designed synthetic bio-material scaffolds preserve their proliferative capacity while exhibiting increased differentiation and immuno-suppressive capabilities. As researchers discovered how short peptide sequences modify the adhesion and proliferative capacities of scaffolds by activating or inhibiting conventional osteogenic pathways, the scaffolds became more effective at priming MSCs. In this review, the many components of tissue engineering applied to bone engineering will be examined, and the impact of biomaterials on periodontal regeneration and bone cellular biology/molecular genetics will be addressed and updated.

B7H3 (CD276) regulation of myeloid cell differentiation in pulmonary fibrosis

Abstract Myeloid-derived suppressor cells (MDSCs) are induced in cancer and fibrosis, while absent in healthy tissues. The expansions of MDSC are correlated with disease severity and lung function deterioration in the latter. B7H3 induced in lung fibrosis causes the recruitment of MDSCs. However, the mechanism underlying the biogenesis of MDSCs is unclear. To study if B7H3-induced expansion of MDSCs is due to inhibition of the differentiation of myeloid progenitors, the role of B7H3 in the regulation of BM-derived myeloid cells was studied. The results showed that B7H3 deficiency in BM LysM+ myeloid cells significantly increased differentiation to mature myeloid cells. In contrast, treatment with B7H3 inhibited such differentiation. In mice, LysM+ cells-specific B7H3 deficiency induced mature myeloid cell differentiation, but significantly decreased immature MDSCs, which was associated with less immunosuppressive capability. Lack of B7H3 caused a significant reduction of MDSC marker genes characteristic. Furthermore, the delayed B7H3 antibody treatment or by ablating of its secretion from collagen-expressing cells reduced BM-derived MDSCs and PD1-expressing progenitors but increased mature myeloid cell number, which was accompanied by attenuated lung fibrosis. These findings suggested that activated fibroblasts in lung fibrosis may be a key source of soluble B7H3 essential for the signal to BM skewing myeloid lineage fate and induced biogenesis of MDSC

Molecular Mimicry in Pathogen Immune Evasion

Abstract Molecular mimicry is the immunological mechanism by which pathogen-derived peptides can modulate immune responses due to sequence similarity with self-peptides. Herein, we report molecular mimicry associated with pathogen immune evasion. A quantitative analysis of the immunopeptidome presented by in vivo mycobacteria tuberculosis (MTB)-matured dendritic cells in HLA-DR0101 (DR1) transgenic mice identified an MTB-processed peptide which presented immunosuppressive capability and shared a DR1 core sequence with a human and mouse self-protein. The TB peptide could expand nTreg with generation of immunosuppressive cytokines in DR1 mice and DR1 subjects diagnosed with active or latent TB. In TB-infected patients the tolerogenic TB peptide reduced the inflammatory response generated to a series of immunogenic TB peptides as quantified by the QuantiFERON test. Additionally, the tolerogenic TB peptide presented an MHC-binding core sequence shared by a multitude of pathogens. Our analysis characterizes a pathogen-derived peptide which, through molecular mimicry facilitate immune evasion by activating/inducing nTreg.

Abstract 2695: A higher percentage of M2 macrophages in non-tumor part predict the tumor recurrence in patients with hepatocellular carcinoma after surgical resection

Abstract The primary hurdle in improving outcomes for hepatocellular carcinoma (HCC) patients after curative treatment is the high early recurrence rate. The existing literature indicates the presence of type 2 macrophages (M2), renowned for their immunosuppressive capabilities, has been implicated in creating a microenvironment conducive to tumor growth and recurrence. However, the intricate interplay involving M2 macrophages and the recurrence of HCC is underexplored. Therefore, we conducted an analysis involving HCC patients who underwent hepatectomy at our hospital between 2013 and 2017. We collected samples from both the tumor and non-tumor regions and subjected them to bulk RNA sequencing for comprehensive molecular profiling. The proportion of immune cells was calculated by CIBERSORTx.In our study, we enrolled fifty patients, with sixty percent presenting with cirrhosis and seventy-three percent having viral hepatitis. Twenty-three patients experienced tumor recurrence, with a median time to recurrence of 12.6 months. First, we found no correlation between five TIMR subtypes defined by TIMELASER (Xue R, Nature, 2022) and recurrence. However, as for the proportions of immune cell, a significantly lower NK/Treg ratio (p= 0.0163) and high within the resected tumor section in recurrent group was found. On the other hand, the ratio of M2 macrophages to total macrophages (M2/M) was significantly higher within the non-tumor region in patients experiencing tumor recurrence after hepatectomy (p=0.0357). Furthermore, the expression of the ACGT2 gene in non-tumor part, which strongly correlates with Treg function, was significantly higher (p=0.0056) in recurrent group. In addition, the innate T cells score was increased in non-tumor pat in recurrent group but with borderline significance (p=0.0628). However, in multivariable analysis, only a higher M2/M ratio within the non-tumor region (HR 3.756, p=0.0072) were identified as independent risk factors for tumor recurrence. We also found that patients with a higher M2/M ratio had a lower percentage of cirrhotic patients (p=0.0049) and less association with TIME-IA (immune activation) subtype of HCC by TIMELASER classification (p=0.0030). In conclusion, a higher M2/M ratio within the non-tumor region predict the tumor recurrence in patients with hepatocellular carcinoma. Citation Format: Po-Ting Lin, Wei-Ting Ku, Tsung-Han Wu, Cheng-Heng Wu, Chan-Keng Yang, Wei Teng, Yung-Chang Lin, Chun-Yen Lin. A higher percentage of M2 macrophages in non-tumor part predict the tumor recurrence in patients with hepatocellular carcinoma after surgical resection [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2695.

Abstract 2642: KEAP1 mutation in lung cancer cells leads to increased immunosuppressive capability

Abstract Considerable advances have been made in lung cancer therapies, but there is still an unmet clinical need to improve survival for lung cancer patients. Immunotherapies have improved survival, although only 20-30% of patients respond to these treatments. Interestingly, cancers with mutations in KEAP1, the negative regulator of the NRF2 cytoprotective pathway, are resistant to immune checkpoint inhibition and correlate with decreased immune cell infiltration. NRF2 is known for promoting an anti-inflammatory phenotype when activated in immune cells, but the study of NRF2 activation in cancer cells has not been adequately assessed. The overall objective of this study is to determine how lung cancer cells with constitutive NRF2 activity interact with the immune microenvironment to promote cancer progression and metastasis. To assess this, we generated CRISPR-edited mouse lung cancer cell lines (Lewis Lung Carcinoma/LL2) with knockouts (KO) of the KEAP1 and NFE2L2 genes. The transcriptomic profiles of 3 KEAP1 KO and 1 NRF2 KO cell lines were compared to the parental wildtype (WT) line using RNA-sequencing. On unsupervised hierarchical clustering of differentially expressed genes, the 3 KEAP1 KO cell lines clustered together and the NRF2 KO clustered with WT cells. Importantly, canonical NRF2 pathway-related genes were significantly increased in KEAP1 KO clones, but the same genes were either decreased or similar to WT in the NRF2 KO clone. We then used flow cytometry to evaluate immunosuppressive surface markers known to suppress T cell function when expressed on cancer cells. Importantly, PD-L1, CD155, CD80, and CD86 were increased in the KEAP1 KO lines compared to WT, but not in the NRF2 KO clone. In addition, the cytokine release profile was differentially regulated in the KEAP1 KO clones in a manner that could alter T cell recruitment and function. These results were also consistent with gene expression in the sequencing dataset. Finally, using an orthotopic allograft model, we completed a preliminary immunophenotyping study of lung tumors for WT, KEAP1 KO, and NRF2 KO cell lines. The activation status of CD8+ T cells and the ratio of CD8+/CD4+CD25+ T cells (a prognostic marker) were decreased in KEAP1 KO tumors. Taken together, these data suggest cancers with KEAP1 mutations may increase tumor growth through suppression of T cells. Citation Format: Christopher John Occhiuto, Karen T. Liby. KEAP1 mutation in lung cancer cells leads to increased immunosuppressive capability [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2642.

Reciprocal relationship between cancer stem cells and myeloid-derived suppressor cells: implications for tumor progression and therapeutic strategies.

Recently, there has been an increased focus on cancer stem cells (CSCs) due to their resilience, making them difficult to eradicate. This resilience often leads to tumor recurrence and metastasis. CSCs adeptly manipulate their surroundings to create an environment conducive to their survival. In this environment, myeloid-derived suppressor cells (MDSCs) play a crucial role in promoting epithelial-mesenchymal transition and bolstering CSCs' stemness. In response, CSCs attract MDSCs, enhancing their infiltration, expansion and immunosuppressive capabilities. This interaction between CSCs and MDSCs increases the difficulty of antitumor therapy. In this paper, we discuss the interplay between CSCs and MDSCs based on current research and highlight recent therapeutic strategies targeting either CSCs or MDSCs that show promise in achieving effective antitumor outcomes.

Gallic acid–coated nanolayer on mineral trioxide aggregate for regulating the inflammatory and differentiation cellular response profile of human dental pulp stem cells

Mineral trioxide aggregate (MTA) is a biomaterial used in endodontics due to its high bioactivity, antibacterial behaviors, and good biocompatibility. However, it has several disadvantages related to certain physical properties, including a long setting time and poor mechanical properties. Therefore, we hypothesized that coating MTA with gallic acid (GA) would regulate physical properties and lead to enhanced adhesion, proliferation, and secretion of angiogenic- and odontogenic-related proteins. This study examined whether MTA can be modified with GA to form GAMTA cement and evaluated its physicochemical and biological behaviors and immune suppression, angiogenesis, and odontogenesis capabilities. We soaked MTA in Tris buffer containing different concentrations of GA to coat the MTA powders. X-ray diffraction (XRD) and diametral tensile strength analyses were conducted to assess the physical characteristics of GAMTA. Then, we immersed GAMTA cement in simulated body fluid to evaluate its hydroxyapatite precipitation capabilities and silicon ion release profile. We used human dental pulp stem cells to assess the cell responses and the immunosuppressive, angiogenic, and odontogenic capabilities of GAMTA. The XRD results showed that GA was successfully coated onto MTA without the disruption or loss of MTA’s advantageous original structural properties. GAMTA demonstrated excellent physicochemical and biological properties, improving hydroxyapatite formation and angiogenic, odontogenic, and anti-inflammatory properties compared with MTA alone. Our results indicate that the GAMTA cement is a useful dental material for future tissue engineering and clinical applications.

Mesenchymal stromal cells, metabolism, and mitochondrial transfer in bone marrow normal and malignant hematopoiesis.

Hematopoietic stem cell (HSC) transplantation-based treatments are in different phases of clinical development, ranging from current therapies to a promise in the repair and regeneration of diseased tissues and organs. Mesenchymal stromal/stem cells (MSCs), which are fibroblast-like heterogeneous progenitors with multilineage differentiation (osteogenic, chondrogenic, and adipogenic) and self-renewal potential, and exist in the bone marrow (BM), adipose, and synovium, among other tissues, represent one of the most widely used sources of stem cells in regenerative medicine. MSCs derived from bone marrow (BM-MSCs) exhibit a variety of traits, including the potential to drive HSC fate and anti-inflammatory and immunosuppressive capabilities via paracrine activities and interactions with the innate and adaptive immune systems. The role of BM-MSC-derived adipocytes is more controversial and may act as positive or negative regulators of benign or malignant hematopoiesis based on their anatomical location and functional crosstalk with surrounding cells in the BM microenvironment. This review highlights the most recent clinical and pre-clinical findings on how BM-MSCs interact with the surrounding HSCs, progenitors, and immune cells, and address some recent insights on the mechanisms that mediate MSCs and adipocyte metabolic control through a metabolic crosstalk between BM microenvironment cells and intercellular mitochondrial transfer in normal and malignant hematopoiesis.

Bone Marrow Stroma Impairs CAR-T Cell Proliferation and Function: Mechanistic Insights

Chimeric Antigen Receptor (CAR)-T cells have proven highly successful in the treatment of some haemopoietic neoplasms. However, in several cases the treatment fails and disease does not respond and/or relapses. Amongst the different factors impacting on a negative clinical outcome, an unfavourable immunosuppressive microenvironment has been proposed as playing a critical role, particularly in the context of acute myeloid leukemia. We hypothesised that bone marrow mesenchymal stromal cells (BM-MSC) acquire immunosuppressive properties after exposure to the by-stander effects of activated CAR-T cells against leukemic cells. We used a CAR-T cell consisting of a CD33 binder and CD28z-OX40 costimulatory moiety. BM-MSC were exposed to the CAR following in vitro activation on CD33-coated plates for 24 hours. To model the different ways by which stromal cells can license their immunosuppressive activity, BM-MSC were exposed to the supernatant harvested from the cultures of activated CARs or in direct contact with the activated CARs themselves. In the first case, after incubation with the CAR-conditioned medium (CAR-cm), BM-MSCs were investigated for their transcriptome by RNASeq. Gene ontology analysis of the transcriptome revealed a strong NF-κB and STAT1 signature in BM-MSC exposed to the CAR-cm compared to those which were not exposed. Amongst the most upregulated molecules, we identified several chemokines (CXCL10, CCL8, CXCL8, and CXCL9), PDL1 and CECAM1, IL-6, indoleamine-2,3 dyoxigenase (IDO), and most prominently PTGES and PTGS2. We then interrogated the immune functional profile by incubating by CAR-cm licensed BM-MSC with fresh CD33-activated CAR-T cells. We observed that CAR proliferation, cytotoxicity and cytokine production was significantly inhibited. CAR function was restored if Rel-A - a REL-associated protein critically involved in NF-κB heterodimer formation, nuclear translocation and activation - was inhibited in BM-MSC by shRNA before exposure to CAR-cm. We previously described that BM-MSC undergo apoptosis when in contact with activated cytotoxic T cells and that this also triggers their immunosuppressive capability. Therefore, we evaluated the impact of cell contact dependent mechanisms on BM-MSC licensing. CD33-activated CAR-T cells were incubated with BM-MSC and the proportion of annexin-V positive BM-MSC were assessed after 4 hours. We observed that a large fraction of BM-MSC underwent apoptosis and that this was dependent on caspase activation, but not RIP kinase 3, and the release of cytolytic granules in a contact-dependent fashion. The supernatant of apoptotic BM-MSC but not the terminally apoptotic and neither the live cells exhibited a strong inhibitory activity on CAR-T cell proliferation, cytotoxicity and effector cytokine production. Similarly to what described with the CAR-cm induced profile, BM-MSC immunosuppression required NF-κB and was effected via the COX2 pathway. We finally tested the impact of apoMSC in vivo in a xenograft model of AML (Fig. 1). CD33-positive KG1 cells were injected in NSG mice and 2 weeks later, CD33-specific CAR-T were administered with or without (controls) apoMSC. Peripheral blood samples were collected 7, 14, and 21 days after. We observed an inhibitory effect of apoMSc on the in vivo expansion of CAR-T cells which was accompanied by disease progression. Accordingly, the survival of the mice treated with apoMSC was markedly reduced compared to those receiving CAR-T cells only. We conclude that BM-MSC can be induced to acquire immunosuppressive properties by activated CAR-T cells through 2 different but overlapping mechanisms, both dependent on NF-κB and COX2 signalling pathway (Fig. 2). Our work provides critical information to overcome resistance to CAR-T cell treatment by neutralising the negative effects of the stromal microenvironment.

Addressing the impact of high glucose microenvironment on the immunosuppressive characteristics of human mesenchymal stem cells.

Mesenchymal stem cells (MSCs) are a therapeutically efficient type of stem cells validated by their ability to treat many inflammatory and chronic conditions. The biological and therapeutic characteristics of MSCs can be modified depending on the type of microenvironment at the site of transplantation. Diabetes mellitus (DM) is a commonly diagnosed metabolic disease characterized by hyperglycemia, which alters over time the cellular and molecular functions of many cells and causes their damage. Hyperglycemia can also impact the success rate of MSCs transplantation; therefore, it is extremely significant to investigate the effect of high glucose on the biological and therapeutic attributes of MSCs, particularly their immunomodulatory abilities. Thus, in this study, we explored the effect of high glucose on the immunosuppressive characteristics of human adipose tissue-derived mesenchymal stem cells (hAD-MSCs). We found that hAD-MSCs cultured in high glucose lost their immunomodulatory abilities and became detectable by immune cells. The decline in the immunosuppressive capabilities of hAD-MSCs was mediated by significant decrease in the levels of IDO, IL-10, and complement factor H and substantial increase in the activity of immunoproteasome. The protein levels of AMP-activated protein kinase (AMPK) and phosphofructokinase-1 (PFK-1), which are integral regulators of glycolysis, revealed a marked decline in high glucose exposed MSCs. The findings of our study indicated the possibility of immunomodulatory shift in MSCs after being cultured in high glucose, which can be translationally employed to explain their poor survival and short-lived therapeutic outcomes in diabetic patients.

Emerging Roles of Mesenchymal Stem/Stromal-Cell-Derived Extracellular Vesicles in Cancer Therapy.

Despite the tremendous efforts of many researchers and clinicians, cancer remains the second leading cause of mortality worldwide. Mesenchymal stem/stromal cells (MSCs) are multipotent cells residing in numerous human tissues and presenting unique biological properties, such as low immunogenicity, powerful immunomodulatory and immunosuppressive capabilities, and, in particular, homing abilities. Therapeutic functions of MSCs are mediated mostly by the paracrine effect of released functional molecules and other variable components, and among them the MSC-derived extracellular vesicles (MSC-EVs) seem to be one of the central mediators of the therapeutic functions of MSCs. MSC-EVs are membrane structures secreted by the MSCs, rich in specific proteins, lipids, and nucleic acids. Amongst these, microRNAs have achieved the most attention currently. Unmodified MSC-EVs can promote or inhibit tumor growth, while modified MSC-EVs are involved in the suppression of cancer progression via the delivery of therapeutic molecules, including miRNAs, specific siRNAs, or suicide RNAs, as well as chemotherapeutic drugs. Here, we present an overview of the characteristics of the MSCs-EVs and describe the current methods for their isolation and analysis, the content of their cargo, and modalities for the modification of MSC-EVs in order for them to be used as drug delivery vehicles. Finally, we describe different roles of MSC-EVs in the tumor microenvironment and summarize current advances of MCS-EVs in cancer research and therapy. MSC-EVs are expected to be a novel and promising cell-free therapeutic drug delivery vehicle for the treatment of cancer.

Stem Cell Therapy in Inflammatory Bowel Disease: A Review of Achievements and Challenges.

Inflammatory bowel disease (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), is a group of chronic inflammatory diseases of the gastrointestinal tract. Repeated inflammation can lead to complications, such as intestinal fistula, obstruction, perforation, and bleeding. Unfortunately, achieving durable remission and mucosal healing (MH) with current treatments is difficult. Stem cells (SCs) have the potential to modulate immunity, suppress inflammation, and have anti-apoptotic and pro-angiogenic effects, making them an ideal therapeutic strategy to target chronic inflammation and intestinal damage in IBD. In recent years, hematopoietic stem cells (HSCs) and adult mesenchymal stem cells (MSCs) have shown efficacy in treating IBD. In addition, numerous clinical trials have evaluated the efficiency of MSCs in treating the disease. This review summarizes the current research progress on the safety and efficacy of SC-based therapy for IBD in both preclinical models and clinical trials. We discuss potential mechanisms of SC therapy, including tissue repair, paracrine effects, and the promotion of angiogenesis, immune regulation, and anti-inflammatory effects. We also summarize current SC engineering strategies aimed at enhancing the immunosuppressive and regenerative capabilities of SCs for treating intestinal diseases. Additionally, we highlight current limitations and future perspectives of SC-related therapy for IBD.

Parasitic nematode secreted phospholipase A2 suppresses cellular and humoral immunity by targeting hemocytes in Drosophila melanogaster.

A key aspect of parasitic nematode infection is the nematodes' ability to evade and/or suppress host immunity. This immunomodulatory ability is likely driven by the release of hundreds of excretory/secretory proteins (ESPs) during infection. While ESPs have been shown to display immunosuppressive effects on various hosts, our understanding of the molecular interactions between individual proteins released and host immunity requires further study. We have recently identified a secreted phospholipase A2 (sPLA2) released from the entomopathogenic nematode (EPN) Steinernema carpocapsae we have named Sc-sPLA2. We report that Sc-sPLA2 increased mortality of Drosophila melanogaster infected with Streptococcus pneumoniae and promoted increased bacterial growth. Furthermore, our data showed that Sc-sPLA2 was able to downregulate both Toll and Imd pathway-associated antimicrobial peptides (AMPs) including drosomycin and defensin, in addition to suppressing phagocytosis in the hemolymph. Sc-sPLA2 was also found to be toxic to D. melanogaster with the severity being both dose- and time-dependent. Collectively, our data highlighted that Sc-sPLA2 possessed both toxic and immunosuppressive capabilities.

Human umbilical cord mesenchymal stem cell-derived TGFBI attenuates streptozotocin-induced type 1 diabetes mellitus by inhibiting T-cell proliferation

MSCs have been demonstrated to have a great benefit for type 1 diabetes mellitus (T1DM) due to their strong immunosuppressive and regenerative capacity. However, the comprehensive mechanism is still unclear. Our previous study indicated that transforming growth factor beta induced (TGFBI) is highly expressed in human umbilical cord-derived mesenchymal stem or stromal cells (hUC-MSCs), which are also implicated in T1DM. In this study, we found that infusion of TGFBI knockdown hUC-MSCs displayed impaired therapeutic effects in T1DM mice and decreased immunosuppressive capability. TGFBI knockdown hUC-MSCs could increase the proportion of T-cell infiltration while increasing the expression of IFN-gamma and interleukin-17A in the spleen. In addition, we also revealed that hUC-MSC-derived TGFBI could repress activated T-cell proliferation by interfering with G1/S checkpoint CyclinD2 expression. Our results demonstrate that TGFBI plays a critical role in MSC immunologic regulation. TGFBI could be a new immunoregulatory molecule controlling MSC function for new treatments of T1DM.Graphical Schematic Representation of the Immunosuppression capacity of hUC-MSC by TGFBI

Toxicity Impacts on Human Adipose Mesenchymal Stem/Stromal Cells Acutely Exposed to Aroclor and Non-Aroclor Mixtures of Polychlorinated Biphenyl.

Polychlorinated biphenyl (PCB) accumulates in adipose where it may impact the growth and function of cells within the tissue. This is particularly concerning during adolescence when adipocytes expand rapidly. Herein, we sought to understand how exposure to PCB mixtures found in U.S. schools affects human adipose mesenchymal stem/stromal cell (MSC) health and function. We investigated how exposure to Aroclor 1016 and Aroclor 1254, as well as a newly characterized non-Aroclor mixture that resembles the PCB profile found in cabinets, Cabinet Mixture, affects adipose MSC growth, viability, and function in vitro. We found that exposure to all three mixtures resulted in two distinct types of toxicity. At PCB concentrations >20 μM, the majority of MSCs die, while at 1-10 μM, MSCs remained viable but display numerous alterations to their phenotype. At these sublethal concentrations, the MSC rate of expansion slowed and morphology changed. Further assessment revealed that PCB-exposed MSCs had impaired adipogenesis and a modest decrease in immunosuppressive capabilities. Thus, exposure to PCB mixtures found in schools negatively impacts the health and function of adipose MSCs. This work has implications for human health due to MSCs' role in supporting the growth and maintenance of adipose tissue.