Toll-Like Receptor Engagement Enhances the Immunosuppressive Properties of Human Bone Marrow-Derived Mesenchymal Stem Cells by Inducing Indoleamine-2,3-dioxygenase-1 via Interferon-β and Protein Kinase R

CEACAM1-engineered MSCs have a broad spectrum of immunomodulatory functions and therapeutic potential via cell-to-cell interaction

Mesenchymal stem cells (MSCs) have garnered attention for their regenerative and immunomodulatory capabilities in clinical trials for various diseases. However, the effectiveness of MSC-based therapies, especially for conditions like graft-versus-host disease (GvHD), remains uncertain. The cytokine interferon (IFN)-γ has been known to enhance the immunosuppressive properties of MSCs through cell-to-cell interactions and soluble factors. In this study, we observed that IFN-γ-treated MSCs upregulated the expression of carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1), associated with immune evasion through the inhibition of natural killer (NK) cell cytotoxicity. To co-opt this immunomodulatory function, we generated MSCs overexpressing CEACAM1 and found that CEACAM1-engineered MSCs significantly reduced NK cell activation and cytotoxicity via cell-to-cell interaction, independent of NKG2D ligand regulation. Furthermore, CEACAM1-engineered MSCs effectively inhibited the proliferation and activation of T cells along with the inflammatory responses of monocytes. In a humanized GvHD mouse model, CEACAM1-MSCs, particularly CEACAM1-4S-MSCs, demonstrated therapeutic potential by improving survival and alleviating symptoms. These findings suggest that CEACAM1 expression on MSCs contributes to MSC-mediated regulation of immune responses and that CEACAM1-engineered MSC could have therapeutic potential in conditions involving immune dysregulation.

The curious case of type I interferon signaling in cancer

Cytokines are the crucial signaling proteins that mediate the crosstalks between the cells of tumor microenvironment (TME). Interferon-1 (IFN-1) are the important cytokines that are widely known for their tumor suppressive roles comprising of cancer cell intrinsic and extrinsic mechanisms. Despite having known antitumor effects, IFN-1 are also reported to have tumor promoting functions under varying circumstances. This dichotomy in the functions of IFN-1 is largely attributed to the acute and chronic activation of IFN-1 signaling in TME. The chronic activation of IFN-1 signaling in tumor cells results in altered stimulation of downstream pathways that result in the expression of tumor promoting proteins, while the acute IFN-1 signaling activation maintains its tumor inhibiting functions. In the present review, we have discussed the anti- and pro-tumor actions of IFN-1 signaling under acute and chronic IFN-1 signaling activation. We have also discussed the downstream changes in signaling components that result in tumor supportive functions of a constitutive IFN-1 signaling. We have further discussed the possible strategies to overcome the detrimental effects of chronic IFN-1 pathway activation and to successfully employ IFN-1 for their beneficial anti-tumor effects.

Toll-like receptor 3-stimulation and aggregate-formation synergistically enhances anti-inflammatory activity of feline mesenchymal stem cells

IMPORTANCE

Mesenchymal stem cells (MSCs) used to treat inflammatory diseases in humans show improved clinical outcomes compared to other treatments. On the other hand, feline MSCs have limited therapeutic effects because of their low bioactivity. Successful clinical treatment requires enhancing the anti-inflammatory ability of feline adipose-derived MSCs (fAdMSCs).

OBJECTIVE

To enhance the anti-inflammatory activity of fAdMSCs.

METHODS

fAdMSCs were treated with the toll-like receptor 3 (TLR3) ligand poly (I:C) and aggregated. Indoleamine 2,3-dioxygenase-1 (IDO-1) expression and kynurenine production were measured to evaluate the anti-inflammatory activity. Anti-inflammatory effects were assessed by culturing fAdMSCs with rat macrophages and transplanting them into the kidney capsules of rats.

RESULTS

IDO-1 expression and kynurenine production in fAdMSCs were increased significantly by a poly (I:C) treatment and enhanced using a basic fibroblast growth factor (bFGF) treatment. The level of fAdMSC aggregation increased IDO-1 expression significantly compared to the monolayer. These effects were enhanced by pretreatment with bFGF and poly (I:C). The bFGF and poly (I:C)-pretreated fAdMSC aggregates suppressed tumor necrosis factor-α expression in rat macrophages. During transplantation, the pretreated fAdMSC aggregates avoided leakage, survived in aggregate form, and induced anti-inflammatory macrophages.

CONCLUSIONS AND RELEVANCE

TLR3-stimulated, bFGF-pretreated fAdMSC aggregates increase the anti-inflammatory activity significantly, providing a potential therapeutic approach for inflammatory diseases in felines.

Influence of mesenchymal stem cells from different origins on the therapeutic effectiveness of systemic lupus erythematosus

Systemic Lupus Erythematosus (SLE) is a chronic autoimmune inflammatory disorder characterized by alterations in the balance between inflammatory and regulatory cytokines. Mesenchymal stem cells (MSCs), which are non-hematopoietic stem cells with multipotent differentiation potential, due to their immunomodulatory, tissue repair, low immunogenicity, and chemotactic properties, have garnered increasing interest in SLE treatment. Studies increasingly reveal the heterogeneous nature of MSC populations. With sources including dental pulp, adipose tissue, bone marrow, and umbilical cord, the therapeutic effects of MSCs on SLE vary depending on their origin. This review consolidates clinical research on MSCs from different sources in treating SLE and analyzes the possible causes underlying these variable outcomes. Additionally, it elucidates five potential factors impacting the outcomes of MSC therapy in SLE: the influence of the microenvironment on MSCs, the complexity and paradoxical aspects of MSC mechanisms in SLE treatment, the heterogeneity of MSCs, the in vivo differentiation potential and post-transplant survival rates of MSCs, and disparities in MSC preparation conditions.

Differential effects of TLR3 and TLR4 activation on MSC-mediated immune regulation

Mesenchymal stromal cells (MSCs) have evolved as an invaluable therapeutic cell type due to their broad therapeutic properties. Bone marrow-derived MSCs are currently being applied in numerous clinical trials, and the initial results have been encouraging. However, heterogeneous responsiveness amongst patients is also being experienced; therefore, the efficacy of MSCs in vivo is still debatable. Host microenvironment plays an essential role in determining the fate of MSCs in vivo. Recent studies have indicated the role of toll-like receptors (TLR) in modulating the biological properties of MSCs. TLRs are expressed by MSCs, and activation of TLR3 and TLR4 can alter the functionality of MSCs. While MSCs can suppress the effector and memory T cell function by promoting regulatory T cells, the effect of TLR activation on MSC-mediated immune cell induction is still not well understood. This study was performed to understand the TLR licensing of MSCs and its impact on MSC-mediated immunomodulation. We found that TLR3 mediated activation of MSCs (TLR3-MSCs) increased the expression of G-CSF & IL-10 while TLR4-mediated activation of MSCs led to an increase in CXCL-1, CXCL-10, and CXCL-12. To study the immunological aspect, an in vitro co-culture model was established-to imitate the brief in vivo interaction of MSCs and immune cells. We found that TLR3-MSCs led to increase in CD4 and CD8 naive T (TNAI) cells and vice versa for effector (TEFF) and memory T (TMEM) cells, while TLR4-MSCs did not show any effect. Moreover, only TLR3-MSCs led to a non-significant increase in the regulatory T cells (TREGS) and Double negative regulatory cells. No change in B cell profile was evident while TLR3-MSCs depicted an increasing trend in regulatory B cells which was not statistically significant. TLR3 MSCs also inhibited the T cell proliferation in our setup. Our data indicate that TLR3 priming may regulate the function of MSCs through immunomodulation. Understanding the role of TLRs and other microenvironmental factors causing subdued responses of MSCs in vivo would allow the uninhibited use of MSCs for many diseased conditions.

The Comparison of Immunomodulatory Properties of Canine and Human Wharton Jelly-Derived Mesenchymal Stromal Cells

Although therapies based on mesenchymal stromal cells (MSCs) are being implemented in clinical settings, many aspects regarding these procedures require further optimization. Domestic dogs suffer from numerous immune-mediated diseases similar to those found in humans. This study aimed to assess the immunomodulatory activity of canine (c) Wharton jelly (WJ)-derived MSCs and refer them to human (h) MSCs isolated from the same tissue. Canine MSC(WJ)s appeared to be more prone to in vitro aging than their human counterparts. Both canine and human MSC(WJ)s significantly inhibited the activation as well as proliferation of CD4+ and CD8+ T cells. The treatment with IFNγ significantly upregulated indoleamine-2,3-dioxygenase 1 (IDO1) synthesis in human and canine MSC(WJ)s, and the addition of poly(I:C), TLR3 ligand, synergized this effect in cells from both species. Unstimulated human and canine MSC(WJ)s released TGFβ at the same level (p > 0.05). IFNγ significantly increased the secretion of TGFβ in cells from both species (p < 0.05); however, this response was significantly stronger in human cells than in canine cells. Although the properties of canine and human MSC(WJ)s differ in detail, cells from both species inhibit the proliferation of activated T cells to a very similar degree and respond to pro-inflammatory stimulation by enhancing their anti-inflammatory activity. These results suggest that testing MSC transplantation in naturally occurring immune-mediated diseases in dogs may have high translational value for human clinical trials.

Effect of Priming With Toll-Like Receptor 3 Agonist on Expression of Long Noncoding RNAs in Human Wharton Jelly Mesenchymal Stem Cells

OBJECTIVES

Mesenchymal stem cells are gaining attention in medicine because of their anti-inflammatory and immunosuppressive properties. Inflammatory conditions can modulate immune responses in mesenchymal stem cells.We investigated the expression of long noncoding RNAs (RMRP, MALT1, NKILA,THRIL, and Linc-MAF-4) in humanWharton jelly mesenchymal stem cells primed with polyinosinicpolycytidylic acid.

MATERIALS AND METHODS

Mesenchymal stem cells were isolated from human Wharton jelly by the explant method. To determine the stem nature of the cells, we performed a differentiation test on bone and fat cells. We used flow cytometry analysis to determine surface markers. Umbilical cord mesenchymal stem cells (1 × 105) were cultured in T75 culture flasks in Dulbecco's modified Eagle medium containing 10% fetal bovine serum. After cells reached approximately 80% confluency, cells were exposed to 50 µg/mL of polyinosinic-polycytidylic acid, a Toll-like receptor 3 ligand, for 24, 48, and 72 hours. The control group were cells not exposed to polyinosinic-polycytidylic acid. Real-time polymerase chain reaction evaluated RMRP, MALAT1, NKILA, THRIL, and Linc-MAF-4 long noncoding RNAs.

RESULTS

We observed significantly increased expression of NKILA inWharton jelly mesenchymal stem cells stimulated with polyinosinic-polycytidylic acid at 72 hours compared with expression level in the control group (P < .001).

CONCLUSIONS

Results indicated that a potential mechanism by which the Toll-like receptor 3 ligand improves immunosuppression of mesenchymal stem cells can be attributed to the regulatory role of long noncoding RNAs, possibly through increased expression of anti-inflammatory long noncoding RNAs such as NKILA.

Mesenchymal Stromal Cells: New Generation Treatment of Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic inflammatory disease of the gastrointestinal tract, which has a high recurrence rate and is incurable due to a lack of effective treatment. Mesenchymal stromal cells (MSCs) are a class of pluripotent stem cells that have recently received a lot of attention due to their strong self-renewal ability and immunomodulatory effects, and a large number of experimental and clinical models have confirmed the positive therapeutic effect of MSCs on IBD. In preclinical studies, MSC treatment for IBD relies on MSCs paracrine effects, cell-to-cell contact, and its mediated mitochondrial transfer for immune regulation. It also plays a therapeutic role in restoring the intestinal mucosal barrier through the homing effect, regulation of the intestinal microbiome, and repair of intestinal epithelial cells. In the latest clinical trials, the safety and efficacy of MSCs in the treatment of IBD have been confirmed by transfusion of autologous or allogeneic bone marrow, umbilical cord, and adipose MSCs, as well as their derived extracellular vesicles. However, regarding the stable and effective clinical use of MSCs, several concerns emerge, including the cell sources, clinical management (dose, route and frequency of administration, and pretreatment of MSCs) and adverse reactions. This article comprehensively summarizes the effects and mechanisms of MSCs in the treatment of IBD and its advantages over conventional drugs, as well as the latest clinical trial progress of MSCs in the treatment of IBD. The current challenges and future directions are also discussed. This review would add knowledge into the understanding of IBD treatment by applying MSCs.

A Review of the Evidence for Tryptophan and the Kynurenine Pathway as a Regulator of Stem Cell Niches in Health and Disease

Stem cells are ubiquitously found in various tissues and organs in the body, and underpin the body's ability to repair itself following injury or disease initiation, though repair can sometimes be compromised. Understanding how stem cells are produced, and functional signaling systems between different niches is critical to understanding the potential use of stem cells in regenerative medicine. In this context, this review considers kynurenine pathway (KP) metabolism in multipotent adult progenitor cells, embryonic, haematopoietic, neural, cancer, cardiac and induced pluripotent stem cells, endothelial progenitor cells, and mesenchymal stromal cells. The KP is the major enzymatic pathway for sequentially catabolising the essential amino acid tryptophan (TRP), resulting in key metabolites including kynurenine, kynurenic acid, and quinolinic acid (QUIN). QUIN metabolism transitions into the adjoining de novo pathway for nicotinamide adenine dinucleotide (NAD) production, a critical cofactor in many fundamental cellular biochemical pathways. How stem cells uptake and utilise TRP varies between different species and stem cell types, because of their expression of transporters and responses to inflammatory cytokines. Several KP metabolites are physiologically active, with either beneficial or detrimental outcomes, and evidence of this is presented relating to several stem cell types, which is important as they may exert a significant impact on surrounding differentiated cells, particularly if they metabolise or secrete metabolites differently. Interferon-gamma (IFN-γ) in mesenchymal stromal cells, for instance, highly upregulates rate-limiting enzyme indoleamine-2,3-dioxygenase (IDO-1), initiating TRP depletion and production of metabolites including kynurenine/kynurenic acid, known agonists of the Aryl hydrocarbon receptor (AhR) transcription factor. AhR transcriptionally regulates an immunosuppressive phenotype, making them attractive for regenerative therapy. We also draw attention to important gaps in knowledge for future studies, which will underpin future application for stem cell-based cellular therapies or optimising drugs which can modulate the KP in innate stem cell populations, for disease treatment.

The effects of whole grain cereals on tryptophan metabolism and intestinal barrier function: underlying factors of health impact

This review aims to investigate the relationship between the health impact of whole grains mediated via the interaction with intestinal microbiota and intestinal barrier function with special interest on tryptophan metabolism, focusing on the role of the intestinal microbiota and their impact on barrier function. Consuming various types of whole grains can lead to the growth of different microbiota species, which in turn leads to the production of diverse metabolites, including those derived from tryptophan metabolism, although the impact of whole grains on intestinal microbiota composition results remains inconclusive and vary among different studies. Whole grains can exert an influence on tryptophan metabolism through interactions with the intestinal microbiota, and the presence of fibre in whole grains plays a notable role in establishing this connection. The impact of whole grains on intestinal barrier function is closely related to their effects on the composition and activity of intestinal microbiota, and SCFA and tryptophan metabolites serve as potential links connecting whole grains, intestinal microbiota and the intestinal barrier function. Tryptophan metabolites affect various aspects of the intestinal barrier, such as immune balance, mucus and microbial barrier, tight junction complexes and the differentiation and proliferation of epithelial cells. Despite the encouraging discoveries in this area of research, the evidence regarding the effects of whole grain consumption on intestine-related activity remains limited. Hence, we can conclude that we are just starting to understand the actual complexity of the intestinal factors mediating in part the health impacts of whole grain cereals.

Xenogenic Application of Human Placenta-Derived Mesenchymal Stromal Cells in a Porcine Large Animal Model

In animal models, cell therapies for different diseases or injuries have been very successful. Preclinical studies with cells aiming at a stroke, heart attack, and other emergency situations were promising but sometimes failed translation in clinical situations. We, therefore, investigated if human placenta-derived mesenchymal stromal cells can be injected in pigs without provoking rejection to serve as a xenogenic transplantation model to bridge preclinical animal studies to more promising future preclinical studies. Male human placenta-derived mesenchymal stromal cells were isolated, expanded, and characterized by flow cytometry, in vitro differentiation, and quantitative reverse-transcription polymerase chain reaction to prove their nature. Such cells were injected into the sphincter muscle of the urethrae of female pigs under visual control by cystoscopy employing a Williams needle. The animals were observed over 7 days of follow-up. Reactions of the host to the xenogeneic cells were explored by monitoring body temperature, and inflammatory markers including IL-1ß, CRP, and haptoglobin in blood. After sacrifice on day 7, infiltration of inflammatory cells in the tissue targeted was investigated by histology and immunofluorescence. DNA of injected human cells was detected by PCR. Upon injection in vascularized porcine tissue, human placenta-derived mesenchymal stromal cells were tolerated, and systemic inflammatory parameters were not elevated. DNA of injected cells was detected in situ 7 days after injection, and moderate local infiltration of inflammatory cells was observed. The therapeutic potential of human placenta-derived mesenchymal stromal cells can be explored in porcine large animal models of injury or disease. This seems a promising strategy to explore technologies for cell injections in infarcted hearts or small organs and tissues in therapeutically relevant amounts requiring large animal models to yield meaningful outcomes.

Alteration of PBMC transcriptome profile after interaction with multipotent mesenchymal stromal cells under "physiological" hypoxia

Multipotent mesenchymal stromal cells (MSCs) have demonstrated a pronounced immunosuppressive activity, the manifestation of which depends on the microenvironmental factors, including O2 level. Here we examined the effects of MSCs on transcriptomic profile of allogeneic phytohemagglutinin-stimulated peripheral blood mononuclear cells (PBMCs) after interaction at ambient (20%) or "physiological" hypoxia (5%) O2. As revealed with microarray analysis, PBMC transcriptome at 20% O2 was more affected, which was manifested as differential expression of more than 300 genes, whereas under 5% O2 220 genes were changed. Most of genes at 20% O2 were downregulated, while at hypoxia most of genes were upregulated. Altered gene patterns were only partly overlapped at different O2 levels. A set of altered genes at hypoxia only was of particular interest. According to Gene Ontology a part of above genes was responsible for adhesion, cell communication, and immune response. At both oxygen concentrations, MSCs demonstrated effective immunosuppression manifested as attenuation of T cell activation and proliferation as well as anti-inflammatory shift of cytokine profile. Thus, MSC-mediated immunosuppression is executed with greater efficacy at a "physiological" hypoxia, since the same result has been achieved through a change in the expression of a fewer genes in target PBMCs.

Exploring therapeutic avenues: mesenchymal stem/stromal cells and exosomes in confronting enigmatic biofilm-producing fungi

Fungal infections concomitant with biofilms can demonstrate an elevated capacity to withstand substantially higher concentrations of antifungal agents, contrasted with infectious diseases caused by planktonic cells. This inherent resilience intrinsic to biofilm-associated infections engenders a formidable impediment to effective therapeutic interventions. The different mechanisms that are associated with the intrinsic resistance of Candida species encompass drug sequestration by the matrix, drug efflux pumps, stress response cell density, and the presence of persister cells. These persisters, a subset of fungi capable of surviving hostile conditions, pose a remarkable challenge in clinical settings in virtue of their resistance to conventional antifungal therapies. Hence, an exigent imperative has arisen for the development of novel antifungal therapeutics with specific targeting capabilities focused on these pathogenic persisters. On a global scale, fungal persistence and their resistance within biofilms generate an urgent clinical need for investigating recently introduced therapeutic strategies. This review delves into the unique characteristics of Mesenchymal stem/stromal cells (MSCs) and their secreted exosomes, which notably exhibit immunomodulatory and regenerative properties. By comprehensively assessing the current literature and ongoing research in this field, this review sheds light on the plausible mechanisms by which MSCs and their exosomes can be harnessed to selectively target fungal persisters. Additionally, prospective approaches in the use of cell-based therapeutic modalities are examined, emphasizing the importance of further research to overcome the enigmatic fungal persistence.

The effect of TLR3 priming conditions on MSC immunosuppressive properties

BACKGROUND

Mesenchymal stromal cells (MSCs) have regenerative and immunomodulatory properties, making them suitable for cell therapy. Toll-like receptors (TLRs) in MSCs respond to viral load by secreting immunosuppressive or proinflammatory molecules. The expression of anti-inflammatory molecules in MSCs can be altered by the concentration and duration of exposure to the TLR3 ligand polyinosinic-polycytidylic acid (poly(I:C)). This study aimed to optimize the preconditioning of MSCs with poly(I:C) to increase immunosuppressive effects and to identify MSCs with activated TLR3 (prMSCs).

METHODS

Flow cytometry and histochemical staining were used to analyze MSCs for immunophenotype and differentiation potential. MSCs were exposed to poly(I:C) at 1 and 10 μg/mL for 1, 3, and 24 h, followed by determination of the expression of IDO1, WARS1, PD-L1, TSG-6, and PTGES2 and PGE2 secretion. MSCs and prMSCs were cocultured with intact (J-) and activated (J+) Jurkat T cells. The proportion of proliferating and apoptotic J+ and J- cells, IL-10 secretion, and IL-2 production after cocultivation with MSCs and prMSCs were measured. Liquid chromatography-mass spectrometry and bioinformatics analysis identified proteins linked to TLR3 activation in MSCs.

RESULTS

Poly(I:C) at 10 μg/mL during a 3-h incubation caused the highest expression of immunosuppression markers in MSCs. Activation of prMSCs caused a 18% decrease in proliferation and a one-third increase in apoptotic J+ cells compared to intact MSCs. Cocultures of prMSCs and Jurkat cells had increased IL-10 and decreased IL-2 in the conditioned medium. A proteomic study of MSCs and prMSCs identified 53 proteins with altered expression. Filtering the dataset with Gene Ontology and Reactome Pathway revealed that poly(I:C)-induced proteins activate the antiviral response. Protein‒protein interactions by String in prMSCs revealed that the antiviral response and IFN I signaling circuits were more active than in native MSCs. prMSCs expressed more cell adhesion proteins (ICAM-I and Galectin-3), PARP14, PSMB8, USP18, and GBP4, which may explain their anti-inflammatory effects on Jurkat cells.

CONCLUSIONS

TLR3 activation in MSCs is dependent on exposure time and poly(I:C) concentration. The maximum expression of immunosuppressive molecules was observed with 10 µg/mL poly(I:C) for 3-h preconditioning. This priming protocol for MSCs enhances the immunosuppressive effects of prMSCs on T cells.

Regulation of Immune Checkpoint Antigen CD276 (B7-H3) on Human Placenta-Derived Mesenchymal Stromal Cells in GMP-Compliant Cell Culture Media

Therapies utilizing autologous mesenchymal cell delivery are being investigated as anti-inflammatory and regenerative treatments for a broad spectrum of age-related diseases, as well as various chronic and acute pathological conditions. Easily available allogeneic full-term human placenta mesenchymal stromal cells (pMSCs) were used as a potential pro-regenerative, cell-based therapy in degenerative diseases, which could be applied also to elderly individuals. To explore the potential of allogeneic pMSCs transplantation for pro-regenerative applications, such cells were isolated from five different term-placentas, obtained from the dissected maternal, endometrial (mpMSCs), and fetal chorion tissues (fpMSCs), respectively. The proliferation rate of the cells in the culture, as well as their shape, in vitro differentiation potential, and the expression of mesenchymal lineage and stem cell markers, were investigated. Moreover, we studied the expression of immune checkpoint antigen CD276 as a possible modulation of the rejection of transplanted non-HLA-matched homologous or even xeno-transplanted pMSCs. The expression of the cell surface markers was also explored in parallel in the cryosections of the relevant intact placenta tissue samples. The expansion of pMSCs in a clinical-grade medium complemented with 5% human platelet lysate and 5% human serum induced a significant expression of CD276 when compared to mpMSCs expanded in a commercial medium. We suggest that the expansion of mpMSCs, especially in a medium containing platelet lysate, elevated the expression of the immune-regulatory cell surface marker CD276. This may contribute to the immune tolerance towards allogeneic pMSC transplantations in clinical situations and even in xenogenic animal models of human diseases. The endurance of the injected comparably young human-term pMSCs may promote prolonged effects in clinical applications employing non-HLA-matched allogeneic cell therapy for various degenerative disorders, especially in aged adults.

Mesenchymal stem cells: A promising antimicrobial therapy in veterinary medicine

Growing antimicrobial resistance (AMR) is a threat to human and animal populations citing the limited available options. Alternative antimicrobial options or functional enhancement of currently available antimicrobials remains only options. One of the potential options seems stem cells especially the mesenchymal stem cells (MSCs) that show antimicrobial properties. These cells additionally have pro-healing effects that may plausibly improve healing outcomes. MSCs antimicrobial actions are mediated either through direct cell-cell contact or their secretome that enhances innate immune mediated antimicrobial activities. These cells synergistically enhance efficacy of currently available antimicrobials especially against the biofilms. Reciprocal action from antimicrobials on the MSCs functionality remains poorly understood. Currently, the main limitation with MSCs based therapy is their limited efficacy. This demands further understanding and can be enhanced through biotechnological interventions. One of the interventional options is the 'priming' to enhance MSCs resistance and specific expression potential. The available literature shows potential antimicrobial actions of MSCs both ex vivo as well as in vivo. The studies on veterinary species are very promising although limited by number and extensiveness in details for their utility as standard therapeutic agents. The current review aims to discuss the role of animals in AMR and the potential antimicrobial actions of MSCs in veterinary medicine. The review also discusses the limitations in their utilization as standard therapeutics.

Immunotherapy as a potential treatment approach for currently incurable bone metastasis

Once cancer metastasizes to the bone, the prognosis of cancer patients becomes extremely poor. Unfortunately, the current most successful treatment for bone metastasis can extend their survival by only a few months. Although recent studies have revealed promising impacts of cancer immunotherapies, their treatment efficacy on bone metastatic diseases remains controversial. Therefore, in this review, we discussed (i) preclinical and clinical evidence of the immunotherapeutic strategies for cancer bone metastasis, mainly focusing on cell-based immunotherapy, cytokine-based immunotherapy, and immune checkpoint blockade, and (ii) current shortcomings of immunotherapy for bone metastasis and their potential future directions. Although the evidence on treatment efficacy and safety, as well as long-term effects, is limited, immunotherapies could induce partial or complete remissions in a few cancer patients with bone metastasis. However, there are still hurdles, such as the immunosuppressive nature of the bone marrow microenvironment and poor distribution of cell-based immunotherapies to bone, that need to be overcome to enhance the treatment efficacy of immunotherapies on bone metastasis. While it is apparent that further investigation is needed regarding immunotherapeutic treatment efficacy in patients with bone metastasis, this therapy may prove to be clinically novel in this subset of cancer patients.

The critical role of apoptosis in mesenchymal stromal cell therapeutics and implications in homeostasis and normal tissue repair

Mesenchymal stromal cells (MSCs) have been extensively tested for the treatment of numerous clinical conditions and have demonstrated good safety but mixed efficacy. Although this outcome can be attributed in part to the heterogeneity of cell preparations, the lack of mechanistic understanding and tools to establish cell pharmacokinetics and pharmacodynamics, as well as the poorly defined criteria for patient stratification, have hampered the design of informative clinical trials. We and others have demonstrated that MSCs can rapidly undergo apoptosis after their infusion. Apoptotic MSCs are phagocytosed by monocytes/macrophages that are then reprogrammed to become anti-inflammatory cells. MSC apoptosis occurs when the cells are injected into patients who harbor activated cytotoxic T or NK cells. Therefore, the activation state of cytotoxic T or NK cells can be used as a biomarker to predict clinical responses to MSC treatment. Building on a large body of preexisting data, an alternative view on the mechanism of MSCs is that an inflammation-dependent MSC secretome is largely responsible for their immunomodulatory activity. We will discuss how these different mechanisms can coexist and are instructed by two different types of MSC "licensing": one that is cell-contact dependent and the second that is mediated by inflammatory cytokines. The varied and complex mechanisms by which MSCs can orchestrate inflammatory responses and how this function is specifically driven by inflammation support a physiological role for tissue stroma in tissue homeostasis, and it acts as a sensor of damage and initiator of tissue repair by reprogramming the inflammatory environment.

Strategies for organ preservation: Current prospective and challenges

In current therapeutic approaches, transplantation of organs provides the best available treatment for a myriad of end-stage organ failures. However, shortage of organ donors, lacunae in preservation methods, and lack of a suitable match are the major constraints in advocating this life-sustaining therapy. There has been continuous progress in the strategies for organ preservation since its inception. Current strategies for organ preservation are based on the University of Wisconsin (UW) solution using the machine perfusion technique, which allows successful preservation of intra-abdominal organs (kidney and liver) but not intra-thoracic organs (lungs and heart). However, novel concepts with a wide range of adapted preservation technologies that can increase the shelf life of retrieved organs are still under investigation. The therapeutic interventions of in vitro-cultured stem cells could provide novel strategies for replacement of nonfunctional cells of damaged organs with that of functional ones. This review describes existing strategies, highlights recent advances, discusses challenges and innovative approaches for effective organ preservation, and describes application of stem cells to restore the functional activity of damaged organs for future clinical practices.

PPARs and the Kynurenine Pathway in Melanoma-Potential Biological Interactions

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors involved in various physiological and pathological processes within the skin. PPARs regulate several processes in one of the most aggressive skin cancers, melanoma, including proliferation, cell cycle, metabolic homeostasis, cell death, and metastasis. In this review, we focused not only on the biological activity of PPAR isoforms in melanoma initiation, progression, and metastasis but also on potential biological interactions between the PPAR signaling and the kynurenine pathways. The kynurenine pathway is a major pathway of tryptophan metabolism leading to nicotinamide adenine dinucleotide (NAD+) production. Importantly, various tryptophan metabolites exert biological activity toward cancer cells, including melanoma. Previous studies confirmed the functional relationship between PPAR and the kynurenine pathway in skeletal muscles. Despite the fact this interaction has not been reported in melanoma to date, some bioinformatics data and biological activity of PPAR ligands and tryptophan metabolites may suggest a potential involvement of these metabolic and signaling pathways in melanoma initiation, progression, and metastasis. Importantly, the possible relationship between the PPAR signaling pathway and the kynurenine pathway may relate not only to the direct biological effect on melanoma cells but also to the tumor microenvironment and the immune system.

Use of Mesenchymal Stem Cells in Crohn's Disease and Perianal Fistulas: A Narrative Review

Crohn's Disease (CD), which usually leads to anal fistulas among patients, is the most important inflammatory bowel disease that causes morbidity in many people around the world. This review article proposes using MSCs as a hopeful therapeutic strategy for CD and anal fistula treatment in both preclinical and clinical conditions. Finally, darvadstrocel, a cell-based medication to treat complex anal fistulas in adults, as the only European Medicines Agency (EMA)-approved product for the treatment of anal fistulas in CD is addressed. Although several common therapies, such as surgery and anti-tumor necrosis factor-alpha (TNF-α) drugs as well as a combination of these methods is used to improve this disease, however, due to the low effectiveness of these treatments, the use of new strategies with higher efficiency is still recommended. Cell therapy is among the new emerging therapeutic strategies that have attracted great attention from clinicians due to its unique capabilities. One of the most widely used cell sources administrated in cell therapy is mesenchymal stem cell (MSC). This review article will discuss preclinical and clinical studies about MSCs as a potent and promising therapeutic option in the treatment of CD and anal fistula.

Mesenchymal stromal cells as treatment for acute respiratory distress syndrome. Case Reports following hematopoietic cell transplantation and a review

Acute respiratory distress syndrome (ARDS) is a life-threatening lung disease. It may occur during the pancytopenia phase following allogeneic hematopoietic cell transplantation (HCT). ARDS is rare following HCT. Mesenchymal stromal cells (MSCs) have strong anti-inflammatory effect and first home to the lung following intravenous infusion. MSCs are safe to infuse and have almost no side effects. During the Covid-19 pandemic many patients died from ARDS. Subsequently MSCs were evaluated as a therapy for Covid-19 induced ARDS. We report three patients, who were treated with MSCs for ARDS following HCT. Two were treated with MSCs derived from the bone marrow (BM). The third patient was treated with MSCs obtained from the placenta, so-called decidua stromal cells (DSCs). In the first patient, the pulmonary infiltrates cleared after infusion of BM-MSCs, but he died from multiorgan failure. The second patient treated with BM-MSCs died of aspergillus infection. The patient treated with DSCs had a dramatic response and survived. He is alive after 7 years with a Karnofsky score of 100%. We also reviewed experimental and clinical studies using MSCs or DSCs for ARDS. Several positive reports are using MSCs for sepsis and ARDS in experimental animals. In man, two prospective randomized placebo-controlled studies used adipose and BM-MSCs, respectively. No difference in outcome was seen compared to placebo. Some pilot studies used MSCs for Covid-19 ARDS. Positive results were achieved using umbilical cord and DSCs however, optimal source of MSCs remains to be elucidated using randomized trials.

Immune Activated Cellular Therapy for Drug Resistant Infections: Rationale, Mechanisms, and Implications for Veterinary Medicine

Antimicrobial resistance and biofilm formation both present challenges to treatment of bacterial infections with conventional antibiotic therapy and serve as the impetus for development of improved therapeutic approaches. Mesenchymal stromal cell (MSC) therapy exerts an antimicrobial effect as demonstrated in multiple acute bacterial infection models. This effect can be enhanced by pre-conditioning the MSC with Toll or Nod-like receptor stimulation, termed activated cellular therapy (ACT). The purpose of this review is to summarize the current literature on mechanisms of antimicrobial activity of MSC with emphasis on enhanced effects through receptor agonism, and data supporting use of ACT in treatment of bacterial infections in veterinary species including dogs, cats, and horses with implications for further treatment applications. This review will advance the field's understanding of the use of activated antimicrobial cellular therapy to treat infection, including mechanisms of action and potential therapeutic applications.

Peripheral blood monocytes as a therapeutic target for marrow stromal cells in stroke patients

Background

Systemic administration of marrow stromal cells (MSCs) leads to the release of a broad range of factors mediating recovery in rodent stroke models. The release of these factors could depend on the various cell types within the peripheral blood as they contact systemically administered MSCs. In this study, we assessed the immunomodulatory interactions of MSCs with peripheral blood derived monocytes (Mϕ) collected from acute stroke patients.

Methods

Peripheral blood from stroke patients was collected at 5–7 days (N = 5) after symptom onset and from age-matched healthy controls (N = 5) using mononuclear cell preparation (CPT) tubes. After processing, plasma and other cellular fractions were removed, and Mϕ were isolated from the mononuclear fraction using CD14 microbeads. Mϕ were then either cultured alone or co-cultured with MSCs in a trans-well cell-culture system. Secretomes were analyzed after 24 h of co-cultures using a MAGPIX reader.

Results

Our results show that there is a higher release of IFN-γ and IL-10 from monocytes isolated from peripheral blood at day 5–7 after stroke compared with monocytes from healthy controls. In trans-well co-cultures of MSCs and monocytes isolated from stroke patients, we found statistically significant increased levels of IL-4 and MCP-1, and decreased levels of IL-6, IL-1β, and TNF-α. Addition of MSCs to monocytes increased the secretions of Fractalkine, IL-6, and MCP-1, while the secretions of TNF-α decreased, as compared to the secretions from monocytes alone. When MSCs were added to monocytes from stroke patients, they decreased the levels of IL-1β, and increased the levels of IL-10 significantly more as compared to when they were added to monocytes from control patients.

Conclusion

The systemic circulation of stroke patients may differentially interact with MSCs to release soluble factors integral to their paracrine mechanisms of benefit. Our study finds that the effect of MSCs on Mϕ is different on those derived from stroke patients blood as compared to healthy controls. These findings suggest immunomodulation of peripheral immune cells as a therapeutic target for MSCs in patients with acute stroke.

Strategies for the induction of anti-inflammatory mesenchymal stem cells and their application in the treatment of immune-related nephropathy

Mesenchymal stem cells (MSCs) have potent immunomodulatory functions. Animal studies and clinical trials have demonstrated that MSCs can inhibit immune/inflammatory response in tissues and have good therapeutic effects on a variety of immune-related diseases. However, MSCs currently used for treatment are a mixed, undefined, and heterogeneous cell population, resulting in inconsistent clinical treatment effects. MSCs have dual pro-inflammatory/anti-inflammatory regulatory functions in different environments. In different microenvironments, the immunomodulatory function of MSCs has plasticity; therefore, MSCs can transform into pro-inflammatory MSC1 or anti-inflammatory MSC2 phenotypes. There is an urgent need to elucidate the molecular mechanism that induces the phenotypic transition of MSCs to pro-inflammatory or anti-inflammatory MSCs and to develop technical strategies that can induce the transformation of MSCs to the anti-inflammatory MSC2 phenotype to provide a theoretical basis for the future clinical use of MSCs in the treatment of immune-related nephropathy. In this paper, we summarize the relevant strategies and mechanisms for inducing the transformation of MSCs into the anti-inflammatory MSC2 phenotype and enhancing the immunosuppressive function of MSCs.

Comparison of EV-free fraction, EVs, and total secretome of amniotic mesenchymal stromal cells for their immunomodulatory potential: a translational perspective

Amniotic mesenchymal stromal cells (hAMSCs) have unique immunomodulatory properties demonstrated in vitro and in vivo in various diseases in which the dysregulated immune system plays a major role. The immunomodulatory and pro-regenerative effects of MSCs, among which hAMSCs lie in the bioactive factors they secrete and in their paracrine activity, is well known. The mix of these factors (i.e., secretome) can be either freely secreted or conveyed by extracellular vesicles (EV), thus identifying two components in the cell secretome: EV-free and EV fractions. This study aimed to discern the relative impact of the individual components on the immunomodulatory action of the hAMSC secretome in order to obtain useful information for implementing future therapeutic approaches using immunomodulatory therapies based on the MSC secretome. To this aim, we isolated EVs from the hAMSC secretome (hAMSC-CM) by ultracentrifugation and validated the vesicular product according to the International Society for Extracellular Vesicles (ISEV) criteria. EVs were re-diluted in serum-free medium to maintain the EV concentration initially present in the original CM. We compared the effects of the EV-free and EV fractions with those exerted by hAMSC-CM in toto on the activation and differentiation of immune cell subpopulations belonging to both the innate and adaptive immune systems.

We observed that the EV-free fraction, similar to hAMSC-CM in toto, a) decreases the proliferation of activated peripheral blood mononuclear cells (PBMC), b) reduces the polarization of T cells toward inflammatory Th subsets, and induces the induction of regulatory T cells; c) affects monocyte polarization to antigen-presenting cells fostering the acquisition of anti-inflammatory macrophage (M2) markers; and d) reduces the activation of B lymphocytes and their maturation to plasma cells. We observed instead that all investigated EV fractions, when used in the original concentrations, failed to exert any immunomodulatory effect, even though we show that EVs are internalized by various immune cells within PBMC. These findings suggest that the active component able to induce immune regulation, tested at original concentrations, of the hAMSC secretome resides in factors not conveyed in EVs. However, EVs isolated from hAMSC could exert actions on other cell types, as reported by others.

Advances in mesenchymal stromal cell therapy for acute lung injury/acute respiratory distress syndrome

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) develops rapidly and has high mortality. ALI/ARDS is mainly manifested as acute or progressive hypoxic respiratory failure. At present, there is no effective clinical intervention for the treatment of ALI/ARDS. Mesenchymal stromal cells (MSCs) show promise for ALI/ARDS treatment due to their biological characteristics, easy cultivation, low immunogenicity, and abundant sources. The therapeutic mechanisms of MSCs in diseases are related to their homing capability, multidirectional differentiation, anti-inflammatory effect, paracrine signaling, macrophage polarization, the polarization of the MSCs themselves, and MSCs-derived exosomes. In this review, we discuss the pathogenesis of ALI/ARDS along with the biological characteristics and mechanisms of MSCs in the treatment of ALI/ARDS.

Extracellular vesicles derived from GMSCs stimulated with TNF-α and IFN-α promote M2 macrophage polarization via enhanced CD73 and CD5L expression

Immunoregulatory properties of mesenchymal stem cell (MSC)-derived extracellular vesicles (EVs) are promising. Gingival tissue-derived MSCs (GMSCs) have unique immunoregulatory capacity and secrete large amounts of EVs. Recent findings suggest that priming MSCs with inflammatory stimuli is an effective strategy for cell-free therapy. However, the precise mechanism by which the contents of EVs are customized has not been fully elucidated. Here, we show that EVs derived from GMSCs primed with a combination of two pro-inflammatory cytokines, tumor necrosis factor-α (TNF-α) and interferon-α (IFN-α), synergistically promote anti-inflammatory M2 macrophage polarization by increasing the expression of cluster of differentiation 73 (CD73) and CD5 molecule-like (CD5L). Expression of CD73 by TNF-α/IFN-α stimulation was transcriptionally upregulated by the activation of mammalian target of rapamycin signaling and nuclear translocation of hypoxia-inducible factor 1α in GMSCs. TNF-α/IFN-α treatment also significantly increased the expression of CD5L mRNA via the transcription factor DNA-binding protein inhibitor ID3 and liver X receptor. Interestingly, exosomal CD5L is a prerequisite for the synergistic effect of EVs-mediated M2 macrophage polarization. These results indicate that combined pre-licensing with TNF-α and IFN-α in GMSCs is ideal for enhancing the anti-inflammatory function of EVs, which contributes to the establishment of a therapeutic tool.

Interferon-γ enhances the immunosuppressive ability of canine bone marrow-derived mesenchymal stem cells by activating the TLR3-dependent IDO/kynurenine pathway

BACKGROUND

The immunomodulatory function of mesenchymal stem cells (MSCs) has been considered to be vital for MSC-based therapies. Many works have been devoted to excavate effective strategies for enhancing the immunomodulation effect of MSCs. Nonetheless, canine MSC-mediated immunomodulation is still poorly understood.

METHODS AND RESULTS

The inflammatory microenvironment was simulated through the employment of interferon-γ (IFN-γ) in a culture system. Compared with unstimulated cBMSCs, IFN-γ stimulation increased the mRNA levels of Toll-like receptor 3 (TLR3) and indoleamine 2, 3-dioxygenase 1 (IDO-1), and simultaneously enhanced the secretion of immunosuppressive molecules, including interleukin (IL)-10, hepatocyte growth factor (HGF), and kynurenine in cBMSCs. IFN-γ stimulation significantly enhanced the ability of cBMSCs and their supernatant to suppress the proliferation of murine spleen lymphocytes. Lymphocyte subtyping evaluation revealed that cBMSCs and their supernatant diminished the percentage of CD3⁺CD4⁺ and CD3⁺CD8⁺ lymphocytes compared with the control group, with a decreasing CD4⁺/CD8⁺ ratio. Notably, exposure to IFN-γ decreased the CD4⁺/CD8⁺ ratio more effectively than unstimulated cells or supernatant. Additionally, IFN-γ-stimulation increased the mRNA levels of the Th1 cytokines TNF-α, and remarkably decreased the mRNA level of the Th2 cytokine IL-4 and IL-10.

CONCLUSION

Our findings substantiate that IFN-γ stimulation can enhance the immunomodulatory properties of cBMSCs by promoting TLR3-dependent activation of the IDO/kynurenine pathway, increasing the secretion of immunoregulatory molecules and strengthening interactions with T lymphocytes, which may provide a meaningful strategy for the clinical application of cBMSCs in immune-related diseases.

Role of indoleamine 2,3-dioxygenase 1 (IDO1) and kynurenine pathway in the regulation of the aging process

Indoleamine 2,3-dioxygenase 1 (IDO1) is activated in chronic inflammatory states, e.g., in the aging process and age-related diseases. IDO1 enzyme catabolizes L-tryptophan (L-Trp) into kynurenine (KYN) thus stimulating the KYN pathway. The depletion of L-Trp inhibits the proliferation of immune cells in inflamed tissues and it also reduces serotonin synthesis predisposing to psychiatric disorders. Interestingly, IDO1 protein contains two immunoreceptor tyrosine-based inhibitory motifs (ITIM) which trigger suppressive signaling through the binding of PI3K p110 and SHP-1 proteins. This immunosuppressive activity is not dependent on the catalytic activity of IDO1. KYN and its metabolite, kynurenic acid (KYNA), are potent activators of the aryl hydrocarbon receptor (AhR) which can enhance immunosuppression. IDO1-KYN-AhR signaling counteracts excessive pro-inflammatory responses in acute inflammation but in chronic inflammatory states it has many harmful effects. A chronic low-grade inflammation is associated with the aging process, a state called inflammaging. There is substantial evidence that the activation of the IDO1-KYN-AhR pathway robustly increases with the aging process. The activation of IDO1-KYN-AhR signaling does not only suppress the functions of effector immune cells, probably promoting immunosenescence, but it also impairs autophagy, induces cellular senescence, and remodels the extracellular matrix as well as enhancing the development of osteoporosis and vascular diseases. I will review the function of IDO1-KYN-AhR signaling and discuss its activation with aging as an enhancer of the aging process.

Highlighting the interaction between immunomodulatory properties of mesenchymal stem cells and signaling pathways contribute to Graft Versus Host Disease management

Background Allogeneic hematopoietic stem cell transplantation (Allo-HSCT) has been increasingly used as a therapeutic approach for hematological malignancies. Several potential strategies have been developed for treating or preventing allo-HSCT complications, specifically graft-versus-host disease (GVHD). GVHD could significantly affect the morbidity and mortality of patients after allo-HSCT. Curative treatment and prophylaxis regimens for GVHD could reduce GVHD incidence and improve survival rate. Among these therapeutic strategies, mesenchymal stem cell (MSCs) mediated immunomodulation has been explored widely in clinical trials. MSCs immunomodulation ability in GVHD correlates with the interactions of MSCs with innate and adaptive immune cells. However, signaling pathways responsible for MSCs' impact on GVHD regulation, like JAK/STAT, NOTCH, MAPK/ERK, and NFκβ signaling pathways, have not been clearly described yet. This review aims to illuminate the effect of MSCs-mediated immunomodulation in GVHD management after allo-HSCT representing the role of MSCs therapy on signaling pathways in GVHD. Conclusion MSCs could potentially modulate immune responses, prevent GVHD, and improve survival after allo-HSCT. Previous studies have investigated different signaling pathways' contributions to MSCs immunoregulatory ability. Accordingly, targeting signaling pathways components involved in MSCs related GVHD regulation is proven to be beneficial.

Poly(I:C)-Induced Mesenchymal Stem Cells Protect the Kidney Against Ischemia/Reperfusion Injury via the TLR3/PI3K Pathway

Objective: To investigate the effect and protective mechanism of mesenchymal stem cell subpopulations on acute kidney injury by establishing a mouse model of renal ischemia-reperfusion injury.

Methods: Male C57BL/6 mice were randomly divided into five groups, namely, sham-operation group and those treated with normal saline, untreated mesenchymal stem cells, mesenchymal stem cells treated with lipopolysaccharide (LPS, pro-inflammatory phenotype) and mesenchymal stem cells treated with polyinosinic-polycytidylic acid (poly[I:C], anti-inflammatory phenotype) respectively. The renal function, histopathological damage, circulating inflammation levels and antioxidant capacity of mice were evaluated. The PI3 kinase p85 (PI3K) inhibitor was added into the conventional mesenchymal stem cell cultures in vitro to observe its effects on the secretion of anti-inflammatory cytokines.

Results: Mesenchymal stem cells treated with poly(I:C) (anti-inflammatory phenotype) could effectively reduce serum creatinine and blood urea nitrogen, attenuate histopathological damage and apoptosis level, decrease the level of circulating pro-inflammatory cytokines and increase the level of circulating anti-inflammatory cytokines, enhance peroxidase activity and reduce malondialdehyde content at each time point. After the addition of the PI3K inhibitor, the mRNA expression and protein secretion of indoleamine 2,3-dioxygenase 1 and heme oxygenase 1 of various mesenchymal stem cells were significantly reduced, and that of mesenchymal stem cells treated with poly(I:C) (anti-inflammatory phenotype) was more obvious.

Conclusions: Polyriboinosinic-polyribocytidylic acid (poly[I:C]), a synthetic double-stranded RNA, whose pretreatment induces mesenchymal stem cells to differentiate into the anti-inflammatory phenotype. Anti-inflammatory mesenchymal stem cells induced by poly(I:C) can better protect renal function, alleviate tissue damage, reduce circulating inflammation levels and enhance antioxidant capacity, and achieve stronger anti-inflammatory effects through the TLR3/PI3K pathway.

Integrative analysis of long non-coding RNA and messenger RNA expression in toll-like receptor 4-primed mesenchymal stem cells of ankylosing spondylitis

Background

The precise pathogenesis of ankylosing spondylitis (AS) is still largely unknown at present. Our previous study found that toll-like receptor 4 (TLR4) downregulated and performed immunoregulatory dysfunction in mesenchymal stem cells from AS patients (AS-MSCs). The aim of this study was to explore the expression profiles of long non-coding RNAs (lncRNAs) and messenger RNAs (mRNAs) in TLR4-primed AS-MSCs, and to clarify the potential mechanisms.

Methods

The immunoregulatory effects of MSCs were determined after TLR4 activation. Next, the differentially-expressed (DE) lncRNAs and mRNAs between AS-MSCs and TLR4-primed AS-MSCs [stimulated by lipopolysaccharide (LPS)] were identified via high-throughput sequencing followed by quantitative real-time PCR (qRT-PCR) confirmation. Finally, bioinformatics analyses were performed to identify the critical biological functions, signaling pathways, and associated functional networks involved in the TLR4-primed immunoregulatory function of AS-MSCs.

Results

A total of 147 DE lncRNAs and 698 DE mRNAs were identified between TLR4-primed AS-MSCs and unstimulated AS-MSCs. Of these, 107 lncRNAs were upregulated and 40 were downregulated (fold change ≥2, P<0.05), while 504 mRNAs were upregulated and 194 were downregulated (fold change ≥2, P<0.05). Five lncRNAs and five mRNAs with the largest fold changes were respectively verified by qRT-PCR. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses demonstrated that the DE mRNAs and lncRNAs were highly associated with the inflammatory response, such as NOD-like receptor (NLR) signaling pathway, the TNF signaling pathway and the NF-κB signaling pathway. Cis-regulation prediction revealed eight novel lncRNAs, while trans-regulation prediction revealed 15 lncRNAs, respectively. Eight core pairs of lncRNA and target mRNA in the lncRNA-transcription factor (TF)-mRNA network were as follows: PACERR-PTGS2, LOC105378085-SOD2, LOC107986655-HIVEP2, MICB-DT-MICB, LOC105373925-SP140L, LOC107984251-IFIT5, LOC112268267-GBP2, and LOC101926887-IFIT3, respectively.

Conclusions

TLR4 activation in AS can enhance the immunoregulatory ability of MSCs. Eight core pairs of lncRNA and target mRNA were observed in TLR4-primed AS-MSCs, which could contribute to understanding the potential mechanism of AS-MSC immunoregulatory dysfunction.

In Vivo Studies of Mesenchymal Stem Cells in the Treatment of Meniscus Injury

This review summarizes the literature of preclinical studies and clinical trials on the use of mesenchymal stem cells (MSCs) to treat meniscus injury and promote its repair and regeneration and provide guidance for future clinical research. Due to the special anatomical features of the meniscus, conservative or surgical treatment can hardly achieve complete physiological and histological repair. As a new method, stem cells promote meniscus regeneration in preclinical research and human preliminary research. We expect that, in the near future, in vivo injection of stem cells to promote meniscus repair can be used as a new treatment model in clinical treatment. The treatment of animal meniscus injury, and the clinical trial of human meniscus injury has begun preliminary exploration. As for the animal experiments, most models of meniscus injury are too simple, which can hardly simulate the complexity of actual meniscal tears, and since the follow-up often lasts for only 4-12 weeks, long-term results could not be observed. Lastly, animal models failed to simulate the actual stress environment faced by the meniscus, so it needs to be further studied if regenerated meniscus has similar anti-stress or anti-twist features. Despite these limitations, repair of the meniscus by MSCs has great potential in clinics. MSCs can differentiate into fibrous chondrocytes, which can possibly repair the meniscus and provide a new strategy for repairing meniscus injury.

Proteomic and Biological Analysis of the Effects of Metformin Senomorphics on the Mesenchymal Stromal Cells

Senotherapeutics are new drugs that can modulate senescence phenomena within tissues and reduce the onset of age-related pathologies. Senotherapeutics are divided into senolytics and senomorphics. The senolytics selectively kill senescent cells, while the senomorphics delay or block the onset of senescence. Metformin has been used to treat diabetes for several decades. Recently, it has been proposed that metformin may have anti-aging properties as it prevents DNA damage and inflammation. We evaluated the senomorphic effect of 6 weeks of therapeutic metformin treatment on the biology of human adipose mesenchymal stromal cells (MSCs). The study was combined with a proteome analysis of changes occurring in MSCs’ intracellular and secretome protein composition in order to identify molecular pathways associated with the observed biological phenomena. The metformin reduced the replicative senescence and cell death phenomena associated with prolonged in vitro cultivation. The continuous metformin supplementation delayed and/or reduced the impairment of MSC functions as evidenced by the presence of three specific pathways in metformin-treated samples: 1) the alpha-adrenergic signaling, which contributes to regulation of MSCs physiological secretory activity, 2) the signaling pathway associated with MSCs detoxification activity, and 3) the aspartate degradation pathway for optimal energy production. The senomorphic function of metformin seemed related to its reactive oxygen species (ROS) scavenging activity. In metformin-treated samples, the CEBPA, TP53 and USF1 transcription factors appeared to be involved in the regulation of several factors (SOD1, SOD2, CAT, GLRX, GSTP1) blocking ROS.

Human Wharton's Jelly-Derived Mesenchymal Stromal Cells Primed by Tumor Necrosis Factor-α and Interferon-γ Modulate the Innate and Adaptive Immune Cells of Type 1 Diabetic Patients

The unique immunomodulation and immunosuppressive potential of Wharton’s jelly-derived mesenchymal stromal cells (WJ-MSCs) make them a promising therapeutic approach for autoimmune diseases including type 1 diabetes (T1D). The immunomodulatory effect of MSCs is exerted either by cell-cell contact or by secretome secretion. Cell-cell contact is a critical mechanism by which MSCs regulate immune-responses and generate immune regulatory cells such as tolerogenic dendritic cells (tolDCs) and regulatory T cell (Tregs). In this study, we primed WJ-MSCs with TNF-α and IFN-γ and investigated the immunomodulatory properties of primed WJ-MSCs on mature dendritic cells (mDCs) and activated T cells differentiated from mononuclear cells (MNCs) of T1D patient’s. Our findings revealed that primed WJ-MSCs impaired the antigen-mediated immunity, upregulated immune-tolerance genes and downregulated immune-response genes. We also found an increase in the production of anti-inflammatory cytokines and suppression of the production of pro-inflammatory cytokines. Significant upregulation of FOXP3, IL10 and TGFB1 augmented an immunosuppressive effect on adaptive T cell immunity which represented a strong evidence in support of the formation of Tregs. Furthermore, upregulation of many critical genes involved in the immune-tolerance mechanism (IDO1 and PTGES2/PTGS) was detected. Interestingly, upregulation of ENTPD1/NT5E genes express a strong evidence to switch immunostimulatory response toward immunoregulatory response. We conclude that WJ-MSCs primed by TNF-α and IFN-γ may represent a promising tool to treat the autoimmune disorders and can provide a new evidence to consider MSCs- based therapeutic approach for the treatment of TID.

Dissecting the relationship between antimicrobial peptides and mesenchymal stem cells

Among the various biological properties presented by Mesenchymal Stem Cells (MSCs), their ability to control the immune response and fight pathogen infection through the production of antimicrobial peptides (AMPs) have been the subject of intense research in recent years. AMPs secreted by MSCs exhibit activity against a wide range of microorganisms, including bacteria, fungi, yeasts, and viruses. The main AMPs produced by these cells are hepcidin, cathelicidin LL-37, and β-defensin-2. In addition to acting against pathogens, those AMPs have also been shown to interact with MSCs to modulate MSC proliferation, migration, and regeneration, indicating that such peptides exert a more diverse biological effect than initially thought. In the present review, we discuss the production of AMPs by MSCs, revise the multiple functions of these peptides, including their influence over MSCs, and present an overview of clinical situations in which the antimicrobial properties of MSCs may be explored for therapy. Finally, we discuss possibilities of combining MSCs and AMPs to generate improved therapeutic strategies.

Toll-Like Receptors in Stem/Progenitor Cells

One of the bridges that control the cross-talk between the innate and adaptive immune systems is toll-like receptors (TLRs). TLRs interact with molecules shared and maintained by the source pathogens, but also with endogenous molecules derived from injured tissues (damage/danger-associated molecular patterns - DAMPs). This is likely why some kinds of stem/progenitor cells (SCs) have been found to express TLRs. The role of TLRs in regulating basal motility, proliferation, processes of differentiation, self-renewal, and immunomodulation has been demonstrated in these cells. In this book chapter, we will discuss the many different functions assumed by the TLRs in SCs, pointing out that, depending on the context and the type of ligands they perceive, they may have different effects. In addition, the role of TLR in SC's response to specific tissue damage and in reparative processes will be addressed, as well as how the discovery of molecules mediating TLR signaling's differential function may be decisive for the development of new therapeutic strategies. Given the available studies on TLRs in SCs, the significance of TLRs in sensing an injury to stem/progenitor cells and evaluating their action and reparative activity, which depends on the circumstances, will be discussed here. It could also be possible that SCs used in therapy could theoretically be exposed to TLR ligands, which could modulate their in vivo therapeutic potential. In this context, we need to better understand the mechanisms of action of TLRs on SCs and learn how to regulate these receptors and their downstream pathways in a precise way in order to modulate SC proliferation, survival, migration, and differentiation in the pathological environment. In this way, cell therapy may be strengthened and made safer in the future.

TNF-α and IFN-γ Participate in Improving the Immunoregulatory Capacity of Mesenchymal Stem/Stromal Cells: Importance of Cell-Cell Contact and Extracellular Vesicles

Mesenchymal stem/stromal cells (MSCs) have an immunoregulatory capacity and have been used in different clinical protocols requiring control of the immune response. However, variable results have been obtained, mainly due to the effect of the microenvironment on the induction, increase, and maintenance of MSC immunoregulatory mechanisms. In addition, the importance of cell–cell contact for MSCs to efficiently modulate the immune response has recently been highlighted. Because these interactions would be difficult to achieve in the physiological context, the release of extracellular vesicles (EVs) and their participation as intermediaries of communication between MSCs and immune cells becomes relevant. Therefore, this article focuses on analyzing immunoregulatory mechanisms mediated by cell contact, highlighting the importance of intercellular adhesion molecule-1 (ICAM-1) and the participation of EVs. Moreover, the effects of tumor necrosis factor-alpha (TNF-α) and interferon-gamma (IFN-γ), the main cytokines involved in MSC activation, are examined. These cytokines, when used at the appropriate concentrations and times, would promote increases in the expression of immunoregulatory molecules in the cell and allow the acquisition of EVs enriched with these molecules. The establishment of certain in vitro activation guidelines will facilitate the design of conditioning protocols to obtain functional MSCs or EVs in different pathophysiological conditions.

Embelin downregulated cFLIP in breast cancer cell lines facilitate anti-tumor effect of IL-1β-stimulated human umbilical cord mesenchymal stem cells

Breast cancer is the leading cause of cancer-related death for women. In breast cancer treatment, targeted therapy would be more effective and less harmful than radiotherapy or systemic chemotherapy. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been shown to induce apoptosis in cancer cells but not in normal cells. Mesenchymal stem cells have shown great therapeutic potential in cancer therapy owing to their ability of homing to tumor sites and secreting many kinds of anti-tumor proteins including TRAIL. In this study, we found that IL-1β-stimulated human umbilical cord-derived mesenchymal stem cells (hUCMSCs) enhance the expression of membrane-bound and soluble TRAIL. Cellular FADD-like IL-1β-converting enzyme inhibitory protein (cFLIP) is an important regulator in TRAIL-mediated apoptosis and relates to TRAIL resistance in cancer cells. Previous studies have shown that embelin, which is extracted from Embelia ribes, can increase the TRAIL sensitivity of cancer cells by reducing cFLIP expression. Here we have demonstrated that cFLIP_L is correlated with TRAIL-resistance and that embelin effectively downregulates cFLIP_L in breast cancer cells. Moreover, co-culture of IL-1β-stimulated hUCMSCs with embelin-treated breast cancer cells could effectively induce apoptosis in breast cancer cells. The combined effects of embelin and IL-1β-stimulated hUCMSCs may provide a new therapeutic strategy for breast cancer therapy.

Allogenic Use of Human Placenta-Derived Stromal Cells as a Highly Active Subtype of Mesenchymal Stromal Cells for Cell-Based Therapies

The application of mesenchymal stromal cells (MSCs) from different sources, including bone marrow (BM, bmMSCs), adipose tissue (atMSCs), and human term placenta (hPSCs) has been proposed for various clinical purposes. Accumulated evidence suggests that the activity of the different MSCs is indirect and associated with paracrine release of pro-regenerative and anti-inflammatory factors. A major limitation of bmMSCs-based treatment for autologous application is the limited yield of cells harvested from BM and the invasiveness of the procedure. Similar effects of autologous and allogeneic MSCs isolated from various other tissues were reported. The easily available fresh human placenta seems to represent a preferred source for harvesting abundant numbers of human hPSCs for allogenic use. Cells derived from the neonate tissues of the placenta (f-hPSC) can undergo extended expansion with a low risk of senescence. The low expression of HLA class I and II on f-hPSCs reduces the risk of rejection in allogeneic or xenogeneic applications in normal immunocompetent hosts. The main advantage of hPSCs-based therapies seems to lie in the secretion of a wide range of pro-regenerative and anti-inflammatory factors. This renders hPSCs as a very competent cell for therapy in humans or animal models. This review summarizes the therapeutic potential of allogeneic applications of f-hPSCs, with reference to their indirect pro-regenerative and anti-inflammatory effects and discusses clinical feasibility studies.

Expression of CD146 and Regenerative Cytokines by Human Placenta-Derived Mesenchymal Stromal Cells upon Expansion in Different GMP-Compliant Media

Mesenchymal stromal cells (MSCs) have been successfully employed in clinical applications. In most studies, autologous MSCs from the bone marrow (bmMSCs) were used, and others employed autologous adipose tissue-derived stromal cells (ADSCs). Recently, clinical feasibility studies provided evidence that MSCs from human term placenta (pMSCs) can be used for homologous therapy facilitating access to regenerative cells in emergency situations, when autologous cells are not available or not suitable. We therefore investigated the expression of MSC stemness marker CD146 and the expression of neuro- and myoregenerative cytokines by human pMSCs after expansion in three different media compliant with good manufacturing protocols (GMP) in comparison to pMSCs expanded in a commercial MSC expansion media. To replace xenobiotic serum in the GMP-compliant media employed in this study, either human serum, human serum plus platelet lysate (PLL), or human plasma plus PLL was used. We report that enrichment of media with PLL accelerates pMSC proliferation but reduces the expression of the stemness marker CD146 significantly, while PLL deprivation enhanced the CD146 expression. In contrast, the reduced expression of CD146 by PLL deprivation was not observed on bmMSCs. The expression of the cytokines investigated was not modulated significantly by PLL. We conclude that accelerated expansion of pMSCs in GMP-compliant media enriched by PLL reduces the expression of stemness marker CD146, but does not influence the expression of neuro- and myoregenerative cytokines.

Stem Cells Therapy as a Possible Therapeutic Option in Treating COVID-19 Patients

An unfortunate emergence of a new virus SARS-CoV-2, causing a disease known as COVID-19, has spread all around the globe and has caused a pandemic. It primarily affects the respiratory tract and lungs in some cases causing severe organ damage and pneumonia due to overwhelming immune responses. Clinical reports show that the most commons symptoms are fever, dry cough, and shortness of breath, along with several other symptoms. It is thought that an immense cytokine dysregulation in COVID-19 patients is caused following the virus infection. Notably, if patients present with pre-existing specific comorbidities like diabetes or high blood pressure, rates of COVID-19 induced complications and deaths are escalated. Mesenchymal stem cell (MSC) therapy has been shown to alleviate pneumonia and acute respiratory syndrome (ARDS) symptoms, through their immunomodulatory activities in COVID-19 patients. Although more research studies and clinical trial results are needed to elucidate the exact mechanism by which MSCs provide relief to COVID-19 infected patients. Results from clinical trials are encouraging as patients treated with MSCs, regain lung functions and have restored levels of cytokines and trophic factors underscoring the fact that stem cell therapy can be, at least, a complementary therapy to alleviate sufferings in COVID-19 patients. This review discusses the possible therapeutic uses of MSCs for treating COVID-19. Graphical Abstract.

Promising role for mesenchymal stromal cells in coronavirus infectious disease-19 (COVID-19)-related severe acute respiratory syndrome?

Mesenchymal stromal cells (MSC) have immune regulatory and tissue regenerative properties. MSCs are being studied as a therapy option for many inflammatory and immune disorders and are approved to treat acute graft-versus-host disease (GvHD). The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) pandemic and associated coronavirus infectious disease-19 (COVID-19) has claimed many lives. Innovative therapies are needed. Preliminary data using MSCs in the setting of acute respiratory distress syndrome (ARDS) in COVID-19 are emerging. We review mechanisms of action of MSCs in inflammatory and immune conditions and discuss a potential role in persons with COVID-19.

Latest advances to enhance the therapeutic potential of mesenchymal stromal cells for the treatment of immune-mediated diseases

Mesenchymal stromal cells (MSCs) present the capacity to secrete multiple immunomodulatory factors in response to their microenvironment. This property grants them a golden status among the novel alternatives to treat multiple diseases in which there is an unneeded or exaggerated immune response. However, important challenges still make difficult the clinical implementation of MSC-based therapies, being one of the most remarkable the lack of efficacy due to their transient immunomodulatory effects. To overcome this issue and boost the regulatory potential of MSCs, multiple strategies are currently being explored. Some of them consist of ex vivo pre-conditioning MSCs prior to their administration, including exposure to pro-inflammatory cytokines or to low oxygen concentrations. However, currently, alternative strategies that do not require such ex vivo manipulation are gaining special attention. Among them, the recreation of a three dimensional (3D) environment is remarkable. This approach has been reported to not only boost the immunomodulatory potential of MSCs but also increase their in vivo persistence and viability. The present work revises the therapeutic potential of MSCs, highlighting their immunomodulatory activity as a potential treatment for diseases caused by an exacerbated or unnecessary immune response. Moreover, it offers an updated vision of the most widely employed pre-conditioning strategies and 3D systems intended to enhance MSC-mediated immunomodulation, to conclude discussing the major challenges still to overcome in the field.

Multipotent Mesenchymal Stromal Cells in Rheumatoid Arthritis and Systemic Lupus Erythematosus; From a Leading Role in Pathogenesis to Potential Therapeutic Saviors?

The pathogenesis of the autoimmune rheumatological diseases including rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) is complex with the involvement of several immune cell populations spanning both innate and adaptive immunity including different T-lymphocyte subsets and monocyte/macrophage lineage cells. Despite therapeutic advances in RA and SLE, some patients have persistent and stubbornly refractory disease. Herein, we discuss stromal cells' dual role, including multipotent mesenchymal stromal cells (MSCs) also used to be known as mesenchymal stem cells as potential protagonists in RA and SLE pathology and as potential therapeutic vehicles. Joint MSCs from different niches may exhibit prominent pro-inflammatory effects in experimental RA models directly contributing to cartilage damage. These stromal cells may also be key regulators of the immune system in SLE. Despite these pro-inflammatory roles, MSCs may be immunomodulatory and have potential therapeutic value to modulate immune responses favorably in these autoimmune conditions. In this review, the complex role and interactions between MSCs and the haematopoietically derived immune cells in RA and SLE are discussed. The harnessing of MSC immunomodulatory effects by contact-dependent and independent mechanisms, including MSC secretome and extracellular vesicles, is discussed in relation to RA and SLE considering the stromal immune microenvironment in the diseased joints. Data from translational studies employing MSC infusion therapy against inflammation in other settings are contextualized relative to the rheumatological setting. Although safety and proof of concept studies exist in RA and SLE supporting experimental and laboratory data, robust phase 3 clinical trial data in therapy-resistant RA and SLE is still lacking.

Obesity-induced inflammation: The impact of the hematopoietic stem cell niche

Obesity and obesity-related diseases like type 2 diabetes (T2D) are prominent global health issues; therefore, there is a need to better understand the mechanisms underlying these conditions. The onset of obesity is characterized by accumulation of proinflammatory cells, including Ly6c^hi monocytes (which differentiate into proinflammatory macrophages) and neutrophils, in metabolic tissues. This shift toward chronic, low-grade inflammation is an obese-state hallmark and highly linked to metabolic disorders and other obesity comorbidities. The mechanisms that induce and maintain increased inflammatory myelopoiesis are of great interest, with a recent focus on how obesity affects more primitive hematopoietic cells. The hematopoietic system is constantly replenished by proper regulation of hematopoietic stem and progenitor (HSPC) pools in the BM. While early research suggests that chronic obesity promotes expansion of myeloid-skewed HSPCs, the involvement of the hematopoietic stem cell (HSC) niche in regulating obesity-induced myelopoiesis remains undefined. In this review, we explore the role of the multicellular HSC niche in hematopoiesis and inflammation, and the potential contribution of this niche to the hematopoietic response to obesity. This review further aims to summarize the potential HSC niche involvement as a target of obesity-induced inflammation and a driver of obesity-induced myelopoiesis.

Overexpression of alpha-1 antitrypsin in mesenchymal stromal cells improves their intrinsic biological properties and therapeutic effects in nonobese diabetic mice

Islet/β cell dysfunction and death caused by autoimmune-mediated injuries are major features of type 1 diabetes (T1D). Mesenchymal stromal cells (MSCs) have been used for the treatment of T1D in animal models and clinical trials. Based on the anti-inflammatory effects of alpha-1 antitrypsin (AAT), we generated human AAT engineered MSCs (hAAT-MSCs) by infecting human bone marrow-derived MSCs with the pHAGE CMV-a1aT-UBC-GFP-W lentiviral vector. We compared the colony forming, differentiation, and migration capacity of empty virus-treated MSCs (hMSC) and hAAT-MSCs and tested their protective effects in the prevention of onset of T1D in nonobese diabetic (NOD) mice. hAAT-MSCs showed increased self-renewal, better migration and multilineage differentiation abilities compared to hMSCs. In addition, polymerase chain reaction array for 84 MSC-related genes showed that 23 genes were upregulated, and 3 genes were downregulated in hAAT-MSCs compared to hMSCs. Upregulated genes include those critical for the stemness (ie, Wnt family member 3A [WNT3A], kinase insert domain receptor [KDR]), migration (intercellular adhesion molecule 1 [ICAM-1], vascular cell adhesion protein 1 [VICAM-1], matrix metalloproteinase-2 [MMP2]), and survival (insulin-like growth factor 1 [IGF-1]) of MSCs. Pathway analysis showed that changed genes were related to growth factor activity, positive regulation of cell migration, and positive regulation of transcription. In vivo, a single intravenous infusion of hAAT-MSCs significantly limited inflammatory infiltration into islets and delayed diabetes onset in the NOD mice compared with those receiving vehicle or hMSCs. Taken together, overexpression of hAAT in MSCs improved intrinsic biological properties of MSCs needed for cellular therapy for the treatment of T1D.

Nutritional Support of Neurodevelopment and Cognitive Function in Infants and Young Children-An Update and Novel Insights

Proper nutrition is crucial for normal brain and neurocognitive development. Failure to optimize neurodevelopment early in life can have profound long-term implications for both mental health and quality of life. Although the first 1000 days of life represent the most critical period of neurodevelopment, the central and peripheral nervous systems continue to develop and change throughout life. All this time, development and functioning depend on many factors, including adequate nutrition. In this review, we outline the role of nutrients in cognitive, emotional, and neural development in infants and young children with special attention to the emerging roles of polar lipids and high quality (available) protein. Furthermore, we discuss the dynamic nature of the gut-brain axis and the importance of microbial diversity in relation to a variety of outcomes, including brain maturation/function and behavior are discussed. Finally, the promising therapeutic potential of psychobiotics to modify gut microbial ecology in order to improve mental well-being is presented. Here, we show that the individual contribution of nutrients, their interaction with other micro- and macronutrients and the way in which they are organized in the food matrix are of crucial importance for normal neurocognitive development.