Interaction of multipotent mesenchymal stromal and immune cells: Bidirectional effects

Nanotechnology and bioengineering approaches to improve the potency of mesenchymal stem cell as an off-the-shelf versatile tumor delivery vehicle

Targeting actionable mutations in oncogene-driven cancers and the evolution of immuno-oncology are the two prominent revolutions that have influenced cancer treatment paradigms and caused the emergence of precision oncology. However, intertumoral and intratumoral heterogeneity are the main challenges in both fields of precision cancer treatment. In other words, finding a universal marker or pathway in patients suffering from a particular type of cancer is challenging. Therefore, targeting a single hallmark or pathway with a single targeted therapeutic will not be efficient for fighting against tumor heterogeneity. Mesenchymal stem cells (MSCs) possess favorable characteristics for cellular therapy, including their hypoimmune nature, inherent tumor-tropism property, straightforward isolation, and multilineage differentiation potential. MSCs can be loaded with various chemotherapeutics and oncolytic viruses. The combination of these intrinsic features with the possibility of genetic manipulation makes them a versatile tumor delivery vehicle that can be used for in vivo selective tumor delivery of various chemotherapeutic and biological therapeutics. MSCs can be used as biofactory for the local production of chemical or biological anticancer agents at the tumor site. MSC-mediated immunotherapy could facilitate the sustained release of immunotherapeutic agents specifically at the tumor site, and allow for the achievement of therapeutic concentrations without the need for repetitive systemic administration of high therapeutic doses. Despite the enthusiasm evoked by preclinical studies that used MSC in various cancer therapy approaches, the translation of MSCs into clinical applications has faced serious challenges. This manuscript, with a critical viewpoint, reviewed the preclinical and clinical studies that have evaluated MSCs as a selective tumor delivery tool in various cancer therapy approaches, including gene therapy, immunotherapy, and chemotherapy. Then, the novel nanotechnology and bioengineering approaches that can improve the potency of MSC for tumor targeting and overcoming challenges related to their low localization at the tumor sites are discussed.

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.

Immunomodulation by mesenchymal stem cells during osteogenic differentiation: Clinical implications during bone regeneration

Critical bone defects resulting in delayed and non-union are a major concern in the field of orthopedics. Over the past decade, mesenchymal stem cells (MSCs) have become a promising frontier for bone repair and regeneration owing to their high expansion rate and osteogenic differentiation potential ex vivo. MSCs have also long been associated with their ability to modulate immune response in the recipients. These can even skew the immune response towards pro-inflammatory or anti-inflammatory type by sensing their local microenvironment. MSCs adopt anti-inflammatory phenotype at bone injury site and secrete various immunomodulatory factors such as IDO, NO, TGFβ1 and PGE-2 which have redundant role in osteoblast differentiation and bone formation. As such, several studies have also sought to decipher the immunomodulatory effects of osteogenically differentiated MSCs. The present review discusses the immunomodulatory status of MSCs during their osteogenic differentiation and summarizes few mechanisms that cause immunosuppression by osteogenically differentiated MSCs and its implication during bone healing.

Microgravity Effects and Aging Physiology: Similar Changes or Common Mechanisms?

Despite the use of countermeasures (including intense physical activity), cosmonauts and astronauts develop muscle atony and atrophy, cardiovascular system failure, osteopenia, etc. All these changes, reminiscent of age-related physiological changes, occur in a healthy person in microgravity quite quickly - within a few months. Adaptation to the lost of gravity leads to the symptoms of aging, which are compensated after returning to Earth. The prospect of interplanetary flights raises the question of gravity thresholds, below which the main physiological systems will decrease their functional potential, similar to aging, and affect life expectancy. An important role in the aging process belongs to the body's cellular reserve - progenitor cells, which are involved in physiological remodeling and regenerative/reparative processes of all physiological systems. With age, progenitor cell count and their regenerative potential decreases. Moreover, their paracrine profile becomes pro-inflammatory during replicative senescence, disrupting tissue homeostasis. Mesenchymal stem/stromal cells (MSCs) are mechanosensitive, and therefore deprivation of gravitational stimulus causes serious changes in their functional status. The review compares the cellular effects of microgravity and changes developing in senescent cells, including stromal precursors.

Short-term assays for mesenchymal stromal cell immunosuppression of T-lymphocytes

Introduction

Trauma patients are susceptible to coagulopathy and dysfunctional immune responses. Mesenchymal stromal cells (MSCs) are at the forefront of the cellular therapy revolution with profound immunomodulatory, regenerative, and therapeutic potential. Routine assays to assess immunomodulation activity examine MSC effects on proliferation of peripheral blood mononuclear cells (PBMCs) and take 3-7 days. Assays that could be done in a shorter period of time would be beneficial to allow more rapid comparison of different MSC donors. The studies presented here focused on assays for MSC suppression of mitogen-stimulated PBMC activation in time frames of 24 h or less.

Methods

Three potential assays were examined-assays of apoptosis focusing on caspase activation, assays of phosphatidyl serine externalization (PS+) on PBMCs, and measurement of tumor necrosis factor alpha (TNFα) levels using rapid ELISA methods. All assays used the same initial experimental conditions: cryopreserved PBMCs from 8 to 10 pooled donors, co-culture with and without MSCs in 96-well plates, and PBMC stimulation with mitogen for 2-72 h.

Results

Suppression of caspase activity in activated PBMCs by incubation with MSCs was not robust and was only significant at times after 24 h. Monitoring PS+ of live CD3+ or live CD4+/CD3+ mitogen-activated PBMCs was dose dependent, reproducible, robust, and evident at the earliest time point taken, 2 h, although no increase in the percentage of PS+ cells was seen with time. The ability of MSC in co-culture to suppress PBMC PS+ externalization compared favorably to two concomitant assays for MSC co-culture suppression of PBMC proliferation, at 72 h by ATP assay, or at 96 h by fluorescently labeled protein signal dilution. TNFα release by mitogen-activated PBMCs was dose dependent, reproducible, robust, and evident at the earliest time point taken, with accumulating signal over time. However, suppression levels with MSC co-culture was reliably seen only after 24 h.

Discussion

Takeaways from these studies are as follows: (1) while early measures of PBMC activation is evident at 2-6 h, immunosuppression was only reliably detected at 24 h; (2) PS externalization at 24 h is a surrogate assay for MSC immunomodulation; and (3) rapid ELISA assay detection of TNFα release by PBMCs is a robust and sensitive assay for MSC immunomodulation at 24 h.

TITLE: New therapeutic approaches in pediatric diseases: Mesenchymal stromal cell and mesenchymal stromal cell-derived extracellular vesicles as new drugs

Mesenchymal Stromal Cell (MSC) clinical applications have been widely reported and their therapeutic potential has been documented in several diseases. MSCs can be isolated from several human tissues and easily expanded in vitro, they are able to differentiate in a variety of cell lineages, and they are known to interact with most immunological cells, showing immunosuppressive and tissue repair properties. Their therapeutic efficacy is closely associated with the release of bioactive molecules, namely Extracellular Vesicles (EVs), effective as their parental cells. EVs isolated from MSCs act by fusing with target cell membrane and releasing their content, showing a great potential for the treatment of injured tissues and organs, and for the modulation of the host immune system. EV-based therapies provide, as major advantages, the possibility to cross the epithelium and blood barrier and their activity is not influenced by the surrounding environment. In the present review, we deal with pre-clinical reports and clinical trials to provide data in support of MSC and EV clinical efficacy with particular focus on neonatal and pediatric diseases. Considering pre-clinical and clinical data so far available, it is likely that cell-based and cell-free therapies could become an important therapeutic approach for the treatment of several pediatric diseases.

The Experience of Using Multipotent Mesenchymal Stromal Cells in the Treatment of Severe Recurrent Cholangitis in Children with Biliary Atresia after Kasai Surgery

This article describes the experience of application of multipotent mesenchymal stromal cells in the complex therapy of severe recurrent cholangitis in 2 children with biliary atresia after Kasai surgery. In both children, hepatic cellular insufficiency and portal hypertension developed against the background of long-term inflammatory process poorly controlled by standard therapy, which was the indication for liver transplantation. During the course of mesenchymal stromal cells therapy, the relief of the inflammatory process and functional recovery of the liver were achieved. At the time of preparing the article, the follow-up of two children since the start of multipotent mesenchymal stromal cell therapy was 3 years 9 months and 2 years 6 months. No recurrence of cholangitis was observed in the patients during the follow-up period, the liver function was preserved. There are no indications for liver transplantation at this moment. Thus, despite the fact that the mechanisms of therapeutic action of multipotent mesenchymal stromal cells in biliary atresia require further investigation, we obtained promising results suggesting the possibility of using mesenchymal stromal cells in the treatment of postoperative complications in children with biliary atresia.

Translating MSC Therapy in the Age of Obesity

Mesenchymal stromal cell (MSC) therapy has seen increased attention as a possible option to treat a number of inflammatory conditions including COVID-19 acute respiratory distress syndrome (ARDS). As rates of obesity and metabolic disease continue to rise worldwide, increasing proportions of patients treated with MSC therapy will be living with obesity. The obese environment poses critical challenges for immunomodulatory therapies that should be accounted for during development and testing of MSCs. In this review, we look to cancer immunotherapy as a model for the challenges MSCs may face in obese environments. We then outline current evidence that obesity alters MSC immunomodulatory function, drastically modifies the host immune system, and therefore reshapes interactions between MSCs and immune cells. Finally, we argue that obese environments may alter essential features of allogeneic MSCs and offer potential strategies for licensing of MSCs to enhance their efficacy in the obese microenvironment. Our aim is to combine insights from basic research in MSC biology and clinical trials to inform new strategies to ensure MSC therapy is effective for a broad range of patients.

Ibuprofen in Therapeutic Concentrations Affects the Secretion of Human Bone Marrow Mesenchymal Stromal Cells, but Not Their Proliferative and Migratory Capacity

Mesenchymal stromal cells (MSCs) are able to modulate the immune system activity and the regeneration processes mainly through the secretion of multiple soluble factors, including prostaglandin E2 (PGE₂). PGE₂ is produced as a result of cyclooxygenases (COX) activity. In the present study, we investigated how ibuprofen, a nonselective COX inhibitor, affects the proliferation, migration and secretion of human bone marrow MSCs (hBM-MSCs). For this purpose, six hBM-MSCs populations were treated with ibuprofen at doses which do not differ from maximum serum concentrations during standard pharmacotherapy. Ibuprofen treatment (25 or 50 µg/mL) substantially reduced the secretion of PGE₂ in all tested populations. Following ibuprofen administration, MSCs were subjected to proliferation (BrdU), transwell migration, and scratch assays, while its effect on MSCs secretome was evaluated by Proteome Profiler and Luminex immunoassays. Ibuprofen did not cause statistically significant changes in the proliferation rate and migration ability of MSCs (p > 0.05). However, ibuprofen (25 µg/mL for 3 days) significantly decreased mean secretion of: CCL2 (by 44%), HGF (by 31%), IL-6 (by 22%), VEGF (by 20%) and IL-4 (by 8%) compared to secretion of control MSCs (p < 0.05). Our results indicate that ibuprofen at therapeutic concentrations may impair the pro-regenerative properties of hBM-MSCs.

Genetic deletion of the cannabinoid receptors CB1 and CB2 enhances inflammation with diverging effects on skin wound healing in mice

AIMS

Inflammation during wound healing is both essential and critical for restoring tissue integrity. Participating cells secrete soluble factors to regulate the inflammatory phase and to induce the adjacent regenerative processes. If pro-inflammatory signals are overexpressed, the wound stagnates in the inflammatory phase, which decelerates regular wound healing. The endocannabinoid system is ascribed great significance in maintenance of tissue homeostasis. It mediates several effects through the cannabinoid receptors CB1 and CB2.

MAIN METHODS

In order to clarify the role of these receptors in wound healing, excisional wounds were created on wildtype and CB1 and CB2 knockout mice. The wound closure was analyzed over a period of 14 days, and cytokine concentrations of tissue homogenisates were measured by ELISA. MSCs were isolated from the animals' subcutaneous adipose tissue and analyzed for viability and differentiation capacity, in vitro.

KEY FINDINGS

Deletion of CB2 increased Interleukin (IL)-6 and tumor necrosis factor (TNF)-α but did not affect tissue regeneration. In CB1-deficient animals, wound closure was delayed during early phases of healing, which was accompanied by increased concentrations of monocyte chemoattractant protein (MCP)-1 and TNF-α. CB1 and CB2 knockout MSCs presented altered viability and differentiation capacity compared to wildtype MSCs. The CB1-deficient MSCs released high levels of MCP-1 upon stimulation with TNF-α and IL-1β.

SIGNIFICANCE

The data indicate that both cannabinoid receptors regulate inflammation, and this study emphasizes the important role of CB1 in wound repair. Furthermore, our findings suggest that the secretome of CB1-deficient MSCs may contribute to the wound healing delay, in vivo.

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.

Mesenchymal Stromal Cells: an Antimicrobial and Host-Directed Therapy for Complex Infectious Diseases

There is an urgent need for new antimicrobial strategies for treating complex infections and emerging pathogens. Human mesenchymal stromal cells (MSCs) are adult multipotent cells with antimicrobial properties, mediated through direct bactericidal activity and modulation of host innate and adaptive immune cells. More than 30 in vivo studies have reported on the use of human MSCs for the treatment of infectious diseases, with many more studies of animal MSCs in same-species models of infection. MSCs demonstrate potent antimicrobial effects against the major classes of human pathogens (bacteria, viruses, fungi, and parasites) across a wide range of infection models. Mechanistic studies have yielded important insight into their immunomodulatory and bactericidal activity, which can be enhanced through various forms of preconditioning. MSCs are being investigated in over 80 clinical trials for difficult-to-treat infectious diseases, including sepsis and pulmonary, intra-abdominal, cutaneous, and viral infections. Completed trials consistently report MSCs to be safe and well tolerated, with signals of efficacy against some infectious diseases. Although significant obstacles must be overcome to produce a standardized, affordable, clinical-grade cell therapy, these studies suggest that MSCs may have particular potential as an adjunct therapy in complex or resistant infections.

Engineered Chitosan-based Nanoparticles Modulate Macrophage-Periodontal Ligament Fibroblast Interactions in Biofilm-mediated Inflammation

INTRODUCTION

Crosstalk between immune cells and tissue-resident cells regulates the pathophysiology and posttreatment healing of apical periodontitis. This investigation aimed to understand the influence of residual root canal biofilm on macrophage (MQ)-periodontal ligament fibroblast (PdLF) interaction and evaluate the effect of engineered chitosan-based nanoparticles (CSnp) on MQ-PdLF interactions in residual biofilm-mediated inflammation.

METHODS

Six-week-old Enterococcus faecalis biofilms in root canal models were disinfected conventionally using sodium hypochlorite alone or followed by calcium hydroxide medication or CSnp dispersed in carboxymethylated chitosan (CMCS). The effect of the treated biofilms (n = 25/group) on the inflammatory response of THP-1-differentiated MQ monoculture versus coculture with PdLF was evaluated for cell viability, MQ morphometric characterization, inflammatory mediators (nitric oxide, tumor necrosis factor alpha, interleukin [IL]-1 beta, IL-1RA, IL-6, transforming growth factor beta 1 [TGF-β1], and IL-10), and the expression of transcription factors (pSTAT1/pSTAT6)/cluster of differentiation markers (CD80/206) after 24, 48, and 72 hours of interaction. PdLF transwell migration was evaluated after 8 and 24 hours. Unstimulated cells served as the negative control, whereas untreated biofilm was the positive control.

RESULTS

Biofilm increased nitric oxide and IL-1β but suppressed IL-10, IL-1RA, and PdLF migration with significant cytotoxic effects. CSnp/CMCS reduced nitric oxide and IL-1β (P < .01) while maintaining ≥90% cell survival up to 72 hours with evident M2-like MQ phenotypic changes in coculture. CSnp/CMCS also increased the IL-1RA/IL-1β ratio and enhanced TGF-β1 production over time (P < .05, 72 hours). In coculture, CSnp/CMCS showed the highest IL-10 level at 72 hours (P < .01), reduced the pSTAT1/pSTAT6 ratio, and enhanced PdLF migration (P < .01, 24 hours).

CONCLUSIONS

CSnp/CMCS medication facilitated MQ switch toward M2 (regulatory/anti-inflammatory) phenotype and PdLF migration via paracrine signaling.

Sustained calcium ion release from bioceramics promotes CaSR-mediated M2 macrophage polarization for osteoinduction

Innate immune cells, especially macrophages, play a dual role in tissue repair and the defense against foreign bodies. Although biphasic calcium phosphate (BCP) ceramics have been confirmed as an excellent osteoimmunoregulatory biomaterial, it is unclear whether the ions release of BCP directly affects macrophage polarization and the mechanism by which the ions release is involved in osteoimmunomodulation. Herein, we verified the superior osteoinductive capacity of BCP in wild-type mice and showed its inability to promote this process in macrophage-deficient (LysM^-/- ) mice. Moreover, scanning electron microscopy, ion release curve, and calcein AM-staining results confirmed that BCP-released Ca²⁺ in a sustained manner, thereby maintaining the long-term induction of M2 macrophage polarization and promoting the differentiation of mesenchymal stem cells into osteoblasts during osteogenesis. Furthermore, Ca²⁺ targeted the Wnt/β-catenin signaling pathway and activated Arg1 and IL-10 (M2 marker genes) transcription through the calcium-sensing receptor (CaSR) in macrophages. Under treatment with a CaSR antagonist, macrophages cultured with the BCP fluid extract exhibited lower Ca²⁺ intake and weaker M2 macrophage polarization. These findings underscore the critical role of macrophages in bone regeneration and clarify the molecular mechanisms of Ca²⁺ -mediated osteoinduction by biomaterials, which is of great significance for the future design of biomaterial-oriented tissue regeneration engineering.

Interactions of human mesenchymal stromal cells with peripheral blood mononuclear cells in a Mitogenic proliferation assay

BACKGROUND

Immunomodulation by mesenchymal stromal cells (MSCs) is a potentially important therapeutic modality. MSCs suppress peripheral blood mononuclear cell (PBMC) proliferation in vitro, suggesting a mechanism for suppressing inflammatory responses in vivo. This study details the interactions of PBMCs and MSCs.

METHODS

Pooled human PBMCs and MSCs were co-cultured at different MSC:PBMC ratios and harvested from 0 to 120 h, with and without phytohaemagglutin A (PHA) stimulation. Proliferation of adherent MSCs and non-adherent PBMCs was assessed by quantitation of ATP levels. PBMC surface marker expression was analyzed by flow cytometry. Indoleamine 2,3-dioxygenase (IDO) activity was determined by kynurenine assay and IDO mRNA by RT-PCR. Cytokine release was measured by ELISA. Immunofluorescent microscopy detected MSC, PBMC, monocyte (CD14+) and apoptotic events.

RESULTS

PBMC proliferation in response to PHA gave a robust ATP signal by 72 h, which was suppressed by co-culture with densely plated MSCs. Very low level MSC seeding densities relative to PBMC number reproducibly stimulated PBMC proliferation. The CD4+/CD3+ population significantly decreased over time while the CD8+/CD3+ population significantly increased. No change in CD4+/CD8+ ratio is seen with high density MSC co-culture; very low density MSCs augment the changes seen in PHA stimulated PBMCs alone. IDO activity in MSCs co-cultured with PBMCs correlated with PBMC suppression. MSCs increased the secretion of IL-10 and IL-6 from stimulated co-cultures and decreased TNF-α secretion. In stimulated co-culture, low density MSCs decreased in number; fluorescence immunomicroscopy detected association of PBMC with MSC and phosphatidyl serine externalization in both cell populations.

CONCLUSIONS

A bidirectional interaction between MSCs and PBMCs occurs during co-culture. High numbers of MSCs inhibit PHA-stimulated PBMC proliferation and the PBMC response to stimulation; low numbers of MSCs augment these responses. Low density MSCs are susceptible to attrition, apparently by PBMC-induced apoptosis. These results may have direct application when considering therapeutic dosing of patients; low MSC doses may have unintended detrimental consequences.

Enhancement of the Therapeutic Capacity of Mesenchymal Stem Cells by Genetic Modification: A Systematic Review

Background

The therapeutic capacity of mesenchymal stem cells (also known as mesenchymal stromal cells/MSCs) depends on their ability to respond to the need of the damaged tissue by secreting beneficial paracrine factors. MSCs can be genetically engineered to express certain beneficial factors. The aim of this systematic review is to compile and analyze published scientific literatures that report the use of engineered MSCs for the treatment of various diseases/conditions, to discuss the mechanisms of action, and to assess the efficacy of engineered MSC treatment.

Methods

We retrieved all published studies in PubMed/MEDLINE and Cochrane Library on July 27, 2019, without time restriction using the following keywords: “engineered MSC” and “therapy” or “manipulated MSC” and “therapy.” In addition, relevant articles that were found during full text search were added. We identified 85 articles that were reviewed in this paper.

Results

Of the 85 articles reviewed, 51 studies reported the use of engineered MSCs to treat tumor/cancer/malignancy/metastasis, whereas the other 34 studies tested engineered MSCs in treating non-tumor conditions. Most of the studies reported the use of MSCs in animal models, with only one study reporting a trial in human subjects. Thirty nine studies showed that the expression of beneficial paracrine factors would significantly enhance the therapeutic effects of the MSCs, whereas thirty three studies showed moderate effects, and one study in humans reported no effect. The mechanisms of action for MSC-based cancer treatment include the expression of “suicide genes,” induction of tumor cell apoptosis, and delivery of cytokines to induce an immune response against cancer cells. In the context of the treatment of non-cancerous diseases, the mechanism described in the reviewed papers included the expression of angiogenic, osteogenic, and growth factors.

Conclusion

The therapeutic capacity of MSCs can be enhanced by inducing the expression of certain paracrine factors by genetic modification. Genetically engineered MSCs have been used successfully in various animal models of diseases. However, the results should be interpreted cautiously because animal models might not perfectly represent real human diseases. Therefore, further studies are needed to explore the translational potential of genetically engineered MSCs.

Effects of degradable magnesium on paracrine signaling between human umbilical cord perivascular cells and peripheral blood mononuclear cells

Human mesenchymal stem cells (MSC) interact with numerous immune cells that can promote regenerative processes and inhibit inflammatory responses. We hypothesised that the cross-talk between human umbilical cord perivascular cells (HUCPV; an alternative source of MSC) and peripheral blood mononuclear cells (PBMC) could be influenced by degradable transwell magnesium (Mg). To study the correlations between paracrine signaling and specific cellular behaviour during the host response to Mg, we used a transwell coculture system for up to 7 days. The proliferation and viability of both cell types were not significantly influenced by Mg. When HUCPV were cultured with degradable Mg, a moderate inflammation (e.g., lower secretions of pro-inflammatory interleukin 1 beta and IL2, and tumour necrosis factor alpha, interferon gamma, anti-inflammatory interleukins 4, 5, 10, 13, and 1 receptor antagonists and granulocyte colony stimulating factor), and an increased pro-healing M2 macrophage phenotype were observed. Moreover, when PBMC were cultured with degradable Mg, the expression of migration/wound healing related cytokines (interleukin 8, granulocyte-macrophage colony-stimulating factor, monocyte chemoattractant protein 1 and macrophage inflammatory protein 1α/β) was upregulated, accompanied by an increase in the migration ability of HUCPV (cell scratch assay). In addition, an increased pro-osteogenic potential was demonstrated via an increase of osteoblastic markers (e.g., alkaline phosphatase activity, specific gene expression and cytokine release). These results collectively imply that Mg possesses osteo-immunomodulatory properties. They also help to design Mg-based bone substitute biomaterials capable of exhibiting desired immune reactions and good clinical performance.

Prognostic and predictive value of immune/stromal-related gene biomarkers in renal cell carcinoma

Immune/stromal-associated genes may be promising biomarkers for cancer diagnosis and the determination of clinical cancer treatment options. The aim of the present study was to identify prognostic stromal/immune-associated genes in renal cell carcinoma (RCC). RCC gene expression data (885 cases) were obtained from The Cancer Genome Atlas database. Immune/stromal scores were calculated by using the ESTIMATE package in R. Immune/stromal scores were significantly associated with Tumor-Node-Metastasis stage, clinical stage and overall survival rate (P<0.05). There were 419 differentially expressed genes (DEGs) based on immune scores and 738 DEGs based on stromal scores. Among these DEGs, 406 DEGs based on stromal scores and 252 DEGs based on immune scores were significantly associated with overall survival rate (P<0.05). The biological functions of these DEGs were primarily enriched in the 'immune response' and 'regulation of cell migration and proliferation'. These DEGs were observed in a protein-protein interaction network. A LASSO Cox regression model was used to build a prognostic 6 gene-based classifier, including the IL21R, ATP6V1C2, GBP1, P2RY10, GBP4 and TNNC2 genes [area under the curve (AUC) =0.776]. The predictive model which combined this classifier with clinical prognostic factors had a high accuracy in predicting patient survival in RCC (combined AUC =0.899). Taken together, these results demonstrated that there are significant associations between immune/stromal scores and clinicopathological staging. A set of tumor microenvironment-associated genes that have powerful prognostic value in patients with RCC were identified in the present study.

Multipotent mesenchymal stromal cells in kidney transplant recipients: The next big thing?

Bone marrow-derived multipotent mesenchymal stromal cells (BM-MSCs) are non-haematopoietic cells present in the bone marrow stroma. They have the potential to modulate immune responses and exhibit a capacity to promote immune tolerance. Although the efficacy of immunosuppressive drugs has improved significantly, thereby ameliorating renal graft outcome, the use of these drugs still carries an increased risk of malignancies and opportunistic infections, and sometimes fail to prevent chronic allograft rejection or recurrence of the original kidney disease. As such, there is strong interest in ways to induce immune tolerance and thereby tempering or avoiding conventional immunosuppressive drugs. Cellular immunomodulation by MSCs can create a new way to induce transplant tolerance. This review will give a critical overview of the use of BM-MSCs as a cell-based immunosuppressive therapy in kidney transplant recipients. In vitro studies revealed several mechanisms that can clarify the immunomodulatory potential of BM-MSCs. Several clinical studies showed that BM-MSCs can modulate T-cell proliferation and can alter the ratio of T-cell subsets, favoring immune tolerance. However, this immunomodulation was often not associated with better clinical outcome during follow-up when compared to control groups. Some clinical studies found that BM-MSCs allow a reduction in dose of conventional immunosuppressive drugs and prevent acute graft dysfunction. Most clinical studies emphasized that BM-MSC infusion was safe. This review suggests that the use of BM-MSCs as cell-based immunosuppression therapy in kidney transplant recipients has potential, however some caution regarding their clinical use is appropriate. Mechanisms by which BM-MSCs induce transplant tolerance and factors that can alter their functionality need to be analyzed in more detail before clinical use.

Manipulated Mesenchymal Stem Cells Applications in Neurodegenerative Diseases

Mesenchymal stem cells (MSCs) are multipotent stem cells that have multilinear differentiation and self-renewal abilities. These cells are immune-privileged as they express no or low level of class-II major histocompatibility complex (MHC-II) and other costimulatory molecules. Having neuroprotective and regenerative properties, MSCs can be used to ameliorate several intractable neurodegenerative disorders by affecting both innate and adaptive immune systems. Several manipulations like pretreating MSCs with different conditions or agents, and using molecules derived from MSCs or genetically manipulating them, are the common and practical ways that can be used to strengthen MSCs survival and potency. Improved MSCs can have significantly enhanced impacts on diseases compared to MSCs not manipulated. In this review, we describe some of the most important manipulations that have been exerted on MSCs to improve their therapeutic functions and their applications in ameliorating three prevalent neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, and Huntington's disease.

Therapeutic Mesenchymal Stromal Cells for Immunotherapy and for Gene and Drug Delivery

Mesenchymal stromal cells (MSCs) possess several fairly unique properties that, when combined, make them ideally suited for cellular-based immunotherapy and as vehicles for gene and drug delivery for a wide range of diseases and disorders. Key among these are: (1) their relative ease of isolation from a variety of tissues; (2) the ability to be expanded in culture without a loss of functionality, a property that varies to some degree with tissue source; (3) they are relatively immune-inert, perhaps obviating the need for precise donor/recipient matching; (4) they possess potent immunomodulatory functions that can be tailored by so-called licensing in vitro and in vivo; (5) the efficiency with which they can be modified with viral-based vectors; and (6) their almost uncanny ability to selectively home to damaged tissues, tumors, and metastases following systemic administration. In this review, we summarize the latest research in the immunological properties of MSCs, their use as immunomodulatory/anti-inflammatory agents, methods for licensing MSCs to customize their immunological profile, and their use as vehicles for transferring both therapeutic genes in genetic disease and drugs and genes designed to destroy tumor cells.

The Immunomodulatory Properties of the Human Amnion-Derived Mesenchymal Stromal/Stem Cells Are Induced by INF-γ Produced by Activated Lymphomonocytes and Are Mediated by Cell-To-Cell Contact and Soluble Factors

Human mesenchymal stromal/stem cells (MSCs), being immunoprivileged and having immunomodulatory ability, represent a promising tool to be applied in the field of regenerative medicine. Based on numerous in vitro evidences, the immunological effects of MSCs on immune cells could depend on different mechanisms as cell-to-cell contact and paracrine signals. Furthermore, recent studies have shown that the immunomodulatory activity of MSCs is initiated by activated immune cells; thus, their interaction represents a potential homeostatic mechanism by which MSCs regulate the immune response. MSCs also release exosomes able to give different effects, in a paracrine manner, by influencing inflammatory processes. In this study, we aimed to establish the potential role of human amnion-derived MSCs (hAMSCs), in immunomodulation. We found that the immunosuppressive properties of hAMSCs are not constitutive, but require "supportive signals" capable of promoting these properties. Indeed, we observed that hAMSCs alone are not able to produce an adequate amount of soluble immunomodulatory factors. Here, we studied, in depth, the strong immunomodulatory licensing signal deriving from the direct interaction between hAMSCs and stimulated peripheral blood mononuclear cells. We found that the immunomodulatory effect of hAMSCs also depends on cell-to-cell contact through the contribution of the PDL-1/PD-1 axis. We then investigated the IFN-γ priming of hAMSCs (γ-hAMSCs), which induce the increase of PDL-1 expression, high production of IDO, and upregulation of different immunomodulatory exosome-derived miRNAs. Our miRNA-target network analysis revealed that nine of the deregulated miRNAs are involved in the regulation of key proteins that control both T cell activation/anergy and monocyte differentiation pathways. Finally, we observed that γ-hAMSCs induce in monocytes both M2-like phenotype and the increase of IL-10 production. The extensive implications of MSCs in modulating different aspects of the immune system make these cells attractive candidates to be employed in therapeutic application in immune-based diseases. For these reasons, we aimed, with this study, to shed light on the potential of hAMSCs, and how they could become a useful tool for treating different inflammatory diseases, including end-stage pathologies or adverse effects in transplanted patients.

Adipose-derived stromal cell immunosuppression of T cells is enhanced under "physiological" hypoxia

Multipotent mesenchymal stromal cells (MSCs) are characterized by immunomodulatory properties along with the high proliferative and paracrine activity, as well as multilineage potency. The effects of MSCs on the T cell adaptive immunity are of a special interest. Low O₂ level (1-7 %) is known to be typical for the putative site of the MSC - T cell interactions. A comparative evaluation of the effects of adipose tissue derived MSC (ASCs) on the mitogen-stimulated T cells at the ambient (20 %) and tissue-related (5 %) O₂ levels demonstrated reduced T cell activation by the HLA-DR expression, decreased pro-inflammatory and increased anti-inflammatory cytokine production in co-culture, inhibited T cell proliferation, with the effects increased at hypoxia. T cell interactions with ASCs resulted in the up-regulation of PDCD1, Foxp3, and TGFβ1 known to play an important role in the immune response suppression, and in the down-regulation of genes involved in the inflammatory reaction (IL2, IFNG). These changes were significantly increased under hypoxia. At the same time, neither ASCs nor the reduced O₂ level had negative effects on the viability of T cells.

Harnessing the Properties of Biomaterial to Enhance the Immunomodulation of Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) have great therapeutic potential for tissue engineering and regenerative medicine due to their multipotency and paracrine functions. However, shortly after in vivo implantation, MSCs tend to migrate to the lungs and undergo apoptosis, which impairs their clinical efficacy. In addition, the ex vivo two-dimensional expansion of MSCs results in changes in their immunophenotype and functional activities compared to those in vivo. The use of biomaterials to culture and deliver MSCs has the potential to overcome these limitations. MSC-biomaterial constructs retain MSCs in situ and prolong their survival, while the MSCs ameliorate the foreign body reaction and fibrosis caused by the biomaterial. Biomaterial scaffolds can both preserve the tissue architecture and provide a three-dimensional biomimetic milieu for embedded MSCs, which enhance their paracrine functions, including their immunomodulatory potential. The dimensionality, physical characteristics, topographical cues, biochemistry, and microstructure can enhance the immunomodulatory potential of MSCs. Here, we review the link between the properties of biomaterial and the immunomodulatory potential of MSCs. Impact Statement Regeneration of cells, tissues, and whole organs is challenging. Mesenchymal stem cells (MSCs) have therapeutic potential in tissue engineering and regenerative medicine due to their paracrine functions, including immunomodulatory activity. The dimensionality, physical characteristics, topographical cues, biochemistry, and microstructure of biomaterial can be harnessed to enhance the immunomodulatory potential of MSCs for tissue engineering, which will increase their clinical efficacy, particularly for immune-related diseases.

A novel direct co-culture assay analyzed by multicolor flow cytometry reveals context- and cell type-specific immunomodulatory effects of equine mesenchymal stromal cells

The immunomodulatory potential of multipotent mesenchymal stromal cells (MSC) provides a basis for current and future regenerative therapies. In this study, we established an approach that allows to address the effects of pro-inflammatory stimulation and co-culture with MSC on different specific leukocyte subpopulations. Equine peripheral blood leukocyte recovery was optimized to preserve all leukocyte subpopulations and leukocyte activation regimes were evaluated. Allogeneic labeled equine adipose-derived MSC were then subjected to direct co-culture with either non-stimulated, concanavalin A (ConA)-activated or phosphate 12-myristate 13-acetate and ionomycin (PMA/I)-activated leukocytes. Subsequently, production of the cytokines interferon-γ (IFN- γ), interleukin-1 (IL-1) and tumor necrosis factor-α (TNF-α) and presence of FoxP3 were determined in specific cell populations using multicolor flow cytometry. Prostaglandin E2 (PGE2) was measured in the supernatants. ConA-stimulation induced mild activation of leukocytes, whereas PMA/I-stimulation led to strong activation. In T cells, PMA/I promoted production of all cytokines, with no distinct suppressive effects of MSC. However, increased numbers of CD25/FoxP3-positive cells indicated that MSC supported regulatory T cell differentiation in PMA/I-activated leukocyte cultures. MSC also reduced numbers of cytokine-producing B cells and granulocytes, mostly irrespective of preceding leukocyte activation, and reversed the stimulatory effect of ConA on IFN-γ production in monocytes. Illustrating the possible suppressive mechanisms, higher numbers of MSC produced IL-10 when co-cultured with non-stimulated or ConA-activated leukocytes. This was not observed in co-culture with PMA/I-activated leukocytes. However, PGE2 concentration in the supernatant was highest in the co-culture with PMA/I-activated leukocytes, suggesting that PGE2 could still mediate modulatory effects in strongly inflammatory environment. These context- and cell type-specific modulatory effects observed give insight into the interactions between MSC and different types of immune cells and highlight the roles of IL-10 and PGE2 in MSC-mediated immunomodulation. The approach presented could provide a basis for further functional MSC characterization and the development of potency assays.

Simulated microgravity modulates the mesenchymal stromal cell response to inflammatory stimulation

The duration and distance of manned space flights emphasizes the importance of advanced elucidation of space flight factors and their effects on human beings. The exposure to inflammatory mediators under microgravity may contribute to the activity of different cells, perivascular stromal cells (MSCs) in particular. Inflammatory activation is now considered as a principal cue of MSC engagement in reparative remodeling. In the present paper, the effect of simulated microgravity (sµg) on TNFα-mediated priming of adipose tissue-derived MSC (ASCs) was examined. Sµg per se did not induce inflammatory-related changes, such as elevation of ICAM-1 and HLA-ABC expression, soluble mediator production, or shifting of the transcription profile in ASCs. Moreover, the attenuated ASC response to TNFα priming under sµg was manifested in decreased production of TNFα-dependent pleiotropic cytokines (IL-8 and MCP-1), matrix remodeling proteases, and downregulation of some genes encoding growth factors and cytokines. Time-dependent analysis detected the first signs of priming attenuation after 48 hours of 3D-clinorotation. A reduced response of MSCs to priming under sµg can be a negative factor in terms of MSC involvement in tissue remodeling processes.

Reciprocal modulation of cell functions upon direct interaction of adipose mesenchymal stromal and activated immune cells

The interaction of adipose mesenchymal stromal cells (ASCs) and allogeneic peripheral blood mononuclear cells (PBMCs) is regulated either through direct or paracrine mechanisms. Here, we examined the impact of direct contact in reciprocal regulation of ASC-PBMC functions. Activated PBMCs in vitro induced ASC immunomodulatory activity, while direct and paracrine intercellular interactions regulated PBMCs themselves: the functional state of the organelles was altered, and activation decreased. Direct contact with immune cells affected the activity of ASC intracellular compartments, in particular, reactive oxygen species (ROS) production, and decreased the growth rate. Some ASC properties, including motility, intercellular adhesion molecule-1 (ICAM-1), and major histocompatibility complex class I and II antigens (HLA-ABC and HLA-DR, respectively) expression, did not depend on contact with PBMCs and were only regulated by paracrine means. Direct ASC and PBMC contact favoured an angiogenesis-supportive microenvironment, possibly due to the greater production of VEGF by ASCs; this microenvironment also contained a higher leukemia inhibitory factor (LIF) level. Thus, a change in the functional activity of ASCs and PBMCs upon interaction promoted the formation of an immunosuppressive, anti-inflammatory, and proangiogenic microenvironment. This environment could help resolve inflammation and further restore damaged tissue. SIGNIFICANCE OF THE STUDY: Numerous studies have demonstrated the beneficial effects of transplanted mesenchymal stromal cells, particularly ASCs, for the treatment of a number of autoimmune diseases as well as various tissue injuries. To improve the efficiency of these methods, it is necessary to understand the principal events that occur when ASCs are introduced, primarily the molecular mechanisms of interaction between ASCs and the recipient immune system. We demonstrated that an anti-inflammatory, immunosuppressive, and angiostimulatory shift in the paracrine profile upon the interaction of activated PBMCs and ASCs changes the functional activity of both cell types, a phenomenon that is potentiated by direct cell-cell contact.

Transient Cell-to-Cell Signaling Before Mitosis in Cultures of Human Bone Marrow-Derived Mesenchymal Stem/Stromal Cells

Some types of cells, if not all, that undergo signal exchanges in culture need to contact other cells for various reasons, such as cell-to-cell contact for growth inhibition. However, signal exchanges by cell-to-cell contact before proliferation have never been reported. Using time-lapse recording, we discovered the emergence of several astonishing cell-to-cell contact modes in bone marrow-derived mesenchymal stem/stromal cells (MSCs) before the cells divided. When the cells contacted with another, a huge temporary synapse-like structure formed for molecule exchanges; a cell-tissue particle was taken in by a recipient cell; two cell membranes formed infusion-like structure for a short time; and even a 20-μm long and 5-μm wide cell tail was grafted to another cell. A total of 87% of cells underwent cell-to-cell contact before dividing. After epidermal growth factor-green fluorescent protein (EGF-GFP) vectors were transfected into MSCs and the cells were cocultured with unmanipulated MSCs, the unmanipulated MSCs took in EGF-GFP particles from EGF-GFP expressed MSCs, immediately increased in mitogen genes, and then divided. These results suggest that cells which may lack signal molecules may need to obtain these molecules from other cells through various types of cell-to-cell contact, as mentioned above. Our study provided valuable information to better understand the behaviors of cell-to-cell contact and communication before mitosis.

Mesenchymal Stromal Cell Preconditioning: The Next Step Toward a Customized Treatment For Severe Burn

Over the last century, the clinical management of severe skin burns significantly progressed with the development of burn care units, topical antimicrobials, resuscitation methods, early eschar excision surgeries, and skin grafts. Despite these considerable advances, the present treatment of severe burns remains burdensome, and patients are highly susceptible to skin engraftment failure, infections, organ dysfunction, and hypertrophic scarring. Recent researches have focused on mesenchymal stromal cell (MSC) therapy and hold great promises for tissue repair, as reported in several animal studies and clinical cases. In the present review, we will provide an up-to-date outlook of the pathophysiology of severe skin burns, clinical treatment modalities and current limitations. We will then focus on MSCs and their potential in the burn wound healing both in in vitro and in vivo studies. A specific attention will be paid to the cell preconditioning approach, as a means of improving the MSC efficacy in the treatment of major skin burns. In particular, we will debate how several preconditioning cues would modulate the MSC properties to better match up with the burn pathophysiology in the course of the cell therapy. Finally, we will discuss the clinical interest and feasibility of a MSC-based therapy in comparison to their paracrine derivatives, including microvesicles and conditioned media for the treatment of major skin burn injuries.

Adaptive Regulation of Osteopontin Production by Dendritic Cells Through the Bidirectional Interaction With Mesenchymal Stromal Cells

Mesenchymal stromal cells (MSCs) exert immunosuppressive effects on immune cells including dendritic cells (DCs). However, many details of the bidirectional interaction of MSCs with DCs are still unsolved and information on key molecules by which DCs can modulate MSC functions is limited. Here, we report that osteopontin (OPN), a cytokine involved in homeostatic and pathophysiologic responses, is constitutively expressed by DCs and regulated in the DC/MSC cocultures depending on the activation state of MSCs. Resting MSCs promoted OPN production, whereas the production of OPN was suppressed when MSCs were activated by proinflammatory cytokines (i.e., TNF-α, IL-6, and IL-1β). OPN induction required cell-to-cell contact, mediated at least in part, by β1 integrin (CD29). Conversely, activated MSCs inhibited the release of OPN via the production of soluble factors with a major role played by Prostaglandin E₂ (PGE₂). Accordingly, pretreatment with indomethacin significantly abrogated the MSC-mediated suppression of OPN while the direct addition of exogenous PGE₂ inhibited OPN production by DCs. Furthermore, DC-conditioned medium promoted osteogenic differentiation of MSCs with a concomitant inhibition of adipogenesis. These effects were paralleled by the repression of the adipogenic markers PPARγ, adiponectin, and FABP4, and induction of the osteogenic markers alkaline phosphatase, RUNX2, and of the bone-anabolic chemokine CCL5. Notably, blocking OPN activity with RGD peptides or with an antibody against CD29, one of the OPN receptors, prevented the effects of DC-conditioned medium on MSC differentiation and CCL5 induction. Because MSCs have a key role in maintenance of bone marrow (BM) hematopoietic stem cell niche through reciprocal regulation with immune cells, we investigated the possible MSC/DC interaction in human BM by immunohistochemistry. Although DCs (CD1c⁺) are a small percentage of BM cells, we demonstrated colocalization of CD271⁺ MSCs with CD1c⁺ DCs in normal and myelodysplastic BM. OPN reactivity was observed in occasional CD1c⁺ cells in the proximity of CD271⁺ MSCs. Altogether, these results candidate OPN as a signal modulated by MSCs according to their activation status and involved in DC regulation of MSC differentiation.