Human adipose tissue−derived mesenchymal stem cells facilitate the immunosuppressive effect of cyclosporin A on T lymphocytes through Jagged-1−mediated inhibition of NF-κB signaling

Factors Defining Human Adipose Stem/Stromal Cell Immunomodulation in Vitro

Human adipose tissue-derived stem/stromal cells (hASCs) are adult multipotent mesenchymal stem/stromal cells with immunomodulatory capacities. Here, we present up-to-date knowledge on the impact of different experimental and donor-related factors on hASC immunoregulatory functions in vitro. The experimental determinants include the immunological status of hASCs relative to target immune cells, contact vs. contactless interaction, and oxygen tension. Factors such as the ratio of hASCs to immune cells, the cellular context, the immune cell activation status, and coculture duration are also discussed. Conditioning of hASCs with different approaches before interaction with immune cells, hASC culture in xenogenic or xenofree culture medium, hASC culture in two-dimension vs. three-dimension with biomaterials, and the hASC passage number are among the experimental parameters that greatly may impact the hASC immunosuppressive potential in vitro, thus, they are also considered. Moreover, the influence of donor-related characteristics such as age, sex, and health status on hASC immunomodulation in vitro is reviewed. By analysis of the literature studies, most of the indicated determinants have been investigated in broad non-standardized ranges, so the results are not univocal. Clear conclusions cannot be drawn for the fine-tuned scenarios of many important factors to set a standard hASC immunopotency assay. Such variability needs to be carefully considered in further standardized research. Importantly, field experts' opinions may help to make it clearer.

Mesenchymal stem cell-based therapy for autoimmune-related fibrotic skin diseases-systemic sclerosis and sclerodermatous graft-versus-host disease

BACKGROUND

Systemic sclerosis (SSc) and sclerodermatous graft-versus-host disease (Scl-GVHD)-characterized by similar developmental fibrosis, vascular abnormalities, and innate and adaptive immune response, resulting in severe skin fibrosis at the late stage-are chronic autoimmune diseases of connective tissue. The significant immune system dysfunction, distinguishing autoimmune-related fibrosis from mere skin fibrosis, should be a particular focus of treating autoimmune-related fibrosis. Recent research shows that innovative mesenchymal stem cell (MSC)-based therapy, with the capacities of immune regulation, inflammation suppression, oxidation inhibition, and fibrosis restraint, shows great promise in overcoming the disease.

MAIN BODY

This review of recent studies aims to summarize the therapeutic effect and theoretical mechanisms of MSC-based therapy in treating autoimmune-related fibrotic skin diseases, SSc and Scl-GVHD, providing novel insights and references for further clinical applications. It is noteworthy that the efficacy of MSCs is not reliant on their migration into the skin. Working on the immune system, MSCs can inhibit the chemotaxis and infiltration of immune cells to the skin by down-regulating the expression of skin chemokines and chemokine receptors and reducing the inflammatory and pro-fibrotic mediators. ​Furthermore, to reduce levels of oxidative stress, MSCs may improve vascular abnormalities, and enhance the antioxidant defenses through inducible nitric oxide synthase, thioredoxin 1, as well as other mediators. The oxidative stress environment does not weaken MSCs and may even strengthen certain functions. Regarding fibrosis, MSCs primarily target the transforming growth factor-β signaling pathway to inhibit fibroblast activation. Here, miRNAs may play a critical role in ECM remodeling. Clinical studies have demonstrated the safety of these approaches, though outcomes have varied, possibly owing to the heterogeneity of MSCs, the disorders themselves, and other factors. Nevertheless, the research clearly reveals the immense potential of MSCs in treating autoimmune-related fibrotic skin diseases.

CONCLUSION

The application of MSCs presents a promising approach for treating autoimmune-related fibrotic skin diseases: SSc and Scl-GVHD. Therapies involving MSCs and MSC extracellular vesicles have been found to operate through three primary mechanisms: rebalancing the immune and inflammatory disorders, resisting oxidant stress, and inhibiting overactivated fibrosis (including fibroblast activation and ECM remodeling). However, the effectiveness of these interventions requires further validation through extensive clinical investigations, particularly randomized control trials and phase III/IV clinical trials. Additionally, the hypothetical mechanism underlying these therapies could be elucidated through further research.

Influence of type 2 diabetes and obesity on adipose mesenchymal stem/stromal cell immunoregulation

Type 2 diabetes (T2D), associated with obesity, represents a state of metabolic inflammation and oxidative stress leading to insulin resistance and progressive insulin deficiency. Adipose-derived stem cells (ASCs) are adult mesenchymal stem/stromal cells identified within the stromal vascular fraction of adipose tissue. These cells can regulate the immune system and possess anti-inflammatory properties. ASCs are a potential therapeutic modality for inflammatory diseases including T2D. Patient-derived (autologous) rather than allogeneic ASCs may be a relatively safer approach in clinical perspectives, to avoid occasional anti-donor immune responses. However, patient characteristics such as body mass index (BMI), inflammatory status, and disease duration and severity may limit the therapeutic utility of ASCs. The current review presents human ASC (hASC) immunoregulatory mechanisms with special emphasis on those related to T lymphocytes, hASC implications in T2D treatment, and the impact of T2D and obesity on hASC immunoregulatory potential. hASCs can modulate the proliferation, activation, and functions of diverse innate and adaptive immune cells via direct cell-to-cell contact and secretion of paracrine mediators and extracellular vesicles. Preclinical studies recommend the therapeutic potential of hASCs to improve inflammation and metabolic indices in a high-fat diet (HFD)-induced T2D disease model. Discordant data have been reported to unravel intact or detrimentally affected immunomodulatory functions of ASCs, isolated from patients with obesity and/or T2D patients, in vitro and in vivo. Numerous preconditioning strategies have been introduced to potentiate hASC immunomodulation; they are also discussed here as possible options to potentiate the immunoregulatory functions of hASCs isolated from patients with obesity and T2D.

Obesity and prostate cancer - microenvironmental roles of adipose tissue

Obesity is known to have important roles in driving prostate cancer aggressiveness and increased mortality. Multiple mechanisms have been postulated for these clinical observations, including effects of diet and lifestyle, systemic changes in energy balance and hormonal regulation and activation of signalling by growth factors and cytokines and other components of the immune system. Over the past decade, research on obesity has shifted towards investigating the role of peri-prostatic white adipose tissue as an important source of locally produced factors that stimulate prostate cancer progression. Cells that comprise white adipose tissue, the adipocytes and their progenitor adipose stromal cells (ASCs), which proliferate to accommodate white adipose tissue expansion in obesity, have been identified as important drivers of obesity-associated cancer progression. Accumulating evidence suggests that adipocytes are a source of lipids that are used by adjacent prostate cancer cells. However, results of preclinical studies indicate that ASCs promote tumour growth by remodelling extracellular matrix and supporting neovascularization, contributing to the recruitment of immunosuppressive cells, and inducing epithelial-mesenchymal transition through paracrine signalling. Because epithelial-mesenchymal transition is associated with cancer chemotherapy resistance and metastasis, ASCs are considered to be potential targets of therapies that could be developed to suppress cancer aggressiveness in patients with obesity.

The secretome of mesenchymal stem cells and oxidative stress: challenges and opportunities in cell-free regenerative medicine

Over the last decade, mesenchymal stem cells (MSCs) have been considered a suitable source for cell-based therapy, especially in regenerative medicine. First, the efficacy and functions of MSCs in clinical applications have been attributed to their differentiation ability, called homing and differentiation. However, it has recently been confirmed that MSCs mostly exert their therapeutic effects through soluble paracrine bioactive factors and extracellular vesicles, especially secretome. These secreted components play critical roles in modulating immune responses, improving the survival, and increasing the regeneration of damaged tissues. The secretome content of MSCs is variable under different conditions. Oxidative stress (OS) is one of these conditions that is highly important in MSC therapy and regenerative medicine. High levels of reactive oxygen species (ROS) are produced during isolation, cell culture, and transplantation lead to OS, which induces cell death and apoptosis and limits the efficacy of their regeneration capability. In turn, the preconditioning of MSCs in OS conditions contributes to the secretion of several proteins, cytokines, growth factors, and exosomes, which can improve the antioxidant potential of MSCs against OS. This potential of MSC secretome has turned it into a new promising cell-free tissue regeneration strategy.This review provides a view of MSC secretome under OS conditions, focusing on different secretome contents of MSCs and thier possible therapeutic potential against cell therapy.

Regulatory Effect of Mesenchymal Stem Cells on T Cell Phenotypes in Autoimmune Diseases

Research on mesenchymal stem cells (MSCs) starts from the earliest assumption that cells derived from the bone marrow have the ability to repair tissues. Several scientists have since documented the crucial role of bone marrow-derived MSCs (BM-MSCs) in processes such as embryonic bone and cartilage formation, adult fracture and tissue repair, and immunomodulatory activities in therapeutic applications. In addition to BM-MSCs, several sources of MSCs have been reported to possess tissue repair and immunoregulatory abilities, making them potential treatment options for many diseases. Therefore, the therapeutic potential of MSCs in various diseases including autoimmune conditions has been explored. In addition to an imbalance of T cell subsets in most patients with autoimmune diseases, they also exhibit complex disease manifestations, overlapping symptoms among diseases, and difficult treatment. MSCs can regulate T cell subsets to restore their immune homeostasis toward disease resolution in autoimmune conditions. This review summarizes the role of MSCs in relieving autoimmune diseases via the regulation of T cell phenotypes.

Human mesenchymal stem cell treatment of premature ovarian failure: new challenges and opportunities

Premature ovarian failure (POF) is one of the common disorders found in women leading to 1% female infertility. Clinical features of POF are hypoestrogenism or estrogen deficiency, increased gonadotropin level, and, most importantly, amenorrhea. With the development of regenerative medicine, human mesenchymal stem cell (hMSC) therapy brings new prospects for POF. This study aimed to describe the types of MSCs currently available for POF therapy, their biological characteristics, and their mechanism of action. It reviewed the latest findings on POF to provide the theoretical basis for further investigation and clinical therapy.

Therapeutic potential of mesenchymal stem cells in treating both types of diabetes mellitus and associated diseases

Diabetes mellitus is a common lifestyle disease which can be classified into type 1 diabetes mellitus and type 2 diabetes mellitus. While both result in hyperglycemia due to lack of insulin action and further associated chronic ailments, there is a marked distinction in the cause for each type due to which both require a different prophylaxis. As observed, type 1 diabetes is caused due to the autoimmune action of the body resulting in the destruction of pancreatic islet cells. On the other hand, type 2 diabetes is caused either due to insulin resistance of target cells or lack of insulin production as per physiological requirements. Attempts to cure the disease have been made by bringing drastic changes in the patients' lifestyle; parenteral administration of insulin; prescription of drugs such as biguanides, meglitinides, and amylin; pancreatic transplantation; and immunotherapy. While these attempts cause a certain degree of relief to the patient, none of these can cure diabetes mellitus. However, a new treatment strategy led by the discovery of mesenchymal stem cells and their unique immunomodulatory and multipotent properties has inspired therapies to treat diabetes by essentially reversing the conditions causing the disease. The current review aims to enumerate the role of various mesenchymal stem cells and the different approaches to treat both types of diabetes and its associated diseases as well.

Impaired Function of Bone Marrow Mesenchymal Stem Cells from Immune Thrombocytopenia Patients in Inducing Regulatory Dendritic Cell Differentiation Through the Notch-1/Jagged-1 Signaling Pathway

Immune thrombocytopenia (ITP) is an autoimmune disease in which dendritic cells (DCs) play a crucial role in the breakdown of self-tolerance. Studies have identified the function of mesenchymal stem cells (MSCs) in promoting the development of regulatory DCs (regDCs). Our previous work revealed that MSCs in ITP exerted senescence, apoptosis, and impaired immunosuppressive effects on T and B cells. However, it is unclear whether the effects of MSCs on regDC induction are altered in ITP. Our data demonstrated that MSCs in ITP were impaired in inhibiting CD1a⁺ DC and CD14⁺ DC differentiation from CD34⁺ hematopoietic progenitor cells (CD34⁺ HPCs). DCs differentiated with MSCs in ITP exhibited an increased expression of costimulatory molecules CD80/CD86 and secretion of proinflammatory interleukin-12 (IL-12). Accordingly, the tolerogenic characteristics were deficient in DCs induced by MSCs in ITP. DCs differentiated with MSCs in ITP exhibited an impaired ability to inhibit CD3⁺ T cell proliferation, to suppress T helper (Th)1 cell differentiation, and to induce anergic and regulatory T cells (Tregs). The expression of Notch signaling components was measured in MSCs in ITP. Reduced expression of the ligand Jagged-1, the receptor Notch-1 intracellular domain (NICD-1), and the target gene Hes-1 was identified in MSCs in ITP. The addition of biologically active Jagged-1 to CD34⁺ HPCs was observed to promote regDC differentiation. When cultured on Jagged-1-coated plates, MSCs in ITP showed an enhancement of the Notch-1 pathway activation, Jagged-1 expression, and the function in inducing regDCs. Pretreatment with all-trans retinoic acid (ATRA) was found to partially restore the capacity of MSCs in both ITP patients and healthy controls in inducing CD34⁺-derived regDCs. Our data elucidated that MSCs in ITP were impaired in inducing CD34⁺-regDCs, associated with the Notch-1/Jagged-1 signaling pathway. ATRA could partially correct the impairment of MSCs, suggesting that ATRA could serve as a potential therapeutic alternative for ITP.

TLR3 preconditioning enhances the therapeutic efficacy of umbilical cord mesenchymal stem cells in TNBS-induced colitis via the TLR3-Jagged-1-Notch-1 pathway

Toll-like receptor-3 (TLR3) priming may enhance mesenchymal stem cell (MSC) immunosuppressive activity, but this mechanism has not been investigated in the context of inflammatory bowel disease. Thus, we assessed the immunosuppressive properties of TLR3-primed MSCs using a trinitrobenzene sulfonate (TNBS)-induced mouse model of colitis. Intraperitoneally injected polyribocytidylic acid (poly (I:C)- (a ligand of TLR3) primed human umbilical cord-derived MSCs (hUC-MSCs) migrated to the inflamed colon and effectively improved clinical and pathological manifestations in colitic mice compared with mice treated with unstimulated hUC-MSCs (UCMs). Poly (I:C)-MSCs decreased a wide range of inflammatory cytokines and increased systemic interleukin-10 (IL-10) levels in colonic tissues. Poly (I:C)-MSCs also impaired T-helper type 1/17 (Th1/17) cell expansion and enhanced the suppressive effects of regulatory T cells (Treg) in vitro and in vivo. Poly (I:C)-MSCs suppressed the proliferation of activated mesenteric lymph node (MLN) cells via the overproduction of prostaglandin E₂ (PGE₂) and upregulation of Jagged-1. PGE₂ produced by hUC-MSCs in response to poly (I:C) increased the production of IL-10 and promoted the differentiation of Treg, which could be reversed by inhibition of Notch-1. Collectively, preconditioning MSCs with poly (I:C) enhanced the therapeutic effects of hUC-MSCs in TNBS-induced colitis, and TLR3-activated Notch-1 signaling regulated the immune suppression of hUC-MSCs through the production of PGE₂.

Interferon-γ alters the immune-related miRNA expression of microvesicles derived from mesenchymal stem cells

Increasing studies have demonstrated that interferon gamma (IFN-γ), which serves as a critical inflammatory cytokine, is essential to induce the immunosuppressive effects of mesenchymal stem cells (MSCs). However, the mechanisms underlying the enhanced immunosuppressive effects of IFN-γ-stimulated MSCs (γMSCs) are not fully understood. MSC-derived microvesicles (MSC-MVs) have been viewed as potential pivotal mediators of the immunosuppressive effects of MSCs. Moreover, microRNAs (miRNAs) are important regulators of immunological processes and can be shuttled from cell to cell by MVs. The aim of our study was to analyze the the miRNA expression signature of MVs derived from γMSCs (γMSC-MVs), which may provide better understanding of the immunosuppressive property of their parent cells. Through miRNA microarray and bioinformatics analysis, we found 62 significantly differentially expressed miRNAs (DEMs) in γMSC-MVs compared with MSC-MVs. And the potential target genes and signaling pathways regulated by DEMs were predicted and analyzed. Interestingly, many DEMs and predicted signaling pathways had been demonstrated to be involved in immunoregulation. Furthermore, the network between immunoregulation-related pathways and relevant DEMs was constructed. Collectively, our research on the miRNA repertoires of γMSC-MVs not only provides new perspectives into the mechanisms underlying the enhanced immunosuppressive property of γMSCs, but also paves the way to clinical application of these potent organelles in the future.

LL-37 boosts immunosuppressive function of placenta-derived mesenchymal stromal cells

BACKGROUND

Although promising for graft-versus-host disease (GvHD) treatment, MSC therapy still faces important challenges. For instance, increasing MSC migratory capacity as well as potentializing immune response suppression are of interest. For GvHD management, preventing opportunistic infections is also a valuable strategy, since immunocompromised patients are easy targets for infections. LL-37 is a host defense peptide (HDP) that has been deeply investigated due to its immunomodulatory function. In this scenario, the combination of MSC and LL-37 may result in a robust combination to be clinically used.

METHODS

In the present study, the effects of LL-37 upon the proliferation and migratory capacity of human placenta-derived MSCs (pMSCs) were assessed by MTT and wound scratch assays. The influence of LL-37 over the immunosuppressive function of pMSCs was then investigated using CFSE cell division kit. Flow cytometry and real-time PCR were used to investigate the molecular mechanisms involved in the effects observed.

RESULTS

LL-37 had no detrimental effects over MSC proliferation and viability, as assessed by MTT assay. Moreover, the peptide promoted increased migratory behavior of pMSCs and enhanced their immunomodulatory function over activated human PBMCs. Strikingly, our data shows that LL-37 treatment leads to increased TLR3 levels, as shown by flow cytometry, and to an increased expression of factors classically related to immunosuppression, namely IDO, IL-10, TGF-β, IL-6, and IL-1β.

CONCLUSIONS

Taken together, our observations may serve as groundwork for the development of new therapeutic strategies based on the combined use of LL-37 and MSCs, which may provide patients not only with an enhanced immunosuppression regime, but also with an agent to prevent opportunistic infections.

Synergistic Effects of Combined Cell Therapy for Chronic Ischemic Cardiomyopathy

BACKGROUND

Both bone marrow-derived mesenchymal stem cells (MSCs) and c-kit(+) cardiac stem cells (CSCs) improve left ventricular remodeling in porcine models and clinical trials. Using xenogeneic (human) cells in immunosuppressed animals with acute ischemic heart disease, we previously showed that these 2 cell types act synergistically.

OBJECTIVES

To more accurately model clinical applications for heart failure, this study tested whether the combination of autologous MSCs and CSCs produce greater improvement in cardiac performance than MSCs alone in a nonimmunosuppressed porcine model of chronic ischemic cardiomyopathy.

METHODS

Three months after ischemia/reperfusion injury, Göttingen swine received transendocardial injections with MSCs alone (n = 6) or in combination with cardiac-derived CSCs (n = 8), or placebo (vehicle; n = 6). Cardiac functional and anatomic parameters were assessed using cardiac magnetic resonance at baseline and before and after therapy.

RESULTS

Both groups of cell-treated animals exhibited significantly reduced scar size (MSCs -44.1 ± 6.8%; CSC/MSC -37.2 ± 5.4%; placebo -12.9 ± 4.2%; p < 0.0001), increased viable tissue, and improved wall motion relative to placebo 3 months post-injection. Ejection fraction (EF) improved (MSCs 2.9 ± 1.6 EF units; CSC/MSC 6.9 ± 2.8 EF units; placebo 2.5 ± 1.6 EF units; p = 0.0009), as did stroke volume, cardiac output, and diastolic strain only in the combination-treated animals, which also exhibited increased cardiomyocyte mitotic activity.

CONCLUSIONS

These findings illustrate that interactions between MSCs and CSCs enhance cardiac performance more than MSCs alone, establish the safety of autologous cell combination strategies, and support the development of second-generation cell therapeutic products.

Adipose stem cells: biology, safety, regulation, and regenerative potential

This article discusses adipose-derived stem cell (ASC) biology, describes the current knowledge in the literature for the safety and regulation of ASCs, and provides a brief overview of the regenerative potential of ASCs. It is not an exhaustive listing of all available clinical studies or every study applying ASCs in tissue engineering and regenerative medicine, but is an objective commentary of these topics.

Bone marrow mesenchymal stem cells altered the immunoregulatory activities of hepatic natural killer cells

We explored the biological characteristics of bone marrow-derived mesenchymal stem cells (BMSCs) and their immunological effects in vivo. To establish the characteristics of BMSCs, we first examined their morphology, differentiation ability, phenotype, and growth patterns. We further explored the effects of intravenous infusion of BMSCs on the immunological activities in vivo and the possible mechanism involved in it. The results showed that BMSCs displayed a fibroblast-like morphology and could differentiate into bone, fat and cartilage cells. Phenotypic analysis indicated the cells were negative for CD34 and CD31 but positive for Flk1, CD29, CD44 and CD105. In addition, BMSC culture supernatants could not improve the resistance against H2O2-induced apoptosis in L02 cells. We also found that infusion of BMSCs suppressed the activity of intrahepatic natural killer T cells. In summary, BMSCs are an ideal candidate for therapeutic application because they are relatively easy to harvest, easily expandable in vitro, and can be isolated from adult bone marrow while retaining their differentiation potential. BMSCs have stem cell properties, and BMSC therapy is an alternative treatment for acute liver disease.

Allogeneic bone marrow mesenchymal stem cell transplantation in patients with UDCA-resistant primary biliary cirrhosis

The objective of this study was to evaluate the safety and efficacy of allogeneic bone marrow mesenchymal stromal/stem cell transplantation (BM-MSCT) for patients with ursodeoxycholic acid (UDCA)-resistant primary biliary cirrhosis (PBC). Ten patients were enrolled in this trial of BM-MSCT. All patients were permitted to concurrently continue their previous UDCA treatment. The efficacy of BM-MSCT in UDCA-resistant PBC was assessed at various time points throughout the 12-month follow up. No transplantation-related side effects were observed. The life quality of the patients was improved after BM-MSCT as demonstrated by responses to the PBC-40 questionnaire. Serum levels of ALT, AST, γ-GT, and IgM significantly decreased from baseline after BM-MSCT. In addition, the percentage of CD8+ T cells was reduced, while that of CD4+CD25+Foxp3+ T cells was increased in peripheral lymphocytic subsets. Serum levels of IL-10 were also elevated. Notably, the optimal therapeutic outcome was acquired in 3 to 6 months and could be maintained for 12 months after BM-MSCT. In conclusion, allogeneic BM-MSCT in UDCA-resistant PBC is safe and appears to be effective.

Regulation of mouse microglia activation and effector functions by bone marrow-derived mesenchymal stem cells

Mesenchymal stems or stromal cells (MSCs) are rare multipotent cells with potent regenerative and immunomodulatory properties. Microglial cells (MGs) are specialized tissue macrophages of the central nervous system (CNS) that continuously survey their environment with highly motile extensions. Recently, several studies have shown that MSCs are capable of reprogramming microglia into an "M2-like" phenotype characterized by increased phagocytic activity and upregulated expression of anti-inflammatory mediators in vitro. However, the precise polarization states of microglia in the presence of MSCs under physiological or under inflammatory conditions remain largely unknown. In this study, we found that MSCs induce a mixed microglia phenotype defined as Arg1-high, CD86-high, CD206-high, IL-10-high, PGE2-high, MCP-1/CCL2-high, IL-1β-moderate, NALP-3-low, and TNF-α-low cells. These MSC-elicited MGs have high phagocytic activity and antigen-presenting ability. Lipopolysaccharide is able to shape this microglia phenotype quantitatively, but not qualitatively in the presence of MSCs. This unique polarization state resembles a novel regulatory microglia phenotype, which might contribute to the resolution of inflammation and to tissue repair in the CNS.

Combined 4-1BB and CD28 costimulation could unleash lymphocytes from immunosuppression induced by adipose derived stem cell soluble products

Adipose derived stem cells (ASCs) have the potential to differentiate into multiple cell lineages with the capacity to suppress immune cells. However, the exact mechanism of this suppression is not fully understood. We hypothesized that supplying additional lymphocyte costimulation through CD28 and 4-1BB could overturn the inhibitory effect of ASCs. To that end, PHA-activated human PBMCs were cocultured with ASCs or with conditioned media (CM) prepared from cultured ASCs. Growth was analyzed in the presence or absence of anti-CD28 and anti-4-1BB antibodies. Results from CFSE dilution analysis with flow cytometry showed that significant and dose-dependent suppression of PHA-activated lymphocytes occurred in the presence of ASC-like cells or ASC's CM. However, additional costimulation of T cells through CD28 and 4-1BB was able to fully recover lymphocyte proliferative capacity in the presence of ASC's CM. Neither of the costimulatory antibodies could fully recover lymphocyte proliferation following coculture with ASCs. Reversal of ASC's immunosuppression through costimulation suggests that further investigation of ASC suppression mechanisms is warranted, since many clinical applications of ASCs are based on this feature. Moreover, such findings have the potential to boost the usefulness of ASCs in the treatment of autoimmune disease.

Mechanisms of T-cell immunosuppression by mesenchymal stromal cells: what do we know so far?

Mesenchymal stromal cells (MSCs) are multipotent cells, which can give rise to several cell types including osteoblasts, adipocytes, and chondroblasts. These cells can be found in a variety of adult and fetal tissues, such as bone marrow, adipose tissue, cord blood, and placenta. In recent years, the biological properties of MSCs have attracted the attention of researchers worldwide due to their potential application for treating a series of clinical situations. Among these properties, special attention should be given to the immunoregulatory potential of those cells. MSCs are able to act on all cells of the immune system, which includes the capacity to inhibit the proliferation and function of T-cells. This feature renders them natural candidates to treat several diseases in which cellular immune response is exacerbated. In this review, we outline the main mechanisms by which MSCs immunosuppress T-cell response, focusing on cell-cell contact, secretion of soluble factors, and regulatory T-cell generation. The influence of surface markers in the immunosuppression process and features of MSCs isolated from different sources are also discussed. Finally, the influences of toll-like receptors and cytokines on the inflammatory microenvironment are highlighted regarding the activation of MSCs to exert their immunoregulatory function.

Stimulating the neurotrophic and angiogenic properties of human adipose-derived stem cells enhances nerve repair

In future, adipose-derived stem cells (ASC) might be used to treat neurological disorders. In this study, the neurotrophic and angiogenic properties of human ASC were evaluated, and their effects in a peripheral nerve injury model were determined. In vitro growth factor stimulation of the cells resulted in increased secretion of brain-derived neurotrophic factor (BDNF), glial cell-derived neurotrophic factor (GDNF), vascular endothelial growth factor-A (VEGF-A), and angiopoietin-1 proteins. Conditioned medium from stimulated cells increased neurite outgrowth of dorsal root ganglia (DRG) neurons. Similarly, stimulated cells showed an enhanced ability to induce capillary-like tube formation in an in vitro angiogenesis assay. ASC were seeded into a fibrin conduit that was used to bridge a 10 mm rat nerve gap. After 2 weeks, the animals treated with control or stimulated ASC showed an enhanced axon regeneration distance. Stimulated cells evoked more total axon growth. Analysis of regeneration and apoptosis-related gene expression showed that both ASC and stimulated ASC enhanced GAP-43 and activating transcription factor 3 (ATF-3) expression in the spinal cord and reduced c-jun expression in the DRG. Caspase-3 expression in the DRG was reduced by stimulated ASC. Both ASC and stimulated ASC also increased the vascularity of the fibrin nerve conduits. Thus, ASC produce functional neurotrophic and angiogenic factors, creating a more desirable microenvironment for nerve regeneration.

Repeated systemic administration of human adipose-derived stem cells attenuates overt diabetic nephropathy in rats

Adipose-derived stem cells (ASCs) can alleviate acute kidney injury and promote kidney cell regeneration and repair. To investigate the role of ASCs in diabetic nephropathy (DN), Sprague-Dawley rats were made diabetic by intraperitoneal injection of streptozotocin (STZ) after uninephrectomy. After 12 weeks, proteinuria was well established. Five times of 5×10(6) human ASCs repeatedly injected through a tail vein at 4 weekly intervals. A reduction in proteinuria was not observed in diabetic rats until 24 weeks. However, urinary protein excretion was significantly suppressed at 28 weeks and persisted up to 32 weeks after STZ treatment. ASC treatment significantly attenuated glomerulus hypertrophy and tubular interstitial injury, and led to the downregulation of WT-1 and synaptopodin expression. CFSE labeled ASCs were injected into DN rats via the tail vein. Within 24 h after injection, the cells were detected in lung, spleen, and peritubular regions, but rarely in pancreas. Human Alu gene expression was detected in lung and spleen up to 4 weeks after ASCs injection. ASC treatment did not improve hyperglycemia or pancreatic damage. In vitro, recombinant human glial cell line-derived neurotrophic factor (GDNF) prevented podocyte injury by high glucose similarly to ASC-conditioned medium. After blocking GDNF in ASC-CM with neutralizing antibody, the therapeutic effect of ASC-CM was significantly decreased. ASCs cocultured with podocytes restored the downregulation of synaptopodin expression, which was weakened by GDNF-RNA interfering. These findings indicate that repeated intravenous ASC can reduce diabetic kidney damage in rats even at the progressive stage, and promote podocyte recovery via GDNF secretion.

Review of the adipose derived stem cell secretome

Recent advances in protein detection and analysis have lead to multiple in depth studies that analyze the adipose-derived stem cell (ASC) secretome. These studies differ significantly in their methods of secretome preparation and analysis. Most of them use a pro-differentiation or pro-inflammatory stimulus to observe differential expression of secreted proteins. In spite of the variance in methodologies used, 68 proteins are reported to be commonly expressed in a majority of the studies and may serve as potential candidates for conserved secretome proteins. Multiple recent clinical and basic science studies demonstrate the beneficial role played by secreted proteins in augmenting ASC effects in scenarios involving angiogenesis, wound healing, tissue regeneration and immunomodulation. Furthermore, 3-D formulations of ASCs that preserve the niche environment of cells and their secreted proteins have also shown enhanced clinical effects. In light of the lack of uniformity in prior secretome-analysis studies, and the growing clinical importance of the ASC secretome, more in depth studies that use uniform and standardized means of protein detection and analysis are necessary.

Cell therapy with autologous mesenchymal stem cells-how the disease process impacts clinical considerations

The prospective clinical use of multipotent mesenchymal stromal cells (MSCs) holds enormous promise for the treatment of a large number of degenerative and age-related diseases. In particular, autologous MSCs isolated from bone marrow (BM) are considered safe and have been extensively evaluated in clinical trials. Nevertheless, different efficacies have been reported, depending on the health status and age of the donor. In addition, the biological functions of BM-MSCs from patients with various diseases may be impaired. Furthermore, medical treatments such as long-term chemotherapy and immunomodulatory therapy may damage the BM microenvironment and affect the therapeutic potential of MSCs. Therefore, a number of practical problems must be addressed before autologous BM-MSCs can be widely applied with higher efficiency in patients. As such, this review focuses on various factors that directly influence the biological properties of BM-MSCs, and we discuss the possible mechanisms of these alterations.

Cyclosporine-assisted adipose-derived mesenchymal stem cell therapy to mitigate acute kidney ischemia-reperfusion injury

Introduction

This study tested the hypothesis that cyclosporine (CsA)-supported syngeneic adipose-derived mesenchymal stem cell (ADMSC) therapy offered superior attenuation of acute ischemia–reperfusion (IR) kidney injury to either therapy alone.

Methods

Adult Sprague–Dawley rats (n = 40) were equally divided into group 1 (sham controls), group 2 (IR injury), group 3 (IR + CsA (20 mg/kg at 1 and 24 hours after procedure)), group 4 (syngeneic ADMSC (1.2×10⁶) at 1, 6 and 24 hours after procedure), and group 5 (IR + CsA-ADMSC).

Results

By 72 hours after the IR procedure, the creatinine level and the ratio of urine protein to creatinine were highest in group 2 and lowest in group 1, and significantly higher in groups 3 and 4 than in group 5 (all P <0.05 for inter-group comparisons), but showed no differences between groups 3 and 4 (P >0.05). The inflammatory biomarkers at mRNA (matrix metalloproteinase-9, RANTES, TNF-α), protein (TNF-α, NF-κB, intercellular adhesion molecule-1, platelet-derived growth factor), and cellular (CD68⁺) levels of IR kidney showed a similar pattern compared with that of creatinine in all groups (all P <0.05 for inter-group comparisons). The protein expressions of oxidative stress (oxidized protein), reactive oxygen species (NADPH oxidases NOX-1, NOX-2), apoptosis (Bcl-2–associated X protein, caspase-3 and poly(ADP-ribose) polymerase) and DNA damage (phosphorylated H2A histone family member X-positive, proliferating cell nuclear antigen-positive cells) markers exhibited a pattern similar to that of inflammatory mediators amongst all groups (all P <0.05 for inter-group comparisons). Expressions of antioxidant biomarkers at cellular (glutathione peroxidase, glutathione reductase, heme oxygenase-1 (HO-1)) and protein (NADPH dehydrogenase (quinone)-1, HO-1, endothelial nitric oxide synthase) levels, and endothelial progenitor cell markers (C-X-C chemokine receptor type 4-positive, stromal cell-derived factor-1α-positive) were lowest in groups 1 and 2, higher in groups 3 and 4, and highest in group 5 (all P <0.05 for inter-group comparisons).

Conclusion

Combination therapy using CsA plus ADMSCs offers improved protection against acute IR kidney injury.

Mesenchymal stromal cells to promote solid organ transplantation tolerance

PURPOSE OF REVIEW

Mesenchymal stromal cells (MSCs) possess unique immunomodulatory features. MSCs dampen effector T-cell response while promoting the emergence of regulatory T cells. By skewing this balance, MSC could represent the ideal strategy for tolerance induction in organ transplantation. Here we review recent evidence on the efficacy of MSC-based therapy in experimental models of solid organ transplantation as well as the early clinical experiences in kidney transplantation.

RECENT FINDINGS

MSC infusion in experimental models of solid organ transplantation resulted in a Treg-mediated tolerance. MSC also synergized with low-dose or transient pharmacological immunosuppression in inducing long-term graft survival indicating that these cells could allow safe minimization of maintenance drug therapy. Early results from clinical studies in kidney transplant recipients reported encouraging results on the immunoregulatory effect of MSC, although posttransplant MSC infusion could associate with acute graft dysfunction (engraftment syndrome).

SUMMARY

Immunoregulatory functions of MSC are not fixed but rather the result of microenvironment they encounter in vivo. Further studies are needed to establish how and wherein these cells have to be administered and how they may function to safely modulate host immune response in vivo in clinical transplant setting.

Adipose-derived stromal/stem cells: a primer

Until recently, the complexity of adipose tissue and its physiological role was not well appreciated. This changed with the discovery of adipokines such as leptin. The cellular composition of adipose tissue is heterogeneous and changes as a function of diabetes and disease states such as diabetes. Tissue engineers view adipose tissue as a rich source of adult stromal/stem cells isolated by collagenase digestion. In vitro and in vivo studies have documented that adipose stromal/stem cells are multipotent, with the ability to differentiate along the adipocyte, chondrocyte, osteoblast and other lineage pathways. The adipose stromal/stem cells secrete a wide range of cytokines and growth factors with potential paracrine actions. Furthermore, adipose stromal/stem cells exert immunomodulatory functions when added to mixed lymphocyte reactions, suggesting that they can be transplanted allogeneically. This review article focuses on these mechanisms of adipose stromal/stem cell action and their potential utility as cellular therapeutics.

Human adipose tissue stem cells: relevance in the pathophysiology of obesity and metabolic diseases and therapeutic applications

Stem cells are unique cells exhibiting self-renewing properties and the potential to differentiate into multiple specialised cell types. Totipotent or pluripotent stem cells are generally abundant in embryonic or fetal tissues, but the use of discarded embryos as sources of these cells raises challenging ethical problems. Adult stem cells can also differentiate into a wide variety of cell types. In particular, adult adipose tissue contains a pool of abundant and accessible multipotent stem cells, designated as adipose-derived stem cells (ASCs), that are able to replicate as undifferentiated cells, to develop as mature adipocytes and to differentiate into multiple other cell types along the mesenchymal lineage, including chondrocytes, myocytes and osteocytes, and also into cells of endodermal and neuroectodermal origin, including beta-cells and neurons, respectively. An impairment in the differentiation potential and biological functions of ASCs may contribute to the development of obesity and related comorbidities. In this review, we summarise different aspects of the ASCs with special reference to the isolation and characterisation of these cell populations, their relation to the biochemical features of the adipose tissue depot of origin and to the metabolic characteristics of the donor subject and discuss some prospective therapeutic applications.

Effects of transplanted bone-marrow-derived mesenchymal stem cells in animal models of acute hepatitis

Our aim was to evaluate the therapeutic effects of bone-marrow-derived mesenchymal stem cells (BMMSCs) on ConA-induced hepatitis and to elucidate the possible mechanism involved. MSCs were isolated from bone marrow and their characteristics and anti-apoptotic effects on the L02 cell line were analyzed. The effect of intravenous infusion of BMMSCs on liver damage was also tested. Furthermore, the recruitment of donor BMMSCs to the liver of recipient animals and their effects on the activity of intrahepatic natural killer T (NKT) cells were investigated. BMMSCs ameliorated liver damage in a time- and dose-dependent manner. Donor BMMSCs were detected in the livers of recipient animals, suggesting that tissue damage stimulated the migration of BMMSCs. Transplanted BMMSCs also suppressed the activity of intrahepatic NKT cells, not only in the liver but throughout the body. The general infusion of BMMSCS ameliorated immunoregulatory activities by the suppression of intrahepatic NKT cells.

Human adipose-derived cells: an update on the transition to clinical translation

The pace of discovery involving adipose-derived cells continues to accelerate at both the preclinical and clinical translational levels. Adipose tissue is a source of freshly isolated, heterogeneous stromal vascular fraction cells and culture-expanded, adherent and relatively homogeneous adipose stromal/stem cells. Both populations display regenerative capacity in soft and hard tissue repair, ischemic insults and autoimmune diseases. While their major mechanism of action has been attributed to both direct lineage differentiation and/or paracrine factor release, current evidence favors a paracrine mechanism. Over 40 clinical trials using adipose-derived cells conducted in 15 countries have been registered with the NIH, the majority of which are Phase I or Phase I/II safety studies. This review focuses on the literature of the past 2 years in order to assess the status of clinical and preclinical studies on adipose-derived cell therapies for regenerative medicine.

Anti-inflammatory and immunomodulatory activities of stem cells

The recent interest in equine stem cell biology and the rapid increase in experimental data highlight the growing attention that this topic has been receiving over the past few years. Within the field of stem cell biology, the relevance of immunobiology is of particular intrigue. It appears that optimal and effective stem cell therapy for equine patients will require a thorough analysis of the immune properties of stem cells as well as their response to immune mediators. The main goal of this review is to discuss the biology of adult mesenchymal stem cells in the context of immunology.

Mesenchymal stromal cells orchestrate follicular lymphoma cell niche through the CCL2-dependent recruitment and polarization of monocytes

Accumulating evidence indicates that infiltrating stromal cells contribute directly and indirectly to tumor growth in a wide range of cancers. In follicular lymphoma (FL), malignant B cells are found admixed with heterogeneous lymphoid-like stromal cells within invaded lymph nodes and BM. In addition, mesenchymal stromal cells (MSCs) support in vitro FL B-cell survival, in particular after their engagement toward lymphoid differentiation. We show here that BM-MSCs obtained from patients with FL (FL-MSCs) display a specific gene expression profile compared with MSCs obtained from healthy age-matched donors (HD-MSCs). This FL-MSC signature is significantly enriched for genes associated with a lymphoid-like commitment. Interestingly, CCL2 could be detected at a high level within the FL-cell niche, is up-regulated in HD-MSCs by coculture with malignant B cells, and is overexpressed by FL-MSCs, in agreement with their capacity to recruit monocytes more efficiently than HD-MSCs. Moreover, FL-MSCs and macrophages cooperate to sustain malignant B-cell growth, whereas FL-MSCs drive monocyte differentiation toward a proangiogenic and lipopolysaccharide-unresponsive phenotype close to that of tumor-associated macrophages. Altogether, these results highlight the complex role of FL stromal cells that promote direct tumor B-cell growth and orchestrate FL-cell niche, thus emerging as a potential therapeutic target in this disease.

Mesenchymal-stem-cell-based experimental and clinical trials: current status and open questions

INTRODUCTION

Mesenchymal stem cells (MSCs) possess remarkable self-renewal ability and are able to differentiate into various cell lineages. MSCs can also enhance tissue repair and angiogenesis through a paracrine mechanism. It has been recognized that these cells hold great promise for tissue regeneration and treatment of immune-related diseases.

AREAS COVERED

This review aims at discussing the mechanisms of MSC-mediated immunomodulation and tissue repair and the related clinical trials, with special emphasis on factors that influence the efficiency of MSC-based therapy, including the source of MSCs, cell passage, cell dose, timing and route of administration.

EXPERT OPINION

MSCs may facilitate tissue repair through cell replacement and/or improving the microenvironment by releasing growth factors. Some of these factors also mediate the immunomodulatory effects of MSCs. It is important to establish global guidelines, protocols and standards for production and clinical trials of MSCs, so that MSCs can become a therapeutic agent with a reliable efficacy and good safety.