Priming Equine Bone Marrow-Derived Mesenchymal Stem Cells with Proinflammatory Cytokines: Implications in Immunomodulation–Immunogenicity Balance, Cell Viability, and Differentiation Potential

The Potential of Mesenchymal Stem Cells to Treat Systemic Inflammation in Horses

One hallmark of mesenchymal stem cells (MSCs) is the ability to differentiate into multiple tissue types which assists in tissue regeneration. Another hallmark of MSCs is their potent anti-inflammatory and immunomodulatory properties and the potential to treat inflammatory, immune-mediated, and ischemic conditions. In equine practice, MSCs have shown efficacy in the treatment of musculoskeletal disorders such as tendinopathy, meniscal tears and cartilage injury. However, there are many equine disease processes and conditions that may benefit from the immunomodulatory properties of MSCs. Examples include conditions associated with overwhelming acute inflammatory response such as systemic inflammatory response syndrome to chronic diseases characterized by a prolonged low level of inflammation such as equine asthma and recurrent uveitis. For the acute inflammatory response processes, there is often high morbidity and mortality with no effective immunomodulatory treatment to prevent the overwhelming synthesis of proinflammatory mediators. For chronic inflammatory disease processes, frequently long-term corticosteroid treatment is the therapeutic mainstay, with serious potential complications. Thus, there is an unmet need for alternative anti-inflammatory treatments for both acute and chronic illnesses in horses. While MSCs show promise for such conditions, much research is needed before a clinically safe and effective treatment will be available. Optimal MSC tissue source, patient vs. donor source (autologous vs. allogeneic) and cell growth conditions need to be determined for each problem. For immediate use, allogeneic MSC treatments is preferable, but immune tolerance and adequate safety require further study. MSC collection and cryopreservation from horses before they are injured or ill, whether from umbilical cord tissue, bone marrow or adipose might become more widespread. Once these fundamental approaches to treating specific diseases with MSCs are determined, the route of administration, dose and timing of administration also need to be studied. To provide a framework for development of MSC immunomodulatory treatments, this article reviews the current understanding of equine MSC anti-inflammatory and immunomodulatory properties and proposes how MSC therapy may be further developed to treat acute onset systemic inflammatory processes and chronic inflammatory diseases.

Autologous bone marrow expanded mesenchymal stem cells in patellar tendinopathy: protocol for a phase I/II, single-centre, randomized with active control PRP, double-blinded clinical trial

Introduction

Patellar tendon overuse injuries are common in athletes. Imaging may show a change in tissue structure with tendon thickening and disruption of the intratendinous substance. We wish to test the hypothesis that both autologous bone marrow expanded mesenchymal stem cells and autologous leukocyte-poor platelet-rich plasma (LP-PRP) implanted into the area of the disrupted tendinopathic patellar tendon will restore function, but tendon regeneration tissue will only be observed in the subjects treated with autologous bone marrow expanded mesenchymal stem cells.

Methods and analysis

This is a single-centre, pilot phase I/II, double-blinded clinical trial with randomisation with active control. Twenty patients with a diagnosis of patellar tendinopathy with imaging changes (tendon thickening and disruption of the intratendinous substance at the proximal portion of the patellar tendon) will be randomised in a 1:1 ratio to receive a local injection of either bone-marrow autologous mesenchymal stem cells (MSC), isolated and cultured under GMP at The Institute of Biology and Molecular Genetics (IBGM) (Spain) or P-PRP. The study will have two aims: first, to ascertain whether a clinically relevant improvement after 3, 6 and 12 months according to the visual analogue scale (VAS), Victorian Institute of Sport Assessment for patellar tendons (VISA-P) and dynamometry scales (DYN) will be achieved; and second, to ascertain whether the proposed intervention will restore tendon structure as determined by ultrasonography (US), Doppler ultrasonography (DUS), and innovative MRI and ultrasound techniques: Magnetic Resonance T2 FAT SAT (UTE, Ultrashort Echo TE) sequence and Ultrasound Tissue Characterization (UTC). Patients who are randomised to the P-PRP treatment group but do not achieve a satisfactory primary endpoint after 6 months will be offered treatment with MSC.

Trial registration

NCT03454737.

Equine Fetal, Adult, and Embryonic Stem Cell-Derived Tenocytes Are All Immune Privileged but Exhibit Different Immune Suppressive Properties In Vitro

In horses and humans, tendon injuries are a significant problem. Not only can they occur in both athletes and nonathletes, they require lengthy periods of recuperation and undergo poor natural regeneration, which leads to high reinjury rates. Embryonic stem cells (ESCs) may provide a renewable source of allogeneic cells to use in clinical applications to aid tissue regeneration. Equine ESCs can undergo tenocyte differentiation in vivo and in vitro, but the immune properties of tenocytes isolated from either ESCs or tissues have not previously been characterized. Here, we demonstrate that equine tenocytes derived from fetal and adult tendon tissue and ESCs express robust levels of major histocompatibility complex (MHC) I but no MHC II in response to inflammatory cytokine interferon gamma (IFNγ). However, MHC expression does not affect their allorecognition by peripheral blood mononuclear cells in vitro. Adult and fetal tenocytes remain immune privileged and strongly immune suppressive in both the presence and absence of exogenously applied IFNγ. In contrast, ESC-derived tenocytes are immune privileged even in the presence of IFNγ, but they are only weakly immune suppressive in the presence but not in the absence of exogenously applied IFNγ. This is despite ESC-tenocytes expressing a number of genes involved in immune modulation at significantly higher levels than those expressed by adult and fetal tenocytes when in standard, nonstimulated monolayer culture. Together, this work suggests that, similar to other fibroblasts, tenocytes have immune modulatory properties, and that culture-expanded tenocytes derived from primary tissues or ESCs may be safe to use in clinical transplantations to injured tendons of unrelated animals.

Effect of allogeneic platelet lysate on equine bone marrow derived mesenchymal stem cell characteristics, including immunogenic and immunomodulatory gene expression profile

Propagation ex vivo of mesenchymal stem cells (MSCs) requires culture medium supplementation. Fetal bovine serum (FBS) has long been the gold standard supplement, but its use is being questioned mainly due to ethical and safety issues. The use of platelet lysate (PL) as substitute of FBS has been proposed but little is known about its effects on equine MSCs characteristics including their immune profile. The aim of this work was to investigate for the first time the effect of allogenic PL on the immunogenic and immunomodulatory gene expression profile of equine bone marrow derived MSCs (eBM-MSCs) as well as on their proliferation ability, phenotype markers, and viability post-cryopreservation. The eBM-MSCs (n = 3) cultures were supplemented with 20% of allogeneic pooled concentrated PL (CPL; 591 × 10³ platelets/μL) or basal PL (BPL; 177 × 10³ platelets/μL) from three donors, using 10% FBS supplementation as control. The proliferative ability of eBM-MSCs under the three conditions was evaluated by calculating the cell doubling times (DT) up to passage 3 (P₃) and by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay at P₃. Viability of eBM-MSCs post-cryopreserved with CPL or FBS was assessed at 15, 30 and 60 days. The gene expression profile of eBM-MSCs was evaluated in P₃ by RT-qPCR for characterization, immunogenic and immunomodulatory markers. The cells cultured in CPL had significantly higher ability to proliferate than with FBS or BPL (P < 0.001) in the MTT assay. Post-cryopreserved viability was similar between cells cultured and preserved in FBS and CPL at all time-points. Gene expression of MSC characterization markers was similar among the three conditions. The gene expression of the immunogenic markers MHC-I, MHC-II and CD40 was slightly (non-significant) increased in CPL condition compared to FBS and BPL. The CPL condition showed higher expression of the genes coding for the immunomodulatory molecules VCAM-1 (non-significant) and IL-6 (P < 0.05), and similar for COX-2; whereas iNOS and IDO were not expressed under any condition. In conclusion, the replacement of FBS by allogeneic CPL as a supplement for ex vivo propagation of eBM-MSCs provides appropriate proliferation and cryopreservation, and mildly upregulates the gene expression of immunomodulatory markers, thus constituting a potentially suitable alternative to the use of FBS. Further studies are needed to clarify the composition and effects of CPL supplementation on equine MSCs immunological profile.

The Differences in the Characteristics of Insulin-producing Cells Using Human Adipose-tissue Derived Mesenchymal Stem Cells from Subcutaneous and Visceral Tissues

The aim of this study was to investigate the characteristics of insulin producing cells (IPCs) differentiated from adipose-tissue derived stem cells (ADSCs) isolated from human subcutaneous and visceral adipose tissues and identify ADSCs suitable for differentiation into efficient and functional IPCs. Subcutaneous and visceral adipose tissues collected from four (4) patients who underwent digestive surgeries at The Tokushima University (000035546) were included in this study. The insulin secretion of the generated IPCs was investigated using surface markers by: fluorescence activated cell sorting (FACS) analysis; cytokine release; proliferation ability of ADSCs; in vitro (glucose-stimulated insulin secretion: (GSIS) test/in vivo (transplantation into streptozotocin-induced diabetic nude mice). The less fat-related inflammatory cytokines secretions were observed (P < 0.05), and the proliferation ability was higher in the subcutaneous ADSCs (P < 0.05). Insulin expression and GISI were higher in the subcutaneous IPCs (P < 0.01 and P < 0.05, respectively). The hyperglycaemic state of all mice that received IPCs from subcutaneous fat tissue converted into normo-glycaemia in thirty (30) days post-transplantation (4/4,100%). Transplanted IPCs were stained using anti-insulin and anti-human leukocyte antigen antibodies. The IPCs generated from the ADSCs freshly isolated from the human fat tissue had sufficient insulin secreting ability in vitro and in vivo.

Different Culture Times Affect MicroRNA Cargo in Equine Amniotic Mesenchymal Cells and Their Microvesicles

Conditioned medium (CM) and microvesicles (MVs) are produced using different protocols: CM is collected following 12-96 h of cell culture without renewal of tissue culture medium, while MVs are collected after overnight cell culture. For future comparative studies in regenerative medicine looking at the efficacy of CM and MVs, it is important to understand how the quality of cell secretions is affected by culture. The aim of this study was to evaluate whether the duration of culturing influences the micro-RNAs (miRNAs) cargo of equine amniotic mesenchymal cells (AMCs) and their MVs. The analysis identified 990 miRNAs. After one night, there were 347 differently expressed (DE)-miRNAs between MVs and cells, whereas after four nights there were 359. About 58.3% of the DE-miRNAs were shared between samples produced under the two conditions. The comparison between miRNA content in AMC cells cultured for one night versus four nights showed eight DE-Equus caballus (eca)-miRNAs, which target genes were involved in immune response to external stimulus, inflammatory response, and production of reactive oxygen species. Comparing MVs isolated from one or four nights, four DE-miRNAs that target genes regulating cell cycle progression and production of reactive oxygen species were found, but only eca-miR-214 was enriched in the MVs after four nights. In conclusion, after 4 days of cell culture, the profile of AMC miRNAs was altered, indicating a probable phenotypic transition versus a new cell culture environment and aging. After this time, MVs accumulated eca-miR-214, which may help cells survive or adapt to new culture conditions.

Skin tissue engineering: wound healing based on stem-cell-based therapeutic strategies

Normal wound healing is a dynamic and complex multiple phase process involving coordinated interactions between growth factors, cytokines, chemokines, and various cells. Any failure in these phases may lead wounds to become chronic and have abnormal scar formation. Chronic wounds affect patients' quality of life, since they require repetitive treatments and incur considerable medical costs. Thus, much effort has been focused on developing novel therapeutic approaches for wound treatment. Stem-cell-based therapeutic strategies have been proposed to treat these wounds. They have shown considerable potential for improving the rate and quality of wound healing and regenerating the skin. However, there are many challenges for using stem cells in skin regeneration. In this review, we present some sets of the data published on using embryonic stem cells, induced pluripotent stem cells, and adult stem cells in healing wounds. Additionally, we will discuss the different angles whereby these cells can contribute to their unique features and show the current drawbacks.

Immunomodulatory and immunogenic properties of mesenchymal stem cells derived from bovine fetal bone marrow and adipose tissue

Little information is currently available on therapeutic features of bovine mesenchymal stem cells (MSCs), despite the development of large animal experimental models including cattle may open alternative strategies for investigating MSC physiology and eventual applications for regenerative therapy. The aim of the present study was to compare in vitro immunomodulatory and immunogenic potentials of bovine fetal MSCs (bfMSCs) derived from bovine fetal bone marrow (BM-MSCs) and adipose tissue (AT-MSCs). Immunomodulatory analyses in bfMSCs were performed by determination of the effect of interferon-γ (IFNγ) on mRNA levels of indoleamine 2, 3-dioxygenase (IDO), transforming growth factor β1 (TGFβ1), prostaglandin E receptor 2 (PTGER2), interleukin-6 and -10 (IL-6 and IL-10), and IDO enzymatic activity. The effect of conditioned medium from IFNγ-stimulated bfMSCs on the proliferation of alloantigen-activated peripheral blood lymphocytes (PBLs) was assessed. Immunogenicity of bfMSCs was determined by quantification of mRNA levels of major histocompatibility complex I and II (MHC-I and -II), CD80 and CD86, and the proportion of cells positive for MHC-I and -II by flowcytometry (FACS) analyses. IFNγ treatment increased IL-6, PTGER2 and IDO gene expression and activity in bfMSCs but did not affect suppressive effect on proliferation of PBLs. Lower proportion of AT-MSCs expressed MHC-I and MHC-II in comparison to BM-MSCs. In conclusion, BM-MSCs and AT-MSCs upregulated expression of immunomodulatory genes in a similar way after IFNγ stimuli. BM-MSCs and AT-MSCs in basal condition and treated with IFNγ displayed similar in vitro immunomodulatory ability. Lower expression of MHC-I and MHC-II suggest that AT-MSCs might be less immunogenic compared to BM-MSCs.

Manufacturing of primed mesenchymal stromal cells for therapy

Mesenchymal stromal cells (MSCs) for basic research and clinical applications are manufactured and developed as unique cell products by many different manufacturers and laboratories, often under different conditions. The lack of standardization of MSC identity has limited consensus around which MSC properties are relevant for specific outcomes. In this Review, we examine how the choice of media, cell source, culture environment and storage affects the phenotype and clinical utility of MSC-based products, and discuss the techniques better suited to prime MSCs with specific phenotypes of interest and the need for the continued development of standardized assays that provide quality assurance for clinical-grade MSCs. Bioequivalence between cell products and batches must be investigated rather than assumed, so that the diversity of phenotypes between differing MSC products can be accounted for to identify products with the highest therapeutic potential and to preserve their safety in clinical treatments.

Assessment of effectiveness and safety of repeat administration of proinflammatory primed allogeneic mesenchymal stem cells in an equine model of chemically induced osteoarthritis

Background

This study aimed at assessing the effectiveness and safety of repeated administrations of allogeneic bone marrow-derived mesenchymal stem cells (BM-MSCs) primed with tumor necrosis factor (TNF)-α and interferon-γ in an equine model of chemically-induced osteoarthritis. Arthritis was induced in both radio-carpal (RC)-joints by amphotericin-B in 18 ponies, divided into three groups depending on the treatment injected: MSC-naïve (n = 7), MSC-primed (n = 7) and control (n = 4). The study consisted of two phases and used one RC-joint of each animal in each phase, with four months time-lapse, in order to assess two end-points. Clinical, synovial, radiological and ultrasonographic follow-up was performed. At six months, animals were euthanized and both carpi were assessed by magnetic resonance imaging (MRI), gross anatomy, histopathology, histochemistry and gene expression.

Results

Clinical and synovial inflammatory signs were quicker reduced in MSC-treated groups and repeated allogeneic administration did not produce adverse reactions, but MSC-primed group showed slight and transient local inflammation after second injection. Radiology and MRI did not show significant differences between treated and control groups, whereas ultrasonography suggested reduced synovial effusion in MSC-treated groups. Both MSC-treated groups showed enhanced cartilage gross appearance at two compared to six months (MSC-naïve, p < 0.05). Cartilage histopathology did not reveal differences but histochemistry suggested delayed progression of proteoglycan loss in MSC-treated groups. Synovium histopathology indicated decreased inflammation (p < 0.01) in MSC-primed and MSC-naïve at two and six months, respectively. At two months, cartilage from MSC-primed group significantly (p < 0.05) upregulated collagen type II (COL2A1) and transforming growth factor (TGF)-β1 and downregulated cyclooxygenase-2 and interleukin (IL)-1β. At six months, MSC-treatments significantly downregulated TNFα (p < 0.05), plus MSC-primed upregulated (p < 0.05) COL2A1, aggrecan, cartilage oligomeric protein, tissue inhibitor of metalloproteinases-2 and TGF-β1. In synovium, both MSC-treatments decreased (p < 0.01) matrix metalloproteinase-13 expression at two months and MSC-primed also downregulated TNFα (p < 0.05) and IL-1β (p < 0.01).

Conclusions

Both MSC-treatments provided beneficial effects, mostly observed at short-term. Despite no huge differences between MSC-treatments, the findings suggested enhanced anti-inflammatory and regulatory potential of MSC-primed. While further research is needed to better understand these effects and clarify immunogenicity implications, these findings contribute to enlarge the knowledge about MSC therapeutics and how they could be influenced.

Electronic supplementary material

The online version of this article (10.1186/s12917-018-1556-3) contains supplementary material, which is available to authorized users.

The therapeutic potential of the mesenchymal stem cell secretome in ischaemic stroke

Mesenchymal stem cells (MSCs) hold great potential as a regenerative therapy for stroke, leading to increased repair and functional recovery in animal models of cerebral ischaemia. While it was initially hypothesised that cell replacement was an important mechanism of action of MSCs, focus has shifted to their paracrine actions or the so called "bystander" effect. MSCs secrete a wide array of growth factors, chemokines, cytokines and extracellular vesicles, commonly referred to as the MSC secretome. There is evidence suggesting the MSC secretome can promote repair through a number of mechanisms including preventing cell apoptosis, modulating the inflammatory response and promoting endogenous repair mechanisms such as angiogenesis and neurogenesis. In this review, we will discuss the in vitro approaches currently being employed to drive the MSC secretome towards a more anti-inflammatory and regenerative phenotype. We will then examine the role of the secretome in promoting repair and improving recovery in preclinical models of cerebral ischaemia.

Practical considerations for clinical use of mesenchymal stem cells: From the laboratory to the horse

Since the clinical use of mesenchymal stem cells (MSCs) for treating musculoskeletal injuries is gaining popularity, practitioners should be aware of the factors that may affect MSCs from tissue harvesting for MSC isolation to cell delivery into the injury site. This review provides equine practitioners with up-to-date, practical knowledge for the treatment of equine patients using MSCs. A brief overview of laboratory procedures affecting MSCs is provided, but the main focus is on shipping conditions, routes of administration, injection methods, and which commonly used products can be combined with MSCs and which products should be avoided as they have deleterious effects on cells. There are still several knowledge gaps regarding MSC-based therapies in horses. Therefore, it is important to properly manage the factors which are currently known to affect MSCs, to further strengthen the evidence basis of this treatment.

Combination of MSC spheroids wrapped within autologous composite sheet dually protects against immune rejection and enhances stem cell transplantation efficacy

Mesenchymal stem cells (MSCs) are widely used in transplantation therapy due to their multilineage differentiation potential, abundance, and immuno-modulating ability. However, the risk of allograft rejection limits their application. Here, we proposed a novel method to facilitate MSC transplantation with enhanced applicability and efficacy. We cultured human adipose-derived MSCs in a 3D culture under in vitro expansion conditions and under conventional 2D adherent culture conditions. MSC spheroids promoted extracellular matrix molecules that stimulate MSC proliferation, and produced more angiogenic cytokines such as vascular endothelial growth factor, hepatocyte growth factor, and fibroblast growth factor than 2D-cultured MSCs. Further, MSC spheroids showed increased IDO expression, increased proportion of M2 macrophages, and decreased macrophage proliferation, compared to 2D-cultured MSCs. Next, we proposed the wrapping of autologous cell sheets from the recipient around in-vitro-grown MSC spheroids to prevent allogenic immune rejection during transplantation. Myoblasts from C57BL/6 mice were used to prepare a stem cell composite sheet containing human-derived MSC spheres. The transplantation of MSC spheroids increased the survival rate and decreased the inflammatory response of the immunocompetent C57BL/6 ischemic mice. Thus, combining 3D-cultured MSC spheroid technology with immune evasion stem cell composite sheet improved the outcome and strengthened the protection against allogenic immune rejection.

Mesenchymal Stem Cell-Based Immunomodulation: Properties and Clinical Application

Mesenchymal stem cells (MSCs) are multipotent stem cells characterized by self-renewal, production of clonal cell populations, and multilineage differentiation. They exist in nearly all tissues and play a significant role in tissue repair and regeneration. Additionally, MSCs possess wide immunoregulatory properties via interaction with immune cells in both innate and adaptive immune systems, leading to immunosuppression of various effector functions. Numerous bioactive molecules secreted by MSCs, particularly cytokines, growth factors, and chemokines, exert autocrine/paracrine effects that modulate the physiological processes of MSCs. These invaluable virtues of MSCs provide new insight into potential treatments for tissue damage and inflammation. In particular, their extensive immunosuppressive properties are being explored for promising therapeutic application in immune disorders. Recently, clinical trials for MSC-mediated therapies have rapidly developed for immune-related diseases following reports from preclinical studies declaring their therapeutic safety and efficacy. Though immunotherapy of MSCs remains controversial, these clinical trials pave the way for their widespread therapeutic application in immune-based diseases. In this review, we will summarize and update the latest research findings and clinical trials on MSC-based immunomodulation.

Canine mesenchymal stem cells treated with TNF-α and IFN-γ enhance anti-inflammatory effects through the COX-2/PGE2 pathway

Mesenchymal stem cells (MSCs) have been used in studies on treatment of various diseases, and their application to immune-mediated diseases has garnered interest. Various methods for enhancing the immunomodulation effect of human MSCs have been used; however, similar approaches for canine MSCs are relatively unexplored. Accordingly, we evaluated immunomodulatory effects and mechanisms in canine MSCs treated with TNF-α and IFN-γ. Lipopolysaccharide (LPS)-stimulated RAW 264.7 cells were incubated with the conditioned media (CM) from canine MSCs for 48 h. Expression of RNA was assessed by quantitative reverse transcription PCR (qRT-PCR), and protein levels were assessed by western blot. Expression of inducible nitric oxide synthase (iNOS), IL-6 and IL-1β was significantly (one-way ANOVA) decreased in LPS-stimulated RAW 264.7 cells incubated with CM from canine MSCs compared to that in LPS-stimulated RAW 264.7 cells alone. Furthermore, anti-inflammatory effects of TNF-α- and IFN-γ-primed canine MSCs were significantly increased compared with those of naïve canine MSCs. Expression of cyclooxygenase 2 (COX-2) and prostaglandin E₂ (PGE₂) were likewise significantly increased in primed canine MSCs. The level of iNOS protein in LPS-stimulated RAW 264.7 cells incubated with CM from the primed canine MSCs was decreased, but it increased when the cells were treated with NS-398(PGE₂ inhibitor). In conclusion, compared with naïve canine MSCs, cells primed with TNF-α and IFN-γ cause a greater reduction in release of anti-inflammatory cytokines from LPS-stimulated RAW 264.7 cells; the mechanism is upregulation of the COX-2/PGE₂ pathway.

Concentration-dependent, dual roles of IL-10 in the osteogenesis of human BMSCs via P38/MAPK and NF-κB signaling pathways

Microenvironmental conditions can influence the differentiation and functional roles of mesenchymal stem cells (MSCs). Recent studies have suggested that an inflammatory microenvironment can significantly affect the osteogenic differentiation of MSCs. Here, we show, for the first time, that IL-10 has concentration-dependent, dual roles in the osteogenesis of human bone marrow mesenchymal stem cells (hBMSCs). Low physiologic concentrations of IL-10 (0.01-1.0 ng/ml) activate the p38/MAPK signaling pathway to promote the osteogenesis of hBMSCs, but higher pathologic doses of IL-10 (10-100 ng/ml) inhibit p38/MAPK signaling by activating NF-κB, inhibiting osteogenesis. These results demonstrate that p38/MAPK and NF-κB signaling mediates the double-edged sword effect of IL-10 on hBMSCs. The osteogenic impairment was reversed at higher doses of IL-10 when cells were supplemented with the NF-κB inhibitor BAY11-7082. These data provide important insights into the regulatory effects of IL-10 on the biologic behavior of hBMSCs.-Chen, E., Liu, G., Zhou, X., Zhang, W., Wang, C., Hu, D., Xue, D., Pan, Z. Concentration-dependent, dual roles of IL-10 in the osteogenesis of human BMSCs via P38/MAPK and NF-κB signaling pathways.

Insights into inflammatory priming of mesenchymal stromal cells: functional biological impacts

Mesenchymal stromal cells (MSCs) are multipotent adult cells with relevant biological properties making them interesting tools for cell-based therapy. These cells have the ability to home to sites of injury and secrete bioactive factors as part of their therapeutic functions. However, depending on the local environment, diverse functions of MSCs can be modulated and thus can influence their therapeutic value. The specific cytokine milieu within the site of inflammation is vital in determining the fate and cell behaviors of MSCs. Indeed, inflammatory signals (called as inflammatory priming), may induce critical changes on the phenotype, multilineage potential, hematopoietic support and immunomodulatory capacity of MSCs. Thus, for appropriate clinical application of MSCs, it is important to well know and understand these effects. In summary, investigating MSC interactions with the inflammatory environment is necessary to empower the therapeutic value of MSCs.

Galectin-1 and galectin-3 expression in equine mesenchymal stromal cells (MSCs), synovial fibroblasts and chondrocytes, and the effect of inflammation on MSC motility

Background

Mesenchymal stromal cells (MSCs) can be used intra-articularly to quell inflammation and promote cartilage healing; however, mechanisms by which MSCs mitigate joint disease remain poorly understood. Galectins, a family of β-galactoside binding proteins, regulate inflammation, adhesion and cell migration in diverse cell types. Galectin-1 and galectin-3 are proposed to be important intra-articular modulators of inflammation in both osteoarthritis and rheumatoid arthritis. Here, we asked whether equine bone marrow-derived MSCs (BMSCs) express higher levels of galectin-1 and -3 relative to synovial fibroblasts and chondrocytes and if an inflammatory environment affects BMSC galectin expression and motility.

Methods

Equine galectin-1 and -3 gene expression was quantified using qRT-PCR in cultured BMSCs, synoviocytes and articular chondrocytes, in addition to synovial membrane and articular cartilage tissues. Galectin gene expression, protein expression, and protein secretion were measured in equine BMSCs following exposure to inflammatory cytokines (IL-1β 5 and 10 ng/mL, TNF-α 25 and 50 ng/mL, or LPS 0.1, 1, 10 and 50 μg/mL). BMSC focal adhesion formation was assessed using confocal microscopy, and BMSC motility was quantified in the presence of inflammatory cytokines (IL-1β or TNF-α) and the pan-galectin inhibitor β-lactose (100 and 200 mM).

Results

Equine BMSCs expressed 3-fold higher galectin-1 mRNA levels as compared to cultured synovial fibroblasts (p = 0.0005) and 30-fold higher galectin-1 (p < 0.0001) relative to cultured chondrocytes. BMSC galectin-1 mRNA expression was significantly increased as compared to carpal synovial membrane and articular cartilage tissues (p < 0.0001). IL-1β and TNF-α treatments decreased BMSC galectin gene expression and impaired BMSC motility in dose-dependent fashion but did not alter galectin protein expression. β-lactose abrogated BMSC focal adhesion formation and inhibited BMSC motility.

Conclusions

Equine BMSCs constitutively express high levels of galectin-1 mRNA relative to other articular cell types, suggesting a possible mechanism for their intra-articular immunomodulatory properties. BMSC galectin expression and motility are impaired in an inflammatory environment, which may limit tissue repair properties following intra-articular administration. β-lactose-mediated galectin inhibition also impaired BMSC adhesion and motility. Further investigation into the effects of joint inflammation on BMSC function and the potential therapeutic effects of BMSC galectin expression in OA is warranted.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0691-2) contains supplementary material, which is available to authorized users.

The immunomodulatory function of equine MSCs is enhanced by priming through an inflammatory microenvironment or TLR3 ligand

Mesenchymal stem cells (MSCs) have the therapeutic potential to treat a variety of inflammatory and degenerative disease processes, however the effects of the tissue environment on MSCs have been overlooked. Our hypothesis was that the immunomodulatory function of MSCs would be impaired by TLR4 stimulation or exposure to inflammatory macrophages, whereas their immunosuppressive properties would be enhanced by TLR3 stimulation. MSCs were exposed to polyinosinic:polycytidylic acid (poly I:C) to stimulate TLR3 receptors or lipopolysaccharide (LPS) to stimulate TLR4 receptors. MSC1 proinflammatory phenotype in human MSCs was associated with increased IL-6 and IL-8 and MSC2 regenerative phenotype was associated with increased CCL2 and CXCL10. MSC immunomodulatory function was assessed by measuring the ability of primed MSCs to suppress mitogen-stimulated T cell proliferation. Peripheral blood monocytes were isolated using CD14 MACs positive selection, differentiated into macrophages, and polarized using interferon-gamma (IFN-γ). Polarization was confirmed by increased gene expression of TNFα, CCL2, and CXCL10. Inflammatory macrophages were co-cultured with MSCs for 6h, and the resultant MSC phenotype was analyzed as described above. Both TLR3 and TLR4 priming and co-culture of MSCs with inflammatory macrophages resulted in increased expression of IL-6, CCL2, and CXCL10 in MSCs. Both TLR3 and TLR4 priming or exposure of MSCs to inflammatory macrophages significantly (p<0.05) enhanced their immunomodulatory function, demonstrated by a decrease in T cell proliferation in the presence of poly I:C primed MSCs (11%), LPS primed MSCs (7%), or MSCs exposed to inflammatory macrophages (12%), compared to unstimulated MSCs. Additionally, MHC class II positive MSCs tended to have a greater magnitude of response to priming compared to MHC class II negative MSCs. These results suggest that MSCs can be activated by a variety of inflammatory stimuli, but the recipient injured tissue bed in chronic injuries may not contain sufficient inflammatory signals to activate MSC immunomodulatory function. Enhancement of MSCs immunomodulatory function through inflammatory priming prior to clinical application might improve the therapeutic effect of MSC treatments.

Mesenchymal stem cells maintain the microenvironment of central nervous system by regulating the polarization of macrophages/microglia after traumatic brain injury

Mesenchymal stem cells (MSCs), which are regarded as promising candidates for cell replacement therapies, are able to regulate immune responses after traumatic brain injury (TBI). Secondary immune response following the mechanical injury is the essential factor leading to the necrosis and apoptosis of neural cells during and after the cerebral edema has subsided and there is lack of efficient agent that can mitigate such neuroinflammation in the clinical application. By means of three molecular pathways (prostaglandin E2 (PGE2), tumor-necrosis-factor-inducible gene 6 protein (TSG-6), and progesterone receptor (PR) and glucocorticoid receptors (GR)), MSCs induce the activation of macrophages/microglia and drive them polarize into the M2 phenotypes, which inhibits the release of pro-inflammatory cytokines and promotes tissue repair and nerve regeneration. The regulation of MSCs and the polarization of macrophages/microglia are dynamically changing based on the inflammatory environment. Under the stimulation of platelet lysate (PL), MSCs also promote the release of pro-inflammatory cytokines. Meanwhile, the statue of macrophages/microglia exerts significant effects on the survival, proliferation, differentiation and activation of MSCs by changing the niche of cells. They form positive feedback loops in maintaining the homeostasis after TBI to relieving the secondary injury and promoting tissue repair. MSC therapies have obtained great achievements in several central nervous system disease clinical trials, which will accelerate the application of MSCs in TBI treatment.