Mesenchymal stem cells: innovative therapeutic tools for rheumatic diseases

Periocular and intra-articular injection of canine adipose-derived mesenchymal stem cells: an in vivo imaging and migration study

PURPOSE

Immune-mediated diseases affect millions of people worldwide with an economic impact measured in the billions of dollars. Mesenchymal stem cells (MSCs) are being investigated in the treatment of certain immune mediated diseases, but their application in the treatment of the majority of these disorders remains largely unexplored. Keratoconjunctivitis sicca can occur as a result of progressive immune-mediated destruction of lacrimal tissue in dogs and humans, and immune-mediated joint disease is common to both species. In dogs, allogeneic MSC engraftment and migration have yet to be investigated in vivo in the context of repeated injections.

METHODS

With these aims in mind, the engraftment of allogeneic canine MSCs after an injection into the periocular and intra-articular regions was followed in vivo using magnetic resonance and fluorescent imaging.

RESULTS

The cells were shown to be resident near the site of the injection for a minimum of 2 weeks. Analysis of 61 tissues demonstrated preferential migration and subsequent engraftment of MSCs in the thymus as well as the gastrointestinal tract. These results also detail a novel in vivo imaging technique and demonstrate the differential spatial distribution of MSCs after migration away from the sites of local delivery.

CONCLUSION

The active engraftment of the MSCs in combination with their previously documented immunomodulatory capabilities suggests the potential for therapeutic benefit in using MSCs for the treatment of periocular and joint diseases with immune involvement.

Concise review: clinical translation of wound healing therapies based on mesenchymal stem cells

There is enormous worldwide demand for therapies to promote the efficient resolution of hard-to-heal wounds with minimal appearance of scarring. Recent in vitro studies with mesenchymal stem cells (MSCs) have identified numerous mechanisms by which these cells can promote the process of wound healing, and there is significant interest in the clinical translation of an MSC-based therapy to promote dermal regeneration. This review provides a systematic analysis of recent preclinical and clinical research to evaluate the use of MSCs in wound healing applications. These in vivo studies provide overwhelming evidence that MSCs can accelerate wound closure by modulating the inflammatory environment, promoting the formation of a well-vascularized granulation matrix, encouraging the migration of keratinocytes, and inhibiting apoptosis of wound healing cells. The trophic effects of MSC therapy also appear to augment wound healing in diabetic tissues, thereby preventing the formation of nonhealing ulcers. Finally, a number of delivery systems have been evaluated and indicate that MSCs could be the basis of a versatile therapy to fulfill the clinical needs for dermal regeneration. However, despite the apparent advantages of MSC-based therapies, there have been only limited clinical investigations of this type of therapy in humans. Thus, our review concludes with a discussion of the translational barriers that are limiting the widespread clinical use of MSCs to enhance wound healing.

Bone marrow stromal cells produce long-term pain relief in rat models of persistent pain

Chronic pain conditions are difficult to treat and are major health problems. Bone marrow stromal cells (BMSCs) have generated considerable interest as a candidate for cell-based therapy. BMSCs are readily accessible and are easy to isolate and expand ex vivo. Clinical studies show that direct injection of BMSCs does not produce unwanted side effects and is well tolerated and safe. Here, we show that a single systemic (intravenous) or local injection (into the lesion site) of rat primary BMSCs reversed pain hypersensitivity in rats after injury and that the effect lasted until the conclusion of the study at 22 weeks. The pain hypersensitivity was rekindled by naloxone hydrochloride, an opioid receptor antagonist that acts peripherally and centrally, when tested at 1-5 weeks after BMSC infusion. In contrast, naloxone methiodide, a peripherally acting opioid receptor antagonist, only rekindled hyperalgesia in the first 3 weeks of BMSC treatment. Focal downregulation of brainstem mu opioid receptors by RNA interference (RNAi) reversed the effect of BMSCs, when RNAi was introduced at 5- but not 1-week after BMSC transplantation. Thus, BMSCs produced long-term relief of pain and this effect involved activation of peripheral and central opioid receptors in distinct time domains. The findings prompt studies to elucidate the cellular mechanisms of the BMSC-induced pain relieving effect and translate these observations into clinical settings.

Dental pulp stem cells, niches, and notch signaling in tooth injury

Stem cells guarantee tissue repair and regeneration throughout life. The decision between cell self-renewal and differentiation is influenced by a specialized microenvironment called the 'stem cell niche'. In the tooth, stem cell niches are formed at specific anatomic locations of the dental pulp. The microenvironment of these niches regulates how dental pulp stem cell populations participate in tissue maintenance, repair, and regeneration. Signaling molecules such as Notch proteins are important regulators of stem cell function, with various capacities to induce proliferation or differentiation. Dental injuries often lead to odontoblast apoptosis, which triggers activation of dental pulp stem cells followed by their proliferation, migration, and differentiation into odontoblast-like cells, which elaborate a reparative dentin. Better knowledge of the regulation of dental pulp stem cells within their niches in pathological conditions will aid in the development of novel treatments for dental tissue repair and regeneration.

Mechanisms of Edible Bird's Nest Extract-Induced Proliferation of Human Adipose-Derived Stem Cells

Although edible bird's nest (EBN) has been shown to potentiate mitogenic responses, scientific evidence of its efficacy is still limited. In addition, human adipose-derived stem cells (hADSCs) are increasingly accepted as a source for stem cell therapy. Therefore, the aim of this study was to investigate the effects of the EBN extract (EBNE) on the proliferation of hADSCs and its action mechanisms. We found that EBNE strongly promoted the proliferation of hADSCs. In addition, EBNE-induced proliferation was found to be mediated through the production of IL-6 and VEGF, which was induced by activation of AP-1 and NF-κB. Specially, we found that production of IL-6 and VEGF was induced by EBNE. In addition, EBNE-induced production of IL-6 and VEGF was inhibited by PD98059 (a p44/42 MAPK inhibitor), SB203580 (a p38 MAPK inhibitor), and PDTC (a NF-κB inhibitor), but not SP600125 (a JNK inhibitor). Similarly, EBNE-induced proliferation of hADSCs was also attenuated by PD98059, SB203580, and PDTC but not SP600125. Taken together, these findings suggest that the EBNE-induced proliferation of hADSCs primarily occurs through increased expression of IL-6 and VEGF genes, which is mediated by the activation of NF-κB and AP-1 through p44/42 MAPK and p38 MAPK.

Stem cell treatment for patients with autoimmune disease by systemic infusion of culture-expanded autologous adipose tissue derived mesenchymal stem cells

Prolonged life expectancy, life style and environmental changes have caused a changing disease pattern in developed countries towards an increase of degenerative and autoimmune diseases. Stem cells have become a promising tool for their treatment by promoting tissue repair and protection from immune-attack associated damage. Patient-derived autologous stem cells present a safe option for this treatment since these will not induce immune rejection and thus multiple treatments are possible without any risk for allogenic sensitization, which may arise from allogenic stem cell transplantations. Here we report the outcome of treatments with culture expanded human adipose-derived mesenchymal stem cells (hAdMSCs) of 10 patients with autoimmune associated tissue damage and exhausted therapeutic options, including autoimmune hearing loss, multiple sclerosis, polymyotitis, atopic dermatitis and rheumatoid arthritis. For treatment, we developed a standardized culture-expansion protocol for hAdMSCs from minimal amounts of fat tissue, providing sufficient number of cells for repetitive injections. High expansion efficiencies were routinely achieved from autoimmune patients and from elderly donors without measurable loss in safety profile, genetic stability, vitality and differentiation potency, migration and homing characteristics. Although the conclusions that can be drawn from the compassionate use treatments in terms of therapeutic efficacy are only preliminary, the data provide convincing evidence for safety and therapeutic properties of systemically administered AdMSC in human patients with no other treatment options. The authors believe that ex-vivo-expanded autologous AdMSCs provide a promising alternative for treating autoimmune diseases. Further clinical studies are needed that take into account the results obtained from case studies as those presented here.

Mesenchymal stem cells induce resistance to chemotherapy through the release of platinum-induced fatty acids

The development of resistance to chemotherapy is a major obstacle for lasting effective treatment of cancer. Here, we demonstrate that endogenous mesenchymal stem cells (MSCs) become activated during treatment with platinum analogs and secrete factors that protect tumor cells against a range of chemotherapeutics. Through a metabolomics approach, we identified two distinct platinum-induced polyunsaturated fatty acids (PIFAs), 12-oxo-5,8,10-heptadecatrienoic acid (KHT) and hexadeca-4,7,10,13-tetraenoic acid (16:4(n-3)), that in minute quantities induce resistance to a broad spectrum of chemotherapeutic agents. Interestingly, blocking central enzymes involved in the production of these PIFAs (cyclooxygenase-1 and thromboxane synthase) prevents MSC-induced resistance. Our findings show that MSCs are potent mediators of resistance to chemotherapy and reveal targets to enhance chemotherapy efficacy in patients.

Administering human adipose-derived mesenchymal stem cells to prevent and treat experimental arthritis

Rheumatoid arthritis is a chronic autoimmune disease and affecting approximately 1% of the population. Human adipose-derived mesenchymal stem cells (hASCs) were recently found to suppress effector T cell and inflammatory responses and, thus, to have beneficial effects in various autoimmune diseases. In this study, we examined whether hASCs could play a protective and/or therapeutic role in collagen-induced arthritis (CIA). We showed that hASCs both prevented and treated CIA by significantly reducing the incidence and severity of experimental arthritis. We further demonstrated that treatment with hASCs inhibited the production of various inflammatory mediators, decreased antigen-specific Th1/Th17 cell expansion, and induced the production of anti-inflammatory cytokine interleukin-10. Moreover, hASCs could induce the generation of antigen-specific Treg cells with the capacity to suppress collagen-specific T cell responses.

Germ-layer and lineage-restricted stem/progenitors regenerate the mouse digit tip

The regrowth of amputated limbs and the distal tips of digits represent models of tissue regeneration in amphibians, fish and mice. For decades it had been assumed that limb regeneration derived from the blastema, an undifferentiated pluripotent cell population thought to be derived from mature cells via dedifferentiation. Here we show that a wide range of tissue stem/progenitor cells contribute towards the restoration of the mouse distal digit. Genetic fate mapping and clonal analysis of individual cells revealed that these stem cells are lineage restricted, mimicking digit growth during development. Transplantation of cyan-fluorescent-protein-expressing haematopoietic stem cells, and parabiosis between genetically marked mice, confirmed that the stem/progenitor cells are tissue resident, including the cells involved in angiogenesis. These results, combined with those from appendage regeneration in other vertebrate subphyla, collectively demonstrate that tissue stem cells rather than pluripotent blastema cells are an evolutionarily conserved cellular mode for limb regeneration after amputation.

Mesenchymal stromal cells for treatment of steroid-refractory GvHD: a review of the literature and two pediatric cases

Severe acute graft versus host disease (GvHD) is a life-threatening complication after allogeneic hematopoietic stem cell transplantation. Human mesenchymal stromal cells (MSCs) play an important role in endogenous tissue repair and possess strong immune-modulatory properties making them a promising tool for the treatment of steroid-refractory GvHD. To date, a few reports exist on the use of MSCs in treatment of GvHD in children indicating that children tend to respond better than adults, albeit with heterogeneous results.

We here present a review of the literature and the clinical course of two instructive pediatric patients with acute steroid-refractory GvHD after haploidentical stem cell transplantation, which exemplify the beneficial effects of third-party transplanted MSCs in treatment of acute steroid-refractory GvHD. Moreover, we provide a meta-analysis of clinical studies addressing the outcome of patients with steroid-refractory GvHD and treatment with MSCs in adults and in children (n = 183; 122 adults, 61 children). Our meta-analysis demonstrates that the overall response-rate is high (73.8%) and confirms, for the first time, that children indeed respond better to treatment of GvHD with MSCs than adults (complete response 57.4% vs. 45.1%, respectively).

These data emphasize the significance of this therapeutic approach especially in children and indicate that future prospective studies are needed to assess the reasons for the observed differential response-rates in pediatric and adult patients.

Synovial fluid of patients with rheumatoid arthritis induces alpha-smooth muscle actin in human adipose tissue-derived mesenchymal stem cells through a TGF-beta1-dependent mechanism

Rheumatoid arthritis (RA) is a chronic, inflammatory autoimmune disorder that causes the immune system to attack the joints. Transforming growth factor-beta1 (TGF-beta1) is a secreted protein that promotes differentiation of synovial fibroblasts to alpha-smooth muscle actin (alpha-SMA)-positive myofibroblasts to repair the damaged joints. Synovial fluid from patients with RA (RA-SF) induced expression of alpha-SMA in human adipose tissue-derived mesenchymal stem cells (hASCs). RA-SF-induced alpha-SMA expression was abrogated by immunodepletion of TGF-beta1 from RA-SF with anti-TGF-beta1 antibody. Furthermore, pretreatment of hASCs with the TGF-beta type I receptor inhibitor SB431542 or lentiviral small hairpin RNA-mediated silencing of TGF-beta type I receptor expression in hASCs blocked RA-SF-induced alpha-SMA expression. Small interfering RNA-mediated silencing of Smad2 or adenoviral overexpression of Smad7 (an inhibitory Smad isoform) completely inhibited RA-SF-stimulated alpha-SMA expression. These results suggest that TGF-beta1 plays a pivotal role in RA-SF-induced differentiation of hASCs to alpha-SMA-positive cells.

The therapeutic efficacy of human adipose tissue-derived mesenchymal stem cells on experimental autoimmune hearing loss in mice

Autoimmune inner ear disease is characterized by progressive, bilateral although asymmetric, sensorineural hearing loss. Patients with autoimmune inner ear disease had higher frequencies of interferon-γ-producing T cells than did control subjects tested. Human adipose-derived mesenchymal stem cells (hASCs) were recently found to suppress effector T cells and inflammatory responses and therefore have beneficial effects in various autoimmune diseases. The aim of this study was to examine the immunosuppressive activity of hASCs on autoreactive T cells from the experimental autoimmune hearing loss (EAHL) murine model. Female BALB/c mice underwent β-tubulin immunization to develop EAHL; mice with EAHL were given hASCs or PBS intraperitoneally once a week for 6 consecutive weeks. Auditory brainstem responses were examined over time. The T helper type 1 (Th1)/Th17-mediated autoreactive responses were examined by determining the proliferative response and cytokine profile of splenocytes stimulated with β-tubulin. The frequency of regulatory T (Treg) cells and their suppressive capacity on autoreactive T cells were also determined. Systemic infusion of hASCs significantly improved hearing function and protected hair cells in established EAHL. The hASCs decreased the proliferation of antigen-specific Th1/Th17 cells and induced the production of anti-inflammatory cytokine interleukin-10 in splenocytes. They also induced the generation of antigen-specific CD4(+) CD25(+) Foxp3(+) Treg cells with the capacity to suppress autoantigen-specific T-cell responses. The experiment demonstrated that hASCs are one of the important regulators of immune tolerance with the capacity to suppress effector T cells and to induce the generation of antigen-specific Treg cells.

Teratogenic potential in cultures optimized for oligodendrocyte development from mouse embryonic stem cells

We describe a rapid and efficient 5-step program of defined factors for the genesis of brain myelin-forming oligodendrocytes (OLs) from embryonic stem cells (ESCs). The OLs emerge on the same time frame in vitro as seen in vivo. Factors promoting neural induction (retinoids, noggin) are required, while exogenous Sonic hedgehog is not. In contrast we were unable to generate OLs by trans-differentiation of ethically neutral mesenchymal stem cells, indicating a requirement for cis-differentiation via neural ectoderm for OL genesis. In the ESC-derived cultures, our optimized protocol generated a mixed population with 49% O4(+), Olig2(+) OL lineage cells. These cultures also retained pluripotential markers including Oct4, and an analysis of embryoid body formation in vitro, and allogeneic grafts in vivo, revealed that the ESC-derived cultures also retained teratogenic cells. The frequency of embryoid body formation from terminal differentiated OL cultures was 0.001%, 100-fold lower than that from ESCs. Our results provide the first quantitative measurement of teratogenicity in ESC-derived, exhaustively differentiated allogeneic grafts, and demonstrate the unequivocal need to purify ESC-derived cells in order to generate a safe population for regenerative therapy.

Hyaluronidase recruits mesenchymal-like cells to the lung and ameliorates fibrosis

Hyaluronidases (HYALs) comprise a group of enzymes that degrade hyaluronic acid (HA). In this report, we reveal that a single intranasal inoculation of HYAL induces an increase in mononuclear cells within the bronchoalveolar space demonstrating a mesenchymal-like phenotype, expressing stem cell antigen-1 (SCA-1), CD44 and CD73 but not CD34, CD45, CD3, CD4, CD8 or CD19. This influx of mesenchymal stem cell (MSC)-like cells was dependent on leukotriene production within the lung parenchyma. These findings prompted experiments demonstrating that HYAL treatment potently blocked bleomycin-induced lung injury and fibrosis while decreasing transforming growth factor (TGF)-β production and collagen deposition. These data suggest that HYAL is a novel and promising tool to use autologous MSC-like cells in the treatment of pulmonary fibrosis.

IL-6-dependent PGE2 secretion by mesenchymal stem cells inhibits local inflammation in experimental arthritis

Background

Based on their capacity to suppress immune responses, multipotent mesenchymal stromal cells (MSC) are intensively studied for various clinical applications. Although it has been shown in vitro that the immunomodulatory effect of MSCs mainly occurs through the secretion of soluble mediators, the mechanism is still not completely understood. The aim of the present study was to better understand the mechanisms underlying the suppressive effect of MSCs in vivo, using cells isolated from mice deficient in the production of inducible nitric oxide synthase (iNOS) or interleukin (IL)-6 in the murine model of collagen-induced arthritis.

Principal Findings

In the present study, we show that primary murine MSCs from various strains of mice or isolated from mice deficient for iNOS or IL-6 exhibit different immunosuppressive potential. The immunomodulatory function of MSCs was mainly attributed to IL-6-dependent secretion of prostaglandin E2 (PGE2) with a minor role for NO. To address the role of these molecules in vivo, we used the collagen-induced arthritis as an experimental model of immune-mediated disorder. MSCs effectively inhibited collagen-induced inflammation during a narrow therapeutic window. In contrast to wild type MSCs, IL-6-deficient MSCs and to a lesser extent iNOS-deficient MSCs were not able to reduce the clinical signs of arthritis. Finally, we show that, independently of NO or IL-6 secretion or Treg cell induction, MSCs modulate the host response by inducing a switch to a Th2 immune response.

Significance

Our data indicate that MSCs mediate their immunosuppressive effect via two modes of action: locally, they reduce inflammation through the secretion of anti-proliferative mediators, such as NO and mainly PGE2, and systemically they switch the host response from a Th1/Th17 towards a Th2 immune profile.

Mining the extracellular matrix for tissue engineering applications

Tissue engineering is a rapidly evolving interdisciplinary field that aims to regenerate new tissue to replace damaged tissues or organs. The extracellular matrix (ECM) of animal tissues is a complex mixture of macromolecules that play an essential instructional role in the development of tissues and organs. Therefore, tissue engineering approaches rely on the need to present the correct cues to cells, to guide them to maintain tissue-specific functions. Recent research efforts have allowed us to mine various sequences and motifs, which play key roles in these guidance functions, from the ECM. Small conserved peptide sequences mined from ECM molecules can mimic some of the biological functions of their large parent molecules. In addition, these peptide sequences can be linked to various biomaterial scaffolds that can provide the cells with mechanical support to ensure appropriate cell growth and aid the formation of the correct tissue structure. The tissue engineering field will continue to benefit from the advent of these mined ECM sequences which have two major advantages over recombinant ECM molecules: material consistency and scalability.

Mesenchymal stem cells immunosuppressive properties: is it specific to bone marrow-derived cells?

Based on their capacity to suppress immune responses, multipotent mesenchymal stromal cells (MSCs) are intensively studied for regenerative medicine. Moreover, MSCs have paracrine effects, including immunomodulation that occurs through the secretion of soluble mediators, including nitric oxide or interleukin-6, transforming growth factor-beta, human leukocyte antigen G5, and prostaglandin E₂. MSCs in the bone marrow are in close contact with T and B cells and regulate immunological memory by organizing defined numbers of dedicated survival niches for plasma cells and memory T cells in the bone marrow. All of these biological effects are probably shared by all stromal cells, including fibroblasts and stem cells isolated from exfoliated deciduous teeth. The therapeutical implications are discussed.

Transplantation of adipose tissue and stem cells: role in metabolism and disease

Humans and other mammals have three main adipose tissue depots: visceral white adipose tissue, subcutaneous white adipose tissue and brown adipose tissue, each of which possesses unique cell-autonomous properties. In contrast to visceral adipose tissue, which can induce detrimental metabolic effects, subcutaneous white adipose tissue and brown adipose tissue have the potential to benefit metabolism by improving glucose homeostasis and increasing energy consumption. In addition, adipose tissue contains adipose-derived stem cells, which possess the ability to differentiate into multiple lineages, a property that might be of value for the repair or replacement of various damaged cell types. Adipose tissue transplantation has primarily been used as a tool to study physiology and for human reconstructive surgery. Transplantation of adipose tissue is, however, now being explored as a possible tool to promote the beneficial metabolic effects of subcutaneous white adipose tissue and brown adipose tissue, as well as adipose-derived stem cells. Ultimately, the clinical applicability of adipose tissue transplantation for the treatment of obesity and metabolic disorders will reside in the achievable level of safety, reliability and efficacy compared with other treatments.

Arthroplasty of the lunate using bone marrow mesenchymal stromal cells

Mesenchymal stromal cells have the potential to differentiate into a variety of mesenchymal tissues such as bone, cartilage and ligaments. The potential for the regeneration of bone with cartilage coverage has still not been achieved. We evaluated the ability of bone marrow mesenchymal stromal cells to regenerate osteochondral defects in the cavity of the lunate in an animal model. Autologous mesenchymal stromal cells were harvested from the iliac crest of New Zealand white rabbits and expanded in vitro. Total lunate excision was performed in 24 animals and the isolated cells were loaded onto scaffolds. Cell-free scaffolds were implanted in the lunate space of the right wrists of all animals, and the left lunate spaces were filled with predifferentiated, cell-loaded scaffolds. Radiographic and histological analyses were performed after two, six and 12 weeks. In addition, the animals were injected with a fluorescent agent every five days, starting at day 30. After two and six weeks there was no radiographic evidence of ossification, whereas after 12 weeks all animals showed radiographic evidence of ossification. Histological sections showed increasing evidence of cartilage-like cell formation at the edges and new bone tissue in the centre of the newly formed tissue in all groups. The histological examinations showed that bone tissue was located around the newly incorporated vascularisation. This study demonstrated that newly formed vascularisation is necessary for the regeneration of bone tissue with cell-loaded scaffolds.

Immunosuppression by mesenchymal stem cells: mechanisms and clinical applications

Mesenchymal stem cells (MSCs) are multipotential nonhematopoietic progenitor cells that are isolated from many adult tissues, in particular from the bone marrow and adipose tissue. Along with their capacity for differentiating into cells of mesodermal lineage, such as adipocytes, osteoblasts and chondrocytes, these cells have also generated great interest for their ability to display immunomodulatory capacities. Indeed, a major breakthrough came with the finding that they are able to induce peripheral tolerance, suggesting they may be used as therapeutic tools in immune-mediated disorders. The present review aims at discussing the current knowledge on the targets and mechanisms of MSC-mediated immunosuppression as well as the potential use of MSCs as modulators of immune responses in a variety of diseases related to alloreactive immunity or autoimmunity

Discrepancy between the in vitro and in vivo effects of murine mesenchymal stem cells on T-cell proliferation and collagen-induced arthritis

INTRODUCTION

The goal of this study is to analyze the potential immunosuppressive properties of mesenchymal stem cells (MSC) on T cell proliferation and in collagen-induced arthritis (CIA). An additional aim is to investigate the role of interferon-gamma (IFN-gamma) in these processes.

METHODS

MSC were isolated from bone marrow of DBA/1 wild type and IFN-gamma receptor knock-out (IFN-gammaR KO) mice and expanded in vitro. Proliferation of anti-CD3-stimulated CD4+ T cells in the presence or absence of MSC was evaluated by thymidine incorporation. CIA was induced in DBA/1 mice and animals were treated with MSC by intravenous or intraperitoneal injections of wild type or IFN-gammaR KO MSC.

RESULTS

Purity of enriched MSC cultures was evaluated by flow cytometry and their ability to differentiate into osteoblasts and adipocytes. In vitro, wild type MSC dose-dependently suppressed anti-CD3-induced T cell proliferation whereas IFN-gammaR KO MSC had a significantly lower inhibitory potential. A role for inducible nitric oxide (iNOS), programmed death ligand-1 (PD-L1) and prostaglandin E2 (PGE2), but not indoleamine 2,3-dioxigenase (IDO), in the T cell inhibition was demonstrated. In vivo, neither wild type nor IFN-gammaR KO MSC were able to reduce the severity of CIA or the humoral or cellular immune response toward collagen type II.

CONCLUSIONS

Whereas MSC inhibit anti-CD3-induced proliferation of T cells in vitro, an effect partially mediated by IFN-gamma, MSC do not influence in vivo T cell proliferation nor the disease course of CIA. Thus there is a clear discrepancy between the in vitro and in vivo effects of MSC on T cell proliferation and CIA.

Regulation of stemness and stem cell niche of mesenchymal stem cells: implications in tumorigenesis and metastasis

Human mesenchymal stem cells (MSCs) derived from adult tissues have been considered a candidate cell type for cell-based tissue engineering and regenerative medicine. These multipotent cells have the ability to differentiate along several mesenchymal lineages and possibly along non-mesenchymal lineages. MSCs possess considerable immunosuppressive properties that can influence the surrounding tissue positively during regeneration, but perhaps negatively towards the pathogenesis of cancer and metastasis. The balance between the naïve stem state and differentiation is highly dependent on the stem cell niche. Identification of stem cell niche components has helped to elucidate the mechanisms of stem cell maintenance and differentiation. Ultimately, the fate of stem cells is dictated by their microenvironment. In this review, we describe the identification and characterization of bone marrow-derived MSCs, the properties of the bone marrow stem cell niche, and the possibility and likelihood of MSC involvement in cancer progression and metastasis.