Mesenchymal stem cells: innovative therapeutic tools for rheumatic diseases

Preconditioning influences mesenchymal stem cell properties in vitro and in vivo

Various diseases and toxic factors easily impair cellular and organic functions in mammals. Organ transplantation is used to rescue organ function, but is limited by scarce resources. Mesenchymal stem cell (MSC)-based therapy carries promising potential in regenerative medicine because of the self-renewal and multilineage potency of MSCs; however, MSCs may lose biological functions after isolation and cultivation for a long time in vitro. Moreover, after they are injected in vivo and migrate into the damaged tissues or organs, they encounter a harsh environment coupled with death signals due to the inadequate tensegrity structure between the cells and matrix. Preconditioning, genetic modification and optimization of MSC culture conditions are key strategies to improve MSC functions in vitro and in vivo, and all of these procedures will contribute to improving MSC transplantation efficacy in tissue engineering and regenerative medicine. Preconditioning with various physical, chemical and biological factors is possible to preserve the stemness of MSCs for further application in studies and clinical tests. In this review, we mainly focus on preconditioning and the corresponding mechanisms for improving MSC activities in vitro and in vivo; we provide a glimpse into the promotion of MSC-based cell therapy development for regenerative medicine. As a promising consequence, MSC transplantation can be applied for the treatment of some terminal diseases and can prolong the survival time of patients in the near future.

Bone marrow mesenchymal stem cells suppress IL-9 in adjuvant-induced arthritis

Interleukin-9 (IL-9) has been shown to be upregulated in rheumatoid arthritis (RA). The exact role of IL-9 has not yet been effectively studied. Mesenchymal stem cells (MSCs) have shown a promising immunomodulatory role towards repairing cartilage and restoring joint function. One of the key problems influencing the therapeutic efficacy of stem cell therapy is the poor cell survival following transplantation. This is attributed to oxidative and inflammatory stresses at the injured sites. Hesperidin (Hsd), a flavanone present in citrus fruits, has been studied as potential therapeutic agents that have anti-oxidant and anti-inflammatory activities. The objective of this study is to evaluate the therapeutic paracrine action of bone marrow MSCs on the IL-9 level in adjuvant-induced arthritis (AIA) and the enhancement effect of Hsd on transplanted MSCs. Articular tissue inflammation and cartilage damage were assessed by histological scoring. Antinuclear autoantibodies, tumour necrosis factor-alpha (TNF-α), IL-9, IL-4, interferon gamma (IFN-δ), and transforming growth factor-beta1 (TGF-β1), as well as malondialdehyde (MDA), glutathione (GSH), and superoxide dismutase (SOD) levels, were assessed in spleen tissue homogenates after treatment with MSCs either alone or combined with Hsd for 4 weeks in an AIA rat model. Results of this study confirmed that MSCs decreased IL-9 levels in AIA and provide novel insights into the application of Hsd on MSC-based treatments. Highlights Adjuvant-induced arthritis (AIA) is one of the most widely used models that has a great similarity to rheumatoid arthritis (RA). Few studies in recent years have estimated IL-9 in rheumatic diseases and it remains an understudied cytokine. For the first time, bone marrow mesenchymal stem cells (MSCs) therapy has a vital role in splenocytes IL-9 level and further studies are required. Combined therapy of MSCs with antioxidants as hesperidin (Hsd) can alleviate oxidative stress and enhance stem cells immunomodulatory action.

Gilz-Activin A as a Novel Signaling Axis Orchestrating Mesenchymal Stem Cell and Th17 Cell Interplay

Mesenchymal stem cells (MSC) are highly immunosuppressive cells able to reduce chronic inflammation through the active release of mediators. Recently, we showed that glucocorticoid-induced leucine zipper (Gilz) expression by MSC is involved in their therapeutic effect by promoting the generation of regulatory T cells. However, the mechanisms underlying this pivotal role of Gilz remain elusive.

Methods and Results In this study, we have uncovered evidence that Gilz modulates the phenotype and function of Th1 and Th17 cells likely by upregulating the level of Activin A and NO₂ secreted by MSC. Adoptive transfer experiments sustained this Gilz-dependent suppressive effect of MSC on Th1 and Th17 cell functions. In immunoregulatory MSC, obtained by priming with IFN-γ and TNF-α, Gilz was translocated to the nucleus and bound to the promoters of inos and Activin βA to induce their expression. The increased expression of Activin A directly impacted on Th17 cells fate by repressing their differentiation program through the activation of Smad3/2 and enhancing IL-10 production.

Conclusion Our results reveal how Gilz controls inos and Activin βA gene expression to ultimately assign immunoregulatory status to MSC able to repress the pathogenic Th17 cell differentiation program and uncover Activin A as a novel mediator of MSC in this process.

Articular and subcutaneous adipose tissues of rheumatoid arthritis patients represent equal sources of immunoregulatory mesenchymal stem cells

Adipose-derived mesenchymal stem cells (ASCs) have immunoregulatory properties, but their activity is dependent on signals provided by the local microenvironment. It is likely that highly inflammatory milieu of rheumatoid joint affects ASCs activity. To test this hypothesis, the function of rheumatoid ASCs derived from articular adipose tissue (AT-ASCs) and ASCs derived from subcutaneous adipose tissue (Sc-ASCs) has been analysed. Articular adipose tissue (infrapatellar fat pad) and subcutaneous adipose tissue (from the site of skin closure with sutures) were obtained from rheumatoid arthritis (RA) patients undergoing total knee joint replacement surgery. ASCs were isolated accordingly to the routinely applied procedure, expanded and treated or not with IFNγ and TNF (10 ng/ml). To evaluate immunomodulatory properties of AT- and Sc-ASCs, co-cultures with peripheral blood mononuclear cells (PBMCs) from healthy donors have been set. Proliferation of activated PBMCs (³H-thymidine incorporation method), secretion of IL-10 and IL-17A in co-culture supernatants (specific ELISA tests) and T regulatory FoxP3⁺ cells (Tregs) percentage have been evaluated (flow cytometry). Performed experiments demonstrated that ASCs from both sources have comparable properties. They suppress proliferation of activated PBMCs to the similar extent, induce IL-10 secretion by resting PBMCs and moderately induce generation of FoxP3⁺ Treg cells. Interestingly, both AT-ASCs and Sc-ASCs cause increase of IL-17A secretion by activated PBMCs as well as induce up-regulation of IL-6 concentration in co-culture supernatants. We demonstrated that AT-ASCs and Sc-ASCs obtained from RA patients possess similar immunomodulatory properties despite different localization and distinct cytokine milieu of tissue of origin. Our results indicate that ASCs derived from rheumatoid adipose tissues are not strongly immunosuppressive in vitro and that they may contribute to the pathogenesis of RA due to IL-17A secretion enhancement.

Polysaccharide Hydrogels Support the Long-Term Viability of Encapsulated Human Mesenchymal Stem Cells and Their Ability to Secrete Immunomodulatory Factors

While therapeutically interesting, the injection of MSCs suffers major limitations including cell death upon injection and a massive leakage outside the injection site. We proposed to entrap MSCs within spherical particles derived from alginate, as a control, or from silanized hydroxypropyl methylcellulose (Si-HPMC). We developed water in an oil dispersion method to produce small Si-HPMC particles with an average size of about 68 μm. We evidenced a faster diffusion of fluorescein isothiocyanate-dextran in Si-HPMC particles than in alginate ones. Human adipose-derived MSCs (hASC) were encapsulated either in alginate or in Si-HPMC, and the cellularized particles were cultured for up to 1 month. Both alginate and Si-HPMC particles supported cell survival, and the average number of encapsulated hASC per alginate and Si-HPMC particle (7102 and 5100, resp.) did not significantly change. The stimulation of encapsulated hASC with proinflammatory cytokines resulted in the production of IDO, PGE₂, and HGF whose concentration was always higher when cells were encapsulated in Si-HPMC particles than in alginate ones. We have demonstrated that Si-HPMC and alginate particles support hASC viability and the maintenance of their ability to secrete therapeutic factors.

* CRISPR-Based Epigenome Editing of Cytokine Receptors for the Promotion of Cell Survival and Tissue Deposition in Inflammatory Environments

Musculoskeletal diseases have been associated with inflammatory cytokine action, particularly action by TNF-α and IL-1β. These inflammatory cytokines promote apoptosis and senescence of cells in diseased tissue and extracellular matrix breakdown. Stem cell-based therapies are being considered for the treatment of musculoskeletal diseases, but the presence of these inflammatory cytokines will have similar deleterious action on therapeutic cells delivered to these environments. Methods that prevent inflammatory-induced apoptosis and proinflammatory signaling, in cell and pathway-specific manners are needed. In this study we demonstrate the use of clustered regularly interspaced short palindromic repeats (CRISPR)-based epigenome editing to alter cell response to inflammatory environments by repressing inflammatory cytokine cell receptors, specifically TNFR1 and IL1R1. We targeted CRISPR/Cas9-based repressors to TNFR1 and IL1R1 gene regulatory elements in human adipose-derived stem cells (hADSCs) and investigated the functional outcomes of repression of these genes. Efficient signaling regulation was demonstrated in engineered hADSCs, as activity of the downstream transcription factor NF-κB was significantly reduced or maintained at baseline levels in the presence of TNF-α or IL-1β. Pellet culture of undifferentiated hADSCs demonstrated improved survival in engineered hADSCs treated with TNF-α or IL-1β, while having little effect on their immunomodulatory properties. Furthermore, engineered hADSCs demonstrated improved chondrogenic differentiation capacity in the presence of TNF-α or IL-1β, as shown by superior production of glycosaminglycans in this inflammatory environment. Overall this work demonstrates a novel method for modulating cell response to inflammatory signaling that has applications in engineering cells delivered to inflammatory environments, and as a direct gene therapy to protect endogenous cells exposed to chronic inflammation, as observed in a broad spectrum of degenerative musculoskeletal pathology.

Mesenchymal Stem Cells Direct the Immunological Fate of Macrophages

Mesenchymal stem cells (MSC) are multipotent stem cells with a broad well-described immunosuppressive potential. They are able to modulate both the innate and the adaptive immune response. Particularly, MSC are able to regulate the phenotype and function of macrophages that are critical for different biological processes including wound healing, inflammation, pathogenesis of several autoimmune diseases, and tumor growth. These multifunctional roles of macrophages are due to their high plasticity, which enable them to adopt different phenotypes such as a pro-inflammatory M1 and anti-inflammatory M2 phenotype. MSC promote macrophage differentiation toward an M2-like phenotype with a high tissue remodeling potential and anti-inflammatory activity but also a pro-tumorigenic function. MSC regulatory effect on macrophages is mediated through the secretion of different immunomodulatory molecules such as PGE₂, IL1RA, and IL-6. Moreover, the presence of macrophages in damaged tissue and inflammation is essential for MSC to exert their therapeutic function. In this chapter, we discuss how the interplay between macrophages and MSC mutually modulates their phenotypes and functions, orchestrates tissue repair, and controls inflammation during autoimmunity and tumor growth.

Interleukin-3 enhances the migration of human mesenchymal stem cells by regulating expression of CXCR4

BACKGROUND

Mesenchymal stem cells (MSCs) represent an important source for cell therapy in regenerative medicine. MSCs have shown promising results for repair of damaged tissues in various degenerative diseases in animal models and also in human clinical trials. However, little is known about the factors that could enhance the migration and tissue-specific engraftment of exogenously infused MSCs for successful regenerative cell therapy. Previously, we have reported that interleukin-3 (IL-3) prevents bone and cartilage damage in animal models of rheumatoid arthritis and osteoarthritis. Also, IL-3 promotes the differentiation of human MSCs into functional osteoblasts and increases their in-vivo bone regenerative potential in immunocompromised mice. However, the role of IL-3 in migration of MSCs is not yet known. In the present study, we investigated the role of IL-3 in migration of human MSCs under both in-vitro and in-vivo conditions.

METHODS

MSCs isolated from human bone marrow, adipose and gingival tissues were used for in-vitro cell migration, motility and wound healing assays in the presence or absence of IL-3. The effect of IL-3 preconditioning on expression of chemokine receptors and integrins was examined by flow cytometry and real-time PCR. The in-vivo migration of IL-3-preconditioned MSCs was investigated using a subcutaneous matrigel-releasing stromal cell-derived factor-1 alpha (SDF-1α) model in immunocompromised mice.

RESULTS

We observed that human MSCs isolated from all three sources express IL-3 receptor-α (IL-3Rα) both at gene and protein levels. IL-3 significantly enhances in-vitro migration, motility and wound healing abilities of MSCs. Moreover, IL-3 preconditioning upregulates expression of chemokine (C-X-C motif) receptor 4 (CXCR4) on MSCs, which leads to increased migration of cells towards SDF-1α. Furthermore, CXCR4 antagonist AMD3100 decreases the migration of IL-3-treated MSCs towards SDF-1α. Importantly, IL-3 also induces in-vivo migration of MSCs towards subcutaneously implanted matrigel-releasing-SDF-1α in immunocompromised mice.

CONCLUSIONS

The present study demonstrates for the first time that IL-3 has an important role in enhancing the migration of human MSCs through regulation of the CXCR4/SDF-1α axis. These findings suggest a potential role of IL-3 in improving the efficacy of MSCs in regenerative cell therapy.

Adipose stromal cells mediated switching of the pro-inflammatory profile of M1-like macrophages is facilitated by PGE2: in vitro evaluation

OBJECTIVE

To define if adipose mesenchymal stromal cell (ASC) treatment mediated switching of the pro-inflammatory profile of M1-like macrophages as a means to develop a tailored in vitro efficacy/potency test.

DESIGN

We firstly performed immunohistochemical analysis of CD68, CD80 (M1-like) and CD206 (M2-like) macrophages in osteoarthritic (OA) synovial tissue. ASC were co-cultured in contact and in transwell with activated (GM-CSF + IFNγ)-M1 macrophages. We analyzed IL1β, TNFα, IL6, MIP1α/CCL3, S100A8, S100A9, IL10, CD163 and CD206 by qRT-PCR or immunoassays. Prostaglandin E2 (PGE2) blocking experiments were performed using PGE2 receptor antagonist.

RESULTS

In moderate grade OA synovium we did not always find a higher percentage of CD80 with respect to CD206. M1-like-activated macrophage factors IL1β, TNFα, IL6, MIP1α/CCL3, S100A8 and S100A9 were down-modulated both in contact and in transwell by ASC. However, in both systems ASC induced the typical M2-like macrophage markers IL10, CD163 and CD206. Activated-M1-like macrophages pre-treated with PGE2 receptor antagonist failed to decrease secretion of TNFα, IL6 and to increase that of IL10, CD163 and CD206 when co-cultured with ASC confirming a PGE2 specific role.

CONCLUSIONS

We demonstrated that ASC are responsible for the switching of activated-M1-like inflammatory macrophages to a M2-like phenotype, mainly through PGE2. This evidenced that activated-M1-like macrophages may represent a relevant cell model to test the efficacy/potency of ASC and suggests a specific role of ASC as important determinants in therapeutic dampening of synovial inflammation in OA.

Monitoring Notch Signaling-Associated Activation of Stem Cell Niches within Injured Dental Pulp

Dental pulp stem/progenitor cells guarantee tooth homeostasis, repair and regeneration throughout life. The decision between renewal and differentiation of these cells is influenced by physical and molecular interactions with stromal cells and extracellular matrix molecules forming the specialized microenvironment of dental pulp stem cell niches. Here we study the activation of putative pulp niches after tooth injury through the upregulation of Notch signaling pathway. Notch1, Notch2, and Notch3 molecules were used as markers of dental pulp stem/progenitor cells. Upon dental injury, Notch1 and Notch3 are detected in cells related to vascular structures suggesting a role of these proteins in the activation of specific pulpal perivascular niches. In contrast, a population of Notch2-positive cells that are actively proliferative is observed in the apical part of the pulp. Kinetics of these cells is followed up with a lipophilic DiI labeling, showing that apical pulp cells migrate toward the injury site where dynamic regenerative/repair events occur. The knowledge of the activation and regulation of dental pulp stem/progenitor cells within their niches in pathologic conditions may be helpful for the realization of innovative dental treatments in the near future.

Single-stage cell-based cartilage repair in a rabbit model: cell tracking and in vivo chondrogenesis of human umbilical cord blood-derived mesenchymal stem cells and hyaluronic acid hydrogel composite

OBJECTIVE

Human umbilical cord blood-derived mesenchymal stem cells (hUCB-MSCs) have gained popularity as a promising cell source for regenerative medicine, but limited in vivo studies have reported cartilage repair. In addition, the roles of MSCs in cartilage repair are not well-understood. The purpose of this study was to investigate the feasibility of transplanting hUCB-MSCs and hyaluronic acid (HA) hydrogel composite to repair articular cartilage defects in a rabbit model and determine whether the transplanted cells persisted or disappeared from the defect site.

DESIGN

Osteochondral defects were created in the trochlear grooves of the knees. The hUCB-MSCs and HA composite was transplanted into the defect of experimental knees. Control knees were transplanted by HA or left untreated. Animals were sacrificed at 8 and 16 weeks post-transplantation and additionally at 2 and 4 weeks to evaluate the fate of transplanted cells. The repair tissues were evaluated by gross, histological and immunohistochemical analysis.

RESULTS

Transplanting hUCB-MSCs and HA composite resulted in overall superior cartilage repair tissue with better quality than HA alone or no treatment. Cellular architecture and collagen arrangement at 16 weeks were similar to those of surrounding normal articular cartilage tissue. Histological scores also revealed that cartilage repair in experimental knees was better than that in control knees. Immunohistochemical analysis with anti-human nuclear antibody confirmed that the transplanted MSCs disappeared gradually over time.

CONCLUSION

Transplanting hUCB-MSCs and HA composite promote cartilage repair and interactions between hUCB-MSCs and host cells initiated by paracrine action may play an important role in cartilage repair.

Adipose derived stem cells for regenerative therapy in osteoarticular diseases

In the recent years, adipose derived stem cells (ASCs) led to significant findings in the field of regenerative therapy. ASCs have various biological properties and capacity as differentiation in three lineages (chondrocytes, osteocytes and adipocytes) or immunomodulation by releasing paracrine factors. Osteoarthritis (OA) is the most frequent osteoarticular disease characterized by none curative treatment. We reviewed all current data on the proof of concept of ASCs in OA pathophysiology as well as an inventory of ASC promising cell therapy in OA.

Synergistic suppression of autoimmune arthritis through concurrent treatment with tolerogenic DC and MSC

Rheumatoid arthritis (RA) is an autoimmune disease characterized by progressive immune-mediated joint deterioration. Current treatments are not antigen specific and are associated with various adverse. We have previously demonstrated that tolerogenic dendritic cells (Tol-DC) are potent antigen-specific immune regulators, which hold great promise in immunotherapy of autoimmune diseases. In this study, we aimed to develop new immunotherapy by combining Tol-DC and mesenchymal stem cells (MSC). We demonstrated that RelB gene silencing resulted in generation of Tol-DC that suppressed T cell responses and selectively promoted Treg generation. The combination of MSC synergized the tolerogenic capacity of Tol-DC in inhibition of T cell responses. In murine collagen-induced arthritis (CIA) model, we demonstrated that progression of arthritis was inhibited with administration of RelB gene-silenced Tol-DC or MSC. This therapeutic effect was remarkably enhanced with concurrent treatment of combination Tol-DC and MSC as demonstrated by improved clinical symptoms, decreased clinical scores and attenuated joint damage. These therapeutic effects were associated with suppression of CII-specific T cell responses, polarization of Th and inhibition of proinflammatory cytokines, and reduced cartilage degeneration. This study for the first time demonstrates a new approach to treat autoimmune inflammatory joint disease with concurrent treatment of RelB gene-silenced Tol-DC and MSC.

In Vivo Chondrogenesis in 3D Bioprinted Human Cell-laden Hydrogel Constructs

BACKGROUND

The three-dimensional (3D) bioprinting technology allows creation of 3D constructs in a layer-by-layer fashion utilizing biologically relevant materials such as biopolymers and cells. The aim of this study is to investigate the use of 3D bioprinting in a clinically relevant setting to evaluate the potential of this technique for in vivo chondrogenesis.

METHODS

Thirty-six nude mice (Balb-C, female) received a 5- × 5- × 1-mm piece of bioprinted cell-laden nanofibrillated cellulose/alginate construct in a subcutaneous pocket. Four groups of printed constructs were used: (1) human (male) nasal chondrocytes (hNCs), (2) human (female) bone marrow-derived mesenchymal stem cells (hBMSCs), (3) coculture of hNCs and hBMSCs in a 20/80 ratio, and (4) Cell-free scaffolds (blank). After 14, 30, and 60 days, the scaffolds were harvested for histological, immunohistochemical, and mechanical analysis.

RESULTS

The constructs had good mechanical properties and keep their structural integrity after 60 days of implantation. For both the hNC constructs and the cocultured constructs, a gradual increase of glycosaminoglycan production and hNC proliferation was observed. However, the cocultured group showed a more pronounced cell proliferation and enhanced deposition of human collagen II demonstrated by immunohistochemical analysis.

CONCLUSIONS

In vivo chondrogenesis in a 3D bioprinted human cell-laden hydrogel construct has been demonstrated. The trophic role of the hBMSCs in stimulating hNC proliferation and matrix deposition in the coculture group suggests the potential of 3D bioprinting of human cartilage for future application in reconstructive surgery.

hMSCs suppress neutrophil-dominant airway inflammation in a murine model of asthma

Although chronic eosinophilic inflammation is a common feature in patients with asthma, some patients have neutrophil-dominant inflammation, which is known to be associated with severe asthma.Human mesenchymal stem cells (hMSCs) have shown promise in treating various refractory immunological diseases. Thus, hMSCs may represent an alternative therapeutic option for asthma patients with neutrophil-dominant inflammation, in whom current treatments are ineffective. BALB/c mice exposed to ovalbumin and polyinosinic:polycytidylic acid (Poly I:C) to induce neutrophilic airway inflammation were systemically treated with hMSCs to examine whether the hMSCs can modulate neutrophilic airway inflammation. In addition, cytokine production was evaluated in co-cultures of hMSCs with either anti-CD3/CD28-stimulated peripheral blood mononuclear cells (PBMCs) obtained from asthmatic patients or cells of the human bronchial epithelial cell line BEAS-2B to assess the response to hMSC treatment. The total number of immune cells in bronchoalveolar lavage fluid (BALF) showed a dramatic decrease in hMSC-treated asthmatic mice, and, in particular, neutrophilic infiltration was significantly attenuated. This phenomenon was accompanied by reduced CXCL15 production in the BALF. BEAS-2B cells co-cultured with hMSCs showed reduced secretion of IL-8. Moreover, decreased secretion of IL-4, IL-13 and IFN-γ was observed when human PBMCs were cultured with hMSCs, whereas IL-10 production was greatly enhanced. Our data imply that hMSCs may have a role in reducing neutrophilic airway inflammation by downregulating neutrophil chemokine production and modulating T-cell responses.

Toll-like receptor 3 pre-conditioning increases the therapeutic efficacy of umbilical cord mesenchymal stromal cells in a dextran sulfate sodium-induced colitis model

BACKGROUND AIMS

Immunomodulatory properties of human umbilical cord-derived mesenchymal stromal cells (UCMSCs) can be differentially modulated by toll-like receptors (TLR) agonists. Here, the therapeutic efficacy of short TLR3 and TLR4 pre-conditioning of UCMSCs was evaluated in a dextran sulfate sodium (DSS)-induced colitis in mice. The novelty of this study is that although modulation of human MSCs activity by TLRs is not a new concept, this is the first time that short TLR pre-conditioning has been carried out in a murine inflammatory model of acute colitis.

METHODS

C57BL/6 mice were exposed to 2.5% dextran sulfate sodium (DSS) in drinking water ad libitum for 7 days. At days 1 and 3, mice were injected intraperitoneally with 1 × 10(6) UCMSCs untreated or TLR3 and TLR4 pre-conditioned UCMSCs. UCMSCs were pre-conditioned with poly(I:C) for TLR3 and LPS for TLR4 for 1 h at 37°C and 5% CO2. We evaluated clinical signs of disease and body weights daily. At the end of the experiment, colon length and histological changes were assessed.

RESULTS

poly(I:C) pre-conditioned UCMSCs significantly ameliorated the clinical and histopathological severity of DSS-induced colitis compared with UCMSCs or LPS pre-conditioned UCMSCs. In contrast, infusion of LPS pre-conditioned UCMSCs significantly increased clinical signs of disease, colon shortening and histological disease index in DSS-induced colitis.

CONCLUSIONS

These results show that short in vitro TLR3 pre-conditioning with poly(I:C) enhances the therapeutic efficacy of UCMSCs, which is a major breakthrough for developing improved treatments to patients with inflammatory bowel disease.

PPARβ/δ: A master regulator of mesenchymal stem cell functions

Peroxisome proliferator-activated receptors (PPARs) have emerged as key regulators of physiological and immunological processes. Recently, one of their members PPARβ/δ has been identified as major player in the maintenance of bone homeostasis, by promoting Wnt signalling activity in osteoblast and mesenchymal stem cells (MSC). PPARβ/δ not only controls the fate of MSC but also regulates their immunosuppressive properties by directly modulating their NF-κB activity. In this review, we discuss how the regulation of PPARβ/δ provides an innovative strategy for an optimisation of MSC-based therapy.

Differential TLR activation of murine mesenchymal stem cells generates distinct immunomodulatory effects in EAE

Background

Recently, it has been observed that mesenchymal stem cells (MSCs) can modulate their immunoregulatory properties depending on the specific in-vitro activation of different Toll-like receptors (TLR), such as TLR3 and TLR4. In the present study, we evaluated the effect of polyinosinic:polycytidylic acid (poly(I:C)) and lipopolysaccharide (LPS) pretreatment on the immunological capacity of MSCs in vitro and in vivo.

Methods

C57BL/6 bone marrow-derived MSCs were pretreated with poly(I:C) and LPS for 1 hour and their immunomodulatory capacity was evaluated. T-cell proliferation and their effect on Th1, Th17, and Treg differentiation/activation were measured. Next, we evaluated the therapeutic effect of MSCs in an experimental autoimmune encephalomyelitis (EAE) model, which was induced for 27 days with MOG_35–55 peptide following the standard protocol. Mice were subjected to a single intraperitoneal injection (2 × 10⁶ MSCs/100 μl) on day 4. Clinical score and body weight were monitored daily by blinded analysis. At day 27, mice were euthanized and draining lymph nodes were extracted for Th1, Th17, and Treg detection by flow cytometry.

Results

Pretreatment of MSCs with poly(I:C) significantly reduced the proliferation of CD3⁺ T cells as well as nitric oxide secretion, an important immunosuppressive factor. Furthermore, MSCs treated with poly(I:C) reduced the differentiation/activation of proinflammatory lymphocytes, Th1 and Th17. In contrast, MSCs pretreated with LPS increased CD3⁺ T-cell proliferation, and induced Th1 and Th17 cells, as well as the levels of proinflammatory cytokine IL-6. Finally, we observed that intraperitoneal administration of MSCs pretreated with poly(I:C) significantly reduced the severity of EAE as well as the percentages of Th1 and Th17 proinflammatory subsets, while the pretreatment of MSCs with LPS completely reversed the therapeutic immunosuppressive effect of MSCs.

Conclusions

Taken together, these data show that pretreatment of MSCs with poly(I:C) improved their immunosuppressive abilities. This may provide an opportunity to better define strategies for cell-based therapies to autoimmune diseases.

Mesenchymal Stem Cell-Derived Exosomes: New Opportunity in Cell-Free Therapy

Mesenchymal stromal/stem cells (MSCs) are involved in tissue homeostasis through direct cell-to-cell interaction, as well as secretion of soluble factors. Exosomes are the sort of soluble biological mediators that obtained from MSCs cultured media in vitro. MSC-derived exosomes (MSC-DEs) which produced under physiological or pathological conditions are central mediators of intercellular communications by conveying proteins, lipids, mRNAs, siRNA, ribosomal RNAs and miRNAs to the neighbor or distant cells. MSC-DEs have been tested in various disease models, and the results have revealed that their functions are similar to those of MSCs. They have the supportive functions in organisms such as repairing tissue damages, suppressing inflammatory responses, and modulating the immune system. MSC-DEs are of great interest in the scope of regenerative medicine because of their unique capacity to the regeneration of the damaged tissues, and the present paper aims to introduce MSC-DEs as a novel hope in cell-free therapy.

Autologous Bone Marrow-Derived Mesenchymal Stem Cells Modulate Molecular Markers of Inflammation in Dogs with Cruciate Ligament Rupture

Mid-substance rupture of the canine cranial cruciate ligament rupture (CR) and associated stifle osteoarthritis (OA) is an important veterinary health problem. CR causes stifle joint instability and contralateral CR often develops. The dog is an important model for human anterior cruciate ligament (ACL) rupture, where rupture of graft repair or the contralateral ACL is also common. This suggests that both genetic and environmental factors may increase ligament rupture risk. We investigated use of bone marrow-derived mesenchymal stem cells (BM-MSCs) to reduce systemic and stifle joint inflammatory responses in dogs with CR. Twelve dogs with unilateral CR and contralateral stable partial CR were enrolled prospectively. BM-MSCs were collected during surgical treatment of the unstable CR stifle and culture-expanded. BM-MSCs were subsequently injected at a dose of 2x10⁶ BM-MSCs/kg intravenously and 5x10⁶ BM-MSCs by intra-articular injection of the partial CR stifle. Blood (entry, 4 and 8 weeks) and stifle synovial fluid (entry and 8 weeks) were obtained after BM-MSC injection. No adverse events after BM-MSC treatment were detected. Circulating CD8⁺ T lymphocytes were lower after BM-MSC injection. Serum C-reactive protein (CRP) was decreased at 4 weeks and serum CXCL8 was increased at 8 weeks. Synovial CRP in the complete CR stifle was decreased at 8 weeks. Synovial IFNγ was also lower in both stifles after BM-MSC injection. Synovial/serum CRP ratio at diagnosis in the partial CR stifle was significantly correlated with development of a second CR. Systemic and intra-articular injection of autologous BM-MSCs in dogs with partial CR suppresses systemic and stifle joint inflammation, including CRP concentrations. Intra-articular injection of autologous BM-MSCs had profound effects on the correlation and conditional dependencies of cytokines using causal networks. Such treatment effects could ameliorate risk of a second CR by modifying the stifle joint inflammatory response associated with cranial cruciate ligament matrix degeneration or damage.

Antifibrotic, Antioxidant, and Immunomodulatory Effects of Mesenchymal Stem Cells in HOCl-Induced Systemic Sclerosis

OBJECTIVE

Systemic sclerosis (SSc) is a rare intractable disease with unmet medical need and fibrosis-related mortality. Absence of efficient treatments has prompted the development of novel therapeutic strategies, among which mesenchymal stem cells/stromal cells (MSCs) or progenitor stromal cells appear to be one of the most attractive options. The purpose of this study was to use the murine model of hypochlorite-induced SSc to investigate the systemic effects of MSCs on the main features of the diffuse form of the disease: skin and lung fibrosis, autoimmunity, and oxidative status.

METHODS

We compared the effects of different doses of MSCs (2.5 × 10(5) , 5 × 10(5) , and 10(6) ) infused at different time points. Skin thickness was assessed during the experiment. At the time of euthanasia, biologic parameters were quantified in blood and tissues (by enzyme-linked immunosorbent assay, quantitative reverse transcription-polymerase chain reaction, assessment of collagen content). Assessments of histology and immunostaining were also performed.

RESULTS

A lower expression of markers of fibrosis (Col1, Col3, Tgfb1, and aSma) was observed in both skin and lung following MSC infusion, which was consistent with histologic improvement and was inversely proportional to the injected dose. Importantly, sera from treated mice exhibited lower levels of anti-Scl-70 autoantibodies and enhanced antioxidant capacity, confirming the systemic effect of MSCs. Of interest, MSC administration was efficient in both the preventive and the curative approach. We further provide evidence that MSCs exerted an antifibrotic role by normalizing extracellular matrix remodeling parameters as well as reducing proinflammatory cytokine levels and increasing antioxidant defenses.

CONCLUSION

The results of this study demonstrate the beneficial and systemic effects of MSC administration in the HOCl murine model of diffuse SSc, which is a promising finding from a clinical perspective.

Human umbilical cord-derived mesenchymal stem cells protect against experimental colitis via CD5(+) B regulatory cells

Background

To clarify the effect of human umbilical cord-derived mesenchymal stem cell (hUC-MSCs) treatment on colitis and to explore the role of CD5⁺ B cells in MSC therapy.

Methods

The trinitrobenzenesulfonic acid (TNBS)-induced colitis mouse model was used. HUC-MSCs were transferred peritoneally. Survival rates, colitis symptoms, and macroscopic and histologic scores were evaluated. CD4⁺ T helper (Th) cell subgroups and CD5⁺ regulatory B cell (Bregs) in lymphocytes were quantitated by flow cytometry. Cytokine levels were detected by ELISA and Bio-plex. CD5⁺ B cells were isolated for in vitro co-culture and adaptive transfer.

Results

HUC-MSC treatment alleviated TNBS-induced colitis by increasing survival rates, relieving symptoms, and improving macroscopic and histologic scores. Labeled hUC-MSCs were located in the inflamed areas of colitis mice. Increases in regulatory T cells (Tregs) and CD5⁺ B cells and decreases in Th1 cells, Th17 cells, and several pro-inflammatory cytokines were observed with hUC-MSC treatment. After adaptive transfer, CD5⁺ B cells, which were located mainly in the peritoneal lavage fluid, improved TNBS-induced colitis by correcting Treg/Th1/Th17 imbalances. CD5⁺ B cells also inhibited T-cell proliferation and produced interleukin (IL)-10.

Conclusions

HUC-MSCs protected against experimental colitis by boosting the numbers of CD5⁺ B cells and IL-10-producing CD5⁺ Bregs, and correcting Treg/Th17/Th1 imbalances.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-016-0376-2) contains supplementary material, which is available to authorized users.

Therapeutic potential of mesenchymal stem cell based therapy for osteoarthritis

Osteoarthritis (OA) is a chronic degenerative disease affecting articular cartilage in joints, and it is a leading cause of disability in the United States. Current pharmacological treatment strategies are ineffective to prevent the OA progression; however, cellular therapies have the potential to regenerate the lost cartilage, combat cartilage degeneration, provide pain relief, and improve patient mobility. One of the most promising sources of cellular regenerative medicine is from mesenchymal stem cells (MSCs). MSCs can be isolated from adipose tissue, bone marrow, synovial tissue, and other sources. The aim of this review is to compile recent advancement in cellular based therapy more specifically in relation to MSCs in the treatment of osteoarthritis.

Adult Mesenchymal Stem Cells and Radiation Injury

Recent understanding of the cellular and molecular signaling activations in adult mesenchymal stem cells (MSCs) has provided new insights into their potential clinical applications, particularly for tissue repair and regeneration. This review focuses on these advances, specifically in the context of self-renewal for tissue repair and recovery after radiation injury. Thus far, MSCs have been characterized extensively and shown to be useful in mitigation and therapy for acute radiation syndrome and cognitive dysfunction. Use of MSCs for treating radiation injury alone or in combination with additional trauma is foreseeable.

IL-12p40 impairs mesenchymal stem cell-mediated bone regeneration via CD4+ T cells

Severe or prolonged inflammatory response caused by infection or biomaterials leads to delayed healing or bone repair failure. This study investigated the important roles of the proinflammatory cytokines of the interleukin-12 (IL-12) family, namely, IL-12 and IL-23, in the inflammation-mediated inhibition of bone formation in vivo. IL-12p40^-/- mice lacking IL-12 and IL-23 exhibited enhanced bone formation. IL-12 and IL-23 indirectly inhibited bone marrow mesenchymal stem cell (BMMSC) differentiation by stimulating CD4⁺ T cells to increase interferon γ (IFN-γ) and IL-17 levels. Mechanistically, IL-17 synergistically enhanced IFN-γ-induced BMMSC apoptosis. Moreover, INF-γ and IL-17 exerted proapoptotic effects by upregulating the expression levels of Fas and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), as well as by activating the caspase cascade in BMMSCs. IL-12p40 depletion in mice could promote ectopic bone formation. Thus, IL-12p40 is an attractive therapeutic target to overcome the inflammation-mediated inhibition of bone formation in vivo.

Mesenchymal stem cells as a double-edged sword in suppression or progression of solid tumor cells

Tumor cells are able to attract mesenchymal stem cells (MSCs) to primary tumor site. On the other hand, MSCs secrete various factors to attract tumor cells towards BM. In this review, in addition to assessment of MSCs function at tumor sites and their impact on growth and metastasis of tumor cells, the importance of MSC in attraction of malignant cells to BM and their involvement in drug resistance of tumor cells have also been studied. Relevant literature was identified by a PubMed search (2000-2015) of English-language literature using the terms mesenchymal stem cells, cancer cell, metastasis, and tumor microenvironment. MSCs migrate towards tumor microenvironment and are involved in both pro-tumorigenic and antitumorigenic functions. The dual function of MSCs at tumor sites is dependent upon a variety of factors, including the type and origin of MSCs, the cancer cell line under study, in vivo or in vitro conditions, the factors secreted by MSCs and interactions between MSCs, host immune cells and cancer cells. Therefore, MSCs can be regarded both as friends and enemies of cancer cells. Although the role of a number of pathways, including IL-6/STAT3 pathway, has been indicated in controlling the interaction between MSCs and tumor cells, other mechanisms by which MSCs can control the tumor cells are not clear yet. A better understanding of these mechanisms through further studies can determine the exact role of MSCs in cancer progression and identify them as important therapeutic agents or targets.

Treatment of Collagen-Induced Arthritis Using Immune Modulatory Properties of Human Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) have immune modulatory properties. We investigated the potential therapeutic effects of human bone marrow (BM)-, adipose tissue (AD)-, and cord blood (CB)-derived MSCs in an experimental animal model of rheumatoid arthritis (RA) and explored the mechanism underlying immune modulation by MSCs. We evaluated the therapeutic effect of clinically available human BM-, AD-, and CB-derived MSCs in DBA/1 mice with collagen-induced arthritis (CIA). CIA mice were injected intraperitoneally with three types of MSCs. Treatment control animals were injected with 35 mg/kg methotrexate (MTX) twice weekly. Clinical activity in CIA mice, degree of inflammation, cytokine expression in the joint, serum cytokine levels, and regulatory T cells (Tregs) were evaluated. Mice treated with human BM-, AD-, and CB-MSCs showed significant improvement in clinical joint score, comparable to MTX-treated mice. Histologic examination showed greatly reduced joint inflammation and damage in MSC-treated mice compared with untreated mice. Microcomputed tomography also showed little joint damage in the MSC-treated group. MSCs significantly decreased serum interleukin (IL)-1β, tumor necrosis factor (TNF)-α, IL-6, and interferon-γ and increased IL-10 and transforming growth factor-β levels. Tregs were increased in mice treated with MSCs compared to untreated or MTX-treated mice. Human BM-, AD-, and CB-MSCs significantly suppressed joint inflammation in CIA mice. The cells decreased proinflammatory cytokines and upregulated anti-inflammatory cytokines and induced Tregs. Therefore, our study suggests that the use of human BM-, AD-, and CB-MSCs could be an effective therapeutic approach for RA.

Mesenchymal stem cell therapy in the treatment of osteoarthritis: reparative pathways, safety and efficacy - a review

Osteoarthritis is a leading cause of pain and disability across the world. With an aging population its prevalence is likely to further increase. Current accepted medical treatment strategies are aimed at symptom control rather than disease modification. Surgical options including joint replacement are not without possible significant complications. A growing interest in the area of regenerative medicine, led by an improved understanding of the role of mesenchymal stem cells in tissue homeostasis and repair, has seen recent focused efforts to explore the potential of stem cell therapies in the active management of symptomatic osteoarthritis. Encouragingly, results of pre-clinical and clinical trials have provided initial evidence of efficacy and indicated safety in the therapeutic use of mesenchymal stem cell therapies for the treatment of knee osteoarthritis. This paper explores the pathogenesis of osteoarthritis and how mesenchymal stem cells may play a role in future management strategies of this disabling condition.

PPARβ/δ directs the therapeutic potential of mesenchymal stem cells in arthritis

OBJECTIVES

To define how peroxisome proliferator-activated receptor (PPAR) β/δ expression level in mesenchymal stem cells (MSCs) could predict and direct both their immunosuppressive and therapeutic properties. PPARβ/δ interacts with factors such as nuclear factor-kappa B (NF-κB) and regulates the expression of molecules including vascular cell adhesion molecule (VCAM)-1 and intercellular adhesion molecule (ICAM)-1. Since these molecules are critical for MSC function, we investigated the role of PPARβ/δ on MSC immunosuppressive properties.

METHODS

We either treated human MSCs (hMSCs) with the irreversible PPARβ/δ antagonist (GSK3787) or derived MSCs from mice deficient for PPARβ/δ (PPARβ/δ^-/- MSCs). We used the collagen-induced arthritis (CIA) as model of immune-mediated disorder and the MSC-immune cell coculture assays.

RESULTS

Modulation of PPARβ/δ expression in hMSCs either using GSK3787 or hMSCs from different origin reveals that MSC immunosuppressive potential is inversely correlated with Ppard expression. This was consistent with the higher capacity of PPARβ/δ^-/- MSCs to inhibit both the proliferation of T lymphocytes, in vitro, and arthritic development and progression in CIA compared with PPARβ/δ^+/+ MSCs. When primed with proinflammatory cytokines to exhibit an immunoregulatory phenotype, PPARβ/δ^-/- MSCs expressed a higher level of mediators of MSC immunosuppression including VCAM-1, ICAM-1 and nitric oxide (NO) than PPARβ/δ^+/+ MSCs. The enhanced NO₂ production by PPARβ/δ^-/- MSCs was due to the increased retention of NF-κB p65 subunit on the κB elements of the inducible nitric oxide synthase promoter resulting from PPARβ/δ silencing.

CONCLUSIONS

Our study is the first to show that the inhibition or knockdown of PPARβ/δ in MSCs primes their immunoregulatory functions. Thus, the regulation of PPARβ/δ expression provides a new strategy to generate therapeutic MSCs with a stable regulatory phenotype.

The murine Pbx1-d lupus susceptibility allele accelerates mesenchymal stem cell differentiation and impairs their immunosuppressive function

Pre–B cell leukemia homeobox 1 (Pbx1)-d is a dominant-negative splice isoform of the gene Pbx1 that corresponds to the NZM2410 lupus susceptibility locus Sle1a1. Pbx1 is required to maintain stem cell self-renewal, including that of mesenchymal stem cells (MSCs). MSCs have immunosuppressive functions that require stem cell maintenance. We tested the hypothesis that the expression of Pbx1-d favors MSC differentiation and impairs their immunosuppressive functions. We demonstrate that Sle1a1 MSCs express high levels of Pbx1-d as compared with congenic C57BL/6J (B6) MSCs. Sle1a1 MSCs grew faster and differentiated significantly more rapidly into osteoblasts than did B6 MSCs. This corresponded to a significant decrease in the expression of genes associated with stemness and an increase in the expression of genes associated with differentiation. Additionally, Sle1a1 MSCs express a gene expression profile associated with an enhanced innate immunity and inflammation. Suppression of Ig production from TLR-activated B6 B cells and IL-2 secretion from activated B6 CD4+ T cells was significantly impaired in Sle1a1 MSCs as compared with B6 MSCs. B6.Sle1a1 MSCs showed intermediate activity in suppressing lupus immunophenotypes in three different mouse models. Taken together, these data suggest that the expression of the lupus susceptibility allele Pbx1-d isoform impairs MSC functions, which may contribute to lupus pathogenesis both through a defective immunosuppression and the promotion of a proinflammatory environment.

Factors secreted from dental pulp stem cells show multifaceted benefits for treating experimental rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease characterized by synovial hyperplasia and chronic inflammation, which lead to the progressive destruction of cartilage and bone in the joints. Numerous studies have reported that administrations of various types of MSCs improve arthritis symptoms in animal models, by paracrine mechanisms. However, the therapeutic effects of the secreted factors alone, without the cell graft, have been uncertain. Here, we show that a single intravenous administration of serum-free conditioned medium (CM) from human deciduous dental pulp stem cells (SHED-CM) into anti-collagen type II antibody-induced arthritis (CAIA), a mouse model of rheumatoid arthritis (RA), markedly improved the arthritis symptoms and joint destruction. The therapeutic efficacy of SHED-CM was associated with an induction of anti-inflammatory M2 macrophages in the CAIA joints and the abrogation of RANKL expression. SHED-CM specifically depleted of an M2 macrophage inducer, the secreted ectodomain of sialic acid-binding Ig-like lectin-9 (ED-Siglec-9), exhibited a reduced ability to induce M2-related gene expression and attenuate CAIA. SHED-CM also inhibited the RANKL-induced osteoclastogenesis in vitro. Collectively, our findings suggest that SHED-CM provides multifaceted therapeutic effects for treating CAIA, including the ED-Siglec-9-dependent induction of M2 macrophage polarization and inhibition of osteoclastogenesis. Thus, SHED-CM may represent a novel anti-inflammatory and reparative therapy for RA.

Injuries to appendage extremities and digit tips: A clinical and cellular update

BACKGROUND

The regrowth of amputated appendage extremities and the distal tips of digits represent models of tissue regeneration in multiple vertebrate taxa. In humans, digit tip injuries, including traumatic amputation and crush injuries, are among the most common type of injury to the human hand. Despite clinical reports demonstrating natural regeneration of appendages in lower vertebrates and human digits, current treatment options are suboptimal, and are complicated by the anatomical complexities and functions of the different tissues within the digits.

RESULTS

In light of these challenges, we focus on recent advancements in understanding appendage regeneration from model organisms. We pay special attention to the cellular programs underlying appendage regeneration, where cumulative data from salamanders, fish, frogs, and mice indicate that regeneration occurs by the actions of lineage-restricted precursors. We focus on pathologic states and the interdependency that exists, in both humans and animal models, between the nail organ and the peripheral nerves for successful regeneration.

CONCLUSIONS

The increased understanding of regeneration in animal models may open new opportunities for basic and translational research aimed at understanding the mechanisms that support limb regeneration, as well as amelioration of limb abnormalities and pathologies.

Mesenchymal Stem Cell-Derived Interleukin 1 Receptor Antagonist Promotes Macrophage Polarization and Inhibits B Cell Differentiation

The role of interleukin 1 receptor antagonist (IL1RA) in mediating the immunosuppressive effect of mesenchymal stem/stromal cells (MSCs) has been reported in several studies. However, how MSC-derived IL1RA influences the host response has not been clearly investigated. We therefore derived MSCs from the bone marrow of IL1RA knockout mice and evaluated their immunosuppressive effect on different immune cell subsets. IL1RA deficient (IL1RA(-/-) ) or wild type (wt) MSCs inhibited to the same extend the proliferation of T lymphocytes. On the contrary, IL1RA(-/-) MSCs were less effective than wt MSCs to induce in vitro the macrophage polarization from M1 to M2 phenotype secreting IL10 and exerting a suppressive effect on CD4(+) T cells. Moreover compared with wt MSCs, IL1RA(-/-) MSCs did not efficiently support the survival of quiescent B lymphocytes and block their differentiation toward CD19(+) CD138(+) plasmablasts secreting IgG antibodies. The effectiveness of IL1RA secreted by MSCs in controlling inflammation was further shown in vivo using the collagen-induced arthritis murine model. MSCs lacking IL1RA expression were unable to protect mice from arthritic progression and even worsened clinical signs, as shown by higher arthritic score and incidence than control arthritic mice. IL1RA(-/-) MSCs were not able to decrease the percentage of Th17 lymphocytes and increase the percentage of Treg cells as well as decreasing the differentiation of B cells toward plasmablasts. Altogether, our results provide evidence of the key role of IL1RA secreted by MSCs to both control the polarization of macrophages toward a M2 phenotype and inhibit B cell differentiation in vivo.

Adipose-derived mesenchymal stem cells from infrapatellar fat pad of patients with rheumatoid arthritis and osteoarthritis have comparable immunomodulatory properties

Adipose-derived mesenchymal stem cells (ASCs) possess immunosuppressive properties, but their activity is dependent on stimuli provided by local environment. It is possible that proinflammatory milieu of rheumatoid joint affects ASCs function. To verify this hypothesis, rheumatoid ASCs (RA-ASCs) and osteoarthritic ASCs (OA-ASCs) derived from infrapatellar fat pad (IPFP) of the knee joint have been compared. RA- and OA-ASCs isolated from patients were cultured in vitro. Their secretory and proliferative activity was measured. Peripheral blood mononuclear cells (PBMCs) from healthy donors were co-cultured with ASCs. Then, PBMCs proliferation was measured by (3)H-thymidine incorporation method, cytokines secretion by immunoassays, T cells activation and regulatory T cells (Tregs) percentage - by flow cytometry. RA- and OA-ASCs properties in vitro were comparable, however, some differences in secretory activity occurred. RA- and OA-ASCs inhibited PBMCs proliferation and induced interleukin 10 production but up-regulated interleukin 17 A secretion and failed to limit release of other proinflammatory mediators (tumor necrosis factor [TNF], interferon γ [IFNγ], CCL5) by PBMCs. RA- and OA-ASCs did not suppress activation markers expression on T cells and did not trigger Tregs expansion. The present study shows that IPFP-ASCs from RA and OA patients have comparable functions in vitro. Their immunosuppressive activity seems to be impaired comparing to available data.

Effect of bone marrow-derived stem cells on chondrocytes from patients with osteoarthritis

Increasing numbers of individuals are suffering from osteoarthritis every year, and the directed intra-articular injection of bone marrow stem cells has provided a promising treatment strategy for osteoarthritis. Although a number of studies have demonstrated that intra-articular injection of bone marrow stem cells produced desirable results, the mechanism underlying this effect has not been elucidated. In the current study, the effect of bone marrow stem cells on chondrocytes from patients with osteoarthritis was observed in a co-culture system. Human chondrocytes were obtained from patients with osteoarthritis who underwent surgical procedures and bone marrow stem cells were obtained from bone marrow aspirates, and then the chondrocytes were then cultured alone or cocultured with bone marrow stem cells in 0.4-µm Transwell inserts. The differentiation and biological activity of chondrocytes in the culture system were measured, and the inflammatory factors and OA-associated markers were also measured. The results indicated that coculture with human bone marrow stem cells increases cell proliferation of chondrocytes and inhibits inflammatory activity in osteoarthritis.

Lack of anti-inflammatory and anti-catabolic effects on basal inflamed osteoarthritic chondrocytes or synoviocytes by adipose stem cell-conditioned medium

OBJECTIVE

To define whether good manufacturing practice (GMP)-clinical grade adipose stem cell (ASC)-derived conditioned medium (CM) is as effective as GMP-ASC in modulating inflammatory and catabolic factors released by both osteoarthritis (OA) chondrocytes or synoviocytes.

METHODS

OA chondrocytes and synoviocytes were treated with ASC-CM or co-cultured with ASC. Inflammatory factors (IL6, CXCL1/GROα,CXCL8/IL8, CCL2/MCP-1, CCL3/MIP-1α and CCL5/RANTES) and proteinases, such as metalloproteinase (MMP13), a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS4, ADAMTS5) and their tissue metalloproteinase inhibitors (TIMP1, TIMP3) were evaluated by qRT-PCR or immunoassays. The involvement of prostaglandin E2 (PGE2) was also analyzed.

RESULTS

Most ASC-CM ratios tested did not decrease IL6, CCL2/MCP-1, CCL3/MIP1-α, CCL5/RANTES on basal inflamed chondrocytes or synoviocytes in contrast to what we found using ASC in co-culture. CXCL8/IL8 and CXCL1/GROα were not decreased by ASC-CM on synoviocytes but were only partially reduced on chondrocytes. Moreover, ASC-CM was less efficient both on basal inflamed OA chondrocytes and synoviocytes in reducing proteinases, such as MMP13, ADAMTS4, ADAMTS5 and increasing TIMP1 and TIMP3 compared to ASC in co-culture. The different ratios of ASC-CM contain lower amounts of PGE2 which were not sufficient to reduce inflammatory factors.

CONCLUSIONS

These data show that ASC-CM has a limited ability to decrease inflammatory and proteinases factors produced by OA chondrocytes or synoviocytes. ASC-CM is not sufficient to recapitulate the beneficial effect demonstrated using ASC in co-culture with inflamed OA chondrocytes and synoviocytes and shows that their use in clinical trials is fundamental to counteract OA progression.

Mesenchymal stem cells for the management of inflammation in osteoarthritis: state of the art and perspectives

Osteoarthritis (OA) is the most common form of degenerative arthritis, mainly characterized by the degradation of articular cartilage and associated with subchondral bone lesions. Novel therapeutic approaches for OA include cell-based therapies that have become thriving areas of research and development. In this context, mesenchymal stem or stromal cells (MSCs) have gained much interest based on their trophic and immunomodulatory properties that can help tissue repair/regeneration. The present review article discusses the interest of using MSCs in cell-therapy approaches with a focus on the mechanisms by which MSCs might exhibit a therapeutic potential in OA. Special attention is given to the anti-inflammatory function of MSCs and on miRNA modulation in OA for possible future innovative strategies. The paper also presents the current data on the undergoing MSCs-based clinical trials in OA.

Engraftability of Murine Bone Marrow-Derived Multipotent Mesenchymal Stem Cell Subpopulations in the Tissues of Developing Mice following Systemic Transplantation

INTRODUCTION

Cell therapies for generalized musculoskeletal diseases would require distribution of cells to all the skeletal tissues; however, there are controversies regarding the transplantability of multipotent mesenchymal stems cells (MSCs). We generated single-cell subpopulations of MSCs from murine bone marrow and assessed them for differences in trafficking through the circulatory system and engraftment in bone and other tissues.

MATERIALS AND METHODS

Seven single-cell clonal subpopulations were generated by serial dilution of GFP-marked MSCs isolated from bone marrow. The subpopulations were examined for putative MSC surface marker expression, in vitro differentiation toward osteogenic and adipogenic lineages, migration and engraftment in different tissues following intravenous delivery in normal, sublethally irradiated neonatal mice.

RESULTS

The surface marker expression profile revealed notable differences among clonal cells, specifically CD44 and CD105. All the cell subpopulations differentiated toward osteogenic and adipogenic lineages, with some committed to only one or the other. Two clones enriched in CXCR4 expression were highly efficient in migrating and engrafting in skeletal tissue including bone; this confirmed the role of this chemokine in cell migration. Donor cells retrieved from various tissues displayed different morphologies and potential differentiation into tissue cell type of engraftment, suggesting modification by the tissues in which the donor cells engrafted.

CONCLUSION

We have reported that, within bone marrow, there are heterogeneous subpopulations of MSCs that may differ in their ability to migrate in the circulatory system and engraft in different tissues.

Therapeutic effects of neuropeptide substance P coupled with self-assembled peptide nanofibers on the progression of osteoarthritis in a rat model

Osteoarthritis (OA) is a progressively degenerative disease that is accompanied by articular cartilage deterioration, sclerosis of the underlying bone and ultimately joint destruction. Although therapeutic medicine and surgical treatment are done to alleviate the symptoms of OA, it is difficult to restore normal cartilage function. Mesenchymal stem cell (MSC) transplantation is one of the therapeutic trials for treating OA due to its potential, and many researchers have recently reported on the effects of MSCs associated with OA therapy. However, cell transplantation has limitations including low stem cell survival rates, limited stem cell sources and long-term ex vivo culturing. In this study, we evaluated the efficacy of neuropeptide substance P coupled with self-assembled peptide hydrogels in a rat knee model to prevent OA by mobilizing endogenous MSCs to the defect site. To assess the effect of the optimal concentration of SP, varying concentrations of bioactive peptides (substance P (SP) with self-assembled peptide (SAP)) were used to treat OA. OA was induced by unilateral anterior cruciate and medial collateral ligament transection of the knee joints. Forty rats were randomly allocated into 5 groups: SAP-0.5SP (17.5 μg of SP), SAP-SP group (35 μg of SP), SAP-2SP group (70 μg of SP), SAP-SP-MSC group, and control group. At 2 weeks post-surgical induction of OA, each mixture was injected into the joint cavity of the left knee. Histologic examination, immunofluorescence staining, quantitative real time-polymerase chain reaction and micro-computed tomography analysis were done at 6 weeks post-surgical induction. As shown by our results, the SAP-SP hydrogel accelerated tissue regeneration by anti-inflammatory modulation shown by an anti-inflammation test using dot-blot in vitro. Additionally, the treatment of OA in the SAP-SP group showed markedly improved cartilage regeneration through the recruitment of MSCs. Thus, these cells could be infiltrating into the defect site for the regeneration of OA defects. In addition, from the behavioral studies on the rats, the number of rears significantly increased 2 and 4 weeks post-injection in all the groups. Our results show that bioactive peptides may have clinical potential for inhibiting the progression of OA as well as its treatment by recruiting autologous stem cells without cell transplantation.

Single-Cell RNA-Seq of Bone Marrow-Derived Mesenchymal Stem Cells Reveals Unique Profiles of Lineage Priming

The plasticity and immunomodulatory capacity of mesenchymal stem cells (MSCs) have spurred clinical use in recent years. However, clinical outcomes vary and many ascribe inconsistency to the tissue source of MSCs. Yet unconsidered is the extent of heterogeneity of individual MSCs from a given tissue source with respect to differentiation potential and immune regulatory function. Here we use single-cell RNA-seq to assess the transcriptional diversity of murine mesenchymal stem cells derived from bone marrow. We found genes associated with MSC multipotency were expressed at a high level and with consistency between individual cells. However, genes associated with osteogenic, chondrogenic, adipogenic, neurogenic and vascular smooth muscle differentiation were expressed at widely varying levels between individual cells. Further, certain genes associated with immunomodulation were also inconsistent between individual cells. Differences could not be ascribed to cycles of proliferation, culture bias or other cellular process, which might alter transcript expression in a regular or cyclic pattern. These results support and extend the concept of lineage priming of MSCs and emphasize caution for in vivo or clinical use of MSCs, even when immunomodulation is the goal, since multiple mesodermal (and even perhaps ectodermal) outcomes are a possibility. Purification might enable shifting of the probability of a certain outcome, but is unlikely to remove multilineage potential altogether.

Glucocorticoid-induced leucine zipper governs the therapeutic potential of mesenchymal stem cells by inducing a switch from pathogenic to regulatory Th17 cells in a mouse model of collagen-induced arthritis

OBJECTIVE

Mesenchymal stem cells (MSCs) are potent immunosuppressive cells that have shown promise in the treatment of rheumatoid arthritis (RA). Deciphering the intrinsic characteristics of MSCs that correlate with their biologic activity will facilitate their clinical use. Recently, the role of glucocorticoid-induced leucine zipper (GILZ) in the development of RA has been documented. The aim of this study was to evaluate whether GILZ expression by MSCs may contribute to their therapeutic effect.

METHODS

MSCs were isolated from GILZ-deficient (GILZ(-/-) ) mice and wild-type mice. MSCs (1 × 10(6) cells) were injected twice via the tail vein into mice with collagen-induced arthritis (CIA).

RESULTS

In vitro, we showed that GILZ is a key factor involved in the immunosuppressive potential of MSCs. MSCs derived from GILZ(-/-) mice did not suppress the proliferation of CD4+ T cells and were less efficient than MSCs derived from WT mice in altering Th17 cell polarization. Thus, we investigated the role of GILZ in an experimental model of arthritis and demonstrated that although WT MSCs significantly reduced paw swelling in arthritic mice, GILZ(-/-) MSCs did not. Moreover, the magnitude of the effects of GILZ(-/-) MSCs on Th17 cell frequency was significantly lower than that of WT MSCs. The therapeutic effect of MSCs correlated with the generation of Treg cells bearing the CD4 + RORγt+IL-17(low) IL-10+ signature, and Th17 cell polarization was GILZ dependent.

CONCLUSION

This study demonstrates that GILZ has an essential role in the therapeutic effectiveness of MSCs in arthritis by favoring Th17 cell polarization toward a regulatory phenotype. Therefore, potentiation of GILZ expression in MSCs could represent a means to enhance their therapeutic effect in autoimmune diseases.

Cartilage regeneration for treatment of osteoarthritis: a paradigm for nonsurgical intervention

Osteoarthritis (OA) is associated with articular cartilage abnormalities and affects people of older age: preventative or therapeutic treatment measures for OA and related articular cartilage disorders remain challenging. In this perspective review, we have integrated multiple biological, morphological, developmental, stem cell and homeostasis concepts of articular cartilage to develop a paradigm for cartilage regeneration. OA is conceptually defined as an injury of cartilage that initiates chondrocyte activation, expression of proteases and growth factor release from the matrix. This regenerative process results in the local activation of inflammatory response genes in cartilage without migration of inflammatory cells or angiogenesis. The end results are catabolic and anabolic responses, and it is the balance between these two outcomes that controls remodelling of the matrix and regeneration. A tantalizing clinical clue for cartilage regrowth in OA joints has been observed in surgically created joint distraction. We hypothesize that cartilage growth in these distracted joints may have a biological connection with the size of organs and regeneration. Therefore we propose a novel, practical and nonsurgical intervention to validate the role of distraction in cartilage regeneration in OA. The approach permits normal wake-up activity while during sleep; the index knee is subjected to distraction with a pull traction device. Comparison of follow-up magnetic resonance imaging (MRI) at 3 and 6 months of therapy to those taken before therapy will provide much-needed objective evidence for the use of this mode of therapy for OA. We suggest that the paradigm presented here merits investigation for treatment of OA in knee joints.

Mesenchymal stem cells are resistant to carbon ion radiotherapy

Mesenchymal stem cells (MSCs) participate in regeneration of tissues damaged by ionizing radiation. However, radiation can damage MSCs themselves. Here we show that cellular morphology, adhesion and migration abilities were not measurably altered by photon or carbon ion irradiation. The potential for differentiation was unaffected by either form of radiation, and established MSC surface markers were found to be stably expressed irrespective of radiation treatment. MSCs were able to efficiently repair DNA double strand breaks induced by both high-dose photon and carbon ion radiation. We have shown for the first time that MSCs are relatively resistant to therapeutic carbon ion radiotherapy. Additionally, this form of radiation did not markedly alter the defining stem cell properties or the expression of established surface markers in MSCs.

Mesenchymal stromal cells and rheumatic diseases: new tools from pathogenesis to regenerative therapies

In recent years, mesenchymal stromal cells (MSCs) have been largely investigated and tested as a new therapeutic tool for several clinical applications, including the treatment of different rheumatic diseases. MSCs are responsible for the normal turnover and maintenance of adult mesenchymal tissues as the result of their multipotent differentiation abilities and their secretion of a variety of cytokines and growth factors. Although initially derived from bone marrow, MSCs are present in many different tissues such as many peri-articular tissues. MSCs may exert immune-modulatory properties, modulating different immune cells in both in vitro and in vivo models, and they are considered immune-privileged cells. At present, these capacities are considered the most intriguing aspect of their biology, introducing the possibility that these cells may be used as effective therapy in autoimmune diseases. Therefore, stem cell therapies may represent an innovative approach for the treatment of rheumatic diseases, especially for the forms that are not responsive to standard treatments or alternatively still lacking a definite therapy. At present, although the data from scientific literature appear to suggest that such treatments might be more effective whether administered as soon as possible, the use of MSCs in clinical practice is likely to be restricted to patients with a long history of a severe refractory disease. Further results from larger clinical trials are needed to corroborate preclinical findings and human non-controlled studies, and advancement in the knowledge of MSCs might provide information about the therapeutic role of these cells in the treatment of many rheumatic diseases.

Cell adhesion and long-term survival of transplanted mesenchymal stem cells: a prerequisite for cell therapy

The literature provides abundant evidence that mesenchymal stem cells (MSCs) are an attractive resource for therapeutics and have beneficial effects in regenerating injured tissues due to their self-renewal ability and broad differentiation potential. Although the therapeutic potential of MSCs has been proven in both preclinical and clinical studies, several questions have not yet been addressed. A major limitation to the use of MSCs in clinical applications is their poor viability at the site of injury due to the harsh microenvironment and to anoikis driven by the loss of cell adhesion. To improve the survival of the transplanted MSCs, strategies to regulate apoptotic signaling and enhance cell adhesion have been developed, such as pretreatment with cytokines, growth factors, and antiapoptotic molecules, genetic modifications, and hypoxic preconditioning. More appropriate animal models and a greater understanding of the therapeutic mechanisms of MSCs will be required for their successful clinical application. Nevertheless, the development of stem cell therapies using MSCs has the potential to treat degenerative diseases. This review discusses various approaches to improving MSC survival by inhibiting anoikis.

Survival and biodistribution of xenogenic adipose mesenchymal stem cells is not affected by the degree of inflammation in arthritis

Background

Application of mesenchymal stem/stromal cells (MSCs) in treating different disorders, in particular osteo-articular diseases, is currently under investigation. We have already documented the safety of administrating human adipose tissue-derived stromal MSCs (hASCs) in immunodeficient mice. In the present study, we investigated whether the persistence of MSC is affected by the degree of inflammation and related to the therapeutic effect in two inflammatory models of arthritis.

Methodology/Principal Findings

We used C57BL/6 or DBA/1 mice to develop collagenase-induced osteoarthritis (CIOA) or collagen-induced arthritis (CIA), respectively. Normal and diseased mice were administered 2.5×10⁵ hASCs in the knee joints (IA) or 10⁶ in the tail vein (IV). For CIA, clinical scores were monitored during the time course of the disease while for CIOA, OA scores were assessed by histology at euthanasia. Thirteen tissues were recovered at different time points and processed for real-time PCR and Alu sequence detection. Immunological analyses were performed at euthanasia. After IV infusion, no significant difference in the percentage of hASCs was quantified in the lungs of normal and CIA mice at day 1 while no cell was detected at day 10 taking into account the sensitivity of the assay, indicating that a high level of inflammation did not affect the persistence of cells. In CIOA mice, we reported the therapeutic efficacy of hASCs at reducing OA clinical scores at day 42 when hASCs were not detected in the joints. However, the percentage and distribution of hASCs were similar in osteoarthritic and normal mice at day 1 and 10 after implantation indicating that moderate inflammation does not alter hASC persistence in vivo.

Conclusions/Significance

While inflammatory signals are required for the immunosuppressive function of MSCs, they do not enhance their capacity to survive in vivo, as evaluated in two xenogeneic inflammatory pre-clinical models of arthritis.