Interleukin‐1β induces differentiation of human mesenchymal stem cells into osteoblasts via the Wnt‐5a/receptor tyrosine kinase–like orphan receptor 2 pathway

Objective

Mesenchymal stem cells (MSCs) are considered to be a novel tool for the treatment of rheumatoid arthritis (RA) because of their multipotency to differentiate into osteoblasts and chondrocytes, their immunosuppressive effects, and availability. The aim of this study was to assess the mechanisms of human MSC differentiation into osteoblasts under inflammatory conditions.

Methods

Human MSCs were cultured in commercialized osteogenic induction medium with inflammatory cytokines for up to 10 days. Osteoblast differentiation was detected by alkaline phosphatase staining and messenger RNA (mRNA) expression of multiple osteoblast markers. Mineralization was assessed by alizarin red S staining.

Results

Among the various cytokines tested, interleukin‐1β (IL‐1β) induced differentiation of human MSCs into osteoblasts, which was confirmed by alkaline phosphatase activity, expression of RUNX2 mRNA, and strong alizarin red S staining. Among various molecules of the Wnt family, Wnt‐5a and receptor tyrosine kinase–like orphan receptor 2 (Ror2), a major receptor of Wnt‐5a, were significantly induced in human MSCs by IL‐1β. Silencing of either WNT5A or ROR2 by small interfering RNA with 2 different sequences reduced alkaline phosphatase activity, RUNX2 expression, and alizarin red S staining of human MSCs induced by IL‐1β.

Conclusion

IL‐1β effectively and rapidly induced human MSC differentiation into osteoblasts and mineralization, mainly through the noncanonical Wnt‐5a/Ror2 pathway. These results suggest potential benefits of IL‐1β–treated human MSCs in the treatment of damaged bone as well as in the induction of self‐renewal and self‐repair of damaged tissue, including osseous tissue.

     

Characterization of the human nucleus pulposus cell phenotype and evaluation of novel marker gene expression to define adult stem cell differentiation

Objective

Development of stem cell therapies for regenerating the nucleus pulposus (NP) are hindered by the lack of specific markers by which to distinguish NP cells from articular chondrocytes (ACs). The purpose of this study was to define the phenotype profile of human NP cells using gene expression profiling and to assess whether the identified markers could distinguish mesenchymal stem cell (MSC) differentiation to a correct NP cell phenotype.

Methods

Affymetrix MicroArray analyses were conducted on human NP cells and ACs, and differential expression levels for several positive (NP) and negative (AC) marker genes were validated by real‐time quantitative polymerase chain reaction (PCR) analysis. Novel marker gene and protein expression was also assessed in human bone marrow–derived MSCs (BM‐MSCs) and adipose tissue–derived MSCs (AD‐MSCs) following differentiation in type I collagen gels.

Results

Analysis identified 12 NP‐positive and 36‐negative (AC) marker genes that were differentially expressed ≥20‐fold, and for a subset of them (NP‐positive genes PAX1, FOXF1, HBB, CA12, and OVOS2; AC‐positive genes GDF10, CYTL1, IBSP, and FBLN1), differential expression was confirmed by real‐time quantitative PCR. Differentiated BM‐MSCs and AD‐MSCs demonstrated significant increases in the novel NP markers PAX1 and FOXF1. AD‐MSCs lacked expression of the AC markers IBSP and FBLN1, whereas BM‐MSCs lacked expression of the AC marker IBSP but expressed FBLN1.

Conclusion

This study is the first to use gene expression profiling to identify the human NP cell phenotype. Importantly, these markers can be used to determine the in vitro differentiation of MSCs to an NP‐like, rather than an AC‐like, phenotype. Interestingly, these results suggest that AD‐MSCs may be a more appropriate cell type than BM‐MSCs for use in engineering intervertebral disc tissue.

     

Large‐scale extraction and characterization of CD271+ multipotential stromal cells from trabecular bone in health and osteoarthritis: Implications for bone regeneration strategies based on uncultured or minimally cultured multipotential stromal cells

Objective

To test the hypothesis that CD45^lowCD271+ bone marrow multipotential stromal cells (MSCs) are abundant in the trabecular bone niche and to explore their functional “fitness” in health and osteoarthritis (OA).

Methods

Following enzymatic extraction, MSC release was evaluated using colony‐forming unit–fibroblast (CFU‐F) and colony‐forming unit–osteoblast assays, flow cytometry, and confocal microscopy. CD45^lowCD271+ cells isolated by fluorescence‐activated cell sorting were enumerated and expanded under standard and clonal conditions. Their proliferative and osteogenic potencies were assessed in relation to donor age and compared with those of aspirated CD45^lowCD271+ cells. In vitro and in vivo MSC “aging” was measured using quantitative polymerase chain reaction–based telomere length analysis, and standard differentiation assays were utilized to demonstrate multipotentiality.

Results

Cellular isolates from trabecular bone cavities contained ∼65‐fold more CD45^lowCD271+ cells compared with aspirates (P < 0.0001) (median 1.89% [n = 39] and 0.029% [n = 46], respectively), concordant with increased CFU‐F release. Aspirated and enzymatically released CD45^lowCD271+ cells had identical MSC phenotypes (∼100% CD73+CD105+CD13+, ∼50–60% CD146+CD106+CD166+) and contained large proportions of highly clonogenic multipotential cells. In vitro osteogenic potency of freshly isolated CD45^lowCD271+ cells was comparable with, and often above, that of early‐passage MSCs (8–14%). Their frequency and in vivo telomere status in OA bone were similar to those in bone from age‐matched controls.

Conclusion

Our findings show that CD45^lowCD271+ MSCs are abundant in the trabecular bone cavity and indistinguishable from aspirated CD45^lowCD271+ MSCs. In OA they display aging‐related loss of proliferation but no gross osteogenic abnormality. These findings offer new opportunities for direct study of MSCs in musculoskeletal diseases without the requirement for culture expansion. They are also relevant for direct therapeutic exploitation of prospectively isolated, minimally cultured MSCs in trauma and OA.

     

Osteoarthritic chondrocyte–secreted morphogens induce chondrogenic differentiation of human mesenchymal stem cells

Objective

The potential of stem cells to repair compromised cartilage tissue, such as in osteoarthritis (OA), depends strongly on how transplanted cells respond to factors secreted from the residing OA chondrocytes. This study was undertaken to determine the effect of morphogenetic signals from OA chondrocytes on chondrogenic differentiation of human mesenchymal stem cells (MSCs).

Methods

The effect of OA chondrocyte–secreted morphogens on chondrogenic differentiation of human MSCs was evaluated using a coculture system involving both primary and passaged OA chondrocytes. The findings were compared against findings for human MSCs cultured in OA chondrocyte–conditioned medium. Gene expression analysis, biochemical assays, and immunofluorescence staining were used to characterize the chondrogenic differentiation of human MSCs. Mass spectrometry analysis was used to identify the soluble factors. Numerical analysis was carried out to model the concentration profile of soluble factors within the human MSC–laden hydrogels.

Results

The human MSCs cocultured with primary OA chondrocytes underwent chondrogenic differentiation even in the absence of growth factors; however, the same effect could not be mimicked using OA chondrocyte–conditioned medium or expanded cells. Additionally, the cocultured environment down‐regulated hypertrophic differentiation of human MSCs. Mass spectrometry analysis demonstrated cell–cell communication and chondrocyte phenotype–dependent effects on cell‐secreted morphogens.

Conclusion

The experimental findings, along with the results of the numerical analysis, suggest a crucial role of soluble morphogens and their local concentrations in the differentiation pattern of human MSCs in a 3‐dimensional environment. The concept of using a small number of chondrocytes to promote chondrogenic differentiation of human MSCs while preventing their hypertrophic differentiation could be of great importance in formulating effective stem cell–based cartilage repair.

     

Changes in surface markers of human mesenchymal stem cells during the chondrogenic differentiation and dedifferentiation processes in vitro

Objective

To investigate surface markers showing specific changes during the chondrogenic differentiation and dedifferentiation of human mesenchymal stem cells (MSCs).

Methods

Human MSCs from adult bone marrow were subjected to chondrogenic differentiation in 3‐dimensional (3‐D) alginate culture with or without transforming growth factor β3 (TGFβ3) for 2 weeks, followed by dedifferentiation in monolayer for 1 week. Surface antigens were selected from those previously reported to show changes in expression during dedifferentiation of human articular chondrocytes (HACs).

Results

Flow cytometry was used to identify 3 groups of surface antigens with differential expression patterns that were quite different from those previously reported on HACs. Two groups of antigens were expressed at high levels on human MSCs. The expression of the first group of antigens (CD44, CD58, CD81, CD90, CD105, and CD166) was decreased reversibly by the 3‐D alginate culture and irreversibly in the presence of TGFβ3, except for CD81, which showed reversible changes regardless of TGFβ3. The expression of the second group of antigens (CD49c, CD49e, and CD151) was decreased during chondrogenic differentiation only in the presence of TGFβ3. During all experimental stages, the expression of the third group of antigens (CD14, CD26, CD49f, CD54, CD106, CD119, and CD140a) was maintained at low levels (expressed on <30% of cells), although with some fluctuations.

Conclusion

We speculate that the second group of surface antigens could be negative markers for chondrogenic differentiation of human MSCs.

     

Cell therapy using allogeneic bone marrow mesenchymal stem cells prevents tissue damage in collagen‐induced arthritis

Objective

Mesenchymal stem cells (MSCs) are precursors of tissue of mesenchymal origin, but they also have the capacity to regulate the immune response by suppressing T and B lymphocyte proliferation in a non–major histocompatibility complex–restricted manner. Use of MSCs as immunosuppressant agents in autoimmune diseases has been proposed and successfully tested in animal models. We explored the feasibility of using allogeneic MSCs as therapy for collagen‐induced arthritis, a mouse model for human rheumatoid arthritis.

Methods

DBA/1 mice were immunized with type II collagen in Freund's complete adjuvant, and some of the animals received an intraperitoneal injection of allogeneic MSCs.

Results

A single injection of MSCs prevented the occurrence of severe, irreversible damage to bone and cartilage. MSCs induced hyporesponsiveness of T lymphocytes as evidenced by a reduction in active proliferation, and modulated the expression of inflammatory cytokines. In particular, the serum concentration of tumor necrosis factor α was significantly decreased. MSCs exerted their immunomodulatory function by educating antigen‐specific Tregs.

Conclusion

Our results suggest an effective new therapeutic approach to target the pathogenic mechanism of autoimmune arthritis using allogeneic MSCs. However, further studies are required before these results can be translated to clinical settings.

     

Prevention of glucocorticoid‐induced bone loss in mice by inhibition of RANKL

Objective

RANKL has been implicated in the pathogenesis of glucocorticoid‐induced osteoporosis. This study was undertaken to evaluate the efficacy of denosumab, a neutralizing monoclonal antibody against human RANKL (hRANKL), in a murine model of glucocorticoid‐induced osteoporosis.

Methods

Eight‐month‐old male homozygous hRANKL‐knockin mice expressing a chimeric RANKL protein with a humanized exon 5 received 2.1 mg/kg of prednisolone or placebo daily over 4 weeks via subcutaneous slow‐release pellets and were additionally treated with phosphate buffered saline or denosumab (10 mg/kg subcutaneously twice weekly). Two groups of wild‐type mice were also treated with either prednisolone or vehicle.

Results

The 4‐week prednisolone treatment induced loss of vertebral and femoral volumetric bone mineral density in the hRANKL‐knockin mice. Glucocorticoid‐induced bone loss was associated with suppressed vertebral bone formation and increased bone resorption, as evidenced by increases in the number of tartrate‐resistant acid phosphatase (TRAP)–positive osteoclasts, TRAP‐5b protein in bone extracts, serum levels of TRAP‐5b, and urinary excretion of deoxypyridinoline. Denosumab prevented prednisolone‐induced bone loss by a pronounced antiresorptive effect. Biomechanical compression tests of lumbar vertebrae revealed a detrimental effect of prednisolone on bone strength that was prevented by denosumab.

Conclusion

Our findings indicate that RANKL inhibition by denosumab prevents glucocorticoid‐induced loss of bone mass and strength in hRANKL‐knockin mice.

     

The antirheumatic drug leflunomide inhibits osteoclastogenesis by interfering with receptor activator of NF‐κB ligand–stimulated induction of nuclear factor of activated T cells c1

Objective

Suppression of bone destruction is required as part of an effective therapeutic strategy for autoimmune arthritis. Although numerous antirheumatic drugs are in clinical use, little is known about whether they inhibit bone destruction by acting on activated T cells or other cell types, such as bone‐resorbing osteoclasts. This study was undertaken to determine whether leflunomide has a direct action on the osteoclast lineage and to gain insights into the molecular basis for the bone‐protective effect of leflunomide.

Methods

The direct effect of leflunomide on osteoclast differentiation was investigated using an in vitro culture system of bone marrow monocyte/macrophages stimulated with receptor activator of NF‐κB ligand (RANKL) and macrophage colony‐stimulating factor. The molecular mechanism of the inhibition was analyzed by genome‐wide screening. The T cell–independent effect of leflunomide was examined in rag‐2^−/− mice.

Results

Leflunomide blocked de novo pyrimidine synthesis and RANKL‐induced calcium signaling in osteoclast precursor cells in vitro; hence, the induction of nuclear factor of activated T cells c1 (NF‐ATc1) was strongly inhibited. The inhibition of this pathway is central to the action of leflunomide, since the inhibition was overcome by ectopic expression of NF‐ATc1 in the precursor cells. Leflunomide suppressed endotoxin‐induced inflammatory bone destruction even in rag‐2^−/− mice.

Conclusion

Leflunomide has a direct inhibitory effect on RANKL‐mediated osteoclast differentiation by inhibiting the induction of NF‐ATc1, the master switch regulator for osteoclast differentiation. Our study suggests that the direct inhibitory action of leflunomide on osteoclast differentiation constitutes an important aspect in the amelioration of bone destruction, and that the RANKL‐dependent NF‐ATc1 induction pathway is a promising target for pharmacologic intervention in arthritic bone destruction.

     

In vitro stage‐specific chondrogenesis of mesenchymal stem cells committed to chondrocytes

Objective

Osteoarthritis is characterized by an imbalance in cartilage homeostasis, which could potentially be corrected by mesenchymal stem cell (MSC)–based therapies. However, in vivo implantation of undifferentiated MSCs has led to unexpected results. This study was undertaken to establish a model for preconditioning of MSCs toward chondrogenesis as a more effective clinical tool for cartilage regeneration.

Methods

A coculture preconditioning system was used to improve the chondrogenic potential of human MSCs and to study the detailed stages of chondrogenesis of MSCs, using a human MSC line, Kp‐hMSC, in commitment cocultures with a human chondrocyte line, hPi (labeled with green fluorescent protein [GFP]). In addition, committed MSCs were seeded into a collagen scaffold and analyzed for their neocartilage‐forming ability.

Results

Coculture of hPi‐GFP chondrocytes with Kp‐hMSCs induced chondrogenesis, as indicated by the increased expression of chondrogenic genes and accumulation of chondrogenic matrix, but with no effect on osteogenic markers. The chondrogenic process of committed MSCs was initiated with highly activated chondrogenic adhesion molecules and stimulated cartilage developmental growth factors, including members of the transforming growth factor β superfamily and their downstream regulators, the Smads, as well as endothelial growth factor, fibroblast growth factor, insulin‐like growth factor, and vascular endothelial growth factor. Furthermore, committed Kp‐hMSCs acquired neocartilage‐forming potential within the collagen scaffold.

Conclusion

These findings help define the molecular markers of chondrogenesis and more accurately delineate the stages of chondrogenesis during chondrocytic differentiation of human MSCs. The results indicate that human MSCs committed to the chondroprogenitor stage of chondrocytic differentiation undergo detailed chondrogenic changes. This model of in vitro chondrogenesis of human MSCs represents an advance in cell‐based transplantation for future clinical use.

     

Interferon‐γ–dependent inhibition of B cell activation by bone marrow–derived mesenchymal stem cells in a murine model of systemic lupus erythematosus

Objective

Bone marrow–derived mesenchymal stem cells (BM‐MSCs) are multipotent cells characterized by immunomodulatory properties and are therefore considered a promising tool for the treatment of immune‐mediated diseases. This study was undertaken to assess the influence of murine BM‐MSCs on the activation of B cells in (NZB × NZW)F₁ mice as an animal model of systemic lupus erythematosus (SLE).

Methods

We evaluated the in vitro effects of BM‐MSCs on the proliferation and differentiation to plasma cells of splenic mature B cell subsets, namely follicular and marginal zone B cells isolated from (NZB × NZW)F₁ mice. Lupus mice were also treated with BM‐MSCs, and serum autoantibodies, proteinuria, histologic changes in the kidney, and survival rates were monitored.

Results

BM‐MSCs inhibited antigen‐dependent proliferation and differentiation to plasma cells of follicular and marginal zone B cells in vitro. This inhibitory effect was dependent on interferon‐γ (IFNγ) and was mediated by cell‐to‐cell contact, involving the programmed death 1 (PD‐1)/PD ligand pathway. In vivo treatment with BM‐MSCs did not affect the levels of anti–double‐stranded DNA antibodies or proteinuria. However, a reduction in glomerular immune complex deposition, lymphocytic infiltration, and glomerular proliferation was observed.

Conclusion

Our findings indicate that BM‐MSCs affect B cell receptor–dependent activation of both follicular and marginal zone B cells from lupus mice. This inhibitory effect is IFNγ‐dependent and cell contact–dependent. MSCs in vivo do not affect the production of autoantibodies, the level of proteinuria, or the mortality rates. Nonetheless, the significant improvement in histologic findings in the kidney supports the potential role of MSCs in the prevention of glomerular damage.

     

Treatment of experimental arthritis by inducing immune tolerance with human adipose‐derived mesenchymal stem cells

Objective

Rheumatoid arthritis (RA) is a chronic autoimmune disease caused by loss of immunologic self tolerance and characterized by chronic joint inflammation. Adult mesenchymal stem cells (MSCs) were recently found to suppress effector T cell responses and to have beneficial effects in various immune disorders. The purpose of this study was to examine a new therapeutic strategy for RA based on the administration of human adipose‐derived MSCs (AD‐MSCs).

Methods

DBA/1 mice with collagen‐induced arthritis were treated with human AD‐MSCs after disease onset, and clinical scores were determined. Inflammatory response was determined by measuring the levels of different mediators of inflammation in the joints and serum. The Th1‐mediated autoreactive response was evaluated by determining the proliferative response and cytokine profile of draining lymph node cells stimulated with the autoantigen. The number of Treg cells and the suppressive capacity on self‐reactive Th1 cells were also determined.

Results

Systemic infusion of human AD‐MSCs significantly reduced the incidence and severity of experimental arthritis. This therapeutic effect was mediated by down‐regulating the 2 deleterious disease components: the Th1‐driven autoimmune and inflammatory responses. Human AD‐MSCs decreased the production of various inflammatory cytokines and chemokines, decreased antigen‐specific Th1/Th17 cell expansion, and induced the production of antiinflammatory interleukin‐10 in lymph nodes and joints. Human AD‐MSCs also induced de novo generation of antigen‐specific CD4+CD25+FoxP3+ Treg cells with the capacity to suppress self‐reactive T effector responses.

Conclusion

Human AD‐MSCs emerge as key regulators of immune tolerance by inducing the generation/activation of Treg cells and are thus attractive candidates for a cell‐based therapy for RA.

     

Transforming growth factor β–transduced mesenchymal stem cells ameliorate experimental autoimmune arthritis through reciprocal regulation of Treg/Th17 cells and osteoclastogenesis

Objective

Bone marrow–derived mesenchymal stem cells (MSCs) can prevent various autoimmune diseases. We examined the therapeutic potential of transforming growth factor β (TGFβ)–transduced MSCs in experimental autoimmune arthritis, using an accepted animal model of collagen‐induced arthritis (CIA).

Methods

DBA/1J mice with CIA were treated with syngeneic TGFβ‐induced MSCs, whereas control mice received either vehicle or MSCs alone. Arthritis severity was assessed by clinical and histologic scoring. TGFβ‐transduced MSCs were tested for their immunosuppressive ability and differential regulation in mice with CIA. T cell responses to type II collagen were evaluated by determining proliferative capacity and cytokine levels. The effects of TGFβ‐transduced MSCs on osteoclast formation were analyzed in vitro and in vivo.

Results

Systemic infusion of syngeneic TGFβ‐transduced MSCs prevented arthritis development and reduced bone erosion and cartilage destruction. Treatment with TGFβ‐transduced MSCs potently suppressed type II collagen–specific T cell proliferation and down‐regulated proinflammatory cytokine production. These therapeutic effects were associated with an increase in type II collagen–specific CD4+FoxP3+ Treg cells and inhibition of Th17 cell formation in the peritoneal cavity and spleen. Furthermore, TGFβ‐transduced MSCs inhibited osteoclast differentiation.

Conclusion

TGFβ‐transduced MSCs suppressed the development of autoimmune arthritis and joint inflammation. These data suggest that enhancing the immunomodulatory activity of MSCs and modulating T cell–mediated immunity using gene‐modified MSCs may be a gateway for new therapeutic approaches to clinical rheumatoid arthritis.

     

Impairment of endothelial cell differentiation from bone marrow–derived mesenchymal stem cells: New insight into the pathogenesis of systemic sclerosis

Objective

Systemic sclerosis (SSc) is a disorder characterized by vascular damage and fibrosis of the skin and internal organs. Despite marked tissue hypoxia, there is no evidence of compensatory angiogenesis. The ability of mesenchymal stem cells (MSCs) to differentiate into endothelial cells was recently demonstrated. The aim of this study was to determine whether impaired differentiation of MSCs into endothelial cells in SSc might contribute to disease pathogenesis by decreasing endothelial repair.

Methods

MSCs obtained from 7 SSc patients and 15 healthy controls were characterized. The number of colony‐forming unit–fibroblastoid colonies was determined. After culture in endothelial‐specific medium, the endothelial‐like MSC (EL‐MSC) phenotype was assessed according to the surface expression of vascular endothelial growth factor receptors (VEGFRs). Senescence, chemoinvasion, and capillary morphogenesis studies were also performed.

Results

MSCs from SSc patients displayed the same phenotype and clonogenic activity as those from controls. In SSc MSCs, a decreased percentage of VEGFR‐2+, CXCR4+, VEGFR‐2+/CXCR4+ cells and early senescence was detected. After culturing, SSc EL‐MSCs showed increased expression of VEGFR‐1, VEGFR‐2, and CXCR4, did not express CD31 or annexin V, and showed significantly decreased migration after specific stimuli. Moreover, the addition of VEGF and stromal cell–derived factor 1 to cultured SSc EL‐MSCs increased their angiogenic potential less than that in controls.

Conclusion

Our data strongly suggest that endothelial repair may be affected in SSc. The possibility that endothelial progenitor cells could be used to increase vessel growth in chronic ischemic tissues may open up new avenues in the treatment of vascular damage caused by SSc.

     

Adoptive Transfer of Human Gingiva‐Derived Mesenchymal Stem Cells Ameliorates Collagen‐Induced Arthritis via Suppression of Th1 and Th17 Cells and Enhancement of Regulatory T Cell Differentiation

Objective

Current approaches offer no cures for rheumatoid arthritis (RA). Accumulating evidence has revealed that manipulation of bone marrow–derived mesenchymal stem cells (BM‐MSCs) may have the potential to control or even prevent RA, but BM‐MSC–based therapy faces many challenges, such as limited cell availability and reduced clinical feasibility. This study in mice with established collagen‐induced arthritis (CIA) was undertaken to determine whether substitution of human gingiva‐derived mesenchymal stem cells (G‐MSCs) would significantly improve the therapeutic effects.

Methods

CIA was induced in DBA/1J mice by immunization with type II collagen and Freund's complete adjuvant. G‐MSCs were injected intravenously into the mice on day 14 after immunization. In some experiments, intraperitoneal injection of PC61 (anti‐CD25 antibody) was used to deplete Treg cells in arthritic mice.

Results

Infusion of G‐MSCs in DBA/1J mice with CIA significantly reduced the severity of arthritis, decreased the histopathology scores, and down‐regulated the production of inflammatory cytokines (interferon‐γ and interleukin‐17A). Infusion of G‐MSCs also resulted in increased levels of CD4+CD39+FoxP3+ cells in arthritic mice. These increases were noted early after infusion in the spleens and lymph nodes, and later after infusion in the synovial fluid. The FoxP3+ Treg cells that were increased in frequency mainly consisted of Helios‐negative cells. When Treg cells were depleted, infusion of G‐MSCs partially interfered with the progression of CIA. Pretreatment of G‐MSCs with a CD39 or CD73 inhibitor significantly reversed the protective effect of G‐MSCs on CIA.

Conclusion

The role of G‐MSCs in controlling the development and severity of CIA mostly depends on CD39/CD73 signals and partially depends on the induction of CD4+CD39+FoxP3+ Treg cells. G‐MSCs provide a promising approach for the treatment of autoimmune diseases.