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Mesenchymal stem cells (MSCs) are critical for immune regulation. Although several microRNAs (miRNAs) have been shown to participate in autoimmune pathogenesis by affecting lymphocyte development and function, the roles of miRNAs in MSC dysfunction in autoimmune diseases remain unclear. Here, we show that patients with systemic lupus erythematosus (SLE) display a unique miRNA signature in bone marrow-derived MSCs (BMSCs) compared with normal controls, among which miR-663 is closely associated with SLE disease activity. MiR-663 inhibits the proliferation and migration of BMSCs and impairs BMSC-mediated downregulation of follicular T helper (T fh ) cells and upregulation of regulatory T (T reg ) cells by targeting transforming growth factor β1 (TGF-β1). MiR-663 overexpression weakens the therapeutic effect of BMSCs, while miR-663 inhibition improves the remission of lupus disease in MRL/lpr mice. Thus, miR-663 is a key mediator of SLE BMSC regulation and may serve as a new therapeutic target for the treatment of lupus.

microRNAs (miRNAs) act as regulatory signals for maintaining stemness, self-renewal, and differentiation of mesenchymal stem cells (MSCs), but whether miRNAs modulate the immunoregulatory function of MSCs remains largely unknown. Here, we show that miR-21 negatively regulates the activity of immunoregulatory cytokine transforming growth factor-β1 (TGF-β1) in MSCs. Consistently, bone marrow MSCs (BMMSCs) from miR-21(-/-) mice show enhanced immunosuppressive function by more TGF-β1 secretion and induce more CD4(+) Foxp3(+) regulatory T cells compared with wild-type BMMSCs in vitro, which anti-TGF-β1 antibody abrogates. Mechanistically, miR-21 inhibits TGF-β1 expression by targeting phosphatase and tensin homolog deleted on chromosome 10 (PTEN) in BMMSCs. Downstream of PTEN, miR-21 promotes activation of Akt, and consequently increases activation of NF-κB pathway. Importantly, adoptive transfer of miR-21(-/-) BMMSCs into mice with experimental colitis more effectively ameliorates colonic inflammation in a TGF-β1-dependent manner. Thus, these findings indicate a previously uncovered mechanism of miR-21 control immunoregulatory function of BMMSCs through TGF-β1 inhibition., (© 2015 AlphaMed Press.)

Objective: Mesenchymal stem cells (MSCs) derived from patients with systemic lupus erythematosus (SLE) exhibit enhanced senescence. Cellular senescence has been reported to be induced by several inflammatory cytokines, including interferon-α (IFNα) and IFNγ, that are involved in the pathogenesis of SLE. We undertook this study to investigate whether the inflammatory environment in SLE could affect MSC senescence., Methods: Cellular senescence was measured by staining of senescence-associated β-galactosidase and by expression of the cell cycle inhibitors p53 and p21. Eighty cytokines and chemokines in serum from healthy controls and patients with SLE were identified by cytokine antibody array., Results: SLE serum promoted senescence of MSCs, which was reversed by the phosphatidylinositol 3-kinase (PI3K)/Akt signaling inhibitor LY294002 but not by the JAK/STAT inhibitor AG490 and not by the MEK/ERK inhibitor PD98059. Cytokine antibody array analysis revealed that leptin and neutrophil-activating peptide 2 (NAP-2) were the 2 factors most significantly elevated in SLE serum compared with normal serum. Blockade of leptin or NAP-2 in MSC cultures abolished SLE serum-induced senescence, while direct addition of these 2 factors could promote senescence in cultures of normal MSCs. Inhibition of PI3K/Akt signaling with LY294002 reduced leptin- and NAP-2-induced senescence in MSCs., Conclusion: Taken together, our data show that leptin and NAP-2 act synergistically to promote MSC senescence through enhancement of the PI3K/Akt signaling pathway in SLE patients., (© 2015, American College of Rheumatology.)

Mesenchymal stem cells (MSC) from healthy human and normal mice can inhibit normal B cell proliferation, differentiation, and Ab secretion in vitro. However, it remains unknown whether MSC from lupus-like mice and patients with systemic lupus erythematosus (SLE) exhibit the same immunoregulatory activity as normal MSC for B cell inhibition and, if not, what the underlying molecular mechanism would be. In this study, we showed that bone marrow-derived MSCs from lupus-like mice and SLE patients had an impairment in suppressing normal B cell proliferation and differentiation, which was caused by the reduction of CCL2 levels. Knockdown of CCL2 in normal MSC damaged their suppressive capacity for B cells. Conversely, overexpression of CCL2 in lupus MSCs restored their immunoregulatory ability for B cells in vitro and ameliorated the pathology of lupus nephritis and serological changes in MRL/lpr mice in vivo. Mechanistically, MSC-mediated B cell inhibition was dependent on matrix metalloproteinase proteolytic processing of CCL2. These findings reveal a novel function of CCL2 in B cell regulation by MSCs and suggest that CCL2 manipulation on MSCs may serve as a potential pathway for developing the more effective MSC-based therapy in autoimmune diseases associated with B cell activation, such as SLE., (Copyright © 2014 by The American Association of Immunologists, Inc.)

Periodontal ligament stem cells (PDLSCs) have provided novel cell sources for tooth and periodontal tissue regeneration. Allogeneic PDLSCs can reconstruct periodontal ligament tissue that has been damaged by periodontal diseases and regulate T-cell immunity. However, the effect of PDLSCs on B cells remains unknown. Here, we treated periodontitis in a miniature pig model using allogeneic PDLSCs and showed a reduction in humoral immunity in the animals. When cocultured with normal B cells, human PDLSCs (hPDLSCs) had similar effects as bone marrow mesenchymal stem cells in suppressing B cell proliferation, differentiation, and migration, while intriguingly, hPDLSCs increased B cell viability by secreting interleukin-6. Mechanistically, hPDLSCs suppressed B cell activation through cell-to-cell contact mostly mediated by programmed cell death protein 1 and programmed cell death 1 ligand 1. Our data revealed a previously unrecognized function of PDLSCs in regulating humoral immune responses, which may represent a novel therapeutic strategy for immune-related disorders., (Copyright © 2013 AlphaMed Press.)

Mesenchymal stem cells (MSCs) are multipotential nonhematopoietic progenitors and are capable of differentiating into several tissues of mesenchymal origin. We have shown that bone marrow-derived MSCs from both SLE patients and lupus-prone MRL/lpr mice are defective structurally and functionally. Here we observe the long-term safety and efficacy of allogeneic MSC transplantation (MSCT) in treatment-resistant SLE patients. Eighty-seven patients with persistently active SLE who were refractory to standard treatment or had life-threatening visceral involvement were enrolled. Allogeneic bone marrow or umbilical cord-derived MSCs were harvested and infused intravenously (1 × 10(6) cells/kg of body weight). Primary outcomes were rates of survival, disease remission and relapse, as well as transplantation-related adverse events. Secondary outcomes included SLE disease activity index (SLEDAI) and serologic features. During the 4-year follow-up and with a mean follow-up period of 27 months, the overall rate of survival was 94% (82/87). Complete clinical remission rate was 28% at 1 year (23/83), 31% at 2 years (12/39), 42% at 3 years (5/12), and 50% at 4 years (3/6). Rates of relapse were 12% (10/83) at 1 year, 18% (7/39) at 2 years, 17% (2/12) at 3 years, and 17% (1/6) at 4 years. The overall rate of relapse was 23% (20/87). Disease activity declined as revealed by significant changes in the SLEDAI score, levels of serum autoantibodies, albumin, and complements. A total of five patients (6%) died after MSCT from non-treatment-related events in the 4-year follow-up, and no transplantation-related adverse event was observed. Allogeneic MSCT resulted in the induction of clinical remission and improvement in organ dysfunction in drug-resistant SLE patients.

Bone marrow mesenchymal stem cells (MSCs) comprise a heterogeneous population of postnatal progenitor cells with profound immunomodulatory properties, such as upregulation of Foxp3(+) regulatory T cells (Tregs) and downregulation of Th17 cells. However, it is unknown whether different MSC subpopulations possess the same range of immunomodulatory function. Here, we show that a subset of single colony-derived MSCs producing IL-17 is different from bulk MSC population in that it cannot upregulate Tregs, downregulate Th17 cells, or ameliorate disease phenotypes in a colitis mouse model. Mechanistically, we reveal that IL-17, produced by these MSCs, activates the NFκB pathway to downregulate TGF-β production in MSCs, resulting in abolishment of MSC-based immunomodulation. Furthermore, we show that NFκB is able to directly bind to TGF-β promoter region to regulate TGF-β expression in MSCs. Moreover, these IL-17(+) MSCs possess anti-Candida albicans growth effects in vitro and therapeutic effect in C. albicans-infected mice. In summary, this study shows that MSCs contain an IL-17(+) subset capable of inhibiting C. albicans growth, but attenuating MSC-based immunosuppression via NFκB-mediated downregulation of TGF-β.

Systemic infusion of bone marrow mesenchymal stem cells (BMMSCs) yields therapeutic benefit for a variety of autoimmune diseases, but the underlying mechanisms are poorly understood. Here we show that in mice systemic infusion of BMMSCs induced transient T cell apoptosis via the FAS ligand (FASL)-dependent FAS pathway and could ameliorate disease phenotypes in fibrillin-1 mutated systemic sclerosis (SS) and dextran-sulfate-sodium-induced experimental colitis. FASL(-/-) BMMSCs did not induce T cell apoptosis in recipients, and could not ameliorate SS and colitis. Mechanistic analysis revealed that FAS-regulated monocyte chemotactic protein 1 (MCP-1) secretion by BMMSCs recruited T cells for FASL-mediated apoptosis. The apoptotic T cells subsequently triggered macrophages to produce high levels of TGFβ, which in turn led to the upregulation of CD4(+)CD25(+)Foxp3(+) regulatory T cells and, ultimately, immune tolerance. These data therefore demonstrate a previously unrecognized mechanism underlying BMMSC-based immunotherapy involving coupling via FAS/FASL to induce T cell apoptosis., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Stem cell-based regenerative medicine is a promising approach in tissue reconstruction. Here we show that proinflammatory T cells inhibit the ability of exogenously added bone marrow mesenchymal stem cells (BMMSCs) to mediate bone repair. This inhibition is due to interferon γ (IFN-γ)-induced downregulation of the runt-related transcription factor 2 (Runx-2) pathway and enhancement of tumor necrosis factor α (TNF-α) signaling in the stem cells. We also found that, through inhibition of nuclear factor κB (NF-κB), TNF-α converts the signaling of the IFN-γ-activated, nonapoptotic form of TNF receptor superfamily member 6 (Fas) in BMMSCs to a caspase 3- and caspase 8-associated proapoptotic cascade, resulting in the apoptosis of these cells. Conversely, reduction of IFN-γ and TNF-α concentrations by systemic infusion of Foxp3(+) regulatory T cells, or by local administration of aspirin, markedly improved BMMSC-based bone regeneration and calvarial defect repair in C57BL/6 mice. These data collectively show a previously unrecognized role of recipient T cells in BMMSC-based tissue engineering.

Subcutaneous transplants of bone marrow mesenchymal stem cells (BMMSCs) are capable of generating ectopic bone and organizing functional hematopoietic marrow elements in animal models. Here we report that immunocompromised mice received subcutaneous BMMSC transplants using hydroxyapatite tricalcium phosphate as a carrier suppressed age-related degeneration in multiple organs and benefited an increase in life span extension compared with control littermates. The newly organized ectopic bone/marrow system restores active hematopoiesis via the erythropoietin receptor/signal transducer and activator of transcription 5 (Stat5) pathway. Furthermore, the BMMSC recipient mice showed elevated level of Klotho and suppression of insulin-like growth factor I signaling, which may be the mechanism contributing to the alleviation of aging-like phenotypes and prolongation of life in the treated mice. This work reveals that erythropoietin receptor/Stat5 pathway contributes to BMMSC-organized ectopic hematopoiesis, which may offer a treatment paradigm of reversing age-related degeneration of multiple organs in adult immunocompromised mice.

Background: Osteoporosis is the most prevalent skeletal disorder, characterized by a low bone mineral density (BMD) and bone structural deterioration, leading to bone fragility fractures. Accelerated bone resorption by osteoclasts has been established as a principal mechanism in osteoporosis. However, recent experimental evidences suggest that inappropriate apoptosis of osteoblasts/osteocytes accounts for, at least in part, the imbalance in bone remodeling as occurs in osteoporosis. The aim of this study is to examine whether aspirin, which has been reported as an effective drug improving bone mineral density in human epidemiology studies, regulates the balance between bone resorption and bone formation at stem cell levels., Methods and Findings: We found that T cell-mediated bone marrow mesenchymal stem cell (BMMSC) impairment plays a crucial role in ovariectomized-induced osteoporosis. Ex vivo mechanistic studies revealed that T cell-mediated BMMSC impairment was mainly attributed to the apoptosis of BMMSCs via the Fas/Fas ligand pathway. To explore potential of using pharmacologic stem cell based intervention as an approach for osteoporosis treatment, we selected ovariectomy (OVX)-induced osteoporosis mouse model to examine feasibility and mechanism of aspirin-mediated therapy for osteoporosis. We found that aspirin can inhibit T cell activation and Fas ligand induced BMMSC apoptosis in vitro. Further, we revealed that aspirin increases osteogenesis of BMMSCs by aiming at telomerase activity and inhibits osteoclast activity in OVX mice, leading to ameliorating bone density., Conclusion: Our findings have revealed a novel osteoporosis mechanism in which activated T cells induce BMMSC apoptosis via Fas/Fas ligand pathway and suggested that pharmacologic stem cell based intervention by aspirin may be a new alternative in osteoporosis treatment including activated osteoblasts and inhibited osteoclasts.

Bone marrow-derived mesenchymal stem cells (BMMSCs) are multipotent postnatal stem cells that have been used for the treatment of bone defects and graft-versus-host diseases in clinics. In this study, we found that subcutaneously transplanted human BMMSCs are capable of organizing hematopoietic progenitors of recipient origin. These hematopoietic cells expressed multiple lineages of hematopoietic cell associated markers and were able to rescue lethally irradiated mice, with successful engraftment in the recipient, suggesting a potential bone marrow (BM) resource for stem cell therapies. Furthermore, we found that platelet-derived growth factor (PDGF) promotes the formation of BMMSC-generated BM niches through upregulation of beta-catenin, implying that the PDGF pathway contributes to the formation of ectopic BM. These results indicate that the BMMSC-organized BM niche system represents a unique hematopoietic progenitor resource possessing potential clinical value.

Despite recent emerging evidence suggesting that cancer stem cells subsist in a variety of tumors, it is not yet fully elucidated whether postnatal stem cells are directly involved in tumorigenesis. We used murine bone marrow-derived mesenchymal stem cells (BMMSCs) as a model to test a hypothesis that tumorigenesis may originate from spontaneous mutation of stem cells. In this study, we demonstrated that murine BMMSCs, after numerous passages, obtained unlimited population doublings and proceeded to a malignant transformation state, resulting in fibrosarcoma formation in vivo. Transformed BMMSCs colonized to multiple organs when delivered systemically through the tail vein. Fibrosarcoma cells formed by transformed BMMSCs contained cancer progenitors, which were capable of generating colony clusters in vitro and fibrosarcoma in vivo by the second administration. The mechanism by which BMMSCs transformed to malignant cells was associated with accumulated chromosomal abnormalities, gradual elevation in telomerase activity, and increased c-myc expression. Moreover, BMMSCs and their transformed counterpart, fibrosarcoma-forming cells, demonstrated different sensitivity to anti-cancer drugs. BMMSCs/fibrosarcoma transformation system may provide an ideal system to elucidate the mechanism of how stem cells become cancer cells and to screen anti-sarcoma drugs.

Bone marrow mesenchymal stem cells (MSCs) comprise a heterogeneous population of postnatal progenitor cells with profound immunomodulatory properties, such as upregulation of Foxp3+ regulatory T cells (Tregs) and downregulation of Th17 cells. However, it is unknown whether different MSC subpopulations possess the same range of immunomodulatory function. Here, we show that a subset of single colony-derived MSCs producing IL-17 is different from bulk MSC population in that it cannot upregulate Tregs, downregulate Th17 cells, or ameliorate disease phenotypes in a colitis mouse model. Mechanistically, we reveal that IL-17, produced by these MSCs, activates the NFκB pathway to downregulate TGF-β production in MSCs, resulting in abolishment of MSC-based immunomodulation. Furthermore, we show that NFκB is able to directly bind to TGF-β promoter region to regulate TGF-β expression in MSCs. Moreover, these IL-17+ MSCs possess anti-Candida albicans growth effects in vitro and therapeutic effect in C. albicans-infected mice. In summary, this study shows that MSCs contain an IL-17+ subset capable of inhibiting C. albicans growth, but attenuating MSC-based immunosuppression via NFκB-mediated downregulation of TGF-β. [ABSTRACT FROM AUTHOR]

The clinical trial of allogenic mesenchymal stem cells (MSCs) transplantation for refractory SLE patients has shown significant safety and efficacy profiles. However, the optimum frequency of the MSCs transplantation (MSCT) is unknown. This study was undertaken to observe whether double transplantations of MSCs is superior to single transplantation. Fifty-eight refractory SLE patients were enrolled in this study, in which 30 were randomly given single MSCT, and the other 28 were given double MSCT. Patients were followed up for rates of survival, disease remission, and relapse, as well as transplantation-related adverse events. SLE disease activity index (SLEDAI) and serologic features were evaluated. Our results showed that no remarkable differences between single and double allogenic MSCT were found in terms of disease remission and relapse, amelioration of disease activity, and serum indexes in an SLE clinical trial with more than one year followup. This study demonstrated that single MSCs transplantation at the dose of one million MSCs per kilogram of body weight was sufficient to induce disease remission for refractory SLE patients. [ABSTRACT FROM AUTHOR]

Stem cell-based regenerative medicine is a promising approach in tissue reconstruction. Here we show that proinflammatory T cells inhibit the ability of exogenously added bone marrow mesenchymal stem cells (BMMSCs) to mediate bone repair. This inhibition is due to interferon ? (IFN-?)-induced downregulation of the runt-related transcription factor 2 (Runx-2) pathway and enhancement of tumor necrosis factor ? (TNF-?) signaling in the stem cells. We also found that, through inhibition of nuclear factor ?B (NF-?B), TNF-? converts the signaling of the IFN-?-activated, nonapoptotic form of TNF receptor superfamily member 6 (Fas) in BMMSCs to a caspase 3- and caspase 8-associated proapoptotic cascade, resulting in the apoptosis of these cells. Conversely, reduction of IFN-? and TNF-? concentrations by systemic infusion of Foxp3+ regulatory T cells, or by local administration of aspirin, markedly improved BMMSC-based bone regeneration and calvarial defect repair in C57BL/6 mice. These data collectively show a previously unrecognized role of recipient T cells in BMMSC-based tissue engineering. [ABSTRACT FROM AUTHOR]

Human umbilical cord-derived mesenchymal stem cells (UCMSCs) show therapeutic effects on systemic lupus erythematosus (SLE). Deficiency in functional polarization and phagocytosis in macrophages has been suggested in the pathogenesis of SLE. We found that macrophages from B6.MRL- Fas lpr mice exhibited lower level of CD206, the marker for alternatively activated macrophage (AAM, also called M2). In addition, the phagocytic activity of B6.MRL- Fas lpr macrophages was also decreased. UCMSC transplantation improved the proportion of CD206 + macrophages and their phagocytic activity in B6.MRL- Fas lpr mice. Importantly, macrophages from SLE patients also showed lower expression of CD206 and reduced phagocytic activity, which were corrected by being co-cultured with UCMSCs in vitro and in SLE patients receiving UCMSC transplantation. Mechanistically, we demonstrated that IL-6 was required for the up-regulation of CD206 expression and phagocytic activity of UCMSC-treated SLE macrophages. Our results indicate that UCMSCs alleviate SLE through promoting CD206 expression and phagocytic activity of macrophages in an IL-6 dependent manner. [ABSTRACT FROM AUTHOR]