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.

     

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.

     

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.

     

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.

     

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.

     

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.

     

Complement regulatory protein Crry/p65 costimulation expands natural Treg cells with enhanced suppressive properties in proteoglycan‐induced arthritis

Objective

To investigate the costimulatory role of Crry/p65 (Crry), a membrane complement regulatory protein, on the expansion and function of natural Treg cells and their ability to ameliorate proteoglycan‐induced arthritis (PGIA), an animal model of inflammatory arthritis in which the role of natural Treg cells is not well established.

Methods

CD4+CD25+ natural Treg cells from BALB/c mice were activated in vitro and costimulated by Crry. The expanded cells were phenotypically characterized, and their suppressive effect on T cell proliferation was assayed in vitro. The potential prophylactic and therapeutic effects of this population versus those of natural Treg cells in PGIA were studied. The clinical score, histology, the antigen‐specific isotype antibody pattern, in vitro T cell responses, and the presence of Treg cells in the paws were studied.

Results

Crry costimulation enhanced the in vitro expansion of natural Treg cells while maintaining their phenotypic and suppressive properties. Crry‐expanded Treg cells had stronger suppressive properties in vivo and a longer ameliorating effect in the PGIA model than did natural Treg cells. Crry‐expanded Treg cells suppressed T cell– and B cell–dependent responses in PGIA, changing the pathogenic antibody isotype pattern and decreasing antigen‐dependent secretion of cytokines, including interferon‐γ, interleukin‐12 (IL‐12), and IL‐17. Increased FoxP3 expression was detected in the paws of mice transferred with Crry‐expanded Treg cells.

Conclusion

Crry‐mediated costimulation facilitates in vitro expansion of natural Treg cells while maintaining their suppressive properties in vitro and in vivo in the PGIA model. These results highlight the potential of the complement regulatory protein Crry to costimulate and expand natural Treg cells capable of suppressing disease in an animal model of chronic inflammatory arthritis.

     

Reversal of the immunosuppressive properties of mesenchymal stem cells by tumor necrosis factor α in collagen‐induced arthritis

Objective

Adult mesenchymal stem cells (MSCs) represent promising tools for therapeutic applications such as tissue engineering and cellular therapy. Recent data suggest that, due to their immunosuppressive nature, MSCs may be of interest to enhance allogeneic hematopoietic engraftment and prevent graft‐versus‐host disease. Using a murine model of rheumatoid arthritis (RA), this study investigated whether the immunosuppressive properties of MSCs could be of therapeutic value to inhibit reactive T cells in autoimmune diseases such as RA.

Methods

In mice with collagen‐induced arthritis (CIA), we injected various doses of C3 MSCs at the time of immunization or booster injection, and subsequently evaluated the clinical and immunologic parameters. The immunosuppressive properties of MSCs were determined in vitro in mixed lymphocyte reactions with or without the addition of tumor necrosis factor α (TNFα).

Results

In the CIA model of arthritis, MSCs did not confer any benefit. Both the clinical and the immunologic findings suggested that MSCs were associated with accentuation of the Th1 response. Using luciferase‐expressing MSCs, we were unable to detect labeled cells in the articular environment of the knee, suggesting that worsening of the symptoms was unlikely due to the homing of MSCs in the joints. Experiments in vitro showed that the addition of TNFα was sufficient to reverse the immunosuppressive effect of MSCs on T cell proliferation, and this observation was associated with an increase in interleukin‐6 secretion.

Conclusion

Our data suggest that environmental parameters, in particular those related to inflammation, may influence the immunosuppressive properties of MSCs.

     

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.

     

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.

     

Reversal of serologic,immunologic, and histologic dysfunction in mice with systemic lupus erythematosus by long‐term serial adipose tissue–derived mesenchymal stem cell transplantation

Objective

To investigate the efficacy of human adipose tissue–derived mesenchymal stem cell (AD‐MSC) transplantation in systemic lupus erythematosus (SLE) and to determine the optimal transplantation window for stem cells either before or after disease onset.

Methods

(NZB × NZW)F₁ mice with SLE were administered human AD‐MSCs (5 × 10⁵) intravenously every 2 weeks from age 6 weeks until age 60 weeks, while the control group received saline vehicle on the same schedule. Another experiment was carried out with a different initiation time point for serial transplantation (age 6 weeks or age 32 weeks).

Results

Long‐term serial administration (total of 28 times) of human AD‐MSCs ameliorated SLE without any adverse effects. Compared with the control group, the human AD‐MSC–treated group had a significantly higher survival rate with improvement of histologic and serologic abnormalities and immunologic function, and also had a decreased incidence of proteinuria. Anti–double‐stranded DNA antibodies and blood urea nitrogen levels decreased significantly with transplantation of human AD‐MSCs, and serum levels of granulocyte–macrophage colony‐stimulating factor, interleukin‐4 (IL‐4), and IL‐10 increased significantly. A significant increase in the proportion of CD4+FoxP3+ cells and a marked restoration of capacity for cytokine production were observed in spleens from the human AD‐MSC–treated group. In the second experiment, an early stage treatment group showed better results (higher survival rates and lower incidence of proteinuria) than an advanced stage treatment group.

Conclusion

Serial human AD‐MSC transplantation had beneficial effects in the treatment of SLE, without adverse effects. Transplantation of human AD‐MSCs before disease onset was preferable for amelioration of SLE and restoration of immune homeostasis.

     

Human articular chondrocytes secrete parathyroid hormone–related protein and inhibit hypertrophy of mesenchymal stem cells in coculture during chondrogenesis

Objective

The use of bone marrow–derived mesenchymal stem cells (MSCs) has shown promise in cell‐based cartilage regeneration. A yet‐unsolved problem, however, is the unwanted up‐regulation of markers of hypertrophy, such as alkaline phosphatase (AP) and type X collagen, during in vitro chondrogenesis and the formation of unstable calcifying cartilage at heterotopic sites. In contrast, articular chondrocytes produce stable, nonmineralizing cartilage. The aim of this study was to address whether coculture of MSCs with human articular chondrocytes (HACs) can suppress the undesired hypertrophy in differentiating MSCs.

Methods

MSCs were differentiated in chondrogenic medium that had or had not been conditioned by parallel culture with HAC pellets, or MSCs were mixed in the same pellet with the HACs (1:1 or 1:2 ratio) and cultured for 6 weeks. Following in vitro differentiation, the pellets were transplanted into SCID mice.

Results

The gene expression ratio of COL10A1 to COL2A1 and of Indian hedgehog (IHH) to COL2A1 was significantly reduced by differentiation in HAC‐conditioned medium, and less type X collagen protein was deposited relative to type II collagen. AP activity was significantly lower (P < 0.05) in the cells that had been differentiated in conditioned medium, and transplants showed significantly reduced calcification in vivo. In mixed HAC/MSC pellets, suppression of AP was dose‐dependent, and in vivo calcification was fully inhibited. Chondrocytes secreted parathyroid hormone–related protein (PTHrP) throughout the culture period, whereas PTHrP was down‐regulated in favor of IHH up‐regulation in control MSCs after 2–3 weeks of chondrogenesis. The main inhibitory effects seen with HAC‐conditioned medium were reproducible by PTHrP supplementation of unconditioned medium.

Conclusion

HAC‐derived soluble factors and direct coculture are potent means of improving chondrogenesis and suppressing the hypertrophic development of MSCs. PTHrP is an important candidate soluble factor involved in this effect.

     

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.

     

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.