Transcriptomic analysis identifies Foxo3A as a novel transcription factor regulating mesenchymal stem cell chrondrogenic differentiation

Inhibition of HOXD11 promotes cartilage degradation and induces osteoarthritis development

The 5'-HOXD genes are important for chondrogenesis in vertebrates, but their roles in osteoarthritis (OA) are still ambiguous. In our study, 5'-HOXD genes involvement contributing to cartilage degradation and OA was investigated. In bioinformatics analysis of 5'-HOXD genes, we obtained the GSE169077 data set related to OA in the GEO and analyzed DEGs using the GEO2R tool attached to the GEO. Then, we screened the mRNA levels of 5'-HOXD genes by quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR). We discovered that OA chondrocyte proliferation was inhibited, and apoptosis was increased. Moreover, it was discovered that SOX9 and COL2A1 were downregulated at mRNA and protein levels, while matrix metalloproteinases (MMPs) and a disintegrin-like and metalloproteinase with thrombospondin motifs (ADAMTSs) were upregulated. According to the results of differentially expressed genes (DEGs) and qRT-PCR, we evaluated the protein level of HOXD11 and found that the expression of HOXD11 was downregulated, reversed to MMPs and ADAMTSs but consistent with the cartilage-specific factors, SOX9 and COL2A1. In the lentivirus transfection experiments, HOXD11 overexpression reversed the effects in OA chondrocytes. In human OA articular cartilage, aberrant subchondral bone was formed in hematoxylin-eosin (H&E) and Safranin O and fast green (SOFG) staining results. Furthermore, according to immunohistochemistry findings, SOX9 and HOXD11 expression was inhibited. The results of this study established that HOXD11 was downregulated in OA cartilage and that overexpression of HOXD11 could prevent cartilage degradation in OA.

Characteristics of the synovial microenvironment and synovial mesenchymal stem cells with hip osteoarthritis of different bone morphologies

BACKGROUND

Variations in bone morphology in patients with hip osteoarthritis (HOA) can be broadly categorized into three types: atrophic, normotrophic, and hypertrophic. Despite the investigations examining clinical elements, such as bone morphology, pain, and range of motion, our understanding of the pathogenesis of HOA remains limited. Previous studies have suggested that osteophytes typically originate at the interface of the joint cartilage, periosteum, and synovium, potentially implicating synovial mesenchymal stem cells (SMSCs) in the process. This study aimed to investigate the potential factors that drive the development of bone morphological features in HOA by investigating the characteristics of the synovium, differentiation potential of SMSCs, and composition of synovial fluid in different types of HOA.

METHODS

Synovial tissue and fluid were collected from 30 patients who underwent total hip arthroplasty (THA) with the variable bone morphology of HOA patients. RNA sequencing analysis and quantitative reverse transcription-polymerase chain reaction (RT-qPCR) were performed to analyse the genes in the normotrophic and hypertrophic synovial tissue. SMSCs were isolated and cultured from the normotrophic and hypertrophic synovial tissues of each hip joint in accordance with the variable bone morphology of HOA patients. Cell differentiation potential was compared using differentiation and colony-forming unit assays. Cytokine array was performed to analyse the protein expression in the synovial fluid.

RESULTS

In the RNA sequencing analysis, 103 differentially expressed genes (DEGs) were identified, predominantly related to the interleukin 17 (IL-17) signalling pathway. Using a protein-protein interaction (PPI) network, 20 hub genes were identified, including MYC, CXCL8, ATF3, NR4A1, ZC3H12A, NR4A2, FOSB, and FOSL1. Among these hub genes, four belonged to the AP-1 family. There were no significant differences in the tri-lineage differentiation potential and colony-forming capacity of SMSCs. However, RT-qPCR revealed elevated SOX9 expression levels in synovial tissues from the hypertrophic group. The cytokine array demonstrated significantly higher levels of CXCL8, MMP9, and VEGF in the synovial fluid of the hypertrophic group than in the normotrophic group, with CXCL8 and MMP9 being significantly expressed in the hypertrophic synovium.

CONCLUSION

Upregulation of AP-1 family genes in the synovium and increased concentrations of CXCL8, MMP9, and VEGF were detected in the synovial fluid of the hypertrophic group of HOA patients, potentially stimulating the differentiation of SMSCs towards the cartilage and thereby contributing to severe osteophyte formation.

Wedelolactone Promotes the Chondrogenic Differentiation of Mesenchymal Stem Cells by Suppressing EZH2

Background and Objectives

Osteoarthritis (OA) is a degenerative disease that leads to the progressive destruction of articular cartilage. Current clinical therapeutic strategies are moderately effective at relieving OA-associated pain but cannot induce chondrocyte differentiation or achieve cartilage regeneration. We investigated the ability of wedelolactone, a biologically active natural product that occurs in Eclipta alba (false daisy), to promote chondrogenic differentiation.

Methods and Results

Real-time reverse transcription-polymerase chain reaction, immunohistochemical staining, and immunofluorescence staining assays were used to evaluate the effects of wedelolactone on the chondrogenic differentiation of mesenchymal stem cells (MSCs). RNA sequencing, microRNA (miRNA) sequencing, and isobaric tags for relative and absolute quantitation analyses were performed to explore the mechanism by which wedelolactone promotes the chondrogenic differentiation of MSCs. We found that wedelolactone facilitates the chondrogenic differentiation of human induced pluripotent stem cell-derived MSCs and rat bone-marrow MSCs. Moreover, the forkhead box O (FOXO) signaling pathway was upregulated by wedelolactone during chondrogenic differentiation, and a FOXO1 inhibitor attenuated the effect of wedelolactone on chondrocyte differentiation. We determined that wedelolactone reduces enhancer of zeste homolog 2 (EZH2)-mediated histone H3 lysine 27 trimethylation of the promoter region of FOXO1 to upregulate its transcription. Additionally, we found that wedelolactone represses miR-1271-5p expression, and that miR-1271-5p post-transcriptionally suppresses the expression of FOXO1 that is dependent on the binding of miR-1271-5p to the FOXO1 3'-untranscribed region.

Conclusions

These results indicate that wedelolactone suppresses the activity of EZH2 to facilitate the chondrogenic differentiation of MSCs by activating the FOXO1 signaling pathway. Wedelolactone may therefore improve cartilage regeneration in diseases characterized by inflammatory tissue destruction, such as OA.

Functional tissue engineering of articular cartilage for biological joint resurfacing-The 2021 Elizabeth Winston Lanier Kappa Delta Award

Biological resurfacing of entire articular surfaces represents a challenging strategy for the treatment of cartilage degeneration that occurs in osteoarthritis. Not only does this approach require anatomically sized and functional engineered cartilage, but the inflammatory environment within an arthritic joint may also inhibit chondrogenesis and induce degradation of native and engineered cartilage. Here, we present the culmination of multiple avenues of interdisciplinary research leading to the development and testing of bioartificial cartilage for tissue-engineered resurfacing of the hip joint. The work is based on a novel three-dimensional weaving technology that is infiltrated with specific bioinductive materials and/or genetically-engineered stem cells. A variety of design approaches have been tested in vitro, showing biomimetic cartilage-like properties as well as the capability for long-term tunable and inducible drug delivery. Importantly, these cartilage constructs have the potential to provide mechanical functionality immediately upon implantation, as they will need to replace a majority, if not the entire joint surface to restore function. To date, these approaches have shown excellent preclinical success in a variety of animal studies, including the resurfacing of a large osteochondral defect in the canine hip, and are now well-poised for clinical translation.

Neuromedin B promotes chondrocyte differentiation of mesenchymal stromal cells via calcineurin and calcium signaling

Background

Articular cartilage is a complex tissue with poor healing capacities. Current approaches for cartilage repair based on mesenchymal stromal cells (MSCs) are often disappointing because of the lack of relevant differentiation factors that could drive MSC differentiation towards a stable mature chondrocyte phenotype.

Results

We used a large-scale transcriptomic approach to identify genes that are modulated at early stages of chondrogenic differentiation using the reference cartilage micropellet model. We identified several modulated genes and selected neuromedin B (NMB) as one of the early and transiently modulated genes. We found that the timely regulated increase of NMB was specific for chondrogenesis and not observed during osteogenesis or adipogenesis. Furthermore, NMB expression levels correlated with the differentiation capacity of MSCs and its inhibition resulted in impaired chondrogenic differentiation indicating that NMB is required for chondrogenesis. We further showed that NMB activated the calcineurin activity through a Ca²⁺-dependent signaling pathway.

Conclusion

NMB is a newly described chondroinductive bioactive factor that upregulates the key chondrogenic transcription factor Sox9 through the modulation of Ca²⁺ signaling pathway and calcineurin activity.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-021-00695-1.

Conditioned medium of IGF1-induced synovial membrane mesenchymal stem cells increases chondrogenic and chondroprotective markers in chondrocyte inflammation

Recently, mesenchymal stem cells (MSCs) have been the most explored cells for cell therapy for osteoarthritis (OA) that can be obtained from various sources. Synovial membrane MSCs (SMMSCs) provide best potential for OA therapy, however they are not widely explored. Conditioned medium of SMMSCs (SMMSCs-CM) rich in growth factors and cytokines can inhibit apoptosis and increase chondrocytes cell proliferation. The aim of the present study was to determine growth factors content in SMMSCs-CM as well as the chondrogenic and chondroprotective markers expression in OA model after insulin-like growth factor (IGF)1-induced and non-induced SMMSCs-CM treatments. Chondrocyte cell line (CHON002) was induced by IL1β as OA model (CHON002 with IL1β (IL1β-CHON002)) and treated with SMMSCs-CM with or without IGF1 induction to determine its effectiveness in repairing OA cells model. ELISA was used to assay BMP2, fibroblast growth factor 18 (FGF18) and transforming growth factor (TGF) β1 (TGFβ1) levels in SMMSCs-CM, matrix metalloproteinase (MMP) 13 (MMP13) and a disintegrin and metalloproteinase with thrombospondin motif 4 (ADAMTS4) levels in OA cells model treated with SMMSCs-CM. RT-qPCR analyses were used to investigate the gene expression of SOX9, COL2, and COL10. CM from SMMSCs cultured and induced by IGF1 150 ng/mL was the most effective concentration for increasing the content of growth factor markers of SMMSCs-CM, which had successfully increased negative cartilage hypertrophy markers (SOX9 and COL2) and reduced hypertrophy markers (COL10, MMP13, and ADAMTS4). Preconditioning with IGF1 has better and very significant results in lowering MMP13 and ADAMTS4 levels. The present study supports IGF1 pre-conditioned SMMSCs-CM to develop a new therapeutic approach in OA improvement through its chondrogenic and chondroprotective roles.

The umbilical cord mesenchymal stem cell-derived exosomal lncRNA H19 improves osteochondral activity through miR-29b-3p/FoxO3 axis

BACKGROUND

Our previous study revealed that the exosomal lncRNA H19 derived from umbilical cord mesenchymal stem cells (UMSCs) plays a pivotal role in osteochondral regeneration. In this study, we investigated whether the exosomal lncRNA H19 could act as a competing endogenous RNA (ceRNA) to potentiate osteochondral activity in chondrocytes.

METHODS

Dual-luciferase reporter assay, RNA pull-down, RNA immunoprecipitation (RIP), and fluorescence in situ hybridization (FISH) were carried to verify the interaction between miR-29b-3p and both lncRNA H19 and the target mRNA FoxO3. Chondrocytes were treated with UMSC-derived exosomes, which highly expressing lncRNA H19 expression, followed by apoptosis, migration, senescence, and matrix secretion assessments. An in vivo SD rat cartilage defect model was carried out to explore the role and mechanism of lncRNA H19/miR-29b-3p.

RESULTS

UMSCs were successfully identified, and exosomes were successfully extracted. Exosomes exhibited the ability to transfer lncRNA H19 to chondrocytes. Mechanistically, exosomal lncRNA H19 potentiated osteochondral activity by acting as a competing endogenous sponge of miR-29b-3p, and miR-29b-3p directly targeted FoxO3. Intra-articular injection of exosomes overexpressing lncRNA H19 could promote sustained cartilage repair; however, this effect could be undermined by miR-29b-3p agomir.

CONCLUSIONS

Our study revealed a significant role in the development of strategies against cartilage defects for UMSC-derived exosomes that overexpress lncRNA H19. Exosomal H19 was found to promote chondrocyte migration, matrix secretion, apoptosis suppression, as well as senescence suppression, both in vitro and in vivo. The specific mechanism lies in the fact that exosomal H19 acts as a ceRNA against miR-29b-3p to upregulate FoxO3 in chondrocytes.

Adipogenesis, Osteogenesis, and Chondrogenesis of Human Mesenchymal Stem/Stromal Cells: A Comparative Transcriptome Approach

Adipogenesis, osteogenesis and chondrogenesis of human mesenchymal stem/stromal cells (MSC) are complex and highly regulated processes. Over the years, several studies have focused on understanding the mechanisms involved in the MSC commitment to the osteogenic, adipogenic and/or chondrogenic phenotypes. High-throughput methodologies have been used to investigate the gene expression profile during differentiation. Association of data analysis of mRNAs, microRNAs, circular RNAs and long non-coding RNAs, obtained at different time points over these processes, are important to depict the complexity of differentiation. This review will discuss the results that were highlighted in transcriptome analyses of MSC undergoing adipogenic, osteogenic and chondrogenic differentiation. The focus is to shed light on key molecules, main signaling pathways and biological processes related to different time points of adipogenesis, osteogenesis and chondrogenesis.

The Roles of FoxO Transcription Factors in Regulation of Bone Cells Function

Forkhead box class O family member proteins (FoxOs) are evolutionarily conserved transcription factors for their highly conserved DNA-binding domain. In mammalian species, all the four FoxO members, FoxO1, FoxO3, FoxO4, and FoxO6, are expressed in different organs. In bone, the first three members are extensively expressed and more studied. Bone development, remodeling, and homeostasis are all regulated by multiple cell lineages, including osteoprogenitor cells, chondrocytes, osteoblasts, osteocytes, osteoclast progenitors, osteoclasts, and the intercellular signaling among these bone cells. The disordered FoxOs function in these bone cells contribute to osteoarthritis, osteoporosis, or other bone diseases. Here, we review the current literature of FoxOs for their roles in bone cells, focusing on helping researchers to develop new therapeutic approaches and prevent or treat the related bone diseases.

Maintenance of SOX9 stability and ECM homeostasis by selenium-sensitive PRMT5 in cartilage

OBJECTIVES

Selenium (Se) plays pivotal roles in maintaining optimal health. Nevertheless, how Se influences the metabolism of extracellular matrix (ECM) in cartilage remains unclear. The aim of the present study was to observe protein dimethylation by certain Se-sensitive PRMT and to elucidate its effects on the key transcriptional factor in cartilage.

METHODS

We observed the expression of selenoproteins and markers of ECM metabolism in chondrocytes and articular cartilage of the rats under Se-deficiency by RT-qPCR, immunoblotting and immunohistochemistry. Then, we analyzed the expression of total dimethylated protein by using specific antibody under different Se statuses. After Se sensitive PRMT was identified, we used siRNA or PRMT inhibitor or stably overexpressing vector to intervene in the PRMT expression and identified the key transcriptional factor. Co-immunoprecipitation was applied to verify the interaction between PRMT and the key transcriptional factor. Finally, we measured the half-life time of the key transcriptional factor by immunoblotting after cycloheximide treatment.

RESULTS

In chondrocytes and cartilage of the rats with Se deficiency, we found an aberrant metabolism manifesting decreased expression of Col2a1 and increased expression of Mmp-3. Then, we identified that PRMT5 was the unique type II PRMT, sensitive to Se status. PRMT5 upregulation led to the increased COL2A1 expression but decreased MMP-3 expression in chondrocytes. Furthermore, we revealed that PRMT5 improved SOX9 stability by dimethylating the protein, which contributed to maintain the matrix metabolic homeostasis of the chondrocytes.

CONCLUSIONS

Se-sensitive PRMT5 increases the half-life of SOX9 protein via PTM and helps to maintain ECM homeostasis of the articular cartilage.

Anatomically shaped tissue-engineered cartilage with tunable and inducible anticytokine delivery for biological joint resurfacing

Biological resurfacing of entire articular surfaces represents an important but challenging strategy for treatment of cartilage degeneration that occurs in osteoarthritis. Not only does this approach require anatomically sized and functional engineered cartilage, but the inflammatory environment within an arthritic joint may also inhibit chondrogenesis and induce degradation of native and engineered cartilage. The goal of this study was to use adult stem cells to engineer anatomically shaped, functional cartilage constructs capable of tunable and inducible expression of antiinflammatory molecules, specifically IL-1 receptor antagonist (IL-1Ra). Large (22-mm-diameter) hemispherical scaffolds were fabricated from 3D woven poly(ε-caprolactone) (PCL) fibers into two different configurations and seeded with human adipose-derived stem cells (ASCs). Doxycycline (dox)-inducible lentiviral vectors containing eGFP or IL-1Ra transgenes were immobilized to the PCL to transduce ASCs upon seeding, and constructs were cultured in chondrogenic conditions for 28 d. Constructs showed biomimetic cartilage properties and uniform tissue growth while maintaining their anatomic shape throughout culture. IL-1Ra-expressing constructs produced nearly 1 µg/mL of IL-1Ra upon controlled induction with dox. Treatment with IL-1 significantly increased matrix metalloprotease activity in the conditioned media of eGFP-expressing constructs but not in IL-1Ra-expressing constructs. Our findings show that advanced textile manufacturing combined with scaffold-mediated gene delivery can be used to tissue engineer large anatomically shaped cartilage constructs that possess controlled delivery of anticytokine therapy. Importantly, these cartilage constructs have the potential to provide mechanical functionality immediately upon implantation, as they will need to replace a majority, if not the entire joint surface to restore function.

Intra-articular administration of xenogeneic neonatal Mesenchymal Stromal Cells early after meniscal injury down-regulates metalloproteinase gene expression in synovium and prevents cartilage degradation in a rabbit model of osteoarthritis

OBJECTIVE

The anti-inflammatory and anti-catabolic effects of neonatal Mesenchymal Stromal Cell (MSC) were investigated in a xenogeneic model of mild osteoarthritis (OA). The paracrine properties of MSC on synoviocytes were further investigated in vitro.

STUDY DESIGN

OA was induced by medial meniscal release (MMR) in 30 rabbit knees. A single early (day 3) or delayed (day 15) intra-articular (IA) injection of MSC isolated from equine Umbilical Cord Wharton's jelly (UC-MSC) was performed. Rabbits were euthanized on days 15 or 56. OA grading was performed and gene expression of inflammatory cytokines and metalloproteinases was measured in synovial tissue. Paracrine effects of UC-MSC were investigated using UC-conditioned vs control medium on rabbit primary synoviocytes stimulated with interleukin 1 beta in vitro.

RESULTS

No adverse local or systemic responses were observed clinically after xenogeneic UC-MSC injection. At study end point, cartilage fibrillation was lower in early treatment than in delayed treatment group. Cellular infiltrate was observed in the synovium of both UC-MSC groups. OA synovium exhibited a reduced expression of metalloproteinases-1, -3, -13 in the early cell-treated group at d56. In vitro, UC-conditioned medium exerted anti-inflammatory and anti-catabolic effects on synoviocytes exposed to pro-inflammatory stimulus.

CONCLUSIONS

Early IA injection of equine UC-MSC was effective in preventing OA signs in rabbit knees following MMR. UC-MSC target the synovium and modulate the gene expression pattern of synoviocytes to promote an anti-catabolic environment. This confirms the synovium is a major target and mediator of MSC therapy, modulating the expression of matrix-degrading enzymes.

Transcriptomics and proteomics in stem cell research

Stem cells are capable of self-renewal and differentiation, and the processes regulating these events are among the most comprehensively investigated topics in life sciences. In particular, the molecular mechanisms of the self-renewal, proliferation, and differentiation of stem cells have been extensively examined. Multi-omics integrative analysis, such as transcriptomics combined with proteomics, is one of the most promising approaches to the systemic investigation of stem cell biology. We reviewed the available information on stem cells by examining published results using transcriptomic and proteomic characterization of the different stem cell processes. Comprehensive understanding of these important processes can only be achieved using a systemic methodology, and employing such method will strengthen the study on stem cell biology and promote the clinical applications of stem cells.

FOXO3A regulation by miRNA-29a Controls chondrogenic differentiation of mesenchymal stem cells and cartilage formation

Skeletal development and cartilage formation require stringent regulation of gene expression for mesenchymal stem cells (MSCs) to progress through stages of differentiation. Since microRNAs (miRNAs) regulate biological processes, the objective of the present study was to identify novel miRNAs involved in the modulation of chondrogenesis. We performed miRNA profiling and identify miR-29a as being one of the most down-regulated miRNAs during the chondrogenesis. Using chromatin immunoprecipitation, we showed that SOX9 down-regulates its transcription. Moreover, the over-expression of miR-29a strongly inhibited the expression of chondrocyte-specific markers during in vitro chondrogenic differentiation of MSCs. We identified FOXO3A as a direct target of miR-29a and showed a down- and up-regulation of FOXO3a protein levels after transfection of, respectively, premiR- and antagomiR-29a oligonucleotides. Finally, we showed that using the siRNA or premiR approach, chondrogenic differentiation was inhibited to a similar extent. Together, we demonstrate that the down-regulation of miR-29a, concomitantly with FOXO3A up-regulation, is essential for the differentiation of MSCs into chondrocytes and in vivo cartilage/bone formation. The delivery of miRNAs that modulate MSC chondrogenesis may be applicable for cartilage regeneration and deserves further investigation.

Chondrogenic differentiation of human umbilical cord blood‑derived mesenchymal stem cells by co‑culture with rabbit chondrocytes

The objective of the current study was to investigate the ability of human umbilical cord blood‑derived mesenchymal stem cells (HUCB‑MSCs) to undergo chondrogenic differentiation, by co‑culture with rabbit chondrocytes. The aim was to obtain more seed cells for tissue engineering research and lay the foundation for the clinical repair of cartilage defects. The studies were performed using isolated rabbit cartilage cells and HUCB‑MSCs in vitro, which were co‑cultured in a 2:1 or 3:1 ratio with or without insulin‑like growth factor‑1 (IGF‑1). Following 7 and 14 days in culture, cell morphology was observed in each group. RNA and protein were extracted to assess the expression levels of aggrecan (ACAN) and collagen type II (COL2A) using quantitative polymerase chain reaction (qPCR) and western blotting, respectively. Groups of cells that were co‑cultured exhibited significantly higher expression levels of ACAN and COL2A mRNA and protein, compared with the reduced effect of IGF‑1 at days 7 and 14 in culture. The addition of IGF‑1 was found to potentiate these effects. Specifically, at day 7, cells co‑cultured at a ratio of 2:1 had a greater induction of ACAN and COL2A compared with cells co‑cultured at a 3:1 ratio. However, following 14 days culture, cells co‑cultured at a 3:1 ratio with additional IGF‑1 exhibited a greater induction of ACAN and COL2A compared with cells co‑cultured at a ratio of 2:1. Human chondrocytes may be successfully induced by co‑culture of HUCB‑MSCs with rabbit chondrocytes, thus providing a theoretical basis to obtain seed cells with the capacity to differentiate into multiple cell types, with low immunogenicity. Notably, these cells may provide a valuable resource for tissue engineering.

Enhanced apoptosis and senescence of bone-marrow-derived mesenchymal stem cells in patients with systemic lupus erythematosus

Previous studies indicated that bone marrow mesenchymal stem cells (BMSCs) from patients with systemic lupus erythematosus (SLE) exhibited impaired capacities of proliferation, differentiation, secretion of cytokines, and immune modulation. In this study, we aimed to investigate whether apoptosis and senescence of SLE BMSCs were dysregulated. We found that there were increased frequencies of apoptotic and aging SLE BMSCs in comparison with those of normal controls. Notably, levels of Bcl-2 expression in SLE BMSCs were markedly decreased both at mRNA and protein levels. When BMSCs were induced to apoptosis by tumor necrosis factor-α (TNF-α) stimulation in vitro, the Bax and caspase 8 expression in SLE BMSCs was significantly increased at mRNA levels. The activity of caspase 8 was also enhanced in SLE BMSCs. More cytochrome-C-positive pellets in the cytosolic fraction of BMSCs were detected in SLE patients than in normal controls. The expression of Fas and tumor necrosis factor-α receptor 1 in SLE BMSCs was significantly upregulated compared with normal controls, and the serum levels of FasL and TNF-α were also elevated. Moreover, intracellular reactive oxygen species levels of SLE BMSCs were higher than those of normal controls, with the activation of PI3K/AKT/FoxO3 signaling pathway. Taken together, our results demonstrate increased apoptosis and senescence in SLE BMSCs, which may be associated with the pathogenesis of SLE.

Mesenchymal stem cells in osteoarticular diseases

Multipotent mesenchymal stromal cells or mesenchymal stem cells (MSCs) are mainly isolated from bone marrow or fat tissue. Owing to their potential for multilineage differentiation towards bone, cartilage and fat tissue, they were initially evaluated in innovative strategies for tissue engineering. More recently, they have gained interest for their immunomodulatory properties and have been tested in various clinical trials that aim to modulate the host immune response in graft-versus-host disease or autoimmune diseases. MSC-mediated immunomodulation occurs through the secretion of soluble mediators. The clinical applications of MSCs for rheumatic diseases focus on their potential to promote tissue repair/regeneration and prevent inflammation. This article will focus on the mechanisms by which MSCs might exhibit a therapeutic potential in rheumatology. Special attention is given to their potential for innovative future strategies.

Comparison of Gene Expression in Human Embryonic Stem Cells, hESC-Derived Mesenchymal Stem Cells and Human Mesenchymal Stem Cells

We present a strategy to identify developmental/differentiation and plasma membrane marker genes of the most primitive human Mesenchymal Stem Cells (hMSCs). Using sensitive and quantitative TaqMan Low Density Arrays (TLDA) methodology, we compared the expression of 381 genes in human Embryonic Stem Cells (hESCs), hESC-derived MSCs (hES-MSCs), and hMSCs. Analysis of differentiation genes indicated that hES-MSCs express the sarcomeric muscle lineage in addition to the classical mesenchymal lineages, suggesting they are more primitive than hMSCs. Transcript analysis of membrane antigens suggests that IL1R1^low, BMPR1B^low, FLT4^low, LRRC32^low, and CD34 may be good candidates for the detection and isolation of the most primitive hMSCs. The expression in hMSCs of cytokine genes, such as IL6, IL8, or FLT3LG, without expression of the corresponding receptor, suggests a role for these cytokines in the paracrine control of stem cell niches. Our database may be shared with other laboratories in order to explore the considerable clinical potential of hES-MSCs, which appear to represent an intermediate developmental stage between hESCs and hMSCs.

Human bone marrow mesenchymal stem cells: a systematic reappraisal via the genostem experience

Genostem (acronym for "Adult mesenchymal stem cells engineering for connective tissue disorders. From the bench to the bed side") has been an European consortium of 30 teams working together on human bone marrow Mesenchymal Stem Cell (MSC) biological properties and repair capacity. Part of Genostem activity has been dedicated to the study of basic issues on undifferentiated MSCs properties and on signalling pathways leading to the differentiation into 3 of the connective tissue lineages, osteoblastic, chondrocytic and tenocytic. We have evidenced that native bone marrow MSCs and stromal cells, forming the niche of hematopoietic stem cells, were the same cellular entity located abluminally from marrow sinus endothelial cells. We have also shown that culture-amplified, clonogenic and highly-proliferative MSCs were bona fide stem cells, sharing with other stem cell types the major attributes of self-renewal and of multipotential priming to the lineages to which they can differentiate (osteoblasts, chondrocytes, adipocytes and vascular smooth muscle cells/pericytes). Extensive transcription profiling and in vitro and in vivo assays were applied to identify genes involved in differentiation. Thus we have described novel factors implicated in osteogenesis (FHL2, ITGA5, Fgf18), chondrogenesis (FOXO1A) and tenogenesis (Smad8). Another part of Genostem activity has been devoted to studies of the repair capacity of MSCs in animal models, a prerequisite for future clinical trials. We have developed novel scaffolds (chitosan, pharmacologically active microcarriers) useful for the repair of both bone and cartilage. Finally and most importantly, we have shown that locally implanted MSCs effectively repair bone, cartilage and tendon.