Différenciation des cellules souches mésenchymateuses adultes humaines : effet chondrogénique de la BMP-2

Spheroid Culture System, a Promising Method for Chondrogenic Differentiation of Dental Mesenchymal Stem Cells

The objective of the present work was to develop a three-dimensional culture model to evaluate, in a short period of time, cartilage tissue engineering protocols. The spheroids were compared with the gold standard pellet culture. The dental mesenchymal stem cell lines were from pulp and periodontal ligament. The evaluation used RT-qPCR and Alcian Blue staining of the cartilage matrix. This study showed that the spheroid model allowed for obtaining greater fluctuations of the chondrogenesis markers than for the pellet one. The two cell lines, although originating from the same organ, led to different biological responses. Finally, biological changes were detectable for short periods of time. In summary, this work demonstrated that the spheroid model is a valuable tool for studying chondrogenesis and the mechanisms of osteoarthritis, and evaluating cartilage tissue engineering protocols.

Osteoarthritis of the Temporomandibular Joint: A Narrative Overview

Background and Objectives: This study reviewed the literature to summarize the current and recent knowledge of temporomandibular joint osteoarthritis (TMJOA). Methods: Through a literature review, this work summarizes many concepts related to TMJOA. Results: Although many signaling pathways have been investigated, the etiopathogenesis of TMJOA remains unclear. Some clinical signs are suggestive of TMJOA; however, diagnosis is mainly based on radiological findings. Treatment options include noninvasive, minimally invasive, and surgical techniques. Several study models have been used in TMJOA studies because there is no gold standard model. Conclusion: More research is needed to develop curative treatments for TMJOA, which could be tested with reliable in vitro models, and to explore tissue engineering to regenerate damaged temporomandibular joints.

Evaluation of Allogeneic Bone-Marrow-Derived and Umbilical Cord Blood-Derived Mesenchymal Stem Cells to Prevent the Development of Osteoarthritis in An Equine Model

Osteoarthritis (OA) is a significant cause of pain in both humans and horses with a high socio-economic impact. The horse is recognized as a pertinent model for human OA. In both species, regenerative therapy with allogeneic mesenchymal stem cells (MSCs) appears to be a promising treatment but, to date, no in vivo studies have attempted to compare the effects of different cell sources on the same individuals. The objective of this study is to evaluate the ability of a single blinded intra-articular injection of allogeneic bone-marrow (BM) derived MSCs and umbilical cord blood (UCB) derived MSC to limit the development of OA-associated pathological changes compared to placebo in a post-traumatic OA model applied to all four fetlock joints of eight horses. The effect of the tissue source (BM vs. UCB) is also assessed on the same individuals. Observations were carried out using clinical, radiographic, ultrasonographic, and magnetic resonance imaging methods as well as biochemical analysis of synovial fluid and postmortem microscopic and macroscopic evaluations of the joints until Week 12. A significant reduction in the progression of OA-associated changes measured with imaging techniques, especially radiography, was observed after injection of bone-marrow derived mesenchymal stem cells (BM-MSCs) compared to contralateral placebo injections. These results indicate that allogeneic BM-MSCs are a promising treatment for OA in horses and reinforce the importance of continuing research to validate these results and find innovative strategies that will optimize the therapeutic potential of these cells. However, they should be considered with caution given the low number of units per group.

MicroRNA-99a regulates early chondrogenic differentiation of rat mesenchymal stem cells by targeting the BMPR2 gene

Mesenchymal stem cells (MSCs) are candidates for the regeneration of articular cartilage as they possess the potential for chondrogenic differentiation. MSCs are easily obtained and expanded in vitro. Specific microRNAs (miRNAs) that regulate chondrogenesis have yet to be identified and the mechanisms involved remain to be defined. The miRNAs regulate biological processes by binding target mRNA to reduce protein synthesis. In this study, we show that expression of miR-99a and miR-125b-3p were increased during early chondrogenic differentiation of MSCs (rMSCs) derived from the Norwegian brown rat (Rattus norvegicus). MiR-99a knockdown promoted proteoglycan deposition and increased the expression of ACAN and COL2A1 during early chondrogenic differentiation. MiR-99a knockdown promoted early chondrogenic differentiation of rMSCs. A dual-luciferase reporter gene assay showed that miR-99a targeted a putative binding site in the 3'-UTR of bone morphogenetic protein (BMP) receptor type 2 (BMPR2). Overexpression of miR-99a reduced the expression levels of BMPR2 protein. The expression of total p38 and p-p38 increased at 7 and 14 days during early chondrogenic differentiation of rMSCs. Reduction in levels of total p38 and p-p38 protein followed miR-99a overexpression during early chondrogenic differentiation of rMSCs. BMPR2 silencing reversed the effects of miR-99a inhibition on proteoglycan deposition and protein expression of ACAN, COL2A1, total p38 and p-p38 during early chondrogenic differentiation of rMSCs. In conclusion, the findings of these in vitro studies in rat MSCs support a role for miR-99a as a negative regulator of early chondrogenic differentiation by directly targeting the BMPR2 gene at an early stage.

Effect of autologous platelet-rich plasma on the chondrogenic differentiation of rabbit adipose-derived stem cells in vitro

This study aimed to isolate rabbit adipose-derived stem cells (ADSCs) and explore the potential of platelet-rich plasma (PRP) in the chondrogenic differentiation of ADSCs, thereby potentially providing a new approach for the repair and regeneration of cartilage injury. Rabbit ADSCs were isolated and characterized by induction towards adipogenic, osteogenic and chondrogenic lineages in vitro. The isolated ADSCs were also cultured with or without 10% PRP. Immunofluorescence staining, toluidine blue staining and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) were used to detect type II collagen (Col II) and aggrecan (AGC) expression. Col II immunofluorescence staining and toluidine blue staining indicated that following induction by autologous PRP, ADSCs manifested Col II and AGC expression. The expression of Col II and AGC mRNA was significantly upregulated in the PRP-treated cells when compared with that in control cells. Autologous PRP produced by laboratory centrifugation was able to promote the chondrogenic differentiation of rabbit ADSCs in vitro.

Decreased BMP2 signal in GIT1 knockout mice slows bone healing

Endochondral ossification, an important stage of fracture healing, is regulated by a variety of signaling pathways. Transforming growth factor β (TGFβ) superfamily plays important roles and comprises TGFβs, bone morphogenetic proteins (BMPs), and growth differentiation factors. TGFβs primarily regulate cartilage formation and endochondral ossification. BMP2 shows diverse efficacy, from the formation of skeleton and extraskeletal organs to the osteogenesis and remodeling of bone. G-protein-coupled receptor kinase 2-interacting protein-1 (GIT1), a shuttle protein in osteoblasts, facilitates fracture healing by promoting bone formation and increasing the secretion of vascular endothelial growth factor. Our study examined whether GIT1 regulates fracture healing through the BMP2 signaling pathway and/or through the TGFβ signaling pathway. GIT1 knockout (KO) mice exhibited delayed fracture healing, chondrocyte accumulation in the fracture area, and reduced staining intensity of phosphorylated Smad1/5/8 (pSmad1/5/8) and Runx2. Endochondral mineralization diminished while the staining intensity of phosphorylated Smad2/3 (pSmad2/3) showed no significant change. Bone marrow mesenchymal stem cells extracted from GIT1 KO mice showed a decline of pSmad1/5/8 levels and of pSmad1/5/8 translocated into the cell nucleus after BMP2 stimulus. We detected no significant change in the pSmad2/3 level after TGFβ1 stimulus. Data obtained from reporter gene analysis of C3H10T1/2 cells cultured in vitro confirmed these findings. GIT1-siRNA inhibited transcription in the cell nucleus via pSmad1/5/8 after BMP2 stimulus but had no significant effect on transcription via pSmad2/3 after TGFβ1 stimulus. Our results indicate that GIT1 regulates Smad1/5/8 phosphorylation and mediates BMP2 regulation of Runx2 expression, thus affecting endochondral ossification at the fracture site.

In vivo ectopic implantation model to assess human mesenchymal progenitor cell potential

Clinical interest on human mesenchymal progenitor cells (hMPC) relies on their potential applicability in cell-based therapies. An in vitro characterization is usually performed in order to define MPC potency. However, in vitro predictions not always correlate with in vivo results and thus there is no consensus in how to really assess cell potency. Our goal was to provide an in vivo testing method to define cell behavior before therapeutic usage, especially for bone tissue engineering applications. In this context, we wondered whether bone marrow stromal cells (hBMSC) would proceed in an osteogenic microenvironment. Based on previous approaches, we developed a fibrin/ceramic/BMP-2/hBMSCs compound. We implanted the compound during only 2 weeks in NOD-SCID mice, either orthotopically to assess its osteoinductive property or subcutaneously to analyze its adequacy as a cell potency testing method. Using fluorescent cell labeling and immunohistochemistry techniques, we could ascertain cell differentiation to bone, bone marrow, cartilage, adipocyte and fibrous tissue. We observed differences in cell potential among different batches of hBMSCs, which did not strictly correlate with in vitro analyses. Our data indicate that the method we have developed is reliable, rapid and reproducible to define cell potency, and may be useful for testing cells destined to bone tissue engineering purposes. Additionally, results obtained with hMPCs from other sources indicate that our method is suitable for testing any potentially implantable mesenchymal cell. Finally, we propose that this model could successfully be employed for bone marrow niche and bone tumor studies.

Cartilage tissue engineering: molecular control of chondrocyte differentiation for proper cartilage matrix reconstruction

BACKGROUND

Articular cartilage defects are a veritable therapeutic problem because therapeutic options are very scarce. Due to the poor self-regeneration capacity of cartilage, minor cartilage defects often lead to osteoarthritis. Several surgical strategies have been developed to repair damaged cartilage. Autologous chondrocyte implantation (ACI) gives encouraging results, but this cell-based therapy involves a step of chondrocyte expansion in a monolayer, which results in the loss in the differentiated phenotype. Thus, despite improvement in the quality of life for patients, reconstructed cartilage is in fact fibrocartilage. Successful ACI, according to the particular physiology of chondrocytes in vitro, requires active and phenotypically stabilized chondrocytes.

SCOPE OF REVIEW

This review describes the unique physiology of cartilage, with the factors involved in its formation, stabilization and degradation. Then, we focus on some of the most recent advances in cell therapy and tissue engineering that open up interesting perspectives for maintaining or obtaining the chondrogenic character of cells in order to treat cartilage lesions.

MAJOR CONCLUSIONS

Current research involves the use of chondrocytes or progenitor stem cells, associated with "smart" biomaterials and growth factors. Other influential factors, such as cell sources, oxygen pressure and mechanical strain are considered, as are recent developments in gene therapy to control the chondrocyte differentiation/dedifferentiation process.

GENERAL SIGNIFICANCE

This review provides new information on the mechanisms regulating the state of differentiation of chondrocytes and the chondrogenesis of mesenchymal stem cells that will lead to the development of new restorative cell therapy approaches in humans. This article is part of a Special Issue entitled Matrix-mediated cell behaviour and properties.

New insights into osteogenic and chondrogenic differentiation of human bone marrow mesenchymal stem cells and their potential clinical applications for bone regeneration in pediatric orthopaedics

Human mesenchymal stem cells (hMSCs) are pluripotent adult stem cells capable of being differentiated into osteoblasts, adipocytes, and chondrocytes. The osteogenic differentiation of hMSCs is regulated either by systemic hormones or by local growth factors able to induce specific intracellular signal pathways that modify the expression and activity of several transcription factors. Runt-related transcription factor 2 (Runx2) and Wnt signaling-related molecules are the major factors critically involved in the osteogenic differentiation process by hMSCs, and SRY-related high-mobility-group (HMG) box transcription factor 9 (SOX9) is involved in the chondrogenic one. hMSCs have generated a great interest in the field of regenerative medicine, particularly in bone regeneration. In this paper, we focused our attention on the molecular mechanisms involved in osteogenic and chondrogenic differentiation of hMSC, and the potential clinical use of hMSCs in osteoarticular pediatric disease characterized by fracture nonunion and pseudarthrosis.

Chondrocytes or adult stem cells for cartilage repair: the indisputable role of growth factors

Articular cartilage is easily injured but difficult to repair and cell therapies are proposed as tools to regenerate the defects in the tissue. Both differentiated chondrocytes and adult mesenchymal stem cells (MSCs) are regarded as cells potentially able to restore a functional cartilage. However, it is a complex process from the cell level to the tissue end product, during which growth factors play important roles from cell proliferation, extracellular matrix synthesis, maintenance of the phenotype to induction of MSCs towards chondrogenesis. Members of the TGF-β superfamily, are especially important in fulfilling these roles. Depending on the cell type chosen to restore cartilage, the effect of growth factors will vary. In this review, the roles of these factors in the maintenance of the chondrocyte phenotype are discussed and compared with those of factors involved in the repair of cartilage defects, using chondrocytes or adult mesenchymal stem cells.

Cartilage-characteristic matrix reconstruction by sequential addition of soluble factors during expansion of human articular chondrocytes and their cultivation in collagen sponges

OBJECTIVE

Articular cartilage has a poor capacity for spontaneous repair. Tissue engineering approaches using biomaterials and chondrocytes offer hope for treatments. Our goal was to test whether collagen sponges could be used as scaffolds for reconstruction of cartilage with human articular chondrocytes. We investigated the effects on the nature and abundance of cartilage matrix produced of sequential addition of chosen soluble factors during cell amplification on plastic and cultivation in collagen scaffolds.

DESIGN

Isolated human articular chondrocytes were amplified for two passages with or without a cocktail of fibroblast growth factor (FGF)-2 and insulin (FI). The cells were then cultured in collagen sponges with or without a cocktail of bone morphogenetic protein (BMP)-2, insulin, and triiodothyronine (BIT). The constructs were cultivated for 36 days in vitro or for another 6-week period in a nude mouse-based contained-defect organ culture model. Gene expression was analyzed using polymerase chain reaction, and protein production was analyzed using Western-blotting and immunohistochemistry.

RESULTS

Dedifferentiation of chondrocytes occurred during cell expansion on plastic, and FI stimulated this dedifferentiation. We found that addition of BIT could trigger chondrocyte redifferentiation and cartilage-characteristic matrix production in the collagen sponges. The presence of FI during cell expansion increased the chondrocyte responsiveness to BIT.