Mesenchymal Stem Cells In Osteoarthritis Research Articles

Factors affecting osteogenesis and chondrogenic differentiation of mesenchymal stem cells in osteoarthritis

Factors affecting osteogenesis and chondrogenic differentiation of mesenchymal stem cells in osteoarthritis

Retracted: Novel Therapeutic Mechanism of Adipose-Derived Mesenchymal Stem Cells in Osteoarthritis via Upregulation of BTG2.

[This retracts the article DOI: 10.1155/2022/9252319.].

Dissection of Cellular Communication between Human Primary Osteoblasts and Bone Marrow Mesenchymal Stem Cells in Osteoarthritis at Single-Cell Resolution.

Osteoblasts are derived from bone marrow mesenchymal stem cells (BMMSCs) and play important role in bone remodeling. While our previous studies have investigated the cell subtypes and heterogeneity in osteoblasts and BMMSCs separately, cell-to-cell communications between osteoblasts and BMMSCs in vivo in humans have not been characterized. The aim of this study was to investigate the cellular communication between human primary osteoblasts and bone marrow mesenchymal stem cells. To investigate the cell-to-cell communications between osteoblasts and BMMSCs and identify new cell subtypes, we performed a systematic integration analysis with our single-cell RNA sequencing (scRNA-seq) transcriptomes data from BMMSCs and osteoblasts. We successfully identified a novel preosteoblasts subtype which highly expressed ATF3, CCL2, CXCL2 and IRF1. Biological functional annotations of the transcriptomes suggested that the novel preosteoblasts subtype may inhibit osteoblasts differentiation, maintain cells to a less differentiated status and recruit osteoclasts. Ligand-receptor interaction analysis showed strong interaction between mature osteoblasts and BMMSCs. Meanwhile, we found FZD1 was highly expressed in BMMSCs of osteogenic differentiation direction. WIF1 and SFRP4, which were highly expressed in mature osteoblasts were reported to inhibit osteogenic differentiation. We speculated that WIF1 and sFRP4 expressed in mature osteoblasts inhibited the binding of FZD1 to Wnt ligand in BMMSCs, thereby further inhibiting osteogenic differentiation of BMMSCs. Our study provided a more systematic and comprehensive understanding of the heterogeneity of osteogenic cells. At the single cell level, this study provided insights into the cell-to-cell communications between BMMSCs and osteoblasts and mature osteoblasts may mediate negative feedback regulation of osteogenesis process.

Mesenchymal stem cells in osteoarthritis: The need for translation into clinical therapy.

Widely used for cell-based therapy in various medical fields, mesenchymal stem cells (MSCs) show capacity for anti-inflammatory effects, anti-apoptotic activity, immunomodulation, and tissue repair and regeneration. As such, they can potentially be used to treat osteoarthritis (OA). However, MSCs from different sources have distinct advantages and disadvantages, and various animal models and clinical trials using different sources of MSCs are being conducted in OA regenerative medicine. It is now widely believed that the primary tissue regeneration impact of MSCs is via paracrine effects, rather than direct differentiation and replacement. Cytokines and molecules produced by MSCs, including extracellular vesicles with mRNAs, microRNAs, and bioactive substances, play a significant role in OA repair. This chapter outlines the properties of MSCs and recent animal models and clinical trials involving MSCs-based OA therapy, as well as how the paracrine effect of MSCs acts in OA cartilage repair. Additionally, it discusses challenges and controversies in MSCs-based OA therapy. Despite its limits and unanticipated hazards, MSCs have the potential to be translated into therapeutic therapy for future OA treatment.

Novel Therapeutic Mechanism of Adipose-Derived Mesenchymal Stem Cells in Osteoarthritis via Upregulation of BTG2.

Background Osteoarthritis (OA) is a debilitating and degenerative joint disease, which is characterized by progressive destruction of articular cartilage. Mesenchymal stem cells (MSCs) have been implicated in the treatment of OA. However, the function of adipose-derived MSCs (AD-MSCs) in OA and its underlying mechanism remain obscure. Aim We aimed to explore the function of AD-MSCs in OA and investigate its potential regulatory mechanism. Methods A guinea pig model of OA was constructed. AD-MSCs injected into the articular cavity of OA guinea pigs were viewed by in vivo bioluminescence imaging. The effect of AD-MSCs on the gonarthritis of OA guinea pigs was evaluated through both macroscopic and microscopic detections. The detailed molecular mechanism was predicted by GEO databases and bioinformatics tools and then verified via mechanism experiments, including ChIP assay, DNA pulldown assay, and luciferase reporter assay. Results AD-MSCs had a significant positive therapeutic effect on the gonarthritis of the OA model, and the overall effects of it was better than that of sodium hyaluronate (SH). B-cell translocation gene 2 (BTG2) was significantly downregulated in the articular cartilage of the OA guinea pigs. Furthermore, BTG2 was positively regulated by Krüppel-like factor 4 (KLF4) in AD-MSCs at the transcriptional level. AD-MSCs performed an effect on KLF4 expression at the transcriptional levels. Conclusion AD-MSCs suppresses OA progression through KLF4-induced transcriptional activation of BTG2. Our findings revealed an AD-MSCs-dominated therapeutic method for OA.

Accentuating the sources of mesenchymal stem cells as cellular therapy for osteoarthritis knees-a panoramic review.

The large economic burden on the global health care systems is due to the increasing number of symptomatic osteoarthritis (OA) knee patients whereby accounting for greater morbidity and impaired functional quality of life. The recent developments and impulses in molecular and regenerative medicine have paved the way for inducing the biological active cells such as stem cells, bioactive materials, and growth factors towards the healing and tissue regenerative process. Mesenchymal stem cells (MSCs) act as a minimally invasive procedure that bridges the gap between pharmacological treatment and surgical treatment for OA. MSCs are the ideal cell-based therapy for treating disorders under a minimally invasive environment in conjunction with cartilage regeneration. Due to the worldwide recognized animal model for such cell-based therapies, global researchers have started using the various sources of MSCs towards cartilage regeneration. However, there is a lacuna in literature on the comparative efficacy and safety of various sources of MSCs in OA of the knee. Hence, the identification of a potential source for therapeutic use in this clinical scenario remains unclear. In this article, we compared the therapeutic effects of various sources of MSCs in terms of efficacy, safety, differentiation potential, durability, accessibility, allogenic preparation and culture expandability to decide the optimal source of MSCs for OA knee.

Senescence did not alter the chondroprotective effect of extracellular vesicles from adipose mesenchymal stem cells in osteoarthritis

Purpose: Age is the most important risk factor in degenerative osteoarthritis (OA) and is associated with the accumulation of senescent cells that contribute to functional decline of joint. We previously demonstrated that extracellular vesicles (EVs) from mesenchymal stromal cells (MSCs) largely mediate the therapeutic effect of parental cells in OA. Here, we assessed the impact of senescence on the characteristics of EVs from adipose tissue-derived MSCs (ASC-EVs) and their properties in an in vitro model of OA Methods: ASCs were induced to senescence using 25μM etoposide for 24 hours. Senescence was assessed at day 12 by quantifying proliferation rate (Trypan blue counting, BrdU incorporation), SA-βGal activity (immunostaining and dedicated quantitative assay), nuclear γH2AX foci number (immunofluorescence), stress fiber visualization (phalloidin staining) and expression of cyclin dependent kinase inhibitors (CDKI) (RT-qPCR). ASC-EVs were isolated by differential ultracentrifugation and characterized by size, concentration, total protein content, structure (cryo-TEM) and immunophenotype (CD9, CD63, CD81, Alix). In vitro OA model used human chondrocytes isolated from OA patients, which were stimulated with IL1β for 48h before culture with ASCs or ASC-EVs for 7 days. Expression of chondrocytic and inflammatory markers was quantified by RT-qPCR and SASP factors were quantified by ELISA in supernatants Results: After 12 days, senescence-induced ASCs experienced growth arrest and increase of SA-βGal staining, of p21 CDKI expression, of nuclear γH2AX foci, of stress fibers and of several SASP factors (IL6, IL8, MMP3) confirming expression of all main features of senescence. Senescent ASCs produced 4-fold more EVs than healthy ASCs and senescent ASC-EVs were larger and contained slightly less total protein amounts. In the in vitro model of OA chondrocytes, both healthy and senescent ASCs decreased fibrotic markers (type III COLLAGEN), catabolic and hypertrophic markers (MMP3, MMP13, AP) and increased COX2. By contrast, healthy ASCs decreased the expression of IL6 while senescent ASCs highly increased IL6 expression in OA chondrocytes. Looking at the role of ASC-EVs on OA chondrocytes, we found out that both healthy and senescent ASC-EVs were able to increase the expression of AGG and type II COLLAGEN while they decreased the expression of MMP13, AP, type X COLLAGEN, HMOX1 and IL6. Finally, healthy and senescent ASC-EVs decreased the number of SA-βGal positive OA chondrocytes but did not impact the expression of p21 in these IL1β-induced chondrocytes. Conclusions: Our Results indicated a chondroprotective effect of ASC-EVs, independently of the senescent state of parental cells and suggested that EVs might act through different mechanisms than ASCs, which warrants further investigation

Characteristics of MSCs in Synovial Fluid and Mode of Action of Intra-Articular Injections of Synovial MSCs in Knee Osteoarthritis.

We have been studying mesenchymal stem cells (MSCs) in synovial fluid and the intra-articular injection of synovial MSCs in osteoarthritis (OA) knees. Here, mainly based on our own findings, we overview the characteristics of endogenous MSCs in the synovial fluid of OA knees and their mode of action when injected exogenously into OA knees. Many MSCs similar to synovial MSCs were detected in the synovial fluid of human OA knees, and their number correlated with the radiological OA grade. Our suspended synovium culture model demonstrated the release of MSCs from the synovium through a medium into a non-contacting culture dish. In OA knees, endogenous MSCs possibly mobilize in a similar manner from the synovium through the synovial fluid and act protectively. However, the number of mobilized MSCs is limited; therefore, OA progresses in its natural course. Synovial MSC injections inhibited the progression of cartilage degeneration in a rat OA model. Injected synovial MSCs migrated into the synovium, maintained their MSC properties, and increased the gene expressions of TSG-6, PRG-4, and BMP-2. Exogenous synovial MSCs can promote anti-inflammation, lubrication, and cartilage matrix synthesis in OA knees. Based on our findings, we have initiated a human clinical study of synovial MSC injections in OA knees.

Implanted 3D gelatin microcryogel enables low-dose cell therapy for osteoarthritis by preserving the viability and function of umbilical cord MSCs

Mesenchymal stem cells (MSCs) have shown promise as a therapy for osteoarthritis (OA). However, to date there is no standardized cell dosage, and the mechanism of action of MSCs in OA is still not completely understood. Biomaterials are considered to improve seeded cell function, so we established biocompatible and biodegradable gelatin microcryogels (GMs) as the carrier for umbilical cord–derived MSCs (UCMSCs) in this study. First, we generated UCMSC-GM complexes, optimized the pore size and cell density, and discovered that GMs enhanced cell viability and growth factor secretion, especially epidermal growth factors (EGF), under different biomechanical conditions, which is possibly mediated by tumor necrosis factor-alpha converting enzyme (TACE), a metalloproteinase crucial for EGF mature and release. In addition, Luciferase tracing and GFP fluorescence assay showed that GMs enhanced the retention of UCMSCs in the knee joint of mice. Then, we treated mice with OA knee joints with either low-dose free MSCs (3 × 104 cells), UCMSC-loaded GMs (3 × 104 cells) or high-dose free MSCs (3 × 105 cells), and found that UCMSC-GMs (3 × 104 cells) promoted cartilage regeneration and inhibited macrophage-mediated synovitis better than low-dose free UCMSCs, and achieved a similar effect to that of high-dose (3 × 105 cells) treatment. Further transwell assay showed that GMs promoted chondrocyte anabolism in vitro, which is greatly blocked by Gefitinib, an EGF receptor (EGFR) signalling pathway inhibitor. In conclusion, this study provides evidence that the UCMSC-GM complex exhibited a significantly stronger effect in attenuating OA progression compared to UCMSCs alone even at a low dose, and these results shed light on the clinical application of cell therapy for OA.

Associations of clinical outcomes and MRI findings in intra-articular administration of autologous adipose-derived stem cells for knee osteoarthritis

IntroductionClinical studies of intra-articular injection of mesenchymal stem cells for osteoarthritis (OA) indicate its efficacy. Here, we retrospectively investigated the associations of pretherapeutic magnetic resonance imaging (MRI) findings with the clinical outcomes up to 6 months, after intra-articular administration of adipose-derived stem cells (ASCs) to knee OA patients.MethodsWe first analyzed alterations of the visual analog scale (VAS) and knee injury and osteoarthritis outcome score (KOOS) in 57 knees of 34 patients from whom clinical scores were obtained before ASC therapy, and at 1, 3, and 6 months. Among the patients, we further examined MRI findings of 34 knees of 19 patients whose pretherapeutic MRI data were available.ResultsThe mean improvement of VAS and KOOS-total during 6 months was 2.6 ± 4.0 (from 6.1 ± 2.5 to 3.5 ± 2.9, P < 0.001) and 10.2 ± 12.4 (from 54.4 ± 12.7 to 64.6 ± 13.8, P < 0.01), respectively. Scales related to pain and symptoms improved earlier than those related to activities of daily living (ADL) and sports/recreation. Improvement of VAS and KOOS-sports/recreation was significantly higher in patients with more severe cartilage lesions. Similarly, osteophyte lesions were associated significantly with improvement of VAS and KOOS-ADL, and BML was associated with KOOS-ADL and KOOS-sports/recreation.ConclusionsIn intra-articular administration of autologous ASCs for knee OA, improvement of VAS and KOOS-sports/recreation was significantly higher in patients with more severe cartilage lesions. Similarly, osteophyte lesions were associated significantly with improvement of VAS and KOOS-ADL, and BML was associated with KOOS-ADL and KOOS-sports/recreation. Clinical studies with larger numbers of patients and various kinds of data are necessary to predict therapeutic effects.

Interleukin-4 Gene Transfection and Spheroid Formation Potentiate Therapeutic Efficacy of Mesenchymal Stem Cells for Osteoarthritis.

Osteoarthritis (OA) is a painful intractable disease that significantly affects patients' quality of life. However, current therapies, such as pain killers and joint replacement surgery, do not lead to cartilage protection. Mesenchymal stem cells (MSCs) have been proposed as an alternative strategy for OA therapy because MSCs can secrete chondroprotective and anti-inflammatory factors. However, interleukin-4 (IL-4), a potent anti-inflammatory cytokine, is barely produced by MSCs, and MSC therapy suffers from rapid MSC death following intra-articular implantation. MSCs in spheroids survive better than naïve MSCs in vitro and in vivo. IL-4-transfected MSCs in spheroids (IL-4 MSC spheroid) show increased chondroprotective and anti-inflammatory effects in an OA chondrocyte model in vitro. Following intra-articular implantation in OA rats, IL-4 MSC spheroids show better cartilage protection and pain relief than naïve MSCs. Thus, IL-4 MSC spheroid may potentiate the therapeutic efficacy of MSCs for OA.

Intra-articular Injection of Cell-laden 3D Microcryogels Empower Low-dose Cell Therapy for Osteoarthritis in a Rat Model

Intra-articular injection of mesenchymal stem cells (MSCs) in an osteoarthritic joint can help slow down cartilage destruction. However, cell survival and the efficiency of repair are generally low due to mechanical damage during injection and a high rate of cell loss. We, thus, investigated an improved strategy for cell delivery to an osteoarthritic joint through the use of three-dimensional (3D) microcryogels. MSCs were seeded into 3D microcryogels. The viability and proliferation of MSCs in microcryogels were determined over 5 d, and the phenotype of MSCs was confirmed through trilineage differentiation tests and flow cytometry. In Sprague Dawley rats with induced osteoarthritis (OA) of the knee joint, a single injection was made with the following groups: saline control, low-dose free MSCs (1 × 105 cells), high-dose free MSCs (1 × 106 cells), and microcryogels + MSCs (1 × 105 cells). Cartilage degeneration was evaluated by macroscopic examination, micro-computed tomographic analysis, and histology. MSCs grown in microcryogels exhibited optimal viability and proliferation at 3 d with stable maintenance of phenotype in vitro. Microcryogels seeded with MSCs were, therefore, primed for 3 d before being used for in vivo experiments. At 4 and 8 wk, the microcryogels + MSCs and high-dose free MSC groups had significantly higher International Cartilage Repair Society macroscopic scores, histological evidence of more proteoglycan deposition and less cartilage loss accompanied by a lower Mankin score, and minimal radiographic evidence of osteoarthritic changes in the joint compared to the other two groups. In conclusion, intra-articular injection of cell-laden 3D microcryogels containing a low dose of MSCs can achieve similar effects as a high dose of free MSCs for OA in a rat model. Primed MSCs in 3D microcryogels can be considered as an improved delivery strategy for cell therapy in treating OA that minimizes cell dose while retaining therapeutic efficacy.

Wharton's Jelly-derived Mesenchymal Stem Cells in Osteoarthritis

Wharton's Jelly-derived Mesenchymal Stem Cells in Osteoarthritis

Intra-articular injection of mesenchymal stem cells for clinical outcomes and cartilage repair in osteoarthritis of the knee: a meta-analysis of randomized controlled trials.

Mesenchymal stem cells (MSCs) have gained popularity for articular cartilage repair. However, efficacy of intra-articular MSCs in osteoarthritis remains unclear. In the setting of a meta-analysis of randomized controlled trials (RCTs), we aimed to investigate the efficacy of intra-articular MSCs on clinical outcomes and cartilage repair in patients with knee osteoarthritis. PubMed, EMBASE, Cochrane Library, CINAHL, and Scopus were searched from inception to March 31, 2017. This study included RCTs using cell population containing MSCs for treatment of knee osteoarthritis. The quality was assessed by Cochrane Collaboration`s risk of bias tool. For meta-analysis, data on clinical outcomes measured by visual analog scale (VAS), Lysholm score, WOMAC and data on cartilage repair measured by MOCART and WORMS were extracted. In studies with several cell concentrations, outcomes of recommended concentration were used mainly to ensure robustness. A total of five RCTs (220 patients) were included. Two studies were deemed to have low risk of bias. In pooled analysis, there was significant difference in VAS score (mean difference [MD], - 9.2; 95% CI: - 17.21, - 1.20) and Lysholm score (MD, 8.70; 95% CI 0.06, 17.34), but not WOMAC (MD, - 7.44; 95% CI - 20.38, 5.50). In cumulative functional analysis using Lysholm score and WOMAC in recommended concentration, there was a significant improvement (standard mean difference [SMD], 0.53; 95% CI 0.13, 0.94) after treatment. In cartilage repair assessed by MRI, there was no significant difference (SMD, 0.53; 95% CI- 0.28, 1.34). This meta-analysis demonstrated that intra-articular MSCs have a limited evidence in pain relief and functional improvement in knee osteoarthritis. While MSCs may result in favorable clinical outcomes with a recommended concentration, use of concomitant treatment should be considered. In addition, current evidence does not support the use of intra-articular MSCs for improving cartilage repair in knee osteoarthritis. Systematic review of Level-II studies.

Therapeutic efficacy of intra-articular delivery of encapsulated human mesenchymal stem cells on early stage osteoarthritis.

Mesenchymal stem cells (MSCs) represent a great therapeutic promise in pre-clinical models of osteoarthritis (OA), but many questions remain as to their therapeutic mechanism of action: engraftment versus paracrine action. Encapsulation of human MSCs (hMSCs) in sodium alginate microspheres allowed for the paracrine signaling properties of these cells to be isolated and studied independently of direct cellular engraftment. The objective of the present study was to quantitatively assess the efficacy of encapsulated hMSCs as a disease-modifying therapeutic for OA, using a medial meniscal tear (MMT) rat model. It was hypothesized that encapsulated hMSCs would have a therapeutic effect, through paracrine-mediated action, on early OA development.Lewis rats underwent MMT surgery to induce OA. 1 d post-surgery, rats received intra-articular injections of encapsulated hMSCs or controls (i.e., saline, empty capsules, non-encapsulated hMSCs). Microstructural changes in the knee joint were quantified using equilibrium partitioning of a ionic contrast agent based micro-computed tomography (EPIC-μCT) at 3 weeks post-surgery, an established time point for early OA.Encapsulated hMSCs significantly attenuated MMT-induced increases in articular cartilage swelling and surface roughness and augmented cartilaginous and mineralized osteophyte volumes.Cellular encapsulation allowed to isolate the hMSC paracrine signaling effects and demonstrated that hMSCs could exert a chondroprotective therapeutic role on early stage OA through paracrine signaling alone. In addition to this chondroprotective role, encapsulated hMSCs augmented the compensatory increases in osteophyte formation. The latter should be taken into strong consideration as many clinical trials using MSCs for OA are currently ongoing.

Global research trends in stem cells for osteoarthritis: a bibliometric and visualized study.

There have been increased interests in the use of stems cells in the research of osteoarthritis (OA). The present study aimed to investigate the global status and trends in this field. Publications related to stem cells search in OA from 1994 to 2017 were retrieved from the Science Citation Index-Expanded Web of Science. The source data were studied and indexed using a bibliometric methodology. For visualized study, VOS viewer software was used to conduct bibliographic coupling, co-authorship, co-citation and co-occurrence analysis and to analyze the publication trends in stem cells for OA research. A total of 1933 articles were included. The relative research interests and number of publications were globally increasing per year. The USA made the highest contributions to the global research with the most citations and the highest H-index. The journal Osteoarthritis and Cartilage had the highest publication number. The Tokyo Medical and Dental University, University of Pittsburgh and Shanghai Jiaotong University were the most contributive institutions. Studies could be divided into four clusters: mechanism study, animal study, clinical trials and tissue engineering. The clinical studies were predicted to be the next popular topic in this field. The number of publications about stem cells for OA would be increasing based on the current global trends. The USA was the largest contributor in this field. Most efforts could be put into clinical studies involving mesenchymal stem cells for OA, which may be the next hot spots in OA and stem cells research.

Molecular characterization of mesenchymal stem cells in human osteoarthritis cartilage reveals contribution to the OA phenotype

Adult human articular cartilage harbors a population of CD166+ mesenchymal stem cell-like progenitors that become more numerous during osteoarthritis (OA). While their role is not well understood, here we report that they are indeed part of cellular clusters formed in OA cartilage, which is a pathological hallmark of this disease. We hypothesize that these cells, termed OA mesenchymal stem cells (OA-MSCs), contribute to OA pathogenesis. To test this hypothesis, we generated and characterized multiple clonally derived stable/immortalized human OA-MSC cell lines, which exhibited the following properties. Firstly, two mesenchymal stem cell populations exist in human OA cartilage. While both populations are multi-potent, one preferentially undergoes chondrogenesis while the other exhibits higher osteogenesis potential. Secondly, both OA-MSCs exhibit significantly higher expression of hypertrophic OA cartilage markers COL10A1 and RUNX2, compared to OA chondrocytes. Induction of chondrogenesis in OA-MSCs further stimulated COL10A1 expression and MMP-13 release, suggesting that they contribute to OA phenotypes. Finally, knocking down RUNX2 is insufficient to inhibit COL10A1 in OA-MSCs and also requires simultaneous knockdown of NOTCH1 thereby suggesting altered gene regulation in OA stem cells in comparison to chondrocytes. Overall, our findings suggest that OA-MSCs may drive pathogenesis of cartilage degeneration and should therefore be a novel cell target for OA therapy.

Thrombospondin-1 Partly Mediates the Cartilage Protective Effect of Adipose-Derived Mesenchymal Stem Cells in Osteoarthritis.

Assuming that mesenchymal stem cells (MSCs) respond to the osteoarthritic joint environment to exert a chondroprotective effect, we aimed at investigating the molecular response setup by MSCs after priming by osteoarthritic chondrocytes in cocultures. We used primary human osteoarthritic chondrocytes and adipose stem cells (ASCs) in mono- and cocultures and performed a high-throughput secretome analysis. Among secreted proteins differentially induced in cocultures, we identified thrombospondin-1 (THBS1) as a potential candidate that could be involved in the chondroprotective effect of ASCs. Secretome analysis revealed significant induction of THBS1 in ASCs/chondrocytes cocultures at mRNA and protein levels. We showed that THBS1 was upregulated at late stages of MSC differentiation toward chondrocytes and that recombinant THBS1 (rTHBS1) exerted a prochondrogenic effect on MSC indicating a role of THBS1 during chondrogenesis. However, compared to control ASCs, siTHBS1-transfected ASCs did not decrease the expression of hypertrophic and inflammatory markers in osteoarthritic chondrocytes, suggesting that THBS1 was not involved in the reversion of osteoarthritic phenotype. Nevertheless, downregulation of THBS1 in ASCs reduced their immunosuppressive activity, which was consistent with the anti-inflammatory role of rTHBS1 on T lymphocytes. THBS1 function was then evaluated in the collagenase-induced OA model by comparing siTHBS1-transfected and control ASCs. The protective effect of ASCs evaluated by histological and histomorphological analysis of cartilage and bone was not seen with siTHBS1-transfected ASCs. Our data suggest that THBS1 did not exert a direct protective effect on chondrocytes but might reduce inflammation, subsequently explaining the therapeutic effect of ASCs in OA.

A consistent and potentially exploitable response during chondrogenesis of mesenchymal stem cells from osteoarthritis patients to the protein encoded by the susceptibility gene GDF5.

Osteoarthritis (OA) is a common joint disease characterised by the focal loss of the protective cartilage layer at the ends of the bones. It is painful, disabling, multifactorial and polygenic. The growth differentiation factor 5 gene GDF5 was one of the first reported OA susceptibility signals that showed consistent association to OA, with the transcript single nucleotide polymorphism (SNP) rs143383 demonstrating association in Asians and Europeans. The functional effect of the signal is reduced expression of the gene. The GDF5 protein is an extracellular matrix signalling molecule that is active during chondrogenesis and in mature chondrocytes. Due to the functional impact of the susceptibility, we previously assessed the effect of supplementing chondrocytes from OA patients with exogenous GDF5. Their response was highly discordant, precluding the application of GDF5 as a simple means of attenuating the genetic deficit. Since GDF5 is also active during development, we have now assessed the effect of exogenous GDF5 on bone marrow derived mesenchymal stem cells (MSCs) that are undergoing chondrogenesis during cartilage disc formation. MSCs from healthy donors and OA patients were studied and the effect of GDF5 was assessed by measuring the wet mass of the discs, by histological staining, and by monitoring the change in expression of anabolic, catabolic and hypertrophic protein-coding genes. The MSCs expressed the three principal GDF5 receptor genes and responded in a significantly anabolic manner (increase in wet mass, p = 0.0022; Bonferroni corrected p = 0.018) to a variant form of GDF5 that targets the most abundantly expressed receptor, BMPR-IA. GDF5 elicited significant (p < 0.05) changes in the expression of anabolic, catabolic and hypertrophic genes with several consistent effects in healthy donors and in OA patients. Our data implies that, unlike OA chondrocytes, OA MSCs do respond in a predictable, anabolic manner to GDF5, which could therefore provide a route to modulate the genetic deficit mediated by the rs143383 association signal.

Pre-Treatment of Human Mesenchymal Stem Cells With Inflammatory Factors or Hypoxia Does Not Influence Migration to Osteoarthritic Cartilage and Synovium

Background: Mesenchymal stem cells (MSCs) are promising candidates as a cell-based therapy for osteoarthritis (OA), although current results are modest. Pre-treatment of MSCs before application might improve their therapeutic efficacy. Hypothesis: Pre-treatment of MSCs with inflammatory factors or hypoxia will improve their migration and adhesion capacities toward OA-affected tissues. Study Design: Controlled laboratory study. Methods: We used real-time polymerase chain reaction to determine the effects of different fetal calf serum (FCS) batches, platelet lysate (PL), hypoxia, inflammatory factors, factors secreted by OA tissues, and OA synovial fluid (SF) on the expression of 12 genes encoding chemokine or adhesion receptors. Migration of MSCs toward factors secreted by OA tissues was studied in vitro, and attachment of injected MSCs was evaluated in vivo in healthy and OA knees of male Wistar rats. Results: Different FCS batches, PL, or hypoxia did not influence the expression of the migration and adhesion receptor genes. Exposure to inflammatory factors altered the expression of CCR1, CCR4, CD44, PDGFRα, and PDGFRβ. MSCs migrated toward factors secreted by OA tissues in vitro. Neither pre-treatment with inflammatory factors nor the presence of OA influenced MSC migration in vitro or adhesion in vivo. Conclusion: Factors secreted by OA tissues increase MSC migration in vitro. In vivo, no difference in MSC adhesion was found between OA and healthy knees. Pre-treatment with inflammatory factors influenced the expression of migration and adhesion receptors of MSCs but not their migration in vitro or adhesion in vivo. Clinical Relevance: To improve the therapeutic capacity of intra-articular injection of MSCs, they need to remain intra-articular for a longer period of time. Pre-treatment of MSCs with hypoxia or inflammatory factors did not increase the migration or adhesion capacity of MSCs and will therefore not likely prolong their intra-articular longevity. Alternative approaches to prolong the intra-articular presence of MSCs should be developed to increase the therapeutic effect of MSCs in OA.