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 PDGFRß. 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.

Mesenchymal stem cells reduce pain but not degenerative changes in a mono-iodoacetate rat model of osteoarthritis.

We studied the effects of intra-articularly injected bone marrow derived mesenchymal stem cells (MSCs), as well as freshly isolated bone marrow mononuclear cells (BMMNCs), on pain, cartilage damage, bone changes and inflammation in an in-vivo rat osteoarthritis (OA) model. OA was induced unilaterally by injection of mono-iodoacetate (MIA) and allowed to develop for 3 weeks. Then, animals were treated by intra-articular injection with MSCs, BMMNCs, or saline as a control. Four weeks later, pain was assessed with an incapitance tester, subchondral bone alterations were measured with µCT and cartilage quality and joint inflammation were assessed by histological analysis. Animals treated with MSCs distributed significantly more weight to the affected limb after treatment, which was not observed in the other groups. No statistically significant differences between treatment groups regarding cartilage damage, subchondral bone alterations and synovial inflammation were observed. Additional cell tracking experiments indicated adequate intra-articular cell injection and cell survival up to 2 weeks. In our OA model, injected MSCs were able to reduce MIA induced pain, as measured by an increased weight distribution to the affected limb. No statistically significant effects of the cellular therapies on structural damage and synovial inflammation were found.

Effect of Arthritic Synovial Fluids on the Expression of Immunomodulatory Factors by Mesenchymal Stem Cells: An Explorative in vitro Study.

BACKGROUND: In diseased joints, the catabolic environment results in progressive joint damage. Mesenchymal stem cells (MSCs) can have immunomodulatory effects by secreting anti-inflammatory factors. To exert these effects, MSCs need to be triggered by pro-inflammatory cytokines. To explore the potential of MSCs as a treatment for diseased joints, we studied the effect of synovial fluid (SF) from donors with different joint diseases and donors without joint pathology on the immunomodulatory capacities of human MSCs in vitro. We hypothesized that SF of diseased joints influences the immunomodulatory effects of MSCs. MATERIALS AND METHODS: MSCs were cultured in medium with SF of six osteoarthritis (OA) or six rheumatoid arthritis (RA) donors and three donors without joint pathology were used as control. Gene expressions of IL-6, HGF, TNFa, TGFb1, and indoleamine 2,3-dioxygenase (IDO) were analyzed. l-kynurenine concentration in conditioned medium (CM) by MSCs with SF was determined as a measure of IDO activity by MSCs. Furthermore, the effect of CM with SF on proliferation of activated lymphocytes was analyzed. RESULTS: Addition of SF significantly up-regulated the mRNA expression of IL-6 and IDO in MSCs. SF(OA) induced significantly higher expression of IDO than SF(control), although no difference in IDO activity of the MSCs could be shown with a l-kynurenine assay. Medium conditioned by MSCs with SF(OA or RA) suppressed activated lymphocyte proliferation in vitro more than medium conditioned by MSCs without SF or with SF(control). DISCUSSION: SF can influence the expression of genes involved in immunomodulation by MSCs and the effect on lymphocyte proliferation. We found indications for disease-specific differences between SFs but the variation between donors, even within one disease group was high. These data warrant further research to examine the potential application of MSC therapy in arthritic joints.