Evolving Utilization of Mesenchymal Stem Cells and Delivery Scaffolds in Osteoarthritis

John Schmidt

Introduction. Osteoarthritis (OA) is a chronic degenerative joint disease that causes pain, decreased range of motion, osteophyte formation, and aberrant bone remodeling in over 27 million adults in the United States alone1,2. Numerous interacting growth factors and inflammatory cytokines modulate the various pathways that lead to chondrocyte hypertrophy or dysregulation and eventual chondrocyte loss with subsequent cartilage degeneration2. Moderate limitations, such as limited availability, donor site morbidity, and increased risk of disease transmission, accompany the currently available treatments, so an alternative treatment capable of regeneration would be impactful clinically3. Studies have shown mesenchymal stem cells (MSCs) to possess chondrogenic and inflammatory modulation capacity3-6. These characteristics make MSCs a viable subject for use in new regenerative treatments targeting OA. Methods. Adipose-derived mesenchymal stem cells (AD-MSCs) from infrapatellar Hoffa fat, subcutaneous (SC) hip fat, and SC abdominal fat were cocultured in Transwells with chondrocytes or synoviocytes. Inflammatory factor levels were evaluated by quantitative reverse transcription–polymerase chain reaction or multiplex bead–based immunoassay4. Attachment of dual-labelled SF-MSCs was assessed in the synovial fluid (SF) of OA patients. SF was digested with hyaluronidase (hyase) and its effect on adhesion was observed using confocal microscopy5. MSCs collected from used bone marrow collection sets were seeded into hyaluronic acid-substituted-by-tyramine (HA-TA) scaffolds and introduced into a standard chondrogenic medium (SCM) culture, a BMP6-enhanced SCM medium culture, in vivo rat models, and in vitro cultures6. Results. AD-MSCs were found to down-regulate key pro-inflammatory factors that contribute to OA pathology, the most notable being IL‐1β, IL‐6, and CXCL8/IL‐84. Hyaluronic acid is directly involved in MSC adhesion inhibition5. The HA-TA scaffold serves as a sufficient environment for MSC chondrogenesis6. BMP6-enhanced SCM is a more potent chondrogenic inducer than the SCM medium6. Conclusions. Studies have found that the HA present in the synovial fluid of joints inhibits the adhesion of MSCs and thus warrants the creation of delivery scaffolds that facilitate MSC binding and chondrogenesis. The HA-TA scaffold may be a successful example of one such scaffold. MSCs have also been shown to treat OA by reducing inflammation that contributes to OA’s pathogenesis.

 

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