| Background and ObjectiveOsteoarthritis is the most common type of arthritis. The number of OA patients steadily rises as the elderly population grows in the world. OA is an important cause of disability. The majority of the drugs for the treatment of OA have been inadequate as they only treat the symptoms of pain and inflammation. The drugs have not the capacity to reverse the molecular changes that occur in OA. A number of surgical methods and procedures have been implemented to restore synovial joint function. These range from minimally invasive procedures such as arthroscopic abrasion and shaving of small cartilage defects, to more extended surgical procedures such as microfracture of the subchondoral bone and mosaicplasty. Surgery for OA, which may involve joint replacement,is generally unsatisfactory. Consequently more effective function-modifying therapeutic strategies will need to be introduced for the clinical treatment of OA.In recent years, regenerative medicine is an emerging field that seeks to repair or replace injured tissues through natural or bioengineered means. A range of methods have been developed including osteochondral transplantation, microfracture and autologous chondrocyte transplantation(ACT), with or without the assistance of scaffold matrix to deliver the cells. ACT has been in clinical for a decade, and many modifications of the technique are also used in the clinic, but these have several major drawbacks. Challenges in treating cartilage defects with ACT are including paucity of the cell source; damage caused to native tissues by cell harvest; inability to restore the original cartilage structure; lack of adhesion between new repair cartilage and the original tissue.Recent research on mesenchymal stem cells has provided a new and exciting opportunity for bone and cartilage tissue engineering. During embryogenesis, cartilage is formed from the condensation of MSCs. Thus far, MSCs have been isolated from bone marrow, periosteum, trabecular bone, adipose tissue, synovium, skeletal muscle and deciduous teeth. MSCs possess the capacity to differentiate into cells of connective tissue lineages, including bone, fat, cartilage, intervertebral disc, ligament and muscle. New strategies have to center around enhancing and prolonging the chondrogenic potential of the chondrocytes during their in vitro expansion phase.MicroRNAs are single-stranded RNAs of 19-23 nucleotides and are found in a wide variety of organisms. Evidence for the requirement of the processing of microRNA in stem cell function and differentiation comes from studies of the Drosha complex partners Loquacious (homolog of human TAR (HIV-1) RNA binding protein 2), which is required for germ-line stem cell maintenance, and DGCR8, which is required for embryonic stem cell selfrenewal. Similarly, Dicer knockouts exhibit defects in stem cell differentiation. Clearly, microRNAs underlie key differentiation mechanisms.Based on our prophase works, we will study on how microRNA works in the differentiation from MSCs to chondrocytes, imploring the mechanism, optimizing the culture conditions, inducing the chondrocytes and denoting a optimized therapy for OA.Methods1. Mesenchymal stem cells were isolated from rat bone marrow and induced into mature chondrocyte in the presence of transforming growth factor-β1 (TGF-β1). Chondrogenesis was assessed by immunohistochemistry and immunofluorescence for typeⅡcollagen, and by alcian blue staining for proteoglycan.2. BMSCs were induced to differentiate into chondrocytes by TGF-β1 in vitro, immunofluorescence and immunohistochemistry were performed to evaluate MSCs differentiation. Real-time reverse transcription polymerase chain reaction was performed to analyze microRNA 130a expression at different time points (before induced culture,7 days later in induced culture and 7 days later in non-induced culture). 3. We have developed a model of arthritis in rabbits and assess the joint using Maknin score in 12 weeks after surgery.Results1. We found clear positive staining of collagenⅡin the cytoplasm in the induced medium during differentian by using immunofluorescence and immunohistochemical performance. And we also found positive staining cells in the induced medium by Alcian blue staing.2. We found microRNA130a was expressing during the differentiation. MicroRNA130a was down-modulated significantly during chondrogenesis after BMSCs had cultured in the present of TGF-β1 for 7 days (P＜0.05)3. The joint was assessed 9-10 scores by Maknin method after 12 weeks in operation.Conclusion1. BMSCs were induced to differentiate into chondrocytes by TGF-β1 in vitro.2. These findings show that, during the early stage of BMSC chondrogenic differentiation, mciroRNA130a expression was specifically repressed, suggesting a role in differentiation of rat bone mesenchymal stromal cells.3. Hulth method can establishes a model of osteoarthritis.
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