The Role of proteoglycans in chondrocyte differentiation of mesenchymal stem cells

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1. We evaluated the effects of ultrasound (US) on differentiation of mesenchymal stem cells (MSCs) toward chondrocyte snarl cartilage matrix formation. When human MSCs cultured in the pellets were treated with transforming growth factor-beta (TGF-b), they differentiated into chondrocytes as assessed by alcian blue staining and immunostaining for aggrecan, but non-treated cell pellets and cell pellets treated with BMP-6 alone did not. Furthermore, when low-intensity US was applied for 20 min everyday to the TGF-beta-treated cell pellets, chondrocyte differentiation was enhanced. These results suggest that TGF-b is essential for chondrocyte differentiation of MSCs in pellets and US enhances the differentiation.2. Using chondrogenic/chondrocytic N1511 cells, we evaluated the role of versican/PG-M in chondrocyet differentiation. N1511 cells exhibited transient high expression of versican at an early stage and that of aggrecan at a late stage, which reflects their in vivo expression patterns during chondrocyte differentiation. When versican expression was inhibited using an antisense technology, the following aggrecan expression was decreased and delayed, as assessed by realtime RT-PCR. These results suggest that transient versican expression at the early stage positively regulate chondrocyte differentiaion.3. In addition to high transient expression, versican is continuously expressed, especially in the articular cartilage. We found that versican is colocalized with both hyaluronan and link protein there. Biochemical analysis further confirmed the presence of versican aggregate. These results suggest the presence of tow proteoglycan aggregates, which may play distinct roles.