Mechanical Stimulation Promotes the Proliferation and the Cartilage Phenotype of Mesenchymal Stem Cells and Chondrocytes Co-Cultured <i>in vitro</i>

Abstract

Mesenchymal stem cells and chondrocytes are an important source of the cells for cartilage tissue engineering. Therefore, the culture and expansion methods of these cells need to be improved to overcome the aging of chondrocytes and induced chondrogenic differentiation of mesenchymal stem cells. The aim of this study was to expand the cells for cartilage tissue engineering by combining the advantages of growing cells in co-culture and under a mechanically-stimulated environment. Rabbit chondrocytes and co-cultured cells (bone mesenchymal stem cells and chondrocytes) were subjected to cyclic sinusoidal dynamic tensile mechanical stimulationusing the FX-4000 tension system. Chondrocyte proliferation was assayed by flow cytometry and CFSE labeling. The cell cartilage phenotype was determined by detecting GAG, collagen II and TGFβ1 protein expression by ELISA and the Col2α1, TGF-β1 and Sox9 mRNA expression by RT-PCR. The results show that the co-culture improved both the proliferation ability of chondrocytes and the cartilage phenotype of co-cultured cells. A proper cyclic sinusoidal dynamic tensile mechanical stimulation improved the proliferation ability and cartilage phenotype of chondrocytes and co-cultured cells. These results suggest that the coculture of mesenchymal stem cells with chondrocytes and proper mechanical stimulation may be an appropriate way to rapidly expand the cells that have an improved cartilage phenotype for cartilage tissue engineering. Funding Statement: This study was supported by the National Natural Science Foundation of China (11802209), the Natural Science Foundation of Shandong Province China (ZR2017PA011), the Medical and Health Technology Development Project of Shandong Province China (2016WS0669) and the Visiting Scholar Program of Weifang Medical University. Declaration of Interests: The authors have no proprietary interest in any of the materials discussed in this article. Ethics Approval Statement: The experimental protocols were approved by the Animal Care and Protection Committee of Weifang Medical University. We confirm that all experiments were performed in accordance with relevant guidelines and regulations.