| Objective To study the effect of stretch strain on the differentiation of rat bone marrow mesenchymal stem cells (BMSCs) into chondrocytes, and what is the best stretch strain loading condition; To research the effect of compressive strain on producing tissue engineered cartilage in vitro.Methods BMSCs were isolated by percoll solution from rat bone marrow sample, cultured and identified. The cells were treated with inductive medium containing dexathemesone, vitamin C and TGF-β1, and stimulated by substrate stretch strain by a four-point-binding device. Tofuidine blue and immunohistochemical studies were performed for chondrogeinc phenotype identification. The content of GAG in ECM was determined by Alcian blue. Different strains (0.1 %, 0.3%, 0.5%, 1%, 3%) and frequencis (0.1Hz, 0.3 Hz, 0.5 Hz, 1 Hz) were provided by flexible-membrane stretch divice, and GAG amount was measured to investigate what is the best stretch condition. Gene expression was analyzed by RT-PCR. Cell-scaffold composites were compressed by compressive strain device, and the composites were implanted in rat 7 days later. And then, correlative estimates on biology and biomechanics were done.Results CD44 and CD54 positively expressed in primarily cultured rat BMSCs. The cells were positively stained by tofuidine blue, and immunohistochemical analysis proved strong type II collagen expression after induction. The inductive process was promoted by stretch strain, and the best stretch strain loading condition was 1% and 1Hz. The tissue engineered cartilage which produced by compressive strain device excreted cartilage matrix, and its elastic modulus increased obviously.Conclusions This study indicates that stretch strain enhances the cartilaginous matrix formation of BMSCs. The inductive effect is significant when the strain is 1% and 1Hz. Due to the compressive strain, junior tissue engineered cartilage canbe formed by cell-scaffold composites.
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