Articular cartilage provides a low-friction bearing surface for transmitting the forces that arise with joint motion. Because cartilage possesses a limited capacity for repair, trauma or progressive joint disease leads to destruction of the joint surface [1]. Limitations in current repair strategies have increased interest in cartilage tissue engineering (TE), although to date, generating a construct with the mechanical complexity of the native tissue remains a challenge. In our previous long-term free swelling studies, and in other gel systems, the tensile properties of cell-seeded hydrogels remain far lower than those of the native tissue [2–4]. One approach for furthering tissue growth is the application of mechanical signals to engineered constructs. In developing joints, inhibition of mechanical forces results in incomplete cartilage formation [5,6]. Mechanical forces continue to play a vital role in cartilage maturation after birth; physiologic loading remodels the tissue and increases the tensile properties and spurs development of anisotropy [7,8]. In chondrocyte-seeded TE constructs, dynamic axial mechanical stimulation improves compressive properties and biochemical content [9], though the collagen content and tensile and dynamic properties remain low. As the tensile properties of cartilage emerge with load-bearing use, more complete recapitulation of the mechanical environment that arises with motion may further the maturation of engineered constructs. To test this hypothesis, we developed a sliding contact bioreactor mimicking two contacting cartilage layers and show that ECM gene expression is modulated by this loading modality depending on the duration of loading and pre-maturation of the construct.

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