(722c) Micrometer Scale Guidance of Mesenchymal Stem Cells to Form Structurally Oriented Cartilage Extracellular Matrix

  Tissue engineering has tremendous potential for long-term repair of cartilage lesions, but current tissue engineered cartilage constructs, while similar in biochemical features, have inferior mechanical properties compared to native cartilage. This problem may be due to a lack of an oriented structure in the constructs at the microscale that is present in the native tissue. The goal of this study is to test the hypothesis that microscale features on scaffolds will cause the differentiating mesenchymal stem cells (MSCs) to preferentially arrange themselves and to create a microscale-oriented extracellular matrix similar to the native tissue structure. Another goal of the study is to investigate a method to convert the findings to form larger 3D cartilage constructs. Channels of varying microscale dimensions (25-1000 micrometers) were formed in collagen-based scaffolds via microfabrication. The channel quality was confirmed through image analysis. Human MSCs were seeded in these channels, and Live/Dead staining was used to confirm the viability of cells within the channels. Selective attachment and spreading of MSCs within the channels was ensured by modifying the plateau regions with triblock copolymer F108. The chondrogenic potential of MSCs seeded in these channels was investigated by culturing them in chondrogenic medium for three weeks, then evaluating them by type II collagen immunohistochemistry, and for mechanical behavior. We show selective adhesion of MSCs in microchannels. MSCs aligned along the length of the channel at optimal channel dimensions of 25-100 micrometers. We further show mature oriented type II collagen formation in smaller channels. In addition, we show the mechanical properties (modulus of elasticity and ultimate stress) were significantly improved in scaffolds with MSCs in smaller channels. More importantly, a new method was developed to obtain large 3D constructs that contain these microscale guidance features. Microscale channels of collagen can guide MSCs and lead to improved mechanical biochemical function of the construct. In addition, we demonstrate that large cartilage constructs with such microscale guidance features can be fabricated for in vivo testing. This work paves the way for developing cartilage constructs with ultrastructure similar to native tissue.