(206a) A Mechanical Model for in Vitro Cartilage Engineering

Healthy articular cartilage, which is found in the diarthroidal joints, is generally characterized by low friction and high wear resistance. However, the lack of vascularization leads to poor regenerative capabilities. This deficiency provides incentive for developing in vitro methodologies to overcome this deficit. Through normal activity of the joint, mechanical, electrical, and physiochemical signals are created that help direct the activity of chondrocytes. Therefore, in order to create a realistic cartilage replacement, biomechanical and biochemical properties of cartilage must be recreated in an in vitro environment. Our experiments were designed to study the effects of tensile strain on cultured chondrocytes in a collagen tube scaffold. Chicken limb bud mesenchyme was extracted from H&H stages 22 embryos. The cells were cultured in the scaffold for up to 1 week and then exposed to a 26 kPa circumferential tensile strain for varying time points. Control tubes scaffold were cultured in the same environment but without any applied strain. Preliminary results demonstrate that the structure of collagen type II was altered in the strained tubes versus the control scaffolds. Confocal images of the collagen type II appeared more organized, more fibril-like, and evenly dispersed throughout the matrix. Preliminary RT-PCR for collagen type II has shown a decrease in the message for collagen type II in the stretched scaffolds possibly due to stability of the primer attaching to the fibrils. Bioreactors have been designed to further investigate these results and to add different types and degrees of strain.