Due to the high incidence of injury and osteoarthritis and the limited nature of articular cartilage self-repair, alternate means are necessary to replace the damaged tissue and regain an articulating surface that not only stops the progression of disease but functions the same as a healthy articular surface. This study focus on the early stages of damage, particularly when the outer surface layer, the superficial tangential zone, becomes damaged and fibrillation begins. We hope to achieve this by creating a tissue replacement product through tissue engineering using an abundant cell source of mesenchymal stems cells seeded in Collagen Type I scaffolds, and treated not only with chondrogenic growth media in culture, but three different stimulation algorithms to improve structural and functional properties.

The cell source was obtained from bone marrow specimens from healthy human subjects undergoing hip replacement surgery. Cells were expanded, seeded on collagen type I scaffolds and grown statically for 1 week. Following 1 week, constructs were either analyzed for histology, SEM, alignment, indentation, tensile, and aggrecan content with Western Blot analysis or stimulated for 2 additional weeks. Each of the following algorithms comprises one of the three stimulation groups, which were chosen to produce characteristics similar to the superficial tangential zone of articular cartilage:​ application of compression and tension without offset, application of compression and tension with offset, and tension alone.

Results showed GAG staining from histology in all test groups, however there was more abundance in the stimulated groups. For SEM results there appeared more matrix components and organization in the stimulation groups with both compression and tension. Evaluation of cell alignment showed the test group with both compression and tension without offset trending toward alignment with the direction of applied tension indicating the stimulation algorithm was producing strain effects to cause the cells to preferentially align. Additionally, this group had the best mechanical property outcome. Western blot results showed the group with compression and tension without offset had similar aggrecan content to native articular cartilage results, as well as the other stimulation groups, indicating stimulation aids in producing aggrecan content similar to the superficial tangential zone.

The overall results showed the group stimulated with both compression and tension without offset had the best structure and functional properties of the group. Although the mechanical properties were inferior to native articular cartilage, they were within range of repair tissue. Further exploration with both compression and tension without offset stimulation in longer culturing can enhance these aspects and lead to prevention of further cartilage degradation in patients with early signs of osteoarthritis or damaged articulating surface.