The Effect of Fluid Shear Force on Tissue Engineered Cartilage Quality

Articular cartilage, a biphasic material located above the bone tissue that functions as a shock absorber, degrades through osteoarthritis and traumatic injury. Degraded tissue can be replaced with engineered cartilage tissue by using chondrocytes seeded onto biodegradable scaffolding inside a bioreactor system. The aim of this project was to determine which stirring rate in the bioreactors promotes the highest quality of tissue growth, as determined by the presence of extracellular matrix molecules. The first step in the experiment was chondrocyte isolation from the cartilage tissue of a calf leg and subsequent insertion into four wavy walled bioreactors loaded with three PCL scaffolds each. The first bioreactor employed a static culture medium while the second, third and fourth bioreactors employed stirring rates of 25 rpm, 50 rpm and 75 rpm, respectively. After fourteen days, the scaffolds were removed and assayed for collagen, glycosaminoglycan and DNA content, as well as cell proliferation. The assays showed that the collagen, glycosaminoglycan, and DNA content of the digested scaffolds was highest in those that experienced the highest fluid shear stimulation and lowest in those that experienced zero fluid shear stimulation. These trends demonstrated that the scaffolds that experienced the highest levels of fluid shear stimulation (75 rpm) yielded the best overall tissue growth. Additionally, cell proliferation data indicated that there was no correlation between chondrocyte attachment rate to the scaffolds and tissue quality. Overall, there was a positive correlation between fluid shear stimulation and higher tissue quality.