%0 PDF %T Investigation of Micropunching Holes in Articular Cartilage for Applications in Tissue Engineering. %A Vandenberg, Theodore. %8 2017-04-20 %R http://localhost/files/gf06gf35d %X Abstract: Articular cartilage degeneration is a central pathological feature of osteoarthritis. Cartilage in the adult does not regenerate in vivo and, as a result, cartilage damage in osteoarthritis is irreversible. With our ever-aging population, osteoarthritis has become a leading cause of disability and unfortunately, no optimal treatments for osteoarthritis are currently available. To address this problem, a research community is focused on the development of both natural and synthetic biodegradable tissue scaffolds. The scaffolds must contain depressions or holes for the purpose of chondrocyte seeding and growth in order to create an implantable construct. Scaffolds also contain artificial microtubules to enhance nutrient diffusion during early cellular development. In addition to chondrocytes, cartilage tissue consists of the extracellular matrix (ECM). Studies of many tissue types have established that ECM plays an important role in regulating cell behavior and controlling processes such as tissue differentiation and tumor progression. Unlike most natural tissues, adult cartilage ECM is exceptionally dense and lacking in vascularity, which makes it difficult for chondrocytes to be transplanted directly into the matrix. Current methods of creating cell home sites through chemical decellularization of the ECM degrade the mechanical integrity of the cartilage tissue. The research conducted in this study used a mechanical, rather than chemical, method to create cell home sites. A novel micropunching machine was developed to fabricate 200 µm diameter holes in cartilage, thereby creating a porous natural scaffold while maintaining a healthy ECM. Equine articular cartilage slices were harvested from the cadaver's back knee joint and cryo-sectioned into 100 µm thick slices. Using various die clearances and hydration levels, micro-scale holes were mechanically punched in cartilage tissue. The maximum force required to punch a hole in the cartilage sample was shown to have a relationship to both clearance of the die and hydration level of the sample. As the die clearance increased, the maximum punching force (MPF) decreased. In addition, as a sample dried out the MPF increased. However, the failure mechanism changed for the different levels of hydration. Saturated samples failed in tension, while dry samples failed in shear, producing larger resulting hole sizes. Upon inspection, a 200 µm punch produced 50 µm holes in saturated and hydrated samples, with fibers extending into the hole. In dry samples, a 200 µm punch produced 200 µm holes with smooth hole walls. An analytical model was developed to predict MPF based on the hydration level of the sample and the diameter of the male punch. The Young's moduli of both porous (micropunched) and nonporous samples were not found to be significantly different at 4% porosity. Yield occurred at strain levels much higher than those encountered for in vivo cartilage. Therefore, results indicate that porous samples maintain their mechanical properties for successful cell culture and integration in vivo. A preliminary cell culture study indicated that seeded cells can position themselves in the micro-holes and along the walls of the holes to successfully take advantage of the three-dimensional architecture. The results of this research indicate that a micropunching process is adequate to create holes in natural cartilage tissue for the purpose of seeding progenitor cells and eventual fabrication of a tissue implant.; Thesis (M.S.)--Tufts University, 2015.; Submitted to the Dept. of Mechanical Engineering.; Advisor: Thomas James.; Committee: Li Zeng, Lauren Black, and Jason Moore.; Keywords: Biomechanics, Mechanical engineering, and Biomedical engineering. %[ 2022-10-12 %9 Text %~ Tufts Digital Library %W Institution