Lanterna Rally

Author: Alexander Lee Rivera

Publisher:

Published: 2015

Total Pages: 194

ISBN-13:

Tissue engineering is viewed as a promising method for repair of articular cartilage injuries. While mesenchymal stem cell (MSC) based tissue engineering strategies have produced tissue constructs that display extracellular matrix similarities to articular cartilage, including glycosaminoglycan (GAG) and collagen type II synthesis, these constructs have failed to provide a clinical solution. One primary limitation is the lack of integration between the engineered construct and the native cartilage. Integration is very difficult to achieve due to the avascular nature of articular cartilage. The use of osteochondral constructs can allow for enhanced integration since the construct is anchored with the subchondral bone, a highly vascularized tissue that displays an intrinsic remodeling capability. We developed a gradient generating bioreactor for biphasic tissue fabrication and investigated the fabrication of osteochondral tissue constructs. We hypothesized that exposure of MSC-scaffold constructs to osteochondral gradients would allow for the production of an osteochondral tissue construct that transitions from a cartilage-like region to a bone-like mineralized region. The bioreactor developed within this dissertation utilizes two flow inlet streams of different compositions, which combine into a single flow channel to form a biomolecular gradient across three-dimensional cell-scaffold constructs. The bioreactor was characterized via COMSOL Multiphysics simulations and fluorescent/dye molecule tracer experiments and was then fabricated from Delrin. Osteochondral gradients were generated across human MSCs seeded within collagen-GAG scaffolds. The developed tissue constructs displayed two distinct regions: a cartilage-like region and a mineralized region. Mineralization was observed via von Kossa staining and energy dispersive x-ray spectroscopy. Production of collagen type II was visualized via immunohistochemistry and was highest in regions of the tissue construct exposed to higher concentrations of chondrogenic medium. GAG production was observed throughout the construct using Safranin O staining and a quantitative GAG/DNA assay. Via mechanical characterization, the osteogenic regions of these samples displayed higher aggregate modulus values compared to the chondrogenic regions. These results indicate the osteochondral tissue constructs displayed both biochemical properties and mechanical properties unique to each tissue region. The novel gradient generating bioreactor developed here to investigate osteochondral tissue construct fabrication serves as promising tool to study the engineering of biphasic tissues.