Ph.D. Proposal Presentation by Blaise D. Porter
Friday, September 24, 2004

(Dr. Robert E. Guldberg, Chair)

"Development and Application of a 3-D Perfusion Bioreactor Cell Culture System for Bone Tissue Engineering"


The need for improved clinical strategies to restore function to damaged or degenerated bone is well recognized. These deficiencies can include the following: segmental defects, spine instability, acute trauma and fractures. The current gold standard treatment to augment repair of bone defects involves harvesting autologous bone chips from the iliac crest of the patient. However, donor site morbidity and pain, lack of structural strength, and limited graft material volume are significant drawbacks. Tissue engineering strategies that combine porous biomaterial scaffolds with cells capable of osteogenesis or bioactive proteins have shown promise as effective bone graft substitutes. Although acellular scaffolds are available clinically, the delivery of osteoprogenitors or osteoblasts has been shown to enhance bone defect repair. Other studies have suggested that in vivo repair may be enhanced by culturing cell-seeded scaffolds in vitro to produce mineralized constructs prior to implantation. However, attempts to culture bone tissue-engineering constructs thicker than 1mm in vitro often result in a shell of viable cells and mineralized matrix surrounding a necrotic core. To address this limitation, we have developed a perfusion bioreactor system that improves mass transport throughout cell-seeded constructs. We have recently shown a 140-fold increase in mineral deposition at the interior of polymer scaffolds seeded with rat bone marrow stromal cells. Furthermore, we have established and validated 3-D computational methods to model flow and shear stresses within the microporosity of perfused constructs. This work will elucidate the relationship, if any, between fluid flow, shear stress and matrix mineralization in order to identify which factors are most influential in producing potentially implantable bone tissue engineering constructs. The overall goal of this proposed work is to enhance the amount and distribution of cell-mediated mineralization within 3-D constructs in vitro using a perfusion bioreactor system.