Title: Controlling Tissue Matrix Assembly of Human Mesenchymal Stem Cells toward Engineering Native-like Bone, Cartilage, and Osteochondral Grafts
Description: Medical complications caused by bone, cartilage, and osteochoondral defects present special challenges to tissue engineers. An ability to fabricate these tissues in vitro will eliminate clinical complications caused by current techniques used in graft reconstruction. These complications include long-term failure of synthetic grafts, inferior success of allografts, and complications from harvesting autografts. The successfully engineered grafts must exhibit biological and structural function similar to that of native tissue in order to withstand physiological conditions and integrate into surrounding tissues. In this dissertation, the ability to control tissue matrix assembly from a clinically relevant cell source, human mesenchymal stem cells, towards generating native-like tissue properties has been demonstrated. The investigational approach was crafted around three specific aims: controlling the matrix assembly of bone mineral (Aim 1), articular cartilage (Aim 2), and osteochondral tissue (Aim 3).

As a result, the assembly of bone mineral structure was accomplished by regulating nucleation, mineral-binding protein deposition sites, and affinity for mineral binding. Native-like articular cartilage with physiologic form and function was created using a cell pellet compression technique, a process mimicking the native developmental mesenchymal cell condensation process. In addition, the key requirements to engineer osteochondral tissue with undifferentiated mesenchymal stem cells were established. A radically novel, imaging-compatible perfusion bioreactor was designed to enhance tissue integration and spatial regulation of supplements to direct stem cell differentiation into chondrogenic and osteogenic lineages and the formation of complete osteochondral constructs. Proof-of-concept experimentation was conducted in a large animal (pig) model of temporomandibular condyle reconstruction. Engineered bone demonstrated markedly better regeneration and remodeling of the TMJ and its integration with the surrounding tissues (bone and muscle) compared to the implantation of acellular scaffolds.

The tissue engineering approaches developed in this dissertation form a basis for promising therapeutic approaches for treating bone, cartilage, and osteochondral defects.