UC San Diego

2.2 million surgical procedures for bone grafting are performed annually worldwide. While natural bones, such as autografts and allografts, and growth factors are commonly utilized in the procedures, they suffer from various shortcomings, such as high cost, donor site morbidity, and potential side effects. Alternatively, inspired by mineralized, dynamic environment of native bone, we developed biomineralized matrix recapitulating calcium phosphate (CaP)-rich mineral microenvironment that undergoes dynamic dissolution and reprecipitation. In this dissertation, we focus on the application of biomineralized matrix to induce osteogenesis of human pluripotent stem cells (hPSCs) for bone formation.

Chapter 1 describes the progress in the development of CaP-based biomaterials and their applications in directing stem cell differentiation and supporting bone tissue formation. It includes our prior findings of biomineralized matrix-mediated osteogenesis of human mesenchymal stem cells (hMSCs) and bone formation in vivo. Chapter 2 demonstrates that biomineralized matrix can direct osteogenic differentiation of human embryonic stem cells (hESCs) by matrix-based cues alone, both in vitro and in vivo. Chapter 3 shows that the biomineralized matrix can solely induce osteogenic commitment of human induced pluripotent stem cells (hiPSCs) that can offer clinical benefits of autologous therapy. In chapter 4, we employ biomineralized matrix to study the effect of mineralized microenvironment on fate decision of hMSCs in presence of adipogenic-inducing medium. We show that biomineralized matrix dominates adipogenic soluble cues to direct osteogenic differentiation of hMSCs through adenosine A2b receptor (A2bR) signaling. Chapter 5 demonstrates utilization of adenosine, naturally small molecule to induce direct conversion of both hESCs and hiPSCs into osteoblasts. The osteoblasts derived from hiPSCs through adenosine treatment were found to contribute to the healing of critical-sized bone defects. Chapter 6 shows the application of biomineralized trilayered scaffold to induce subchondral bone formation for osteochondral tissue engineering in vivo. Chapter 7 concludes the dissertation and presents future directions, including functional bone tissue engineering and mechanistic studies of biomineralized matrix- and small molecule-driven osteogenic differentiation of hPSCs.