Small molecule microenvironment design for craniofacial bone regeneration

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Over 30,000 people per year undergo craniofacial resective surgery and approximately 15% of the US population suffers from periodontal disease severe enough to warrant surgery (Marolt 2015). Currently, craniofacial and periodontal bone tissue engineering faces unique challenges due to the exposure of cranial and periodontal bones to continuous and varying loads (Rah 2000). The effect of continuous loads onto the engineered construct necessitates a gradual augmentation of an engineered regenerate rather than the en bloc insertion of a mechanically inert replacement tissue. In contrast to long bones, which are formed through endochondral ossification, cranial vault and periodontal bones are characterized by their unique mode of intramembranous ossification, which is accomplished through the stepwise mineralization of a specialized extracellular protein matrix rich in collagen and proteoglycans. When cranial and/or periodontal bones are lost due to trauma or disease, this loss not only affects osteoblasts, progenitors, and other bone cells, but also the unique extracellular bone matrix that maintains the instructive signaling environment for continuous bone regeneration and replacement. In the present application we have focused on a recently described small molecule mediator, the SETD7 histone lysine methyltransferase inhibitor PFI-2 that in our preliminary studies has induced osteoblasts to secrete a typical bone-like extracellular matrix enriched in collagen, fibronectin and osteocalcin. In animal studies, PFI-2 has demonstrated extraordinary potential to induce bone regeneration, including alveolar bone regeneration over half of a tooth root’s length and more than 50% new bone coverage of critical size cranial defects. Providing a possible mechanism for these exciting new findings, we have demonstrated that PFI-2 inhibited SETD7 mediated -catenin methylation, resulting in nuclear -catenin translocation and bone matrix protein transcription activation in addition to the stimulation of other processes related to new bone formation, such as cell proliferation and differentiation. In the present application, we seek to exploit PFI-2’s potential for cranial and periodontal bone regeneration, define the mechanism(s) by which PFI-2 triggers new bone extracellular matrix deposition, and engineer scaffolds of sufficient stability to provide a template for PFI-2 nanosphere controlled release toward future applications in clinical use and patient care.