Periodontal Regeneration with Supramolecular Nanomaterials - PROJECT SUMMARY/ABSTRACT Periodontal disease is a chronic infection that results in the host inflammatory responses destroying the periodontal ligament, cementum, alveolar bone and gingiva that anchor the tooth in the jaw. Previous studies have shown that periodontal ligament cells (PDLCs) can be directed to differentiate to osteoblasts, fibroblasts and cementoblast-like cells in vitro and in vivo. The canonical Wnt/β-catenin signaling pathway has been demonstrated to stimulate cell proliferation and osteogenic differentiation of PDLSc. Wnt signaling is required for periodontal homeostasis. Lastly, a commercial product Emdogain, consisting largely of alternatively spliced and processed porcine amelogenins, was shown to induce bone, cementum and periodontal ligament regeneration in primates and humans. We sought to identify the biologically active peptide(s) in Emdogain responsible for activating these differentiation pathways, anticipating such bioactive molecules would make possible a much more targeted approach to periodontal tissue regeneration. We have identified one of the amelogenin splicing isoforms, Leucine-rich Amelogenin Peptide (LRAP) to induce osteogenesis in various adult and embryonic stem cell types. Moreover, LRAP is expressed in the periodontium, with cementum defects and enhanced osteoclastogenesis being observed around tooth roots of amelogenin knockout mice which lack LRAP expression. LRAP treatment significantly reduces the expression of RANKL, a key regulator of osteoclastogenesis, in periodontal ligament cells. Furthermore, LRAP stimulates the proliferation and migration of periodontal ligament cells, as well as affects bone turnover in vivo. Cell signaling involves not only the binding of growth factors and cognate receptors, but also their clustering on the cell membrane. However, little or no work has been directed thus far toward investigating how biomaterials can serve to enhance growth factor or peptide signaling by increasing diffusion of cell surface receptors within membrane lipid rafts. Therefore, a better understanding of the cellular and molecular mechanism(s) operating at the material-cell membrane interface during cell signaling has the potential to change the paradigm in designing future biomaterials and regenerative medicine therapeutics. Previously, we discovered that peptide amphiphile (PA) nanofibers with controlled supramolecular β-sheet cohesion could alter cell membrane raft mobility, resulting in enhanced osteogenic signaling. Recently, we have developed a PA molecule with a cholesterol tail to potentiate canonical Wnt receptor signaling by modulating lipid raft/caveolar dynamics. In this proposal, we will test the hypothesis that the effect of LRAP on periodontal tissue regeneration is mediated by activating the canonical Wnt/β-catenin signaling pathway and the signaling effect can be potentiated by PA molecules through increased receptor sensitivity. Combining PA molecules with the small peptide LRAP may afford more effective interventional strategies to clinicians for regeneration of tooth supporting tissues lost to periodontal disease.
