Project Summary/Abstract: Intramembranous bone regeneration is a carefully orchestrated process of hematoma formation, inflammation, and blood vessel formation and invasion, which are necessary for bone to form. Among these, a lack of proper blood vessel formation and invasion has been identified as one of the factors leading to a failure of orthopaedic, dental, or biomimetic implant placements, all of which are dependent on the success of intramembranous bone regeneration. Therefore, the goal of this proposal is to gain enhanced understanding of vasculogenic or angiogenic processes that occur during intramembranous bone regeneration and explore the endothelial cell plasticity that could lead to novel therapeutic opportunities for several orthopaedic or dental procedures. The current knowledge and preliminary studies for this proposal indicate that both vasculogenesis (new blood vessel formation in the absence of vascular template) and angiogenesis (new blood vessel formation by sprouting from existing blood vessels) occur during intramembranous bone regeneration. Also, endothelial cells exhibit plasticity where the cells undergo endothelial-to-mesenchymal transition (EndMT) within the regenerating bone. Thus, these novel findings set the scientific premise to the central hypothesis that EndMT is integral to intramembranous bone regeneration. To address this hypothesis, we propose to determine the role of EndMT during vasculogenesis and angiogenesis in intramembranous bone regeneration by 1) examining EndMT of fluorescently labeled endothelial cells and 2) determining the effect of EndMT inhibition on regenerating bone. Successful completion of the proposed studies will provide novel insights regarding the role of EndMT in intramembranous bone regeneration that can lead to therapeutic opportunities to enhance orthopaedic and dental care.