The aftermath of periodontal disease frequently includes alveolar bone loss. Contemporary periodontal therapy has not been effective for regenerating alveolar bone. Therefore, the long term goal of the applicants is to design and develop a tissue engineered bone regenerating therapy. The applicants reason that transcriptional control of osteoblast differentiation offers an innovative and powerful new treatment approach for controlled bone regeneration. To accomplish the goal, we will focus on a plasmid (p) encoding for the nuclear transcription factor Osterix (Osx) that will be delivered to bone using an injectable, biodegradable, biocompatible hydrogel of hyaluronate (HA) and polylysine (PL). The overall hypothesis for this application is that controlled, predictable delivery ofp.Osx with HA/PL will promote osteoblast differentiation and bone formation. Testing the hypothesis will be accomplished by four specific aims. Specific aim 1. Will Osx encoded by a plasmid (p.Osx) up regulate osteoblast-like gene expression in a designated cell line? Specific aim 2. Will p.Osx delivered in HA/PL enhance transfection efficiency of p.Osx and therefore increase oseoblast-like gene expression? Specific aim 3. Will the optimized p.Osx/HA_L assessed in vitro promote bone formation in a critical-sized defect (CSD)? We reason a non-dental CSD model is less stringent than the periodontal model. The CSD model will enable a level of control of therapy design and optimization not available in the periodontal model and the CSD is a logical antecedent to aim 4. Specific aim 4. Will the optimized formulation work either as effectively as a contemporary periodontal therapy of demineralized freeze-dried bone allograft in an alveolar bone model in the dog? Data will be analyzed by analysis of variance and post hoc multiple comparison analyses with p less than or equal too 0.05.