P2: Role of PTH in enhancing fracture repair in aging

该项目是基于初步数据显示，年龄相关的定量下降，在骨折愈合， 小鼠模型，具有延迟软骨形成和随后软骨细胞 肥厚此外，矿化软骨的血管化和重塑减少。在 与此同时，随着年龄的增长，骨折骨痂中smurf 2表达下降， 考克斯-2表达。鉴于已知smurf 2对增强软骨细胞成熟和 矿化，以及表明PTH刺激smurf 2表达的初步数据，PTH的作用 将评估在衰老小鼠中恢复Smurf 2表达和增强骨折愈合的作用。 还将使用同种异体移植研究骨膜靶细胞的作用的确定， 骨膜细胞来自基因标记的供体小鼠。具体目标是： 1.使用骨密度计对年轻和老龄小鼠骨折愈合的综合定量表征 组织形态计量学、microCT和生物力学分析将与基因表达相关，重点是 TGF-β/BMP和PTH/PTHrP信号通路。 2.确定年轻和老年小鼠骨膜干细胞的能力差异， 启动骨修复以及COX 2和PTHrP的作用。年轻人和老年人骨膜的修复潜力 将评估老年小鼠以确定来自年轻动物的组织是否可以恢复老年小鼠的骨折愈合。 小鼠基于考克斯-2 -/-小鼠中已知的考克斯-2随衰老和愈合受损而丢失， 将评价来自考克斯-2 -/-和考克斯-2 +/-的骨膜对年轻和年老小鼠愈合的影响。最后， 将在衰老小鼠中评估来自coHAIPTHR转基因小鼠的骨膜，以确定是否存在PTH/PTHrP 信号通路激活可以恢复考克斯-2 -/-或衰老小鼠愈合。愈合将通过以下方式进行评价： 所有病例的显微CT、组织形态学和生物力学测试。 3.确定PTH在老年小鼠骨折修复的各个阶段的作用。 尽管有数据和PTH在骨折愈合刺激中的临床应用，但对PTH的作用还没有明确的认识。 参与的机制或受PTH影响的修复过程的阶段。改善骨折的能力 将评估老年小鼠中的修复，以及PTH补偿考克斯-2损失的能力。影响 smurf 1和2在骨折愈合过程中的表达，目前对此知之甚少，也将被 研究了

The project is based on preliminary data showing an age-related quantitative decline in fracture healing in a murine model, with reproducible findings of delayed chondrogenesis and subsequent chondrocyte hypertrophy. In addition vascularization and remodeling of the mineralized cartilage is diminished. In conjunction with this, a decline in smurf2 expression in fracture callus occurs with aging, as well as a decline in COX-2 expression. Given the known effect of smurf2 on enhancing chondrocyte maturation and mineralization, and preliminary data indicating stimulation of smurf2 expression by PTH, the effects of PTH on restoring smurf2 expression and enhancing healing of fractures in aging mice will be evaluated. Determination of the role of the target cells of the periosteum will also be investigated using allografting with periosteal cells from genetically marked donor mice. The Specific Aims are: 1. Comprehensive quantitative characterization of fracture healing in young and aging mice using histomorphometry, microCT, and biomechanical analysis will be correlated with gene expression, with focus on TGF-beta/BMP and PTH/PTHrP signaling pathways. 2. Determining the differences in the capacity of periosteal stem cells from young and old mice to initiate bone repair and the roles of COX2 and PTHrP. The reparative potential of periosteum in young and old mice will be evaluated to determine if tissue from young animals can restore fracture healing in aged mice. Based on known loss of COX-2 with aging and impaired healing in Cox-2 -/- mice, effects of periosteum from COX-2 -/- and COX-2 +/- on healing in young and old mice will be evaluated. Finally, periosteum from coHAIPTHR transgenic mice will be evaluated in aging mice to determine if PTH/PTHrP signal pathway activation can restore healing in COX-2 -/- or aging mice. Healing will be evaluated by microCT, histomorphometry, and biomechanical testing in all cases. 3. Defining the effect of PTH during the various stages of fracture repair in aged mice. Despite data and clinical use of PTH in fracture healing stimulation, there is not a clear understanding of the mechanisms involved or stage of the repair process affected by PTH. The ability to improve fracture repair in aged mice, and ability of PTH to compensate for the loss of Cox-2 will be evaluated. Effects on smurfl and 2 expression during fracture healing, about which little is currently known, will also be investigated.