P2: Role of PTH in enhancing fracture repair in aging

该项目是基于初步数据显示，在一个年龄相关的骨折愈合的数量下降 小鼠模型，具有延迟软骨形成和随后的软骨细胞的可重复性发现 肥大。此外，矿化软骨的血管化和重塑也减少了。在……里面 与此相关联的是，随着年龄的增长，骨折骨痂中smurf2的表达也会下降 COX-2的表达。鉴于已知的smurf2促进软骨细胞成熟和 矿化和初步数据表明甲状旁腺素刺激smurf2的表达，甲状旁腺素的影响 在恢复smurf2表达和促进衰老小鼠骨折愈合方面将进行评估。 骨膜靶细胞作用的确定也将使用同种异体骨膜移植进行研究。 来自基因标记的供体小鼠的骨膜细胞。具体目标是： 1.青年期和老年期小鼠骨折愈合的综合定量表征 组织形态计量学、显微CT和生物力学分析将与基因表达、病灶相关 在转化生长因子-β/骨形态发生蛋白和甲状旁腺激素/甲状旁腺素信号通路上。 2.测定幼龄和老年小鼠骨膜干细胞能力的差异 启动骨修复以及COX2和PTHrP的作用。青壮年儿童骨膜修复潜能的研究 将对老年小鼠进行评估，以确定幼年动物的组织是否可以恢复老年小鼠的骨折愈合 老鼠。基于已知的COX-2基因缺失与COX-2-/-小鼠衰老和愈合受损的关系， 将评估来自COX-2-/-和COX-2/-的骨膜对幼鼠和老年鼠愈合的影响。最后， 来自coHAIPTHR转基因小鼠的骨膜将在衰老小鼠中进行评估，以确定PTH/PTHrP 信号通路激活可以恢复COX-2-/-或衰老小鼠的愈合。愈合情况将通过以下方式进行评估 所有病例均行显微CT、组织形态计量学和生物力学测试。 3.明确PTH在老年小鼠骨折修复不同阶段的作用。 尽管有数据和临床应用甲状旁腺素促进骨折愈合，但对甲状旁腺素的认识尚不清楚 甲状旁腺激素影响修复过程的机制或阶段。改善骨折的能力 将评估衰老小鼠的修复情况，以及甲状旁腺素补偿COX-2丢失的能力。对……的影响 Smurfl和2在骨折愈合过程中的表达，目前知之甚少，也将是 调查过了。

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.