Enhanced chondrogenesis and Wnt signaling in PTH-treated fractures
Enhanced chondrogenesis and Wnt signaling in PTH-treated fractures
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DOI：
10.1359/jbmr.070724
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发表时间：
2007-12-01
影响因子：
6.2
通讯作者：
Barnes, George L.
中科院分区：
文献类型：
--
作者：
Kakar, Sanjeev;Einhorn, Thomas A.;Barnes, George L.
研究表明，全身 PTH 治疗可提高啮齿动物模型的骨修复率。然而，PTH影响骨修复的机制尚未阐明。在这些研究中，我们表明 PTH 主要通过增加软骨细胞的募集和分化率来增强软骨内骨修复的早期阶段。与这些细胞事件相协调，我们观察到在骨折修复过程中的多个时间点，经 PTH 处理的骨骼中典型 Wnt 信号传导水平有所增加，支持了 PTH 反应至少部分通过 Wnt 信号传导介导的结论。 简介：自 FDA 批准 PTH [PTH(1-34)； Forteo]作为骨质疏松症的治疗方法，人们对其在其他肌肉骨骼疾病中的应用产生了兴趣。骨折修复是 PTH 可能产生重大临床影响的领域之一。多项动物研究表明，骨折愈合过程中全身性 PTH 治疗可增加骨折愈合模型中的骨痂体积和机械能力的恢复。尽管 PTH 的潜力已经确定，但 PTH 产生这些作用的机制仍然难以捉摸。 材料和方法：8 周龄雄性 C57B1/6 小鼠发生闭合性股骨骨折，骨折后每天全身注射生理盐水（对照）或 30 μg/kg PTH(1-34)，持续 14 天。骨折后第 2、3、5、7、10、14、21 和 28 天收获骨骼，并通过放射线照相和组织形态计量学在组织水平上进行分析，并通过 RNase 保护测定 (RPA)、实时 PCR 和蛋白质印迹分析在分子和生化水平上进行分析。 结果：定量 RCT 分析显示，与对照组相比，PTH 治疗诱导了更大的愈伤组织横截面积、长度和总体积。对与软骨生成和成骨相关的细胞外基质基因表达的分子分析表明，在修复过程中，PTH 治疗的骨折的软骨生成相对于成骨而言增加了 3 倍。此外，PTH处理的愈伤组织中软骨细胞肥大发生得较早。对 PTH 作用潜在介质表达的分析表明，PTH 处理显着诱导 Writs 4、5a、5b 和 10b 的表达，并增加非磷酸化核定位 P-catenin 蛋白的水平，这是典型 Writ 信号传导的核心特征。 结论：这些结果表明，PTH 介导的骨折修复增强主要与早期骨折愈伤组织中软骨细胞募集和成熟的放大有关。与这些细胞效应相关，我们观察到经典 Wnt 信号传导的增加，支持这样的结论：PTH 对骨修复的影响至少部分是通过 Wnt 信号传导途径的激活介导的。
tudies have shown that systemic PTH treatment enhanced the rate of bone repair in rodent models. However, the mechanisms through which PTH affects bone repair have not been elucidated. In these studies we show that PTH primarily enhanced the earliest stages of endochondral bone repair by increasing chondrocyte recruitment and rate of differentiation. In coordination with these cellular events, we observed an increased level of canonical Wnt-signaling in PTH-treated bones at multiple time-points across the time-course of fracture repair, supporting the conclusion that PTH responses are at least in part mediated through Wnt signaling.Introduction: Since FDA approval of PTH [PTH(1-34); Forteo] as a treatment for osteoporosis, there has been interest in its use in other musculoskeletal conditions. Fracture repair is one area in which PTH may have a significant clinical impact. Multiple animal studies have shown that systemic PTH treatment of healing fractures increased both callus volume and return of mechanical competence in models of fracture healing. Whereas the potential for PTH has been established, the mechanism(s) by which PTH produces these effects remain elusive.Materials and Methods: Closed femoral fractures were generated in 8-wk-old male C57B1/6 mice followed by daily systemic injections of either saline (control) or 30 mu g/kg PTH(1-34) for 14 days after fracture. Bones were harvested at days 2, 3, 5, 7, 10, 14, 21, and 28 after fracture and analyzed at the tissue level by radiography and histomorphometry and at the molecular and biochemical levels level by RNase protection assay (RPA), real-time PCR, and Western blot analysis.Results: Quantitative RCT analysis showed that PTH treatment induced a larger callus cross-sectional area, length, and total volume compared with controls. Molecular analysis of the expression of extracellular matrix genes associated with chondrogenesis and osteogenesis showed that PTH treated fractures displayed a 3-fold greater increase in chondrogenesis relative to osteogenesis over the course of the repair process. In addition, chondrocyte hypertrophy occurred earlier in the PTH-treated callus tissues. Analysis of the expression of potential mediators of PTH actions showed that PTH treatment significantly induced the expression of Writs 4, 5a, 5b, and 10b and increased levels of unphosphorylated, nuclear localized P-catenin protein, a central feature of canonical Writ signaling.Conclusions: These results showed that the PTH-mediated enhancement of fracture repair is primarily associated with an amplification of chondrocyte recruitment and maturation in the early fracture callus. Associated with these cellular effects, we observed an increase in canonical Wnt signaling supporting the conclusion that PTH effects on bone repair are mediated at least in part through the activation of Wnt-signaling pathways.