Wang Xuemei, Luo En, Bi Ruiye, Ye Bin, Hu Jing, Zou Shujuan
a State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases , West China Hospital of Stomatology, Sichuan University , Chengdu , China.
Connect Tissue Res. 2018 Jan;59(1):45-54. doi: 10.1080/03008207.2017.1300154. Epub 2017 Mar 27.
The Wnt signaling pathway plays crucial roles in embryonic skeletal development and postnatal bone regeneration. However, mechanisms of Wnt signaling functioning in distraction osteogenesis (DO) haven't been well characterized.
We established a DO model using Sprague-Dawley rat tibia. And a Wnt signaling blocking agent, recombinant rat Dickkopf-related protein 1 (rrDkk1), was locally applied in the distracted gap to study the role of Wnt signaling during DO process. Animals in the experimental group received rrDkk1 injections (dose = 25 μg/kg) once daily during distraction period and every third day during consolidation stage (n = 48). Animals in the control group received saline under the same injection strategy (n = 48). Animals at different time points during DO process (1, 3, 6, 12 days after distraction, 10 days and 6 weeks after consolidation) were killed and tissues in the distraction region were harvested for radiography, dual energy X-ray absorptiometry, micro-computed tomography (micro-CT), and histological analyses.
Most Wnt ligands, cofactors, receptors, and antagonists were widely expressed in the distraction callus and were significantly upregulated during DO process. After rrDkk1 administration, the majority of these factors were downregulated at the mRNA level, except sFRP and GSK-3β. At the protein level, both β-catenin and Lef-1 were also suppressed by rrDkk1. In the long term, restricted bone healing was observed in the distracted callus in the rrDkk1 injection group. These findings were confirmed by histological and micro-CT analyses.
Our findings suggest that Wnt signaling participates in the process of DO, and clinical therapeutic approaches of DO may do well to avoid Wnt pathway suppression.
Wnt信号通路在胚胎骨骼发育和出生后骨再生中起关键作用。然而，Wnt信号在牵张成骨（DO）中发挥作用的机制尚未得到充分阐明。
我们使用Sprague-Dawley大鼠胫骨建立了DO模型。并将一种Wnt信号阻断剂，重组大鼠Dickkopf相关蛋白1（rrDkk1）局部应用于牵张间隙，以研究Wnt信号在DO过程中的作用。实验组动物在牵张期每天接受一次rrDkk1注射（剂量=25μg/kg），在巩固期每三天接受一次注射（n=48）。对照组动物按照相同的注射策略接受生理盐水注射（n=48）。在DO过程的不同时间点（牵张后1、3、6、12天，巩固后10天和6周）处死动物，收集牵张区域的组织进行放射照相、双能X线吸收测定、显微计算机断层扫描（micro-CT）和组织学分析。
大多数Wnt配体、辅助因子、受体和拮抗剂在牵张骨痂中广泛表达，并在DO过程中显著上调。给予rrDkk1后，除sFRP和GSK-3β外，这些因子中的大多数在mRNA水平下调。在蛋白质水平上，β-连环蛋白和Lef-1也被rrDkk1抑制。长期来看，rrDkk1注射组牵张骨痂中观察到骨愈合受限。这些发现通过组织学和micro-CT分析得到证实。
我们的研究结果表明Wnt信号参与了DO过程，DO的临床治疗方法可能最好避免Wnt通路抑制。
