Hadjiargyrou Michael, Kotsiopriftis Maria, Lauzier Dominique, Hamdy Reggie C, Kloen Peter
Department of Biological & Chemical Sciences, New York Institute of Technology, Old Westbury, NY 11568, USA.
Division of Orthopaedic Surgery, Shriners Hospital for Children, Montreal Children Hospital, McGill University, Montreal, QC H4A 0A9, Canada.
Bone Rep. 2024 Jun 19;22:101780. doi: 10.1016/j.bonr.2024.101780. eCollection 2024 Sep.
The Wnt signaling pathway is a key molecular process during fracture repair. Although much of what we now know about the role of this pathway in bone is derived from in vitro and animal studies, the same cannot be said about humans. As such, we hypothesized that Wnt signaling will also be a key process in humans during physiological fracture healing as well as in the development of a nonunion (hypertrophic and oligotrophic). We further hypothesized that the expression of Wnt-signaling pathway genes/proteins would exhibit a differential expression pattern between physiological fracture callus and the pathological nonunion tissues. We tested these two hypotheses by examining the mRNA levels of key Wnt-signaling related genes: ligands (WNT4, WNT10a), receptors (FZD4, LRP5, LRP6), inhibitors (DKK1, SOST) and modulators (CTNNB1 and PORCN). RNA sequencing from calluses as well as from the two nonunion tissue types, revealed that all of these genes were expressed at about the same level in these three tissue types. Further, spatial expression experiments identified the cells responsible of producing these proteins. Robust expression was detected in osteoblasts for the majority of these genes except SOST which displayed low expression, but in contrast, was mostly detected in osteocytes. Many of these genes were also expressed by callus chondrocytes as well. Taken together, these results confirm that Wnt signaling is indeed active during both human physiological fracture healing as well as in pathological nonunions.
Wnt信号通路是骨折修复过程中的关键分子过程。尽管我们目前对该通路在骨骼中作用的许多了解都来自体外和动物研究，但对于人类而言并非如此。因此，我们推测Wnt信号在人类生理骨折愈合以及骨不连（肥大性和营养不良性）的发生过程中也将是一个关键过程。我们进一步推测，Wnt信号通路基因/蛋白质的表达在生理骨折骨痂与病理性骨不连组织之间会呈现出差异表达模式。我们通过检测关键Wnt信号相关基因的mRNA水平来验证这两个假设：配体（WNT4、WNT10a）、受体（FZD4、LRP5、LRP6）、抑制剂（DKK1、SOST）和调节剂（CTNNB1和PORCN）。对骨痂以及两种骨不连组织类型进行RNA测序，结果显示所有这些基因在这三种组织类型中的表达水平大致相同。此外，空间表达实验确定了产生这些蛋白质的细胞。除SOST表达较低外，大多数这些基因在成骨细胞中检测到强烈表达，而SOST相反，大多在骨细胞中检测到表达。这些基因中的许多在骨痂软骨细胞中也有表达。综上所述，这些结果证实Wnt信号在人类生理骨折愈合以及病理性骨不连过程中确实是活跃的。
