Sonic Hedgehog Regulates Bone Fracture Healing.

Hiroaki Takebe,Kazuharu Irie,Tsuyoshi Shimo,Akihiro Hosoya,Nazmus Shalehin

doi:10.3390/ijms21020677

Hiroaki Takebe, Kazuharu Irie + Show 3 more

Open Access

https://doi.org/10.3390/ijms21020677

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Abstract

Bone fracture healing involves the combination of intramembranous and endochondral ossification. It is known that Indian hedgehog (Ihh) promotes chondrogenesis during fracture healing. Meanwhile, Sonic hedgehog (Shh), which is involved in ontogeny, has been reported to be involved in fracture healing, but the details had not been clarified. In this study, we demonstrated that Shh participated in fracture healing. Six-week-old Sprague–Dawley rats and Gli-CreERT2; tdTomato mice were used in this study. The right rib bones of experimental animals were fractured. The localization of Shh and Gli1 during fracture healing was examined. The localization of Gli1 progeny cells and osterix (Osx)-positive cells was similar during fracture healing. Runt-related transcription factor 2 (Runx2) and Osx, both of which are osteoblast markers, were observed on the surface of the new bone matrix and chondrocytes on day seven after fracture. Shh and Gli1 were co-localized with Runx2 and Osx. These findings suggest that Shh is involved in intramembranous and endochondral ossification during fracture healing.

Highlights

The fracture healing process consists of four overlapping phases, namely, inflammation, proliferation, callus formation, and bone remodeling
Vascularization supplies mesenchymal stem cells (MSCs), which differentiate into chondrocytes or osteoblasts simultaneously with cartilage tissue development [2,3]
We demonstrated that Sonic hedgehog (Shh) protein and the related proteins Smo and Gli1 were involved in osteoblast differentiation at the fracture healing site via immunohistochemical analysis

Summary

Introduction

The fracture healing process consists of four overlapping phases, namely, inflammation, proliferation, callus formation, and bone remodeling. Hedgehog (HH) proteins are among the signaling molecules required for endochondral bone formation during embryonic development, and they regulate bone homeostasis by controlling MSC proliferation [6,7]. The HH family of intercellular signaling proteins plays important roles in regulating the development of many tissues and organs. Their name is derived from the observation of a hedgehog-like appearance in Drosophila embryos with genetic mutations that block their action. We demonstrated that Shh protein and the related proteins Smo and Gli were involved in osteoblast differentiation at the fracture healing site via immunohistochemical analysis

Results and Discussion

Tissue Preparation

Immunohistochemistry

Image Analysis

Statistical Analysis

Conclusions