Using Inducible Osteoblastic Lineage-Specific Stat3 Knockout Mice to Study Alveolar Bone Remodeling During Orthodontic Tooth Movement

Summary

This study provides a protocol for using inducible osteoblast lineage-specific Stat3 knockout mice to study bone remodeling under orthodontic force and describes methods for analyzing alveolar bone remodeling during orthodontic tooth movement, thus shedding light on skeletal mechanical biology.

Abstract

The alveolar bone, with a high turnover rate, is the most actively-remodeling bone in the body. Orthodontic tooth movement (OTM) is a common artificial process of alveolar bone remodeling in response to mechanical force, but the underlying mechanism remains elusive. Previous studies have been unable to reveal the precise mechanism of bone remodeling in any time and space due to animal model-related restrictions. The signal transducer and activator of transcription 3 (STAT3) is important in bone metabolism, but its role in osteoblasts during OTM is unclear. To provide in vivo evidence that STAT3 participates in OTM at specific time points and in particular cells during OTM, we generated a tamoxifen-inducible osteoblast lineage-specific Stat3 knockout mouse model, applied orthodontic force, and analyzed the alveolar bone phenotype.

Micro-computed tomography (Micro-CT) and stereo microscopy were used to access OTM distance. Histological analysis selected the area located within three roots of the first molar (M1) in the cross-section of the maxillary bone as the region of interest (ROI) to evaluate the metabolic activity of osteoblasts and osteoclasts, indicating the effect of orthodontic force on alveolar bone. In short, we provide a protocol for using inducible osteoblast lineage-specific Stat3 knockout mice to study bone remodeling under orthodontic force and describe methods for analyzing alveolar bone remodeling during OTM, thus shedding new light on skeletal mechanical biology.

Introduction

It is generally known that bone is under constant reconstruction throughout life, in response to mechanical forces according to Wolff's law^1,2. Appropriate mechanical stimulation, such as gravity and daily exercise, maintains bone mass and strength and prevents bone loss by stimulating both osteoblasts and osteoclasts. Osteoclasts, responsible for bone resorption^3,4,5,6,7, and osteoblasts, responsible for bone formation⁸<....

Protocol

All methods involving animals described here were approved by the ethics committee of the Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine (no. 82101048).

1. Establishing inducible osteoblast lineage-specific Stat3 knockout mice

NOTE: Stat3^fl/fl mice were obtained commercially; the Col1α2^CreERT2 strain was a gift (see the Table of Materials

Discussion

As malocclusion is among the most common oral disorders impairing breathing, mastication, speaking, and even appearance, the demand for orthodontics is increasing day by day with the incidence rising from 70% to 93% according to a previous epidemiological survey^31,32. How to accelerate alveolar bone remodeling to raise the efficiency of orthodontic treatment safely has become a hot topic in this field; therefore, it is necessary to clarify the mechanism of alveol.......

Materials

Name	Company	Catalog Number	Comments
1x PBS	Beijing Solarbio Science & Technology Co.,Ltd.	P1020
4% paraformaldehyde	Wuhan Servicebio Technology Co., Ltd.	G1101
Alizarin red	Sigma-Aldrich	A5533
Anti-CTSK antibody	Santa Cruz	sc-48353
Anti-OPN antibody	R&D Systems, Minneapolis, MN, USA	AF808
Calcein	Sigma-Aldrich	C0875
Closed-coil springs	Innovative Material and Devices, Shanghai, China	CS1006B
Col1α2CreERT2 mice			A gift from Bin Zhou, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences.
Dexmedetomidine hydrochloride	Orionintie Corporation, Orion Pharma Espoo site
EDTA	Beyotime Biotechanology	ST069
Embedding tanks	Citotest Labware Manufacturing Co., Ltd	80106-1100-16
Ethanol	Sinopharm Chemical Reagent Co., Ltd.	100092183
ImageJ software	NIH, Bethesda, MD, USA
Mounting medium with DAPI	Beyotime Biotechanology	P0131
Mouse dissection platform	Shanghai Huake Experimental Devices and Materials Co., Ltd.	HK105
Paraffin	Sangon biotech Co., Ltd.	A601889
Primers for genotyping			Stat3 F-TTGACCTGTGCTCCTACAAAAA; Stat3 R-CCCTAGATTAGGCCAGCACA; Cre F-CGATGCAACGAGTGATGAGG; Cre R-CGCATA ACCAGTGAAACAGC
Protease K	Sigma-Aldrich	539480
Self-curing restorative resin	3M ESPE, St. Paul, MN, USA	712-035
Stat3fl/fl mice	GemPharmatech Co., Ltd	D000527
Tamoxifen	Sigma-Aldrich	T5648
TRAP staining kit	Sigma-Aldrich	387A
Tris-HCl	Beyotime Biotechanology	ST780
Universal tissue fixative	Wuhan Servicebio Technology Co., Ltd.	G1105
Xylene	Sinopharm Chemical Reagent Co., Ltd.	10023418
Zoletil	VIRBAC