Impact of the endocannabinoid system on murine cranial and alveolar bone phenotype

Maria Setiawan; Andreas Jäger; Nikolaos Daratsianos; Susanne Reimann; Junliang Chen; Anne-Caroline Schmöle; Daniel Derichs-Schönthal; Anna Konermann

doi:10.1016/j.aanat.2020.151516

Impact of the endocannabinoid system on murine cranial and alveolar bone phenotype

Ann Anat. 2020 Jul:230:151516. doi: 10.1016/j.aanat.2020.151516. Epub 2020 Mar 30.

Authors

Maria Setiawan¹, Andreas Jäger¹, Nikolaos Daratsianos¹, Susanne Reimann², Junliang Chen², Anne-Caroline Schmöle³, Daniel Derichs-Schönthal⁴, Anna Konermann⁵

Affiliations

¹ Department of Orthodontics, Medical Faculty, University of Bonn, Welschnonnenstr.17, D-53111 Bonn, Germany.
² Endowed Professorship for Oral Medical Technology, University of Bonn, Welschnonnenstr. 17, D-53111 Bonn, Germany.
³ Institute of Molecular Psychiatry, Medical Faculty, University of Bonn, Sigmund-Freud-Str. 25, D-53127 Bonn, Germany.
⁴ Orthodontic private practice, Richard-Wagner-Straße 9-11, 50674 Cologne, Germany.
⁵ Department of Orthodontics, Medical Faculty, University of Bonn, Welschnonnenstr.17, D-53111 Bonn, Germany. Electronic address: konermann@uni-bonn.de.

PMID: 32240731
DOI: 10.1016/j.aanat.2020.151516

Abstract

Purpose: The endocannabionoid signaling system has been demonstrated to be present in the skeleton, with involvement in the regulation of skeletal homeostasis. However, investigations substantiating these findings in cranial and alveolar bones are missing to date. The aim of our study was to investigate a potential impact of the endocannabinoid system on cranial and alveolar bone structures and phenotypes.

Basic procedures: CB1^-/-, CB2^-/- and WT mice (n = 5) were scanned via μCT. Reconstructed datasets were processed for analyses. Cranial cephalometric measurements were performed with OnyxCeph^3TMsoftware. Alveolar bone densities were determined via mean grey value measurements with Mimics research 18.0. Alveolar bone heights around teeth in upper and lower jaws were morphometrically analyzed. Alveolar osteoclasts were quantified via TRAP staining of paraffin-embedded histologies. Bone-marrow derived macrophages isolated from murine hind legs were analyzed for CD40 and MMR expression via flow cytometry.

Main findings: CB2^-/- mice exhibited significantly higher bone densities with mean grey values of 138.3 ± 22.6 compared to 121.9 ± 9.3 for WT for upper jaws, and 134.6 ± 22.9 compared to 116.1 ± 12.9 for WT 134.6 ± 22.9. Concurrently, CB2 receptor knockout entailed reduced alveolar bone heights of about 50% compared to WT mice. Antigen-presenting cell marker expression of MMR was significantly diminished in bone-marrow derived macrophages of CB2^-/- mice. Cranium dimensions as much as alveolar osteoclasts were unaffected by receptor knockouts.CB1 receptor knockout did not involve statistically significant alterations in the parameters investigated compared to WT mice.

Principal conclusions: The endoncannabinoid system, and particularly CB2 receptor strongly affects murine alveolar bone phenotypes. These observations suggest CB2 as promising target in the modulation of oral bone phenotypes, probably by impact on bone dynamics via osteal immune cells.

Keywords: Alveolar bone; CB1; CB2; Endocannabinoid; system.

MeSH terms

Analysis of Variance
Animals
Bone Density
Bone Resorption / physiopathology
CD40 Antigens / metabolism
Cephalometry
Endocannabinoids / physiology*
Flow Cytometry
Jaw / anatomy & histology*
Macrophages / cytology
Mice
Mice, Inbred C57BL
Multivariate Analysis
Phenotype
Receptor, Cannabinoid, CB2 / physiology*
Skull / anatomy & histology*

Substances

CD40 Antigens
Endocannabinoids
Receptor, Cannabinoid, CB2