Molecular and cellular characterizations of human cherubism: disease aggressiveness depends on osteoclast differentiation

Natacha Kadlub,Arnaud Picard,Louise Galmiche,Marion Mandavit,Amélie E Coudert,Vianney Descroix,Quentin Sessiecq,Cecile Badoual,Aurore Coulomb L’Hermine,Ariane Berdal

doi:10.1186/s13023-018-0907-2

Abstract

BackgroundCherubism is a rare autosomal dominant disorder of the jaws caused by mutation of the SH3BP2 gene. The bone is replaced by a fibrous granuloma containing multinucleated giant cells. Cells of the cherubism granuloma have never been systematically analyzed. Hence, the aim of this study was to characterize the cells in human cherubism granulomas, to determine the osteoclastic characteristics of the multinucleated giant cells and to investigate the potential role of TNF-α in human cherubism.ResultsSeven granulomas were analyzed in pathology, molecular biology and immunohistochemistry. Granulomas were composed mainly of macrophages or osteoclasts within a fibroblastic tissue, with few lymphoid cells. Myeloid differentiation and nuclear NFATc1 localization were both associated with disease aggressiveness. OPG and RANKL immunohistochemical expression was unexpected in our specimens. Five granuloma cells were cultured in standard and osteoclastogenic media. In culture, cherubism cells were able to differentiate into active osteoclasts, in both osteoclastogenic and standard media. IL-6 was the major cytokine present in the culture supernatants.ConclusionMultinucleated giant cells from cherubism granulomas are CD68 positive cells, which differentiate into macrophages in non-aggressive cherubism and into osteoclasts in aggressive cherubism, stimulated by the NFATc1 pathway. This latter differentiation appears to involve a disturbed RANK-L/RANK/OPG pathway and be less TNF-α dependent than the cherubism mouse model.

Highlights

Cherubism is a rare autosomal dominant disorder of the jaws caused by mutation of the SH3 domain-binding protein 2 (SH3BP2) gene
According to Ueki’s mouse model, cherubism is associated with a high level of Tumor necrosis factor (TNF)-α (Tumor Necrosis Factor α) that is responsible for maintaining the phenotype: hyperactive macrophages secrete a high level of TNF-α that drives systemic inflammation, stimulates secretion of Receptor activator of nuclear factor kappa-B (RANK)-L (Receptor Activator of Nuclear factor Κ B Ligand) and Macrophage colony-stimulating factor (M-CSF) (Macrophage Colony Stimulating Factor) by stromal cells, and results in bone loss [14]
As cherubism was recently described as being an auto-inflammatory bone disease, we focused on the expression of genes involved in osteoclastogenesis (RANK, RANKL, M-CSF, OPG, NFATc1), bone formation (ALP, Osteocalcin), and inflammation (IL6, Interleukin-6 receptor (IL6R), TNFα, TNFR1, TNFR2, IL17) (Additional file 5)

Summary

Introduction

Cherubism is a rare autosomal dominant disorder of the jaws caused by mutation of the SH3BP2 gene. Kadlub et al Orphanet Journal of Rare Diseases (2018) 13:166 unlike human SH3BP2 heterozygotes, heterozygous mice do not exhibit any cherubism phenotype, and homozygous mutants develop severe bone loss due to osteoclast hyperactivity. Despite this important difference in genetic expression, Sh3bp KI mice are considered a cherubism model [14]. Sh3bp KI mice develop systemic inflammation as a result of systemic infiltration by macrophages into tissues, as well as bone loss [14], defining cherubism as an auto-inflammatory bone disease [16,17,18]

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