Rescue of a cherubism bone marrow stromal culture phenotype by reducing TGFβ signaling

Bone. 2018 Jun;111:28-35. doi: 10.1016/j.bone.2018.03.009. Epub 2018 Mar 9.

Abstract

We utilized a bone marrow stromal culture system to investigate changes in TGFβ signaling in a mouse model for cherubism (Sh3bp2KI/KI). Interestingly, bone marrow cultures derived from cherubism mice not only displayed impaired osteoblast differentiation, but also had spontaneous osteoclast formation. PAI1, a target gene of TGFβ signaling, was elevated 2-fold in cherubism CD11b-,CD45- cells compared to wild type cells, while the expression of BAMBI, an inhibitor of TGFβ signaling, was down-regulated. We also discovered that treatment of cherubism cultures with antagonists of the TGFβ signaling pathway could largely rescue osteoblast differentiation and markedly reduce spontaneous osteoclast formation. Treatment with the type I TGFβ receptor small molecule inhibitor SB505124 increased osteoblast reporter gene Col1a1-2.3 expression 24-fold and increased the expression of osteoblast gene markers Osterix (Sp7) 25-fold, Bone Sialoprotein (BSP) 7-fold, Osteocalcin (Bglap1) 100-fold, and Dentin Matrix Protein 1 (DMP1) 35-fold. In contrast, SB505124 treatment resulted in a significant reductions in osteoclast number and size. Gene expression analyses for RANKL, a positive regulator of osteoclast formation was 2.5-fold higher in osteoblast cultures derived from Sh3bp2KI/KI mice compared to wild type cultures, whereas OPG, an inhibitor of RANKL was 5-fold lower. However, SB505124 treatment reduced RANKL almost back down to wild type levels, while increasing OPG expression. Our studies also implicate a role for TGFβ ligands in the etiology of cherubism. Blocking of TGFβ ligands with the monoclonal antibody 1D11 increased Col1a1-2.3 reporter expression 4-fold and 13-fold in cultures derived from Sh3bp2KI/+ and Sh3bp2KI/KI mice, respectively. Serum levels of latent TGFβ1 were also 2-fold higher in SH3BP2KI/KI mice compared to wild type littermates. Taken together, these studies provide evidence that elevated levels of TGFβ signaling may contribute to the disease phenotype of cherubism and a reduction in pathway activity may be an effective therapeutic approach to treat this rare disease.

Keywords: Bone; Cherubism; Osteoblast; Osteoclast; Stromal cell; TGFβ.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics
  • Animals
  • Benzodioxoles / pharmacology
  • Benzodioxoles / therapeutic use*
  • Bone Marrow Cells / cytology
  • Bone Resorption
  • Cell Differentiation / genetics
  • Cells, Cultured
  • Cherubism / drug therapy*
  • Cherubism / pathology*
  • Disease Models, Animal
  • Femur / cytology
  • Genetic Markers / genetics
  • Imidazoles / pharmacology
  • Imidazoles / therapeutic use*
  • Membrane Proteins / genetics
  • Mice
  • Molecular Targeted Therapy
  • Osteoblasts / cytology
  • Osteoclasts / cytology
  • Osteogenesis
  • Phenotype
  • Pyridines / pharmacology
  • Pyridines / therapeutic use*
  • RANK Ligand / genetics
  • Stromal Cells
  • Tibia / cytology
  • Transforming Growth Factor beta / antagonists & inhibitors*
  • Transforming Growth Factor beta / physiology

Substances

  • 2-(5-benzo(1,3)dioxol-5-yl-2-tert-butyl-3H-imidazol-4-yl)-6-methylpyridine hydrochloride
  • Adaptor Proteins, Signal Transducing
  • Bambi protein, mouse
  • Benzodioxoles
  • Genetic Markers
  • Imidazoles
  • Membrane Proteins
  • Pyridines
  • RANK Ligand
  • Sh3bp2 protein, mouse
  • Tnfsf11 protein, mouse
  • Transforming Growth Factor beta