Establishment and Characterization of Cleidocranial Dysplasia Dental Pulp Cells

Cleidocranial Dysplasia (CCD) is an autosomal dominant disorder characterized by bone defects, supernumerary teeth and delayed tooth eruption. Mutations in the runt-related transcription factor 2 (RUNX2), also known as core binding factor a 1 (CBFA1), are associated with CCD. The molecular mechanisms that correlate RUNX2 mutations with CCD dental phenotypes remains obscure. Objectives: 1) To establish dental pulp primary cell cultures from patients with CCD; 2) compare gene expression patterns in these pulp cells versus normal pulp cells; and 3) to identify common  signaling pathways that are altered associated with RUNX2 mutations. Methods: Age- and sex-matched normal and CCD  pulp cells from two families carrying different RUNX2 mutations (CCD-001 & CDD-006) were established in primary cultures isolated from extracted supernumerary teeth with informed consent. Pulp cells were examined by phase contrast microscopy, alkaline phosphatase staining and immunohistochemistry. Several critical signaling pathways for tooth formation and matrix proteins were investigated including SHH, Notch, BMP/TGFbeta, FGF and SIBLING proteins. Gene expression profiles were obtained for the CCD-001, CCD-006 and normal pulp cells using Affymetrix human genome U133 Plus 2.0 chips. Results: CCD-001 and CCD-006 pulp cells showed differences from controls such as enlarged cell size, Runx2 nuclear translocation and decreased proliferation rates. CCD pulp cells showed dysregulation of genes associated with signaling pathways critical for  tooth formation. In particular, alkaline phosphatase, patched, TGFbeta1, Lef1 and Runx3 were down-regulated. Members of the matrix SIBLING family were differentially regulated with dentin matrix protein 1 down-regulated while dentin sialophosphoprotein and osteonectin were up-regulated. Conclusions: This study has established pulp cells from CCD patients with different RUNX2 mutations for the first time.  Our data indicates several genes are commonly regulated associated with CCD however some differences were found associated with the different Runx2 mutations. Support: UAB SOD/IOHR PreDART program & UAB Graduate School.