Altered gene expression in human cleidocranial dysplasia dental pulp cells

Cleidocranial dysplasia (CCD) is an autosomal dominant disorder characterised by defects of bone and tooth development. The dental manifestations in CCD patients include supernumerary teeth, delayed tooth eruption, tooth hypoplasia and absence of cellular cementum formation. This disorder is associated with mutations in the osteoblast-specific transcription factor Runx2. To identify morphological and molecular alterations associated with CCD dental tissues, human primary dental pulp cell cultures were established from age- and sex-matched CCD and normal patients. Dental pulp cells were compared for general morphology, proliferation rates, and gene expression profiles using cDNA microarray technology. CCD pulp cells were about four-fold larger than normal cells, however the normal pulp proliferation rates were two- and three-fold greater at time points tested than the CCD cells. Of the 226 genes analysed by blot microarray, 18.6% displayed significant differences at least two-fold in expression levels. This includes 25 genes (11.1%) that were up-regulated, while 17 (7.5%) that were down-regulated in the CCD cells as compared to the normal cells. Expression of selected genes was further verified by quantitative real-time polymerase chain reaction (qRT-PCR). Comparison between the CDD and normal cells revealed that gene expression of cytokines and growth factors, such as leukemia inhibitory factor (LIF), interleukin-6 (IL-6) and transforming growth factor beta receptor II (TGF-betaRII) and vascular endothelial growth factor B (VEGFB) were higher while bone morphogenetic protein 2 (BMP2) was lower in the CCD cells. Furthermore, potential Runx2 binding sites were found in all putative target gene promoters. This study suggests that in addition to bone and tooth cell differentiation, Runx2 may be involved in controlling cell growth during tooth development.