Expression of Pleiotrophin and receptor PTP b/z /Phosphacan in odontoblasts

Pleiotrophin (PTN; HB-GAM, OSF-1) is a secreted heparin-binding protein that effects osteoblast differentiation and recruitment. PTN and its receptor (protein tyrosine phosphatase beta/zeta) were found to be required for postnatal bone development (Imai et al. (2009) Bone 44: 785-794 and Schinke et al. (2008) Bone 42: 524-34). PTN deficiency results in a late stage developmental change in bone growth (mostly weight-bearing long bones). This indicates the osteogenic effect of PTN may be linked to mechanical stress in bones and be involved in mediating usage-dependent bone formation. Objectives: Investigate the presence of PTN and its receptor RPTPb/z in mice teeth to determine whether PTN and RPTPb/z plays a role in tooth development and mineralization. Methods: Mouse pulp (MD10D3, MD10A11) and odontoblast (MO6-G3) cell lines were grown and collected for RT-PCR analysis, immunohistochemistry, and Western blot analysis.  Results: PTN (mRNA and protein) was expressed in both epithelial/mesenchymal dental cells at different levels. RT-PCR showed that RPTPb/z was expressed in MO6-G3 odontoblasts, specifically as the long extracellular phosphacan form. Immunohistochemistry revealed PTN expression throughout odontogenesis in the mouse (developmental days E16-PN10).  Conclusions: These studies demonstrate that PTN and Phosphacan are expressed during tooth development. Localization of PTN within the PDL and odontoblasts (mechanio-sensing cells) may indicate that PTN is involved in the production or homeostasis of mineralized tissue. The presence of Phosphacan and its function in odontogenesis is being investigate. Support: NIDCR/1R03DE019497-01A1(HE), NIDCR/T35-HL007473(MM).