Bone Abstracts

Among activation of apoptotic machinery, Fas (CD95)/FasL (CD178) were suggested to act in cell proliferation and differentiation. Expression of Fas and FasL was reported during tooth and bone formation. The examination of gld mice showed increased total body bone mass and number of osteoblasts in long bones. However, Fas and FasL functions in osteogenesis remain controversial. As most of studies dealing with Fas/FasL system in bone formation were performed in endochondral models, we turned to intramembranous bones.

The aim of our study was to investigate functions of FasL in development of the mandibular and alveolar bones using immunohistochemistry and impact of FasL deficiency by microCT examination of gld mice. This project continues our earlier published investigations of Fas/FasL in prenatal molar tooth development.

Heads at embryonic (E) 12.5, 15.5, 17.5, and postnatal (P) 0, 1, 4, 11 days were used for immunohistochemical analysis. FasL was localized in the dental epithelium, dental follicle and a few cells of the dental papilla. In general, as the tooth development progressed, FasL expression decreased. Notably, similar pattern was observed in mandibular/alveolar bone; FasL was detected in osteoblasts at the E15.5 and the number of positive cells decreased at later stages. Importantly, FasL expression did not copy the apoptosis pattern suggesting non-apoptotic engagement in formation of hard tissues. Additionally, preliminary results of microCT analysis of the adult gld mice showed increased enamel volume in molars but no impact on crown formation. Detailed analysis of bone parameters is in progress to support the data pointing to dual function of Fas/FasL in odontogenesis and osteogenesis.

Supported by the Grant Agency of the Czech Republic (P302/12/J059), the international cooperation runs under GA AV project M200451201.