Role of Primary Cilia in Odontogenesis.

Primary cilium is a solitary organelle that emanates from the surface of most postmitotic mammalian cells and serves as a sensory organelle, transmitting the mechanical and chemical cues to the cell. Primary cilia are key coordinators of various signaling pathways during development and maintenance of tissue homeostasis. The emerging evidence implicates primary cilia function in tooth development. Primary cilia are located in the dental epithelium and mesenchyme at early stages of tooth development and later during cell differentiation and production of hard tissues. The cilia are present when interactions between both the epithelium and mesenchyme are required for normal morphogenesis. As the primary cilium coordinates several signaling pathways essential for odontogenesis, ciliary defects can interrupt the latter process. Genetic or experimental alterations of cilia function lead to various developmental defects, including supernumerary or missing teeth, enamel and dentin hypoplasia, or teeth crowding. Moreover, dental phenotypes are observed in ciliopathies, including Bardet-Biedl syndrome, Ellis-van Creveld syndrome, Weyers acrofacial dysostosis, cranioectodermal dysplasia, and oral-facial-digital syndrome, altogether demonstrating that primary cilia play a critical role in regulation of both the early odontogenesis and later differentiation of hard tissue-producing cells. Here, we summarize the current evidence for the localization of primary cilia in dental tissues and the impact of disrupted cilia signaling on tooth development in ciliopathies.

Statins do not inhibit the FGFR signaling in chondrocytes.

OBJECTIVE: Statins are widely used drugs for cholesterol lowering, which were recently found to counteract the effects of aberrant fibroblast growth factor receptor (FGFR3) signaling in cell and animal models of FGFR3-related chondrodysplasia. This opened an intriguing therapeutic possibility for human dwarfing conditions caused by gain-of-function mutations in FGFR3, although the mechanism of statin action on FGFR3 remains unclear. Here, we determine the effect of statins on FGFR signaling in chondrocytes. DESIGN: Cultured chondrocyte cell lines, mouse embryonic tibia cultures and limb bud micromasses were treated with FGF2 to activate FGFR signaling. The effects of atorvastatin, fluvastatin, lovastatin and pravastatin on FGFR3 protein stability and on FGFR-mediated chondrocyte growth-arrest, loss of extracellular matrix (ECM), induction of premature senescence and hypertrophic differentiation were evaluated. RESULTS: Statins did not alter the level of FGFR3 protein expression nor produce any effect on FGFR-mediated inhibition of chondrocyte proliferation and hypertrophic differentiation in cultured chondrocyte cell lines, mouse tibia cultures or limb bud micromasses. CONCLUSION: We conclude that statins do not inhibit the FGFR signaling in chondrocytes. Therefore the statin-mediated rescue of FGFR3-related chondrodysplasia, described before, is likely not intrinsic to the growth plate cartilage.