Bone Abstracts

Introduction: The fat-soluble and vitamin K2 homologe Menaquinone-7 (MK-7) is needed for post-translational modification of proteins essential in blood coagulation, and in metabolic pathways in various tissues like bone. Recent studies found an association between long-term anticoagulant treatment (OAC) and reduced bone quality due to reduction of active osteocalcin. OAC is often linked to an undesired soft-tissue calcification in both children and adults and may lead to increased incidence of fractures, reduced bone mineral density/bone mineral content, osteopenia and increased serum levels of undercarboxylated of vitamin K-dependent proteins, known as Gla-proteins. Little is known about the effects of vitamin K2 during tooth development.

Methods: New born Balb C mice were exposed to MK-7 (0.2, 2 or 10 mg/kg body weight) (Kappa Bioscience, Oslo, Norway) using a local s.c. injection on the right side mandibula. The control group was mice injected with vehicle. At 24 h post-injection the pups were sacrificed and first right-hand side molar dissected. Total RNA was isolated from the dissected molar using the RNeasy Mini Kit and used for analysis of gene expression using deoxyoligonucleotide microarrays and RT-PCR. Biological triplicates were used. Microarray results were validated by RT-PCR. Bioinformatic analysis was performed using Ingenuity Pathways Analysis. The results are based on measurements from biological triplicates.

Results: After Treatment with 10 mg/kg body-weight MK-7, 629 genes showed altered gene expression (P<0.05) compared to controll with the molecular and cellular functions: carbohydrate metabolism, Cell-to cell-signaling/interaction and cellular growth and proliferation. Treatment with 0.2 and 2 mg/kg body weight MK-7 influenced the expression of genes associated with ‘ cell death’, with a highly significant association to decreased apoptosis.

Conclusions: A clear effect on gene expression in the developing tooth germ was apparent after 24 h at all dosages. The results indicate increased transcription of genes involved in development of bone (increased biosynthesis of important carbohydrates) and of enamel/dentin, and reduced expression of apoptosis related proteins.