Odanacatib Inhibits Cathepsin-K Activity in Dentin

Objectives: Cathepsin-K has been shown to participate in the degradation of collagen fibrils resulting in the compromised resin-dentin bond durability. The present study aimed to evaluate the inhibitory effect of a specific cathepsin-K inhibitor as a function of concentration in demineralized dentin matrices and compared that to a generic inhibitor.
Methods: Powdered dentin prepared from extracted human teeth was demineralized with 10% H₃PO₄ for 10 min. Demineralized dentin powder was treated with a specific inhibitor odanacatib (2.5µM, 5µM, 12.5µM, 25µM concentrations) or 0.5 mM E-64, nonselective cysteine inhibitor. Untreated dentin powder served as control. After inhibitor pretreatment, groups were incubated with simulated body fluid. After 1 day and 1 week incubation aliquots of dentin powder were tested for the degradation rate of C-telopeptide end products generated by cathepsin K and MMPs using enzyme linked immunoassay. Dentinal cathepsin-K activity was determined using gelatin zymography. Cathepsin-K inhibition was measured with recombinant human cathepsin K by using fluorometric immunoassay for all inhibitor groups. Assays were performed in triplicate.
The data were analyzed using ANOVA at α=0.05.
Results: Odanacatib significantly decreased (p<0.05) the release of CTX telopeptide generated by cathepsin- K in a dose dependent manner up to 16-fold at 1 day and 2-fold after 1 week incubation compared to control. Human recombinant cathepsin-K inhibition ranged between 95.6% to 99.2% and was comparable to 0.5 mM E-64 and kit inhibitor (99.6%). Zymography showed less gelatinolytic activity with the groups treated with various concentration of odanacatib compared to untreated control.
Conclusions: This study, for the first time, showed the dose-dependent inhibitory effect of odanacatib on matrix-bound cathepsin-K activity in dentin. Further studies are needed to clarify if comparable inhibitory effect can be obtained in combination with adhesive blends.