VITAMIN-K-2 INHIBITS OSTEOCLASTIC BONE-RESORPTION BY INDUCING OSTEOCLAST APOPTOSIS

In contrast to vitamin K-1(VK1), vitamin K-2(VK2) inhibited osteoclast ic bone resorption by unfractionated bone cells and isolated osteoclas ts. To investigate the mechanism of inhibition of osteoclastic bone re sorption by VK2, we examined the effect of this vitamin on osteoclast apoptosis using a DNA-binding fluorescent dye, Hoechst 33258. In unfra ctionated bone cells and isolated osteoclasts on dentin slices, we fir st demonstrated that VK2 induced osteoclast apoptosis, but VK1 did not . Moreover, cyclocheximide inhibited VK2-induced osteoclast apoptosis. These results suggest the possibility that VK2 inhibits osteoclastic bone resorption by targeting osteoclasts to undergo apoptosis, Which l eads to cell death. (C) 1996 Academic Press, Inc.