Inhibitory effect of menaquinone-7 (vitamin K2) on the bone-resorbing factors-induced bone resorption in elderly female rat femoral tissues in vitro

The inhibitory effect of menaquinone-7 (MK-7; vitamin K2) on osteoclast-like cell formation and osteoclastic bone resorption in vitro is found (Mol Cell Biochem 228: 39–47, 2001). This study, furthermore, was undertaken to determine the effect of MK-7 on the bone-resorbing factor-induced bone resorption using the femoral-diaphyseal and -metaphyseal tissues obtained from elderly female rats in vitro. Femoral-diaphyseal and -metaphyseal tissues were cultured for 48 h in Dulbecco's modified Eagle's medium (high glucose, 4.5%) supplemented with antibiotics and bovine serum albumin. The experimental cultures contained MK-7 (10-7–10-5 M). The bone-resorbing factors, parathyroid hormone (1–34) (PTH; 10-7 M) and prostaglandin E2 (PGE2; 10-5 M), caused a significant decrease in calcium content in the diaphyseal and metaphyseal tissues. The PTH or PGE2-induced decrease in bone calcium content was completely inhibited in the presence of MK-7 (10-7–10-5 M). In addition, MK-7 (10-7–10-5 M) completely prevented the PTH (10-7 M)- or PGE2 (10-5 M)-induced increase in medium glucose consumption and lactic acid production by bone tissues. These results support the view that MK-7 has a direct inhibitory effect on the bone-resorbing factor-induced bone resorption in bone culture using female aged femoral tissues in vitro.