Modulation of osteoclastic migration by metabolism of 25OH-vitamin D3

We have reported the metabolism of 25(OH) vitamin D3 (25D) into active 1α,25(OH)2 vitamin D3 (1,25D) by osteoclasts derived from human peripheral blood mononuclear cells (PBMC), RAW 264.7cells or giant cell tumor of bone (GCT), which appears to optimize osteoclast differentiation but inhibit their activity. In this study, to elucidate the mechanism by which 25D reduces osteoclast resorption, we further examined the effect of 25D on osteoclast function by using GCT-derived osteoclasts. 25D treated cells on dentine slices resulted in decreased resorption volume and depth in 3D image analysis. Tartrate-resistant acid phosphatase (TRAP) has been reported to enhance the dephosphorylation of substrate binding proteins, resulting in reduced osteoclast attachment. Therefore, we next investigated the effect of 25D on cell migration. Treatment of GCT cells with 25D augmented cell migration, as determined by live cell imaging. These observations suggest that 25D metabolism by osteoclasts reduces their resorptive capacity, in part by modifying their surface adhesion and migration properties. This article is part of a Special Issue entitled "Vitamin D Workshop".