(-)-Epigallocatechin-3-gallate Inhibits Differentiation and Matrix Metalloproteinases Expression in Osteoclasts

The osteoclast is a multinucleated giant cell differentiated from monocyte macrophages that has an important role in bone resorption. Several studies have reported a relationship between tea consumption and decreased risk of bone fracture. Matrix metalloproteinases (MMPs) play an important role in the degeneration of bone and cartilage matrix. Regulation of osteoclast activity is essential in the treatment of bone disease. Moreover, MMPs are associated with osteoclast formation and differentiation. We have reported previously that (-) -epigallocatechin-3-gallate (EGCG) inhibits MMP-2 and MMP-9 expression and activity. However, the effects of EGCG on osteoclasts and other MMPs are not clear. Therefore, in the present study we examined whether EGCG affects MMP expression, as well as osteoclast formation, differentiation and activity, in vitro. We used bone marrow cells from the femur and tibial bones of male ddY mice. Bone marrow cells were cultured in the presence of 1∼100µM EGCG for 6 or 8 days. EGCG decreased the number of mature osteoclasts, as determined by tartrate-resistant acid phosphatase staining. Concentrations as low as 1µM EGCG clearly inhibited the differentiation of osteoclasts from bone marrow cells. EGCG also inhibited the number of osteoclasts with an actin-ring, as determined by rhodamine phalloidin staining, as well as osteoclast activity, as determined by the pit formation assay. Furthermore, EGCG concentration-dependently decreased MMP-9 and membrane type 1-MMP mRNA expression in mouse osteoclasts. However, EGCG had no changing on mRNA levels of tissue inhibitor of metalloprotease (TIMP)-1 and TIMP-3. Together, the results suggest that EGCG may be a suitable agent or lead compound for the development of treatments for bone resorption diseases associated with MMPs.