Secreted Frizzled‐Related Protein‐1 Inhibits RANKL‐Dependent Osteoclast Formation

We determined that sFRP‐1 mRNA was differentially expressed by osteoblast/stromal cell lines and that sFRP‐1 neutralizing antibodies and siRNA complementary to sFRP‐1 coding sequence enhanced, while recombinant sFRP‐1 inhibited, osteoclast formation. In studying the mechanism of action for sFRP‐1, we found that sFRP‐1 could bind recombinant RANKL. These results suggest potential cross‐talk between Wnt and RANKL pathways.