Expression and Role of Adam-19 in Osteoclast Formation and Function

Objectives:A disintegrin and metalloproteases (ADAMs) is a metalloprotease families group of membrane-anchored cell surface proteins, which has a unique domain organization. This study investigated the expression of ADAM-19 messenger ribonucleic acid (mRNA) in mouse osteoclasts in vitro and in 17-day-old fetal murine metatarsal explants. The role of ADAM-19 on osteoclast formation and resorptive activity of osteoclasts was also studied. Methods:Osteoclasts were identified by their multinuclearity, tartrate-resistant acid phosphatase (TRAP) staining and their expression of matrix metalloprotease-9 (MMP-9). The expression of ADAM-19 mRNA in isolated osteoclasts and in 17-day-old fetal murine metatarsal explants was studied using in situ hybridization. The functional analysis of ADAM-19 in osteoclast resorptive activity and osteoclast formation was studied using antisense oligodeoxynucleotides (AS-ODNs). Results: In situ hybridization studies using digoxigenin (DIG)-labelled riboprobes demonstrated expression of ADAM-19 mRNA in isolated mature osteoclasts, and in multinucleated osteoclasts present in 17-day-old fetal murine metatarsals. In isolated osteoclast cultures on ivory slices, disruption of ADAM-19 by addition of AS-ODNs had only minor effects on lacunar formation whereas in bone marrow cultures osteoclast formation was inhibited. However, AS-ODNs to ADAM-19 had no effect on osteoclast formation in spleen cell cultures stimulated with Macrophage-colony stimulating factor (M-CSF) and Receptor activator of nuclear factor kappa B (NF-kB) ligand [RANKL]. Since the spleen cell/RANKL/M-CSF assay for osteoclast generation has no mesenchymal/osteoblastic cells present, these results suggest a role for ADAM-19 in mediating cells interaction between osteoblasts and osteoclasts. Conclusion:These results provide evidence that ADAM-19 may play a key role in osteoclastogenesis and that osteoblast interaction with osteoclasts is a requirement. This demonstration of the role of ADAM-19 in osteoclast formation may have important implications for future studies to elucidate the role of ADAM-19 in bone development, remodelling and disease.