Disruption of the mouse Slc39a14 gene encoding zinc transporter ZIP14 is associated with decreased bone mass, likely caused by enhanced bone resorption

Osteoclasts are bone‐resorbing cells that play an essential role in maintaining bone homeostasis. Zinc (Zn) has been reported to inhibit osteoclast‐mediated bone resorption, but the mechanism of this action has not been clarified. Zn homeostasis is tightly controlled by the coordinated actions of many Zn transporters. The Zn transporter ZIP14/Slc39a14 is involved in various physiological functions; hence, Zip14‐knockout (KO) mice exhibit multiple phenotypes. In this study, we thoroughly investigated the bone phenotypes of Zip14‐KO mice, demonstrating that the KO mice exhibited osteopenia in both trabecular and cortical bones. In Zip14‐KO mice, bone resorption was increased, whereas the bone formation rate was unchanged. Zip14 mRNA was expressed in normal osteoclasts both in vivo and in vitro, but receptor activator of NF‐κB ligand (RANKL)‐induced osteoclastogenesis was not impaired in bone marrow‐derived macrophages prepared from Zip14‐KO mice. These results suggest that ZIP14 regulates bone homeostasis by inhibiting bore resorption and that in Zip14‐KO mice, bone resorption is increased due to the elimination of this inhibitory regulation. Further studies are necessary to conclude whether the enhancement of bone resorption in Zip14‐KO mice is due to a cell‐autonomous or a non‐cell‐autonomous osteoclast defect.