IADR Abstract Archives
Platelet-derived Semaphorin4D Promotes Osteoclastogenesis via Ligation with CD72
Objectives: Semaphorin 4D (Sema4D; CD100) is pluripotent molecule that is engaged in axon guidance, activation of B cells, cancer angiogenesis, and regulation of osteoblastogenesis, via ligation with its receptors, Plexin B1, Plexin B2 and CD72. Furthermore, Sema4D was reported to promote RANKL-induced osteoclastogenesis (Takada at el., Int J Oncol. 2017). Although platelets produce Sema4D, the possible role of such Sema4D produced by platelets in osteoclastogenesis remains unclear. This study investigated the role of Sema4D produced by platelets in RANKL-mediated osteoclastogenesis and the mechanism underlying the activation of osteoclasts.
Methods: The levels of Sema4D and RANKL released from the activated human platelets with thrombin (1 U/ml) were examined by ELISA and W-blot. Those activated and non-activated platelets were applied to RAW264.7 cells for osteoclastogenesis assay in the presence or absence of anti-Sema4D-neutralizing monoclonal antibody (mAb), anti-CD72-neutralizing mAb, anti-PlexinB2-neutralizing mAb or control mAb. TRAP staining and pit formation on Calcium phosphate-coated plates (Corning Osteo-Assay Surface) were performed to evaluate the osteoclastogenesis and bone-resorptive function of osteoclasts.
Results: Platelets stimulated with thrombin released Sema4D as well as RANKL. However, although activated-platelets promoted RANKL-induced osteoclastogenesis, activated-platelets could not induce osteoclastogenesis in the absence of RANKL, indicating that RANKL-produced by platelets is insufficient in osteoclastogenesis. Anti-Sema4D-mAb down-modulated the platelet-mediated osteoclastogenesis. Anti-CD72-mAb, but not anti-PlexinB2-mAb, inhibited the platelet-mediated promotion of osteoclastogenesis. Osteoclasts generated by combination of RANKL and platelets showed the most elevated level of pit-formation which was significantly down-regulated by anti-Sema4D-mAb and anti-CD72-mAb, but not anti-PlexinB2-mAb.
Conclusions: The results indicated that Sema4D produced by platelets can activate RANKL-induced osteoclastogenesis via ligation with CD72. Further studies are warranted to determine the role of platelet-derived Sema4D in the physiological context of periodontitis and other inflammatory bone lytic diseases.
Methods: The levels of Sema4D and RANKL released from the activated human platelets with thrombin (1 U/ml) were examined by ELISA and W-blot. Those activated and non-activated platelets were applied to RAW264.7 cells for osteoclastogenesis assay in the presence or absence of anti-Sema4D-neutralizing monoclonal antibody (mAb), anti-CD72-neutralizing mAb, anti-PlexinB2-neutralizing mAb or control mAb. TRAP staining and pit formation on Calcium phosphate-coated plates (Corning Osteo-Assay Surface) were performed to evaluate the osteoclastogenesis and bone-resorptive function of osteoclasts.
Results: Platelets stimulated with thrombin released Sema4D as well as RANKL. However, although activated-platelets promoted RANKL-induced osteoclastogenesis, activated-platelets could not induce osteoclastogenesis in the absence of RANKL, indicating that RANKL-produced by platelets is insufficient in osteoclastogenesis. Anti-Sema4D-mAb down-modulated the platelet-mediated osteoclastogenesis. Anti-CD72-mAb, but not anti-PlexinB2-mAb, inhibited the platelet-mediated promotion of osteoclastogenesis. Osteoclasts generated by combination of RANKL and platelets showed the most elevated level of pit-formation which was significantly down-regulated by anti-Sema4D-mAb and anti-CD72-mAb, but not anti-PlexinB2-mAb.
Conclusions: The results indicated that Sema4D produced by platelets can activate RANKL-induced osteoclastogenesis via ligation with CD72. Further studies are warranted to determine the role of platelet-derived Sema4D in the physiological context of periodontitis and other inflammatory bone lytic diseases.
