Synthesis of osteoprotegerin and RANKL by megakaryocytes is modulated by oestrogen.
To investigate the mechanisms by which megakaryocytes (MKs) may influence bone remodelling, CD34(+) cells were cultured for 6, 9 and 12 d with or without 17beta-oestradiol (E) and immunolocalized for osteoprotegerin (OPG), receptor activator of nuclear factor (NF)-kappaB ligand (RANKL) and CD61. Specific protein expression was measured quantitatively by image analysis. Fluorescence-based immunocytochemistry was used to co-localize OPG and RANKL with CD61. OPG and RANKL mRNA was assessed in CD61(+) cells with or without E at 24 and 48 h. At 6 d, OPG and RANKL expression was unchanged by E treatment. At 9 d, the E-treated cultures with maturing MKs showed a 1.72-fold (P < 0.01) increase in OPG expression and a 1.8-fold (P < 0.01) reduction in RANKL. Maximal OPG expression was seen at 12 d with a threefold induction of expression (P < 0.001), whilst RANKL levels were further suppressed by 2.3-fold compared with controls (P < 0.001). CD61 co-localized with OPG and RANKL. mRNA data were consistent with that of protein, with a 90-fold induction in OPG expression and a 34-fold suppression of RANKL expression by E (P < 0.001). Thus, E stimulates megakaryocytopoiesis and modulates OPG and RANKL expression, providing evidence that MKs may play a role in bone remodelling and, in particular, in E-induced changes in osteoclastogenesis and bone resorption.
Bord
S
S
University of Cambridge School of Clinical Medicine, Addenbrooke's Hospital, Cambridge, UK. sb201@cam.ac.uk
Frith
E
E
Ireland
D C
DC
Scott
M A
MA
Craig
J I O
JI
Compston
J E
JE
D002352:Carrier Proteins / Q000032:analysis / Q000096:biosynthesis* / Q000235:genetics; D002478:Cells, Cultured; D004958:Estradiol / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D006023:Glycoproteins / Q000032:analysis / Q000096:biosynthesis* / Q000235:genetics; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D008533:Megakaryocytes / Q000187:drug effects / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000032:analysis / Q000096:biosynthesis* / Q000235:genetics; D053244:Osteoprotegerin; D053245:RANK Ligand; D012333:RNA, Messenger / Q000032:analysis; D053246:Receptor Activator of Nuclear Factor-kappa B; D018160:Receptors, Cytoplasmic and Nuclear / Q000032:analysis / Q000096:biosynthesis* / Q000235:genetics; D018124:Receptors, Tumor Necrosis Factor
D002352:Carrier Proteins; D006023:Glycoproteins; D008562:Membrane Glycoproteins; D053244:Osteoprotegerin; D053245:RANK Ligand; D012333:RNA, Messenger; D053246:Receptor Activator of Nuclear Factor-kappa B; D018160:Receptors, Cytoplasmic and Nuclear; D018124:Receptors, Tumor Necrosis Factor; C505686:TNFRSF11A protein, human; C506030:TNFRSF11B protein, human; C505688:TNFSF11 protein, human; D004958:Estradiol