Immunological characterization of circulating osteoprotegerin/osteoclastogenesis inhibitory factor: increased serum concentrations in postmenopausal women with osteoporosis.
Osteoprotegerin (OPG)/osteoclastogenesis inhibitory factor (OCIF) is a soluble member of the tumor necrosis factor receptor family of proteins and plays an important role in the negative regulation of osteoclastic bone resorption. Whether OPG/OCIF circulates in human blood and how its level changes under pathological conditions is not known. To address these issues, a panel of monoclonal antibodies was generated against recombinant OPG/OCIF and screened for reactivity with solid-phase monomeric and homodimeric forms of the recombinant protein. Antibodies that showed high affinity for both forms of OPG/OCIF and those that selectively recognized the homodimer were identified, enabling development of two types of sensitive enzyme-linked immunosorbent assay (ELISA): one that detects both forms of OPG/OCIF equally and one specific for the homodimer. Characterization of circulating OPG/OCIF with these ELISAs revealed that the protein exists in human serum mainly in the monomeric form. The serum concentration of OPG/OCIF increased with age in both healthy Japanese men and women, and was significantly higher in postmenopausal women with osteoporosis than in age-matched controls. Within the osteoporotic group, serum OPG/OCIF concentrations were higher in patients with low bone mass. Serum OPG/OCIF concentrations were also significantly increased in those postmenopausal women with a high rate of bone turnover, as determined by increased serum bone-specific alkaline phosphatase and urinary excretion of pyridinoline and deoxypyridinoline. The results suggested that circulating OPG/OCIF levels are regulated by an age-related factor(s) and that the increased serum concentration may reflect a compensative response to enhanced osteoclastic bone resorption and the resultant bone loss rather than a cause of osteoporosis.
Yano
K
K
Research Institute of Life Science, Snow Brand Milk Products Co., Ltd, Tochigi, Japan.
Tsuda
E
E
Washida
N
N
Kobayashi
F
F
Goto
M
M
Harada
A
A
Ikeda
K
K
Higashio
K
K
Yamada
Y
Y
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D000911:Antibodies, Monoclonal; D000918:Antibody Specificity; D015519:Bone Density; D001851:Bone Diseases, Metabolic / Q000097:blood / Q000378:metabolism; D016022:Case-Control Studies; D019281:Dimerization; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006023:Glycoproteins / Q000097:blood* / Q000737:chemistry / Q000276:immunology; D006801:Humans; D008297:Male; D051379:Mice; D008875:Middle Aged; D015663:Osteoporosis, Postmenopausal / Q000097:blood* / Q000378:metabolism; D053244:Osteoprotegerin; D011487:Protein Conformation; D018160:Receptors, Cytoplasmic and Nuclear; D018124:Receptors, Tumor Necrosis Factor; D011994:Recombinant Proteins / Q000737:chemistry / Q000276:immunology
D000911:Antibodies, Monoclonal; D006023:Glycoproteins; D053244:Osteoprotegerin; D018160:Receptors, Cytoplasmic and Nuclear; D018124:Receptors, Tumor Necrosis Factor; D011994:Recombinant Proteins; C506030:TNFRSF11B protein, human; C506031:Tnfrsf11b protein, mouse