E. Tsuda et al., ISOLATION OF A NOVEL CYTOKINE FROM HUMAN FIBROBLASTS THAT SPECIFICALLY INHIBITS OSTEOCLASTOGENESIS, Biochemical and biophysical research communications, 234(1), 1997, pp. 137-142
A factor which inhibits osteoclast-like cell formation was found in th
e conditioned medium of human embryonic lung fibroblasts, IMR-90. The
factor, termed osteoclastogenesis inhibitory factor, OCIF, was purifie
d to homogeneity. OCIF is a heparin-binding basic glycoprotein and has
been isolated as a monomer with an apparent molecular weight (Mr) of
60,000 and a homodimer with a Mr of 120,000. The N-terminus of OCIF is
blocked and the determination of internal amino acid sequences reveal
ed that OCIF has no homology to known proteins. OCIF inhibited in a do
se-dependent manner osteoclastogenesis elicited through three distinct
signaling pathways stimulated by 1 alpha,25-dihydroxy vitamin D-3, pa
rathyroid hormone, and interleukin-11, respectively, in a dose range o
f 1 to 40 ng/ml (IC50 = 4 to 6 ng/ml). OCIF neither inhibits bone reso
rption by mature osteoclasts nor exerts any other biological activitie
s. These data strongly suggest that OCIF is a novel cytokine which spe
cifically inhibits osteoclastogenesis. (C) 1997 Academic Press.