A. Teti et al., COLONY-STIMULATING FACTOR-1-INDUCED OSTEOCLAST SPREADING DEPENDS ON SUBSTRATE AND REQUIRES THE VITRONECTIN RECEPTOR AND THE C-SRC PROTOONCOGENE, Journal of bone and mineral research, 13(1), 1998, pp. 50-58
The colony stimulating factor 1 (CSF-1) regulates osteoclastogenesis a
nd bone resorption, Mutations in the CSF-1 gene cause an osteopetrosis
characterized by the absence of osteoclasts. Mature osteoclasts respo
nd to CSF-1 with inhibition of bone resorption and an increment of cel
l spreading, Herein we demonstrate that CSF-1-induced osteoclast sprea
ding depends on the substrate the osteoclast interacts with and requir
es integrity of the vitronectin receptor and of the c-src proto-oncoge
ne. Rabbit osteoclasts were allowed to attach to glass, serum, osteopo
ntin, and bone substrates, and were treated with 10 ng/ml human recomb
inant CSF-1 for 4 h, In osteoclasts plated on glass, the cytokine indu
ced 70% inhibition of bone resorption and 1.8-fold stimulation of cell
spreading, without changes in podosome expression and microfilament a
rray. In contrast, CSF-1 induced a 2.5-fold increase of osteoclasts sh
owing filopodia, and a 9.5-fold increase of osteoclasts presenting lam
ellipodia, indicating that membrane motility was required for cell spr
eading. Osteoclasts plated on serum substrates showed a 50% reduction
of spontaneous spreading, However, in this circumstance, CSF-1 still s
timulated an increase of osteoclast area, In osteoclasts cultured on o
steopontin substrate or on bone slices, an inhibition of CSF-1-induced
osteoclast spreading was observed, To establish involvement of the vi
tronectin receptor and c-src proto-oncogene, cells were treated with t
he alpha(v) beta(3) integrin neutralizing antibody, LM609, or c-src an
tisense oligonucleotides, which reduced CSF-1-induced osteoclast sprea
ding by 57% and 60%, respectively. The results demonstrate that CSF-1-
induced osteoclast spreading requires both the vitronectin receptor an
d the c-src proto-oncogene and that this action is modulated by the ad
hesion substrata.