Alterations of matrix- and cell-associated proteoglycans inhibit osteogenesis and growth response to fibroblast growth factor-2 in cultured rat mandibular condyle and calvaria
A. Molteni et al., Alterations of matrix- and cell-associated proteoglycans inhibit osteogenesis and growth response to fibroblast growth factor-2 in cultured rat mandibular condyle and calvaria, CELL TIS RE, 295(3), 1999, pp. 523-536
Matrix and cell surface proteoglycans (PGs) may play important roles in the
control of cellular actions of heparan-binding growth factors such as fibr
oblast growth factor (FGF) during chondrogenesis and osteogenesis. In this
study, we used 4-methylumbelliferyl-beta-D-xyloside, an inhibitor of PG syn
thesis, and sodium chlorate, a competitive inhibitor of glycoconjugate sulf
ation, to determine the functional consequences of alterations of PG metabo
lism on osteogenesis and on FGF actions in neonatal rat condyle and calvari
a in vitro. Biochemical analysis showed that beta-D-xyloside (1 mM) or chlo
rate (15 mM) treatment for 1-8 days inhibited cellular PG synthesis by 60-8
0% in condyle and calvaria, as evaluated by [S-35]sulfate incorporation. Hi
stochemistry and immunohistochemistry showed that the inhibition of PG synt
hesis by beta-D-xyloside resulted in reduced incorporation of chondroitin s
ulfate into cartilage and bone matrix. This was associated with a 75% reduc
tion in cell growth in condyle, determined by DNA synthesis, and in collage
nous matrix synthesis in condyle and calvaria, evaluated by tritiated proli
ne incorporation and type I collagen immunohistochemistry. Morphological an
d quantitative autoradiographic analyses also showed that inhibition of PG
synthesis by beta-B-xyloside blocked bone matrix formation by perichondral
progenitor cells in condyles and by osteoblasts in calvaria. In addition, a
lteration of PG metabolism blocked the mitogenic response to rhFGF-2 in cal
varia. The data show that functional proteoglycans are essential for osteog
enesis and for the growth response to FGF-2 during osteogenic differentiati
on in vitro.