Isolation of three species of proteoglycan synthesized by cloned bone cells

Three proteoglycan fractions have been isolated from clonal populations of osteoblast-like cells derived from fetal rat calvaria. One of these is secreted into the culture medium, is of apparent Mr 350 000, and has a glycosaminoglycan (GAG) composition of 77% chondroitin sulfate (CS) and 20% dermatan sulfate (DS). The remaining two proteoglycan fractions are associated with the cell layer. One of these has an apparent molecular weight of approximately 250 000 and a GAG composition of 54% CS and 40% DS. Both this species and the secreted proteoglycan have GAG chains of Mr 25 000. The other cell-associated proteoglycan contains heparan sulfate (HS), is solubilized by detergents, and appears to be contaminated with a CS proteoglycan. This HS-containing species may be similar to plasma membrane proteoglycans that have been isolated from several other cell types. Rat calvarial clones also synthesize hyaluronic acid and a number of glycoproteins.