Insulinlike growth factor II and transforming growth factor beta regulate collagen expression in human osteoblastlike cells in vitro.
Insulinlike growth factor II (IGF-II) and transforming growth factor beta (TGF-beta) are the most abundant polypeptide growth factors found in human bone matrix and are produced by human bone cells in vitro. IGF-II and TGF-beta 1 increased total protein synthesis, collagenous protein synthesis, and the steady-state level of type I procollagen mRNA in a time-dependent manner in osteoblastlike cells isolated from human bone. Type III procollagen mRNA expression was low in untreated cultures and was not affected by IGF-II or TGF-beta. TGF-beta 1 elevated type I procollagen mRNA rapidly, with the maximal observed change at 10 h. In contrast, procollagen mRNA levels increased more slowly in response to IGF-II and reached a lower maximal level than with TGF-beta, but the response was sustained through 24 h. Collagenous protein synthesis in IGF-II- and TGF-beta-treated cells increased in parallel with increases in procollagen mRNA levels and was higher at 21 h for TGF-beta 1 and at 36 h for IGF-II. The difference in the time course and magnitude of change in type I procollagen mRNA levels in response to IGF-II and TGF-beta 1 suggests that these two growth factors work through distinct mechanisms that provide both a rapid transient response and a later sustained response in bone matrix biosynthetic activity.
Strong
D D
DD
Department of Biochemistry, Loma Linda University, CA.
Beachler
A L
AL
Wergedal
J E
JE
Linkhart
T A
TA
D002478:Cells, Cultured; D003094:Collagen / Q000096:biosynthesis*; D015342:DNA Probes; D006801:Humans; D007335:Insulin-Like Growth Factor II / Q000502:physiology*; D010006:Osteoblasts / Q000378:metabolism*; D011347:Procollagen / Q000235:genetics; D014176:Protein Biosynthesis; D012313:RNA / Q000302:isolation & purification; D012333:RNA, Messenger / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000502:physiology*
D015342:DNA Probes; D011347:Procollagen; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D012313:RNA; D007335:Insulin-Like Growth Factor II; D003094:Collagen