Decreased steady-state insulin-like growth factor binding protein-3 (IGFBP-3) mRNA level is associated with differentiation of cultured porcine myogenic cells.
Insulin-like growth factor binding proteins (IGFBPs) affect the biological activity of IGF-I in several cell types, including cultured muscle cells. Additionally, at least one of the IGFBPs, IGFBP-3, has been shown to have IGF-independent effects on cell proliferation. Numerous studies have shown that immortalized muscle cell lines produce various IGFBPs, but to date no muscle cell line has been reported to produce IGFBP-3 protein or mRNA. Unlike muscle cell lines, primary cultures of porcine embryonic myogenic cells express IGFBP-3 mRNA and secrete a protein that is immunologically identifiable as IGFBP-3. Additionally, steady-state IGFBP-3 levels change significantly during differentiation. Here we report that differentiation of porcine myogenic cells in an IGFBP-3-free medium is accompanied by reduced steady-state IGFBP-3 mRNA levels. Steady-state levels of IGFBP-3 mRNA decreased approximately sevenfold (P < .05) during differentiation and then increased to predifferentiation levels once differentiation was complete. Addition of TGF-beta1 (0.5 ng/ml) to porcine myogenic cultures suppressed fusion and resulted in a sevenfold increase in steady-state IGFBP-3 mRNA and a 1.8-fold increase in IGFBP-3 protein levels as compared to untreated control cultures (P < .05). Results suggest that alterations in IGFBP-3 mRNA and protein may play a role in differentiation of porcine embryonic muscle cells.
Johnson
B J
BJ
Department of Animal Science, University of Minnesota, St. Paul, USA.
White
M E
ME
Hathaway
M R
MR
Dayton
W R
WR
D000818:Animals; D002454:Cell Differentiation / Q000235:genetics; D002460:Cell Line; D003402:Creatine Kinase / Q000378:metabolism; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000235:genetics*; D009132:Muscles / Q000196:embryology / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis*; D013552:Swine; D016212:Transforming Growth Factor beta / Q000494:pharmacology
D018972:Insulin-Like Growth Factor Binding Protein 3; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D003402:Creatine Kinase