BONE MORPHOGENETIC PROTEIN-2 CONVERTS THE DIFFERENTIATION PATHWAY OF C2C12 MYOBLASTS INTO THE OSTEOBLAST LINEAGE

Citation
T. Katagiri et al., BONE MORPHOGENETIC PROTEIN-2 CONVERTS THE DIFFERENTIATION PATHWAY OF C2C12 MYOBLASTS INTO THE OSTEOBLAST LINEAGE, The Journal of cell biology, 127(6), 1994, pp. 1755-1766
Citations number
88
Categorie Soggetti
Cytology & Histology
Journal title
ISSN journal
00219525
Volume
127
Issue
6
Year of publication
1994
Part
1
Pages
1755 - 1766
Database
ISI
SICI code
0021-9525(1994)127:6<1755:BMPCTD>2.0.ZU;2-H
Abstract
The implantation of bone morphogenetic protein (BMP) into muscular tis sues induces ectopic bone formation at the site of implantation. To in vestigate the mechanism underlying this process, we examined whether r ecombinant bone morphogenetic protein-2 (BMP-2) converts the different iation pathway of the clonal myoblastic cell line, C2C12, into that of osteoblast lineage. Incubating the cells with 300 ng/ml of BMP-2 for 6 d almost completely inhibited the formation of the multinucleated my otubes expressing troponin T and myosin heavy chain, and induced the a ppearance of numerous alkaline phosphatase (ALP)-positive cells. BMP-2 dose dependently induced ALP activity, parathyroid hormone (PTH)depen dent 3',5'-cAMP production, and osteocalcin production at concentratio ns above 100 ng/ml. The concentration of BMP-2 required to induce thes e osteoblastic phenotypes was the same as that required to almost comp letely inhibit myotube formation. Incubating primary muscle cells with 300 ng/ml of BMP-2 for 6 d also inhibited myotube formation, whereas induced ALP activity and osteocalcin production. Incubation with 300 n g/ml of BMP-2 suppressed the expression of mRNA for muscle creatine ki nase within 6 h, whereas it induced mRNA expression for ALP, PTH/PTH-r elated protein (PTHrP) receptors, and osteocalcin within 24-48 h. BMP- 2 completely inhibited the expression of myogenin mRNA by day 3. By da y 3, BMP-2 also inhibited the expression of MyoD mRNA, but it was tran siently stimulated 12 h after exposure to BMP-2. Expression of Id-1 mR NA was greatly stimulated by BMP-2. When C2C12 cells pretreated with B MP-2 for 6 d were transferred to a colony assay system in the absence of BMP-2, more than 84% of the colonies generated became troponin T-po sitive and ALP activity disappeared. TGF-beta 1 also inhibited myotube formation in C2C12 cells, and suppressed the expression of myogenin a nd MyoD mRNAs without inducing that of Id-1 mRNA. However, no osteobla stic phenotype was induced by TGF-beta 1 in C2C12 cells. TGF-beta 1 po tentiated the inhibitory effect of BMP-2 on myotube formation, whereas TGF-beta 1 reduced ALP activity and osteocalcin production induced by BMP-2 in C2C12 cells. These results indicate that BMP-2 specifically converts the differentiation pathway of C2C12 myoblasts into that of o steoblast lineage cells, but that the conversion is not heritable.