Effect of osteogenic protein-1 on the development and mineralization of primary cultures of avian growth plate chondrocytes: modulation by retinoic acid.
Osteogenic protein-1 (OP-1), a member of the TGF-beta family of proteins, induces endochondral bone formation. Here we studied the effect of OP-1 on the development of primary cultures of avian growth plate (GP) chondrocytes in either serum-free or serum-containing medium, in the absence or presence of retinoic acid (RA). OP-1 was added on day 7 of culture and continued for 7 days, or until the cultures were harvested, typically on day 21. Alone, OP-1 caused approximately 2-fold increase in proteoglycan synthesis into both the medium and the cell:matrix layer. Additionally, OP-1 caused a dosage-dependent increase in alkaline phosphatase (ALP) activity, and an increase in protein, when given from days 7-14 and examined on day 14. This stimulation was greater in cells grown in serum-free than in serum-containing media (3-5-fold vs. 2-3-fold increase in ALP; approximately 40% vs. approximately 20% increase in protein). Such stimulation of ALP activity and proteoglycan (PG) synthesis in cultured GP cells indicates that OP-1 elicits differentiation of chondrocytes. OP-1 minimally affected cell division (DNA content); however, a slight increase was seen when examined early in the culture. Alone, OP-1 increased mineral (Ca and Pi) content of the cultures by approximately 2-fold in both types of media. As early as day 14, clusters of mineral encircled many of the OP-1 treated cells. Thus, as in vivo, OP-1 strongly promoted mineral formation by the cultured GP chondrocytes. When present together, OP-1 and RA generally blocked the action of the other. Separately OP-1 and RA each stimulated protein synthesis, ALP activity, and Ca2+ deposition; together they were inhibitory to each. Also, RA blocked the stimulation of PG synthesis induced by OP-1; whereas OP-1 decreased cell division engendered by RA. Thus, this GP chondrocyte culture system is a good model for studying factors that influence differentiation and mineral deposition during bone growth in vivo.
Wu
L N
LN
Department of Chemistry and Biochemistry, University of South Carolina, Columbia 29208, USA.
Ishikawa
Y
Y
Genge
B R
BR
Sampath
T K
TK
Wuthier
R E
RE
D000469:Alkaline Phosphatase / Q000096:biosynthesis; D000818:Animals; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology*; D002113:Calcification, Physiologic / Q000187:drug effects* / Q000502:physiology; D002130:Calcium Phosphates / Q000378:metabolism*; D002358:Cartilage, Articular / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D002645:Chickens; D006132:Growth Plate; D007700:Kinetics; D007770:L-Lactate Dehydrogenase / Q000032:analysis; D011509:Proteoglycans / Q000096:biosynthesis; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D014212:Tretinoin / Q000494:pharmacology*
D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins; D002130:Calcium Phosphates; D011509:Proteoglycans; D016212:Transforming Growth Factor beta; D014212:Tretinoin; D007770:L-Lactate Dehydrogenase; D000469:Alkaline Phosphatase