Elevated extracellular calcium concentrations induce type X collagen synthesis in chondrocyte cultures.
Chondrocytes at different stages of cellular differentiation were isolated from the tarsal element (immature chondrocytes) and zones 2 and 3 (mature chondrocytes) of 12-d chick embryo tibiotarsus. The chondrocytes from the two sources differed in their cell morphologies, growth rate and production of type X collagen. In 24 h, zone 2 and 3 chondrocytes synthesized 800 times more type X collagen than tarsal chondrocytes. The effect of exogenous CaCl2 (5 and 10 mM) on the synthesis of type X collagen by both mature and immature chondrocytes was tested. After a 72-h incubation of zone 2 and 3 chondrocytes with CaCl2 type X collagen increased 8-fold with 5 mM and 10-fold with 10 mM Ca2+. [3H]Proline incorporation into culture medium and matrix macromolecules increased 11 and 32% with 5 and 10 mM CaCl2, respectively. Type II collagen synthesis was not affected by elevated extracellular Ca2+ during this 72-h period. Similar studies with tarsal chondrocytes demonstrated a time- and dose-dependent response to CaCl2 with type X collagen levels reaching a 4-fold and 15-fold increase over controls with 5 and 10 mM Ca2+, respectively, at 48 h. Elevated extracellular Ca2+ had no effect on cell proliferation. These observations offer the first direct evidence of the induction of type X collagen synthesis with elevated extracellular Ca2+.
Bonen
D K
DK
Department of Biochemistry, Rush Presbyterian-St. Luke's Medical Center, Chicago, Illinois 60612.
Schmid
T M
TM
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002356:Cartilage / Q000166:cytology*; D002455:Cell Division; D002478:Cells, Cultured; D002642:Chick Embryo; D003094:Collagen / Q000096:biosynthesis*; D004591:Electrophoresis, Polyacrylamide Gel; D007700:Kinetics; D014316:Tritium
D014316:Tritium; D003094:Collagen; D002118:Calcium