scholarly journals Proteoglycan aggregate formation by articular chondrocytes. Decrease in link-protein synthesis during culture

1983 ◽  
Vol 214 (3) ◽  
pp. 855-864 ◽  
Author(s):  
A H K Plaas ◽  
J D Sandy ◽  
H Muir
Keyword(s):  
Hyaluronic Acid ◽  
Articular Chondrocytes ◽  
Core Protein ◽  
Link Protein ◽  
Monolayer Cultures ◽  
Proteoglycan Aggregates ◽  
Primary Monolayer ◽  
Primary Monolayer Cultures ◽  
Stable Aggregate ◽  
Rabbit Articular Chondrocytes

The synthesis of link-stabilized proteoglycan aggregates by rabbit articular chondrocytes was investigated by [35S]sulphate labelling of primary monolayer cultures maintained for up to 21 days. (1) At all culture times the cells secreted a high-molecular-weight cartilage-type proteoglycan monomer of which 75%-80% formed aggregates with hyaluronic acid. (2) At 2 days of culture all of the aggregates were in link-stabilized form, but by 21 days only 5% were link-stabilized, as shown by displacement of monomers from the aggregate by hyaluronic acid oligosaccharides. (3) The addition of purified link protein to 21-day culture medium increased the proportion of link-stable aggregate from 5% to 70%. (4) Analysis of [3H]serine-labelled proteoglycan aggregates in the medium showed a marked decrease with culture time in the ratio of 3H-labelled link protein to 3H-labelled core protein present. The results suggest that the secretion of proteoglycan monomers and link protein by articular chondrocytes changes independently during prolonged monolayer culture.

Characterization of a specific insulin-like growth factor-I/somatomedin-C receptor on high density, primary monolayer cultures of bovine articular chondrocytes: regulation of receptor concentration by somatomedin, insulin and growth hormone

1985 ◽  
Vol 107 (2) ◽  
pp. 275-283 ◽  
Author(s):  
N. Watanabe ◽  
R. G. Rosenfeld ◽  
R. L. Hintz ◽  
L. A. Dollar ◽  
R. L. Smith
Keyword(s):  
Articular Chondrocytes ◽  
Porcine Insulin ◽  
Somatomedin C ◽  
Factor I ◽  
Monolayer Cultures ◽  
Igf I ◽  
Primary Monolayer ◽  
Bovine Articular Chondrocytes ◽  
Specific Insulin ◽  
Primary Monolayer Cultures

ABSTRACT In order to obtain a phenotypically stable cell population of chondrocytes, high density primary monolayer cultures of bovine articular chondrocytes were established. Using these cultures, a specific insulin-like growth factor-I/somatomedin-C (IGF-I/SM-C) receptor was demonstrated and characterized. At 15 °C steady-state binding was attained by 5 h, and averaged 25% per 2·2 × 106 cells. Fifty per cent displacement of 125I-labelled IGF-I/SM-C by unlabelled IGF-I/SM-C occurred at concentrations of only 2·3 ng/ml, whereas IGF-II and porcine insulin were approximately 15-and 1000-fold less potent respectively. Scatchard analysis gave a linear plot, with a calculated association constant of 2·26 × 109 l/mol and a receptor number of 15 400 sites per cell. Preincubation of chondrocyte monolayers with either IGF-I/SM-C or porcine insulin at 37 °C for 20 h resulted in reduction of 125I-labelled IGF-I/SM-C binding in a dose-dependent manner, although higher concentrations were required with insulin. More than 40% down-regulation of the receptor occurred with IGF-I/SM-C at concentrations of 10 nmol/l and nearly 70% reduction at 50 nmol/l. Interestingly, after preincubation with either human (h) or bovine (b)GH, 40% down-regulation of 125I-labelled IGF-I/SM-C binding was observed at concentrations of 10 μmol/l. Local production of IGF-I/SM-C by chondrocytes in response to GH stimulation may have occurred, but, because only 120 pmol IGF-I/SM-C and < 30 pmol IGF-I/SM-C per litre were recovered from serum-free conditioned media preincubated with bGH and hGH respectively, this was not established. These studies demonstrate that cultured bovine articular chondrocytes possess a highly specific IGF-I/SM-C receptor, and that this receptor population is regulated not only by IGF-I/SM-C and insulin but also by high concentrations of either hGH or bGH. These results are consistent with the growth-promoting action of IGF-I/SM-C on skeletal tissues, and suggest the possibility that GH itself may play its own role to modulate IGF-I/SM-C receptors on chondrocytes. J. Endocr. (1985) 107, 275–283

Sign in / Sign up

Export Citation Format

Share Document