Growth of fetal porcine scapular cartilage in vitro
Fetal pig scapular cartilage provides an ideal model to study mammalian cartilage growth in vitro. Growth plate and nongrowth plate cartilages were cultured in serum-free medium for 14 days. These cartilages visibly enlarged, and their wet weight increased over their preincubation weight (86 ± 12% for growth plate; 104 ± 16% for non-growth plate). Addition of insulin 87 nM, somatomedin C (Sm-C) 10 ng/ml, or triiodothyronine (T3) 10 nM to the medium caused an increase in growth plate cartilage weight and radiolabeled precursor incorporation of [3H]proline and 35SO4. Insulin and Sm-C also stimulated nongrowth plate cartilage growth, but T3 had no effect. Since both growth-plate and nongrowth-plate cartilage grew in medium alone, the likelihood that fetal porcine scapular cartilage produced its own growth factor(s) was studied. Conditioned medium was assayed for radioimmunoassayable Sm-C. Sm-C was readily measurable in concentrated conditioned medium (575 ± 20 pg/ml). Since secretion of Sm-like peptides might play a functional role in the growth process, a monoclonal antibody to Sm-C was used to determine whether immunoneutralization of the Sm-like peptides would inhibit cartilage growth. Addition of anti-Sm-C prevented increases in wet weights of growth plate and nongrowth plate cartilages (47% and 49%, respectively below weights of cartilage incubated in medium alone). These studies demonstrate that fetal mammalian cartilage grows and responds to hormonal stimulation in vitro and suggest that these cartilages make Sm-like peptides that may have a functional role in promoting cartilage growth.
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