THE PRODUCTION OF TRANSFORMING GROWTH-FACTOR-BETA BY CHICK GROWTH PLATE CHONDROCYTES IN SHORT-TERM MONOLAYER-CULTURE

Transforming growth factor-β (TGFβ) is capable of regulating the proliferation and phenotypic expression of growth plate chondrocytes in culture. Chondrocytes were isolated from the growth plates from the long bones of 3- to 5- week-old chicks. Conditioned medium was harvested from short term monolayer cultures for the assay of TGFβ production by these cells. A receptor competition assay using [125I]TGFβ was used to quantitate the amount of TGFβ in the conditioned medium. Acid-activated conditioned medium contained 5.0 ± 0.4 ng/ml TGFβ, while conditioned medium that had not been exposed to acid had undetectable levels of the peptide by this assay. The initial cell plating density was inversely related to the amount of TGFβ produced on a per cell basis. Growth plate chondrocytes separated by countercurrent centrifugal elutriation into maturationally distinct subpopulations had different rates of TGF/3 production; hypertropic chondrocytes produced significantly more TGFβ (4.5 ng/106 cells) than the smallest chondrocytes isolated (2.3 ng/106 cells). A variety of other growth mediators were tested for their ability to influence TGFβ production by chondrocytes, and it was found that only basic fibroblast growth factor could significantly influence TGFβ production, producing a 6-fold increase in TGFβ recovered in the conditioned medium. The production of TGFβ by growth plate chondrocytes implicates it as an important autocrine or paracrine regulator in the process of endochondral calcification. © 1990 by The Endocrine Society.