EFFECT OF GROWTH-HORMONE, INSULIN-LIKE GROWTH-FACTOR-I, BASIC FIBROBLAST GROWTH-FACTOR, AND TRANSFORMING GROWTH-FACTOR-BETA ON CELL-PROLIFERATION AND PROTEOGLYCAN SYNTHESIS BY AVIAN POSTEMBRYONIC GROWTH-PLATE CHONDROCYTES

We examined the in vitro effects of pituitary-derived chicken growth h ormone (cGH), recombinant human insulin-like growth factor-I (rhIGF-I) , recombinant human basic fibroblast growth factor (rhbFGF), and porci ne transforming growth factor beta (pTGF-beta) on proliferation ([H-3] thymidine uptake) and matrix proteoglycan synthesis ((SO4)-S-35 incorp oration) by chicken epiphyseal growth plate chondrocytes. Factorial ex periments were used to study the effect of these substances in a serum -free culture system. Basic FGF had to be present in the culture mediu m for mitogenesis to take place. In the presence of this peptide, TGF- beta, TGF-beta + IGF-I, and newborn calf serum (NCS) stimulated mitoge nesis. The mitogenic activity of NCS could be duplicated by adding pla telet-derived growth factor (PDGF) to the culture medium. For matrix s ynthesis, ICE-I was the key factor, with the addition of TGF-beta, TGF -beta + bFGF, or serum producing further stimulation in matrix synthes is. Using this culturing system, homologous cGH did not stimulate cell proliferation or proteoglycan synthesis. The lack of stimulatory acti vity of cGH was consistent, regardless of the age of the birds from wh ich the chondrocytes were isolated, the zone of the growth plate, or t he level of cGH used. None of the growth factors used in this study or several other systemic hormones were found to be permissive factors f or GH to be active. Either other factors must be present for a direct effect of GH on growth plate chondrocytes, or the avian species differ from their mammalian counterpart.