Control of protein and matrix-molecule synthesis in isolated ovine fetal growth-plate chondrocytes by the interactions of basic fibroblast growth factor, insulin-like growth factors-I and -II, insulin and transforming growth factor-β1

Abstract

Chondrogenesis is thought to be controlled by interactions between circulating anabolic hormones and locally produced peptide growth factors, and involves ordered changes in matrix composition which ultimately allow endochondral calcification. We have used a model of isolated ovine fetal growth-plate chondrocytes to examine the actions and interactions of basic fibroblast growth factor (basic FGF), insulin-like growth factors-I and -II (IGF-I and -II), insulin and transforming growth factor-beta 1 (TGF-beta 1) on total protein, collagen or non-collagenous protein and sulphated glycosaminoglycan synthesis. These parameters were determined by assessment of the incorporation by monolayer cultures of early passage chondrocytes of [3H]leucine, [14C]proline and [35S]sulphate respectively, followed by partial molecular characterization. Basic FGF enhanced total protein synthesis with a half-maximal effective concentration of 270 +/- 60 pmol/l (mean +/- S.E.M., four animals) and was sixfold more active on a molar basis than IGF-I or insulin, and 28-fold more active that IGF-II which is the endogenously synthesized IGF. The actions of basic FGF were additive to those of IGF-I or insulin. More detailed analysis of extracellular-matrix component synthesis showed that basic FGF, IGF-I and insulin each caused significant increases in the synthesis of collagen and sulphated glycosaminoglycans. TGF-beta 1 had no effect on total protein synthesis by chondrocytes when present alone at concentrations of 200 pmol/l or less, but was inhibitory at 400 pmol/l. However, the use of this parameter masked a stimulatory action of 50 or 100 pmol TGF-beta 1 on sulphated glycosaminoglycan synthesis and a relative shift in the ratio of collagen: non-collagenous protein synthesis in favour of the former. A synergistic interaction existed between TGF-beta 1 (20-100 pmol/l) and basic FGF which potentiated total protein and collagen synthesis, and their actions on sulphated glycosaminoglycan production were additive. The same concentrations of TGF-beta 1 inhibited the ability of IGF-I or insulin to stimulate total protein or collagen synthesis, but were additive to their stimulatory effects on sulphated glycosaminoglycan synthesis. The results suggest that matrix-molecule composition and the anabolic status of the epiphyseal growth-plate may be modulated in utero by multiple interactions between peptide growth factors produced locally, such as basic FGF, IGF-II and TGF-beta 1, and circulating hormones such as insulin and IGF-I.

Bone mineral density and composition in rat pregnancy: effects of streptozotocin‐induced diabetes mellitus and insulin replacement

“…It may relate to the reduced circulating concentrations of insulin and insulin-like growth factor 1 (IGF-1) in pregnant diabetic animals reported elsewhere (Tein, Birdsey, Garland, Balment, Boyd & Sibley, 1996a). Both hormones initiate chondrocyte proliferation and maturation (Bohme, Conscience-Egli, Tschan, Winterhalter & Bruckner, 1992) and each cause significant increases in the synthesis of collagen and sulphated glycosaminoglycans in isolated ovine growth plate chondrocytes in culture (Hill, Logan, McGarry & De Sousa, 1992). Insulin and IGF-1 are also mitogenic to chondrocytes independently of one another.…”

Studies on insulin‐like growth factor‐I and insulin in chick limb morphogenesis

“…Since exogenous IGF-I, insulin, FGF-2, and FGF-4 can all promote the outgrowth of limb mesoderm in the absence of the AER, it may be that these growth factors interact in a cooperative manner to promote the proliferation and outgrowth of the subridge mesoderm, and that there may be regulatory relationships among these growth factors in limb morphogenesis. Indeed, IGF-I and FGF-2 interact in a coordinated fashion to promote the growth and differentiation of hypothalmic cells (Torres-Aleman et al, 1990), and have a n additive effect on the differentiation of fetal growth plate chondrocytes (Hill et al, 1992). Furthermore, FGF-2 can stimulate IGF-I secretion by mouse 3T3 cells (Villaudy et al, 19911, and can stimulate the expression of IGF-I receptors in muscle cells (Rosenthal et al, 1991).…”

Ultrastructural Characterization of the Rabbit Mandibular Condyle following Experimental Induction of Anterior Disk Displacement

“…Chondrons are connected by pericellular channels [Broom and Myers, 1980;Broom and Poole 1982;Poole et al, 1982Poole et al, , 1984Poole et al, , 1991. The extracellular matrix of the condylar cartilage is composed primarily of type II collagen and noncollagenous proteins such as glycoproteins and proteoglycans [Silbermann et al, 1987;Silbermann and Mark, 1990a, b;BenAmi et al, 1991;Sharawy, 1995c, d, 1996a, b] and a variety of growth factors [Hill et al, 1992], and a subchondral bone contains chondroid bone and marrow spaces. The ultrastructural changes in the rabbit mandibular condylar cartilage 2 weeks following experimental induction of ADD compared to controls will be presented in this report.…”