Effect of insulin-like growth factor on collagen and glycosaminoglycan synthesis by rabbit articular chondrocytes in culture

Guenther, Harald L.; Guenther, Hannelore E.; Froesch, E. R.; Fleisch, H.

doi:10.1007/bf01953688

Cited by 87 publications

(48 citation statements)

References 19 publications

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“…IGF-1 has been shown to stimulate synthesis of cartilage matrix proteins including collagen and proteoglycans (20)(21)(22). This is the first study demonstrating increased levels of integrins on IGF-1-treated cells.…”

Section: Discussionmentioning

confidence: 96%

Growth factor regulation of chondrocyte integrins. Differential effects of insulin‐like growth factor 1 and transforming growth factor β on α1β1 integrin expression and chondrocyte adhesion to type VI collagen

Loeser

1997

Arthritis & Rheumatism

119

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Objective. The ability of growth factors to modulate integrin expression may be important with regard to processes involved in tissue repair and remodeling. This study was undertaken to determine the effect of transforming growth factor β (TGFβ) and insulin‐like growth factor 1 (IGF‐1) on chondrocyte β1 integrin expression and integrin‐mediated adhesion to extracellular matrix proteins. Methods. Chondrocytes obtained from normal bovine articular cartilage were cultured in the presence or absence of 10% fetal bovine serum, 100 pM IGF‐1, or 100 pM TGF β. Integrin expression and function were measured by protein blotting of immunoprecipitated integrins, Northern blot analysis, and cell adhesion assays. Results. Immunoprecipitation with an anti–β1 integrin antibody coprecipitated the α1 integrin subunit and a band representing α3 and α5, as previously reported. Compared with serum‐free cultures, the use of serum resulted in an average 10‐fold increase in the α1 band and a 12‐fold increase in the α3/α5 band. IGF‐1 increased α1 and α3/α5 by an average of 3‐fold and 4‐fold, respectively. TGFβ also increased α3/α5 by >5‐fold but decreased α1 to an average of 24% of that found in serum‐free controls. Northern blot analysis revealed that TGFβ significantly increased α5 integrin subunit RNA levels. IGF‐1 did not have a significant effect on α5 or α1 integrin subunit RNA levels, suggesting that its effects on integrins are posttranscriptional. In cell adhesion assays, TGFβ treatment resulted in a 50% decrease in the adhesion of chondrocytes to type VI collagen, while adhesion to type II collagen and fibronectin was stimulated. IGF‐1 stimulated adhesion to all 3 proteins. An α1 integrin blocking antibody inhibited up to 75% of the adhesion of human chondrocytes to type VI collagen. Conclusion. Both IGF‐1 and TGFβ stimulate chondrocyte cell surface expression of the α3/α5 integrin subunit band and stimulate adhesion of chondrocytes to fibronectin and type II collagen. The 2 growth factors have opposite effects on expression of α1β1, with IGF‐1 increasing and TGFβ decreasing cell surface levels of this integrin. TGFβ‐treated cells also have decreased adhesion to type VI collagen. The opposing effects of IGF‐1 and TGFβ on chondrocyte expression of α1/β1 and on adhesion to type VI collagen suggest that α1β1 mediates chondrocyte adhesion to type VI collagen. This was confirmed by using an antibody to the α1 integrin subunit to block adhesion of chondrocytes to type VI collagen.

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Section: Discussionmentioning

confidence: 96%

Growth factor regulation of chondrocyte integrins. Differential effects of insulin‐like growth factor 1 and transforming growth factor β on α1β1 integrin expression and chondrocyte adhesion to type VI collagen

Loeser

1997

Arthritis & Rheumatism

119

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“…Although IGF-1 has been shown to be moderately mitogenic by itself in human adult articular cartilage, it strongly stimulated production of extracellular matrix components by chondrocytes. More particularly, this growth factor enhances the synthesis of collagen and proteoglycan in normal cartilage, as shown by both in vitro and in vivo studies (2)(3)(4)(5). Moreover, IGF-1 appears to be a differentiating factor in that it enhances the expression of type I1 collagen messenger RNA and prevents the synthesis of type I collagen (6).…”

mentioning

confidence: 91%

Human Osteoarthritic Chondrocytes Possess an Increased Number of Insulin‐Like Growth Factor 1 Binding Sites but are Unresponsive to its Stimulation

Doré

Pelletier

DiBattista

et al. 1994

Arthritis & Rheumatism

186

117

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Objective. To characterize the insulin-like growth factor 1 (IGF-1) receptor in human osteoarthritic (OA) and normal adult chondrocytes. The biologic response of chondrocytes to IGF-1 stimulation was examined, as was the presence and synthesis of IGF binding proteins (IGFBP) in these cells.Methods. Binding studies, Northern blot, immunohistochemical analysis, and affinity cross-linking experiments were performed for characterization of the IGF receptor, and the latter method was also used for IGFBP determination. The biologic response was estimated via the incorporation of radiolabeled proline into a newly synthesized protein.Results histochemical studies with a monoclonal antibody (MAb) against the type 1 IGF receptor (aIR3) showed increased staining in OA cartilage compared with normal tissue. Biologic responses of chondrocytes after IGF-1 stimulation revealed that OA chondrocytes were unresponsive, whereas a 2.5-fold increase in new protein synthesis was observed in normal cells. Competition studies in normal chondrocytes revealed that both IGF-1 and IGF-2 displaced radiolabeled IGF-1 in a comparable manner; however, insulin at high concentration weakly competes. Moreover, MAb aIR3 effectively blocked specific binding in normal chondrocytes (77 %), but not in OA chondrocytes (26%). Northern blot and covalent cross-linking analyses revealed the specific band characteristic of type 1 receptor. With the latter technique, other bands corresponding to the IGFBPs were also detected. Comparison between normal and OA chondrocytes showed increased intensity of the IGFBP bands, particularly those corresponding to the IGFBP-3 doublet.Conclusion. It is shown that type 1 IGF receptor is expressed in human articular cartilage and that the level of binding sites is significantly increased in OA chondrocytes. Interestingly, despite the higher level of binding sites in OA cells, no response to IGF-1 stimulation was found in these cells. Our data suggest that this increase in specific binding may involve not only the type 1 IGF receptor but also IGFBP on the cell surface. The latter, by binding the IGF-1, will diminish the bioavailability of IGF-1 and thus prevent its anabolic action.Osteoarthritis (OA) is the most common of the various arthritic disorders affecting humans. The dis-

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“…In articular cartilage, IGF-I increases the synthesis of extracellular matrix proteins, most notably collagen and proteoglycan [6][7][8]. IGF-I has been shown to be the major stimulator of proteoglycan synthesis present in serum and synovial fluid [9,10] and was originally called serum sulphation factor due to its ability to stimulate sulphate incorporation (a measure of proteoglycan synthesis) by cartilage [11].…”

Section: Introductionmentioning

confidence: 99%

IGF-I stimulation of proteoglycan synthesis by chondrocytes requires activation of the PI 3-kinase pathway but not ERK MAPK

Starkman

Cravero

DelCarlo

et al. 2005

Biochemical Journal

155

160

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The IGF-I (insulin-like growth factor-I) signalling pathway responsible for regulation of proteoglycan synthesis in chondrocytes has not been defined and is the focus of the present study. Chondrocytes isolated from normal human articular cartilage were stimulated with IGF-I in monolayer culture or in suspension in alginate. IGF-I activated members of both the PI3K (phosphoinositide 3-kinase) pathway and the ERK (extracellular-signal-regulated kinase)/MAPK (mitogen-activated protein kinase) pathway. The PI3K inhibitors LY294002 and wortmannin blocked IGF-I-stimulated Akt phosphorylation without blocking ERK phosphorylation and this was associated with complete inhibition of proteoglycan synthesis. A decrease in IGF-I-stimulated proteoglycan synthesis was also observed upon inhibition of mTOR (mammalian target of rapamycin) and p70S6 kinase, both of which are downstream of Akt. The MEK (MAPK/ERK kinase) inhibitors PD98059 and U0126 blocked IGF-I-stimulated ERK phosphorylation but did not block the phosphorylation of Akt and did not decrease proteoglycan synthesis. Instead, in alginate- cultured chondrocytes, the MEK inhibitors increased IGF-I-stimulated proteoglycan synthesis when compared with cells treated with IGF-I alone. This is the first study to demonstrate that IGF-I stimulation of the PI3K signalling pathway is responsible for the ability of IGF-I to increase proteoglycan synthesis. Although IGF-I also activates the ERK/MAPK pathway, ERK activity is not required for proteoglycan synthesis and may serve as a negative regulator

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Effect of insulin-like growth factor on collagen and glycosaminoglycan synthesis by rabbit articular chondrocytes in culture

Cited by 87 publications

References 19 publications

Growth factor regulation of chondrocyte integrins. Differential effects of insulin‐like growth factor 1 and transforming growth factor β on α1β1 integrin expression and chondrocyte adhesion to type VI collagen

Growth factor regulation of chondrocyte integrins. Differential effects of insulin‐like growth factor 1 and transforming growth factor β on α1β1 integrin expression and chondrocyte adhesion to type VI collagen

Human Osteoarthritic Chondrocytes Possess an Increased Number of Insulin‐Like Growth Factor 1 Binding Sites but are Unresponsive to its Stimulation

IGF-I stimulation of proteoglycan synthesis by chondrocytes requires activation of the PI 3-kinase pathway but not ERK MAPK

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