Skeletal growth factor and other growth factors known to be present in bone matrix stimulate proliferation and protein synthesis in human bone cells

The combination of epidermal growth factor (EGF) plus transforming growth factor-beta 1 (TGF-beta 1) causes hypertrophy in renal epithelial cells. One mechanism contributing to hypertrophy is that EGF induces activation of the cell cycle and increases protein synthesis, whereas TGF-beta 1 prevents cell division, thereby converting hyperplasia to hypertrophy. To assess whether suppression of proteolysis is another mechanism causing hypertrophy induced by these growth factors, we measured protein degradation in primary cultures of proximal tubule cells and in cultured NRK-52E kidney cells. A concentration of 10(-8) M EGF alone or EGF plus 10(-10) M TGF-beta 1 decreased proteolysis by approximately 30%. TGF-beta 1 alone did not change protein degradation. Using inhibitors, we examined which proteolytic pathway is suppressed. Neither proteasome nor calpain inhibitors prevented the antiproteolytic response to EGF + TGF-beta 1. Inhibitors of lysosomal proteases eliminated the antiproteolytic response to EGF + TGF-beta 1, suggesting that these growth factors act to suppress lysosomal proteolysis. This antiproteolytic response was not caused by impaired EGF receptor signaling, since lysosomal inhibitors did not block EGF-induced protein synthesis. We conclude that suppression of lysosomal proteolysis contributes to growth factor-mediated hypertrophy of cultured kidney cells.

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Modulation of growth factor incorporation into ECM of human osteoblast-like cells in vitro by 17 beta-estradiol

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1994.267.6.e990 ◽

1994 ◽

Vol 267 (6) ◽

pp. E990-E1001 ◽

Cited By ~ 2

Author(s):

M. Slater ◽

J. Patava ◽

K. Kingham ◽

R. S. Mason

Keyword(s):

Growth Factors ◽

Growth Factor ◽

Transforming Growth Factor Beta ◽

Bone Growth ◽

Transforming Growth Factor ◽

Bone Matrix ◽

Tgf Beta ◽

Subsequent Formation ◽

Igf I

Human fetal osteoblast-like cells formed a regular multilayered structure in vitro with an extensive collagen-based extracellular matrix. With colloidal gold immunocytochemistry, labels for alkaline phosphatase and osteocalcin were distributed in a relatively diffuse pattern, in contrast to the bone growth factors, insulin-like growth factors I and II (IGF-I and IGF-II), transforming growth factor-beta 1 (TGF-beta 1), and basic fibroblast growth factor, which were colocalized in the collagenous matrix of the multilayer. The inclusion of 17 beta-estradiol (10(-11) to 10(-9) M) in the culture medium increased multilayer depths, increased labeling for IGF-I, IGF-II, and TGF-beta 1, and resulted in earlier detection of TGF-beta 1 label. In contrast, the increase in multilayer depth resulting from treatment with human platelets, an exogenous source of growth factors, was not accompanied by an increase in matrix IGF-I, IGF-II, or TGF-beta 1 label, suggesting a particular effect of estradiol to facilitate this process. Because growth factors in bone matrix may act as coupling agents when released during resorption, reduced growth factor incorporation in the presence of reduced sex steroid concentrations may lead to uncoupling of resorption and subsequent formation.

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Differential Effects of Fibroblast Growth Factors on Expression of Genes of the Plasminogen Activator and Insulin-like Growth Factor Systems by Human Breast Fibroblasts

Thrombosis and Haemostasis ◽

10.1055/s-0037-1613065 ◽

2002 ◽

Vol 87 (04) ◽

pp. 674-683 ◽

Cited By ~ 14

Author(s):

John Martens ◽

Lambert Dorssers ◽

Jan Klijn ◽

John Foekens ◽

Anieta Sieuwerts

Keyword(s):

Protein Synthesis ◽

Growth Factors ◽

Growth Factor ◽

Plasminogen Activator ◽

De Novo ◽

Fibroblast Growth Factors ◽

Fibroblast Growth ◽

Human Breast ◽

Short Term ◽

De Novo Protein Synthesis

SummaryIn breast stroma urokinase plasminogen activator (uPA) is predominantly expressed by fibroblasts located in the near vicinity of tumor cells, and fibroblast-derived insulin-like growth factor-1 (IGF-1) may be involved in inhibiting the expression of uPA in these fibroblasts. To investigate a possible role for fibroblast growth factors (FGFs), we evaluated the expression of components of the PA system and the IGF system in normal and tumor-tissue-derived human breast fibroblasts exposed to various FGFs in vitro. mRNA analysis revealed that FGF-1, FGF-2 and FGF-4 induced the mRNA expression levels of uPA, tPA, uPAR, PAI-1 and PAI-2, and reduced those of IGF-1, IGF-1R, IGF-2R and IGFBP-4, without significantly affecting the levels of IGFBP-3, IGFBP-5 and IGFBP-6 mRNA. Concerning the expression of IGF-2 mRNA, the effects mediated by FGF-1, FGF-2 and FGF-4 were divergent. In general, the effects elicited by FGF-1 on the various mRNA levels studied were rapid and short-term. Those mediated by FGF-2 overall lagged behind but were longer-lasting. For FGF-4 an in between pattern was observed. Blocking transcription and translation demonstrated that a) both the FGF-1 and FGF-2 induced effects were the result of altered gene transcription or mRNA stability, b) the short-term effects mediated by FGF-1 and FGF-2 required de novo protein synthesis, and c) the long-term effects elicited by FGF-2 did not depend on de novo protein synthesis during the first 24 h, but were triggered by proteins produced or made available thereafter. The data presented propose that of the FGFs studied (FGF-1, -2, -4, -5, and -7), FGF-2 is the most attractive target for therapeutical strategies aimed at diminishing the contribution of stromal fibroblasts in the PA-directed breast tumor proteolysis.

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TGF-β and CTGF have overlapping and distinct fibrogenic effects on human renal cells

AJP Renal Physiology ◽

10.1152/ajprenal.00007.2002 ◽

2002 ◽

Vol 283 (4) ◽

pp. F707-F716 ◽

Cited By ~ 82

Author(s):

Elizabeth Gore-Hyer ◽

Daniel Shegogue ◽

Malgorzata Markiewicz ◽

Shianlen Lo ◽

Debra Hazen-Martin ◽

...

Keyword(s):

Protein Synthesis ◽

Growth Factors ◽

Growth Factor ◽

Renal Fibrosis ◽

Transforming Growth Factor ◽

Transforming Growth Factor Β ◽

Tissue Growth ◽

Mrna Levels ◽

Potent Inducer ◽

Collagen Promoter

Transforming growth factor-β (TGF-β) and connective tissue growth factor (CTGF) are ubiquitously expressed in various forms of tissue fibrosis, including fibrotic diseases of the kidney. To clarify the common and divergent roles of these growth factors in the cells responsible for pathological extracellular matrix (ECM) deposition in renal fibrosis, the effects of TGF-β and CTGF on ECM expression in primary human mesangial (HMCs) and human proximal tubule epithelial cells (HTECs) were studied. Both TGF-β and CTGF significantly induced collagen protein expression with similar potency in HMCs. Additionally, α2(I)-collagen promoter activity and mRNA levels were similarly induced by TGF-β and CTGF in HMCs. However, only TGF-β stimulated collagenous protein synthesis in HTECs. HTEC expression of tenascin-C (TN-C) was increased by TGF-β and CTGF, although TGF-β was the more potent inducer. Thus both growth factors elicit similar profibrogenic effects on ECM production in HMCs, while promoting divergent effects in HTECs. CTGF induction of TN-C, a marker of epithelial-mesenchymal transdifferentiation (EMT), with no significant induction of collagenous protein synthesis in HTECs, may suggest a more predominant role for CTGF in EMT rather than induction of excessive collagen deposition by HTECs during renal fibrosis.

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Increased serum and bone matrix levels of transforming growth factor β1 in patients with GH deficiency in response to GH treatment

Acta Endocrinologica ◽

10.1530/eje-11-0442 ◽

2011 ◽

Vol 165 (3) ◽

pp. 393-400 ◽

Cited By ~ 3

Author(s):

Thor Ueland ◽

Tove Lekva ◽

Kari Otterdal ◽

Tuva B Dahl ◽

Nicoleta Cristina Olarescu ◽

...

Keyword(s):

Growth Factor ◽

Cortical Bone ◽

Transforming Growth Factor ◽

Bone Cells ◽

Gh Deficiency ◽

Bone Matrix ◽

Transforming Growth Factor Β1 ◽

Gh Treatment

ObjectivePatients with adult onset GH deficiency (aoGHD) have secondary osteoporosis, which is reversed by long-term GH substitution. Transforming growth factor β1 (TGFβ1 or TGFB1) is abundant in bone tissue and could mediate some effects of GH/IGFs on bone. We investigated its regulation by GH/IGF1in vivoandin vitro.Design and methodsThe effects of GH substitution (9–12 months, placebo controlled) on circulating and cortical bone matrix contents of TGFβ1 were investigated in patients with aoGHD. The effects of GH/IGF1 on TGFβ1 secretion in osteoblasts (hFOB), adipocytes, and THP-1 macrophages as well as the effects on release from platelets were investigatedin vitro.ResultsIn vivoGH substitution increased TGFβ1 protein levels in cortical bone and serum.In vitro, GH/IGF1 stimulation induced a significant increase in TGFβ1 secretion in hFOB. In contrast, no major effect of GH/IGF1 on TGFβ1 was found in adipocytes and THP-1 macrophages. Finally, a minor modifying effect on SFLLRN-stimulated platelet release of TGFβ1 was observed in the presence of IGF1.ConclusionGH substitution increases TGFβ1in vivoandin vitro, and this effect could contribute to improved bone metabolism during such therapy, potentially reflecting direct effect of GH/IGF1 on bone cells.

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