Differential expression of IGF system components in proliferating vs. differentiating growth plate chondrocytes: the functional role of IGFBP-5

2006 ◽  
Vol 290 (2) ◽  
pp. E363-E371 ◽  
Author(s):  
Daniela Kiepe ◽  
Sonia Ciarmatori ◽  
Anke Haarmann ◽  
Burkhard Tönshoff
Keyword(s):  
Cell Culture ◽  
Growth Plate ◽  
Functional Role ◽  
Growth Plate Chondrocytes ◽  
Igf System ◽  
System Components ◽  
Igf I ◽  
Culture Models ◽  
Cell Culture Models ◽  
Igfbp 3

The growth plate is an important target tissue for insulin-like growth factors (IGFs), but little is known about the regulation of the IGF system during the developmental sequence of chondrocytes. We therefore examined the expression profile of IGF system components in proliferating vs. differentiating growth plate chondrocytes by use of two cell culture models of the growth cartilage. In rat growth plate chondrocytes in primary culture, IGF-I expression increased twofold during the process of differentiation. IGF-binding protein-3 (IGFBP-3) expression showed a biphasic pattern of with a twofold increase at the onset of differentiation and a downregulation in late differentiating chondrocytes to 25% of baseline levels; the expression patterns of IGFBP-2, -4 and -6 were not dependent on the developmental stage. In IGF- and IGFBP-3-deficient RCJ3.1C5.18 (RCJ) mesenchymal chondrogenic cells, IGFBP-2 and -6 synthesis declined by 50% during differentiation. IGFBP-5 expression was markedly upregulated during the process of differentiation in both cell culture models. Although IGFBP-5 overexpression did not have an IGF-independent effect on RCJ cell differentiation, it promoted IGF-I-enhanced differentiation of these cells. A potential mechanism for this effect is the specific increase of Akt phosphorylation in IGFBP-5-overexpressing cells in the presence of IGF-I, indicating an increased activity of the phosphatidylinositol (PI) 3-kinase pathway. These data suggest that the developmental stage of the chondrocyte is an important determinant of IGF and IGFBP expression and imply a functional role for IGFBP-5 for upregulating IGF action during chondrocyte differentiation in vivo.

scholarly journals Turnover of the Active Fraction of IRS1 Involves Raptor-mTOR- and S6K1-Dependent Serine Phosphorylation in Cell Culture Models of Tuberous Sclerosis

2006 ◽  
Vol 26 (17) ◽  
pp. 6425-6434 ◽  
Author(s):  
O. Jameel Shah ◽  
Tony Hunter
Keyword(s):  
Cell Culture ◽  
Tuberous Sclerosis ◽  
High Speed ◽  
Serine Phosphorylation ◽  
Feedback Signal ◽  
Insulin Receptor Substrates ◽  
Igf I ◽  
Culture Models ◽  
Cell Culture Models

ABSTRACT The TSC1-TSC2/Rheb/Raptor-mTOR/S6K1 cell growth cassette has recently been shown to regulate cell autonomous insulin and insulin-like growth factor I (IGF-I) sensitivity by transducing a negative feedback signal that targets insulin receptor substrates 1 and 2 (IRS1 and -2). Using two cell culture models of the familial hamartoma syndrome, tuberous sclerosis, we show here that Raptor-mTOR and S6K1 are required for phosphorylation of IRS1 at a subset of serine residues frequently associated with insulin resistance, including S307, S312, S527, S616, and S636 (of human IRS1). Using loss- and gain-of-function S6K1 constructs, we demonstrate a requirement for the catalytic activity of S6K1 in both direct and indirect regulation of IRS1 serine phosphorylation. S6K1 phosphorylates IRS1 in vitro on multiple residues showing strong preference for RXRXXS/T over S/T,P sites. IRS1 is preferentially depleted from the high-speed pellet fraction in TSC1/2-deficient mouse embryo fibroblasts or in HEK293/293T cells overexpressing Rheb. These studies suggest that, through serine phosphorylation, Raptor-mTOR and S6K1 cell autonomously promote the depletion of IRS1 from specific intracellular pools in pathological states of insulin and IGF-I resistance and thus potentially in lesions associated with tuberous sclerosis.

scholarly journals Insulin-Like Growth Factor (IGF)-I Stimulates Cell Proliferation and Induces IGF Binding Protein (IGFBP)-3 and IGFBP-5 Gene Expression in Cultured Growth Plate Chondrocytes via Distinct Signaling Pathways

Endocrinology ◽  
2005 ◽  
Vol 146 (7) ◽  
pp. 3096-3104 ◽  
Author(s):  
Daniela Kiepe ◽  
Sonia Ciarmatori ◽  
Andreas Hoeflich ◽  
Eckhard Wolf ◽  
Burkhard Tönshoff
Keyword(s):  
Signaling Pathways ◽  
Growth Plate ◽  
Intracellular Signaling ◽  
De Novo ◽  
Growth Plate Chondrocytes ◽  
Intracellular Signaling Pathways ◽  
Igf I ◽  
Rat Growth ◽  
Igf Binding ◽  
Igfbp 3

Abstract The bioactivity of IGF-I in the cellular microenvironment is modulated by both inhibitory and stimulatory IGF binding proteins (IGFBPs), whose production is partially under control of IGF-I. However, little is known on the IGF-mediated regulation of these IGFBPs in the growth plate. We therefore studied the effect of IGF-I on IGFBP synthesis and the involved intracellular signaling pathways in two cell culture models of rat growth plate chondrocytes. In growth plate chondrocytes in primary culture, incubation with IGF-I increased the concentrations of IGFBP-3 and IGFBP-5 in conditioned cell culture medium in a dose- and time-dependent manner. Coincubation of IGF-I with specific inhibitors of the p42/44 MAPK pathway (PD098059 or U0126) completely abolished the stimulatory effect of IGF-I on IGFBP-3 mRNA expression but did not affect increased IGFBP-5 mRNA levels. In contrast, inhibition of the phosphatidylinositol-3 kinase signaling pathway by LY294002 abrogated both IGF-I-stimulated IGFBP-3 and -5 mRNA expression. Comparable results regarding IGFBP-5 were obtained in the mesenchymal chondrogenic cell line RCJ3.1C5.18, which does not express IGFBP-3. The IGF-I-induced IGFBP-5 gene expression required de novo mRNA transcription and de novo protein synthesis. These data suggest that IGF-I modulates its activity in cultured rat growth plate chondrocytes by the synthesis of both inhibitory (IGFBP-3) and stimulatory (IGFBP-5) binding proteins. The finding that IGF-I uses different and only partially overlapping intracellular signaling pathways for the regulation of two IGFBPs with opposing biological functions might be important for the modulation of IGF bioactivity in the cellular microenvironment.

scholarly journals Factors to consider when interrogating 3D culture models with plate readers or automated microscopes

2021 ◽  
Author(s):  
Terry Riss ◽  
O. Joseph Trask
Keyword(s):  
Cell Culture ◽  
Three Dimensional ◽  
3D Culture ◽  
Fluorescent Imaging ◽  
Culture Models ◽  
Assay Methods ◽  
Diffusion Rates ◽  
Cell Culture Models ◽  
Dimensional Cell ◽  
Cells Cultured

AbstractAlong with the increased use of more physiologically relevant three-dimensional cell culture models comes the responsibility of researchers to validate new assay methods that measure events in structures that are physically larger and more complex compared to monolayers of cells. It should not be assumed that assays designed using monolayers of cells will work for cells cultured as larger three-dimensional masses. The size and barriers for penetration of molecules through the layers of cells result in a different microenvironment for the cells in the outer layer compared to the center of three-dimensional structures. Diffusion rates for nutrients and oxygen may limit metabolic activity which is often measured as a marker for cell viability. For assays that lyse cells, the penetration of reagents to achieve uniform cell lysis must be considered. For live cell fluorescent imaging assays, the diffusion of fluorescent probes and penetration of photons of light for probe excitation and fluorescent emission must be considered. This review will provide an overview of factors to consider when implementing assays to interrogate three dimensional cell culture models.

Cell culture models of the ocular barriers

2005 ◽  
Vol 60 (2) ◽  
pp. 207-225 ◽  
Author(s):  
Margit Hornof ◽  
Elisa Toropainen ◽  
Arto Urtti
Keyword(s):  
Cell Culture ◽  
Culture Models ◽  
Cell Culture Models

Abstract 15951: Palmitate, Not Oleate, is the Preferred Fatty Acid for Cardiac Triacylglycerol Synthesis

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Stephen C Kolwicz ◽  
Rong Tian
Keyword(s):  
Cell Culture ◽  
13C Nmr Spectroscopy ◽  
Culture Studies ◽  
Triacylglycerol Synthesis ◽  
Culture Models ◽  
Contracting Heart ◽  
And Control ◽  
The Relationship ◽  
Cell Culture Models ◽  
Insight Into

Introduction: Previous studies using cell culture models identified cyto-toxic effects of palmitate and that supplementation with oleate was protective by redirecting palmitate into triacylglycerol (TAG) stores. However, other cull culture studies reported that diacylglycerol transferase 1 (DGAT1), the last enzyme in TAG synthesis, demonstrated a preference for oleate. At present, it is not clear whether the supply of exogenous fatty acids (FA) to the heart is differentially allocated into the endogenous TAG pool. Therefore, the purpose of the present study is to examine the influence of palmitate and/or oleate on cardiac TAG incorporation. METHODS/RESULTS: Hearts were isolated from DGAT1-transgenic (DGAT) and control littermates (CON) and perfused in Langendorff mode with a mixed substrate buffer consisting of glucose, lactate, insulin, and FAs. The FA supply was varied with 0.2mM of both labeled (13C) and unlabeled (12C) FAs in 4 different experiments: 1) 13C/12C palmitate; 2) 13C/12C oleate; 3) 13C palmitate/12C oleate; 4) 13C oleate/12C palmitate. The incorporation of 13C palmitate or 13C oleate into the TAG pool was monitored by 13C NMR spectroscopy. In CON hearts (n=3), the incorporation of palmitate was ~65% higher than oleate when the perfusate contained a homogenous supply of FA. This was also observed in DGAT hearts (n=4) although the incorporation of both palmitate and oleate was ~75% higher compared to CON (P <0.05). In the presence of oleate, palmitate incorporation decreased 25-30% in both CON and DGAT hearts. In contrast, oleate incorporation was diminished by ~50% and ~100% in CON and DGAT hearts, respectively, in the presence of palmitate. CONCLUSIONS: These data suggest that when palmitate and oleate are provided in equal concentrations, palmitate is more readily utilized in the synthesis of endogenous TAG stores in the heart. Furthermore, although overexpression of DGAT increases both oleate and palmitate incorporation, the DGAT1 enzyme demonstrates a preference for palmitate. These findings provide insight into the relationship between exogenous FA supply and endogenous TAG dynamics in the contracting heart.

scholarly journals Conjunctival melanoma and electrochemotherapy: preliminary results using 2D and 3D cell culture models in vitro

2018 ◽  
Vol 97 (4) ◽  
pp. e632-e640 ◽  
Author(s):  
Miltiadis Fiorentzis ◽  
Periklis Katopodis ◽  
Helen Kalirai ◽  
Berthold Seitz ◽  
Arne Viestenz ◽  
...  
Keyword(s):  
Cell Culture ◽  
3D Cell Culture ◽  
Conjunctival Melanoma ◽  
Preliminary Results ◽  
Culture Models ◽  
2D And 3D ◽  
Cell Culture Models
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