Effects of platelet-derived growth factor and epidermal growth factor on antigen-induced proliferation of human T-cell lines.

When the serum content of tissue culture medium is reduced from 10% to 1%, the capacity of T cells to proliferate in response to antigen within that medium is dramatically reduced. Physiological concentrations of platelet-derived growth factor (PDGF) or epidermal growth factor (EGF) are able to partially replace the requirement for serum, in that they are able to increase antigen-driven T-cell proliferation at a serum concentration of 1%. Neither growth factor is mitogenic for T cells in the absence of antigen, and neither is able to act synergistically with T-cell growth factor (TCGF) or IL-2) in the absence of antigen. Antigen-presenting cells (APC) pulsed with antigen in the presence of PDGF or EGF are able to stimulate antigen-specific T-cell proliferation to a greater extent than antigen-presenting cells pulsed in the absence of exogenous PDGF or EGF. Both growth factors increase the expression of MHC Class II antigens on antigen-presenting cells.     

Effects of growth factors in vivo. I. Cell ingrowth into porous subcutaneous chambers.

Growth factors secreted by platelets and macrophages may play roles in atherogenesis and in wound repair. The multiple biologic effects of these factors are being studied extensively in vitro, but their roles in vivo are relatively unexplored. The cellular responses to platelet-derived growth factor (PDGF), transforming growth factor beta (TGF beta), basic fibroblast growth factor (bFGF), and epidermal growth factor (EGF) were examined in a wound chamber model in rats. Growth factors were emulsified in bovine dermal collagen suspensions, placed in 1 X 30-mm porous polytetrafluoroethylene tubes, inserted subcutaneously, and removed after 10 days. The presence of PDGF (400 ng), TGF beta (200 ng), or bFGF (100 ng) increased the DNA content of the chambers two- to sixfold, compared with controls. Regardless of dose, EGF (100-800 ng) did not affect the DNA content. The increases in DNA observed for PDGF, TGF beta, or bFGF resulted from accumulations of varying numbers of fibroblasts, capillaries, macrophages, and leukocytes in 10-day chambers. The addition of 250 micrograms/ml heparin to the collagen suspension potentiated the response to PDGF and bFGF, but not to TGF beta or EGF. The clearance of 125I-labeled growth factors from the chambers was biphasic. After an initial rapid phase, the remaining growth factor was slowly cleared. The half-life of the initial phase was rapid for PDGF (12 hours) and bFGF (9 hours) and somewhat slower for TGF beta (22 hours). There was no difference in the rate of clearance between collagen and collagen/heparin matrices for any of the growth factors examined. These studies demonstrate that PDGF, bFGF, and TGF beta can induce granulation tissue development in normal animals. The similarity in cellular responses to three peptides with differing in vitro actions suggests that the responses observed at 10 days reflect a secondary process, possibly mediated by effector cells such as macrophages, lymphocytes, or granulocytes that are attracted into the chamber by each growth factor, rather than a direct effect of the factors themselves.     

Regulation of mesangial cell growth by polypeptide mitogens. Inhibitory role of transforming growth factor beta.

Proliferation of mesangial cells is a common histologic abnormality in glomerular diseases. In vivo studies suggest a role for platelets and monocytes-macrophages in mediating glomerular hypercellularity. The authors recently reported that several peptide growth factors stimulate DNA synthesis and growth of human mesangial cells. This article reports that transforming growth factor beta (TGF-beta), a peptide released by inflammatory cells and platelets, inhibits DNA synthesis and growth of human mesangial cells. The stimulatory and inhibitory effects of these mitogens on DNA synthesis and growth was confirmed by autoradiography and cell counting. The inhibitory effect of TGF-beta is not mediated at the receptor level because TGF-beta did not inhibit the binding of epidermal growth factor (EGF) or platelet-derived growth factor (PDGF) to mesangial cells. Because peptide growth factors that stimulate DNA synthesis in mesangial cells induce expression of PDGF mRNAs, the effect of TGF-beta on PDGF mRNAs expression induced by peptide growth factors was studied. TGF-beta did not lower the increased levels of PDGF mRNAs caused by EGF or PDGF. These data show that TGF-beta is a potent inhibitor of DNA synthesis and growth of mesangial cells. The mechanism of the inhibitory effect of TGF-beta remains to be determined.     

Similar transforming growth factors (TGFs) produced by cells transformed by different isolates of feline sarcoma virus

Fisher rat embryo cells transformed by each of three independent isolates of feline sarcoma virus (FeSV) are shown to release transforming growth factors (TGFs) into cell culture medium. These acid- and heat-stable peptides compete for binding to, and stimulate phosphorylation of, EGF membrane receptors and promote anchorage-independent cell growth. Cells transformed by the Gardner and Snyder-Theilen strains of FeSV produce high titers of TGF (60-200 ng eq EGF/liter) while cells transformed by McDonough FeSV produce TGF at only low levels (<10 ng eq EGF/liter). Growth factors produced by cells transformed by each of the three FeSV isolates functionally and biochemically resemble each other, mouse sarcoma growth factor (SGF), and TGFs produced by human tumor cells.     

Bedeutung der Fibroblasten-Chemotaxis für Wundheilung und Tumorzellevasion

Summary Fibroblast are responsable for the synthesis of the structural proteins of the connective tissue. A further property of these cells, their migratory ability, could be analyzed in the last years. A special form of migration is chemotaxis, which can be quantitatively measured in a modified Boyden chamber in-vitro. Using this method chemoattractive substances could be characterized, which are able to stimulate fibroblasts and tumorcells to chemotactic migration. Furthermore it could be proved, that benign and transformed cell lines react in a different manner towards these chemoattractive substances. The in-vitro results allow some hypotheses about both fibroblast migration in wound healing or chronic inflammation, and the mechanisms of tumor cell evasion in the tumor surrounding tissue or the metastasizing process in other organs.

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Abkürzungen PDGF platelet derived growth factor - LTB₄ Leukotrien B 4 Mit Unterstützung der Deutschen Forschungsgemeinschaft Me 766/1–3     

The effects of ageing on wound healing: immunolocalisation of growth factors and their receptors in a murine incisional model

A number of reports suggest that the process of ageing impairs wound repair and that strategies to manipulate the age-related wound healing environment are necessary in order to stimulate repair. The process of cutaneous wound repair is controlled by growth factors in an autocrine and paracrine fashion: it is therefore surprising that the localisation of specific growth factors and their receptors has not been documented in wound healing with respect to chronological age. In this study the temporal profile of growth factor and receptor immunostaining was assessed within acute incisional wounds in an ageing mouse colony. A delay in appearance of platelet derived growth factor (PDGF) A and B isoforms, and PDGF-α and -β receptors was evident with increasing animal age, paralleled by a similar finding for epidermal growth factor (EGF) and EGF receptor. Transforming growth factor (TGF)-7beta;1 and 2 isoforms were increased at all time points in the wounds of younger animals, but the TGF-β3 isoform increased in intensity from d 7 postwounding in the old mice wounds, and basic fibroblast growth factor (bFGF) from d 14. The quantity and distribution patterns of the various growth factors and their receptors may explain the age-related differences in wound healing speed and quality, and possibly suggest new therapeutic targets for manipulating wound healing in the aged.     

The effects of growth factors on human normal placental cytotrophoblast cell proliferation

The effects of growth factors were investigated on the proliferation of a normal placental cytotrophoblast cell line (NPC). Epidermal growth factor (EGF), transforming growth factor alpha (TGF alpha) and insulin- like growth factor-I (IGF-I) stimulated NPC cell proliferation. In contrast, TGFbeta1 was found to be a negative regulator, inhibiting EGF- induced cell proliferation. When EGF/TGF alpha receptor was analysed by radio-ligand binding, two binding sites of different affinities were revealed in the proliferating NPC cells but only the low affinity binding site was detected in the non-proliferating cytotrophoblast cells in primary cultures. The results suggest that EGF stimulates cytotrophoblast proliferation through high affinity binding sites.      

Modulation of hen granulosa cell steroidogenesis and plasminogen activator activity hy transforming growth factor alpha

Studies were conducted with chicken granulosa cells to evaluate the relative efficacy of human recombinant transforming growth factor alpha (TGF alpha) versus murine epidermal growth factor (EGF) to affect cyclic adenosine monophosphate (cAMP) accumulation and progesterone production stimulated by luteinizing hormone (LH) or steroid output induced by a cAMP analogue, and to modulate plasminogen activator (PA) activity. Increasing concentrations of EGF (33-328 nM) and TGF alpha (0.04-18 nM) were found to inhibit cAMP formation stimulated by LH in a dose-dependent manner, with calculated half-maximal inhibitory doses (ID50's) of 97.1 and 0.27 nM, respectively. Similarly, a 470-fold difference in the ability of TGF alpha (ID50 = 0.13 nM) versus EGF (ID50 = 61.3 nM) to half-maximally suppress LH-induced progesterone production was observed in the same cells. Progesterone production stimulated by a cAMP analogue (8-bromo-cAMP, 1 mM) was also attenuated by EGF (ID50 = 75.9 nM) and TGF alpha (ID50 = 0.08 nM), suggesting a post-cAMP site of inhibition by these growth factors on steroidogenesis. Finally, a 260-fold to 330-fold difference in the efficacy of TGF alpha versus EGF to half-maximally stimulate cell-associated and secreted PA activity was observed. From these data, we propose that TGF alpha may serve an important role in regulating follicular growth and maturation in the domestic hen via its ability to affect granulosa cell steroidogenesis and plasminogen activator activity.     

Growth Promoting Activity of PDGF, EGF and TGF-β on Highly Metastatic Subline of Meth a Cells

The response of a highly metastatic cell line of methylcholanthrene induced A fibrosarcoma (Meth A) to growth factors from platelets was examined. The highly metastatic cell subline (MH) proliferated more rapidly than its parental counterpart cell subline (ML) in a medium containing platelet lysate. However, when the three major growth factors from platelets, ie, platelet-derived growth factor, epidermal growth factor, and transforming growth factor-β(PDGF, EGF, TGF-β), were independently examined for their growth promoting activity, the former 2 growth factors preferentially stimulated the proliferation of ML and the latter growth factor rather suppressed the growth of both cells.

On the other hand, the combined effects of these factors were more marked on MH. This combination effect was supported by the evidence that the number of receptors for EGF (which is probably an essential growth factor for the Meth A cell) was increased by pretreatmenl with PDGF or TGF-β. Thus, the highly metastatic cells of MH were considered to be the most susceptible to growth factors released from platelets. This conclusion is consistent with the concept that platelets may play an important role in the formation of blood-borne metastasis by releasing growth factors to promote the proliferation of tumor cells, following aggregation with tumor cells.     

Modulation of Hen Granulosa Cell Steroidogenesis and Plasminogen Activator Activity by Transforming Growth Factor Alpha

Abstract

Studies were conducted with chicken granulosa cells to evaluate the relative efficacy of human recombinant transforming growth factor alpha (TGFα) versus murine epidermal growth factor (EGF) to affect cyclic adenosine monophosphate (cAMP) accumulation and progesterone production stimulated by luteinizing hormone (LH) or steroid output induced by a cAMP analogue, and to modulate plasminogen activator (PA) activity.

Increasing concentrations of EGF (33–328 nM) and TGFα (0.04–18'nM) were found to inhibit cAMP formation stimulated by LH in a dose-dependent manner, with calculated half-maximal inhibitory doses (ID₃₀s) of 97.1 and 0.27 nM, respectively. Similarly, a 470-fold difference in the ability of TGFa (ID₃₀ = 0.13 nM) versus EGF (ID₃₀ = 61.3 nM) to half-maximally suppress LH-induced progesterone production was observed in the same cells. Progesterone production stimulated by a cAMP analogue (8-bromo-cAMP, 1 mM) was also attenuated by EGF (ID₃₀ = 75.9 nM) and TGFa (ID₃₀ = 0.08 nM), suggesting a post-cAMP site of inhibition by these growth factors on steroidogenesis. Finally, a 260-fold to 330-fold difference in the efficacy of TGFα versus EGF to half-maximally stimulate cell-associated and secreted PA activity was observed.

From these data, we propose that TGFα may serve an important role in regulating follicular growth and maturation in the domestic hen via its ability to affect granulosa cell steroidogenesis and plasminogen activator activity.