scholarly journals Identification of a soluble receptor for platelet-derived growth factor in cell-conditioned medium and human plasma

1993 ◽  
Vol 268 (13) ◽  
pp. 9621-9628
Author(s):  
J. Tiesman ◽  
C.E. Hart
Keyword(s):  
Growth Factor ◽  
Conditioned Medium ◽  
Human Plasma ◽  
Platelet Derived Growth Factor ◽  
Soluble Receptor ◽  
Cell Conditioned Medium

Endothelial cell-conditioned medium downregulates smooth muscle contractile protein expression

1997 ◽  
Vol 272 (2) ◽  
pp. C582-C591 ◽  
Author(s):  
S. M. Vernon ◽  
M. J. Campos ◽  
T. Haystead ◽  
M. M. Thompson ◽  
P. E. DiCorleto ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Endothelial Cell ◽  
Growth Factor ◽  
Protein Expression ◽  
Conditioned Medium ◽  
Transforming Growth Factor Beta ◽  
Transforming Growth Factor ◽  
Contractile Protein ◽  
Alpha Actin ◽  
Cell Conditioned Medium

Smooth muscle cells (SMC) within atherosclerotic lesions proliferate and exhibit phenotypic modulation, but the contribution of vascular endothelium to this process is poorly understood. Our aim was to examine the effects of endothelial cell-conditioned medium (ECCM) on vascular SMC growth and differentiation. Rat aortic ECCM stimulated a ninefold increase in [3H]thymidine incorporation and downregulated smooth muscle-specific myosin heavy chain and alpha-actin synthesis in rat aortic SMC. These effects were not inhibited by antibodies to platelet-derived growth factor (PDGF)-BB or PDGF-AB or with a PDGF beta-receptor subunit. Treatment with PDGF-BB (at a concentration found in ECCM), PDGF-AA, basic fibroblast growth factor, endothelin-1, or transforming growth factor-beta did not reproduce these effects. The ECCM activities were sensitive to heat and trypsinization, were >30 kDa in molecular mass, and bound weakly to heparin-Sepharose. Our data indicate that cultured endothelial cells produce a factor(s) that downregulates contractile protein expression in SMC, which may contribute to SMC dedifferentiation and proliferation.

scholarly journals Proteolytic activation of latent transforming growth factor-beta from fibroblast-conditioned medium.

1988 ◽  
Vol 106 (5) ◽  
pp. 1659-1665 ◽  
Author(s):  
R M Lyons ◽  
J Keski-Oja ◽  
H L Moses
Keyword(s):  
Growth Factor ◽  
Conditioned Medium ◽  
Transforming Growth Factor Beta ◽  
Acid Treatment ◽  
Transforming Growth Factor ◽  
Soft Agar ◽  
Tgf Beta ◽  
Growth Factor Beta ◽  
Mild Acid ◽  
Cell Conditioned Medium

Transforming growth factor-beta (TGF beta) is produced by most cultured cells in an inactive form. Potential activation mechanisms of latent TGF beta were studied using fibroblastic (NRK-49F and AKR-MCA) cell-conditioned medium as a model. Active TGF beta was monitored by radioreceptor and soft agar assays as well as by antibody inhibition and immunoprecipitation. Little or no TGF beta was detected in untreated conditioned medium. Treatment of the medium with extremes of pH (1.5 or 12) resulted in significant activation of TGF beta as shown by radioreceptor assays, while mild acid treatment (pH 4.5) yielded only 20-30% of the competition achieved by pH 1.5. In an effort to define more physiological means of TGF beta activation, the effects of some proteases were tested. Plasmin and cathepsin D were found to generate 25-kD bands corresponding to the active form of TGF beta as shown by immunoprecipitation analysis of radiolabeled cell-conditioned medium. Plasmin treatment of the medium resulted in activity that was quantitatively similar to that of mild acid treatment as measured by radioreceptor and soft agar assays. In addition, the plasmin-generated activity was inhibited by anti-TGF beta antibodies. Sequential treatments of AKR-MCA cell-conditioned medium with mild acid followed by plasmin or plasmin followed by mild acid gave activation comparable to either treatment alone. The data suggest that conditioned medium may contain at least two different pools of latent TGF beta. One pool is resistant to mild acid and/or plasmin and requires strong acid or alkali treatment for activation. A second pool is activated by mild pH change and/or plasmin. Activation of this form of latent TGF beta may take place by dissociation or proteolytic digestion from a precursor molecule or hypothetical TGF beta-binding protein complex.

scholarly journals Human platelet-derived growth factor: radioimmunoassay and discovery of a specific plasma-binding protein.

1983 ◽  
Vol 97 (2) ◽  
pp. 383-388 ◽  
Author(s):  
J S Huang ◽  
S S Huang ◽  
T F Deuel
Keyword(s):  
Growth Factor ◽  
Human Plasma ◽  
Wound Repair ◽  
Cultured Cells ◽  
Binding Protein ◽  
Biological Fluids ◽  
Platelet Derived Growth Factor ◽  
Plasma Binding ◽  
Platelet Factor ◽  
Immunodiffusion Analysis

The platelet-derived growth factor (PDGF) is the principal mitogen in serum for cultured cells of mesenchymal origin. PDGF also is a potent chemotactic protein for inflammatory cells and for cells required for wound repair. Because activity levels of PDGF in biological fluids are difficult to measure, we attempted to develop a radioimmunoassay for PDGF. Rabbits were immunized with purified PDGF; the antiserum obtained was monospecific for PDGF in immunodiffusion analysis against concentrated platelet lysates, serum, and plasma. A radioimmunoassay for PDGF was developed with a sensitivity of congruent to 0.2 ng/ml. Levels of PDGF in plasma/serum were measured and compared with PDGF levels determined by a receptor-competition assay and by a standard biological assay measuring incorporation of [3H]thymidine into 3T3 cells. Radioimmunoassay showed apparent PDGF levels of 50 ng/ml in human plasma and 103 ng/ml in serum. The 50 ng/ml PDGF in plasma was unexpected because the plasma samples contained little or no platelet release products as determined by very low levels of platelet factor 4. We therefore sought an immunologically reactive PDGF molecule in human plasma. No immunologically reactive protein was detected by immunodiffusion analysis or when plasma was treated with an immunoaffinity gel. Subsequently, a 125I-PDGF-binding protein was identified; the 125I-PDGF-plasma-binding protein complex was not reactive with anti-PDGF immunoglobulin. Correction for 125I-PDGF bound by the plasma-binding protein established serum levels of PDGF of congruent to 50 ng/ml; congruent to 50 ng/ml PDGF was found in serum by radioreceptor-competition assays and by mitogenic assays as well. The plasma-binding protein may serve to clear PDGF released in the circulation, thereby limiting PDGF activity to its local interactions at the site of blood-vessel injury.

Sign in / Sign up

Export Citation Format

Share Document