In vitro stimulation of human endothelial cells by derivatized dextrans.

Derivatized dextrans exert a stimulatory effect on the in vitro growth of human umbilical vein endothelial cells (HUVEC). Measurements of growth were monitored by [3H]thymidine uptake and cell numbers. Our results show that some derivatized dextrans at 4 micrograms/ml (88 nM) increase the [3H]thymidine incorporation, whereas starting dextran (40,000 Da), dextran sulfate, and carboxymethyl dextran have no effect. In addition, heparin under similar experimental conditions shows a slight inhibitory effect on the HUVEC growth. The stimulatory effect of derivatized dextrans was also found when HUVEC grew during 7 days in medium containing 2% fetal bovine serum. We also observed that derivatized dextrans had no effect on the mitogenic activity of acidic fibroblast growth factor, a mitogenic factor for several cell types including HUVEC. By assessment of [3H]thymidine uptake at 48 h without serum, we concluded that the exogenous growth factors were not involved in the proliferative activity of these components. The stimulatory effects are related to the chemical nature and the proportion of substituents on the synthetic polysaccharides. The data indicate that benzylamide sulfonated groups play a key role in the stimulation of HUVEC growth. Neither carboxyl nor sulfate groups alone exhibit this effect. Thus, the stimulatory capacity of dextran derivatives depends strongly on the respective ratios of the functional groups.

Biological and binding studies of acidic fibroblast growth factor in the presence of substituted dextran.

Heparin has been shown to interact with acidic fibroblast growth factor (aFGF) and to potentiate the biological activity of aFGF on fibroblastic cells. Water-soluble dextran substituted with methyl carboxylic benzylamine and sulfonate groups has been shown to mimic the effect of heparin in its anticoagulant and anticomplement activity. We have studied the effect of a dextran derivative named E (DDE), which had an anticoagulant activity equivalent to 0.5 IU heparin/mg, on the mitogenic activity of aFGF on Chinese hamster fibroblasts (CCL39). DDE interacts with aFGF in a comparable manner to heparin. We have shown that 20 micrograms of heparin or 400 micrograms of DDE added to 1 ml of culture medium has no effect on cell proliferation alone but potentiates the mitogenic activity of aFGF ten fold if aFGF is added at doses corresponding to half maximum stimulation (ED50). We have also studied the effect of various concentrations of heparin and DDE on the binding of 125I-aFGF on bovine brain membranes. Interestingly, the binding of 125I-aFGF increased three-fold as the concentration of heparin was increased up to 0.2 microgram/ml. At 1 microgram/ml of heparin, the amount of bound 125I-aFGF is comparable to that obtained in the absence of heparin. At higher concentrations, heparin displaces bound 125I-aFGF, and a 50% displacement is seen with 20 micrograms/ml of heparin. In the presence of DDE, no increase in 125I-aFGF binding is seen and a displacement is obtained with increasing doses. A possible explanation of these results may be the existence of specific receptors to heparin on the cellular membrane.(ABSTRACT TRUNCATED AT 250 WORDS)