Site-directed neovessel formation in vivo.

Angiogenesis is an important component of organogenesis and wound repair and occurs during the pathology of oncogenesis, atherogenesis, and other disease processes. Thus, it is important to understand the physiological mechanisms that control neovascularization, especially with methods that permit the molecular dissection of the phenomenon in vivo. Heparin-binding growth factor-1 was shown to bind to collagen type I and type IV. When complexed with gelatin, heparin-binding growth factor-1 can induce neovascularization at polypeptide concentrations that are consistent with the biological activity of the mitogen in vitro. The adsorption strategy induces rapid blood vessel formation at and between organ- and tissue-specific sites and permits recovery of the site-specific implant for examination and manipulation by molecular methods.

Antithrombotic and bleeding effects of a low molecular weight heparin fraction.

Low molecular weight (LMW) heparin prevents venous thrombosis by potentiating the inhibition of coagulation factor Xa. Heparin, however, has other biological properties whose role in the prevention of thrombosis is still unknown. The aim of our study was to compare the antithrombotic activity of a LMW heparin and its parent molecule in an attempt to understand better the mechanism and structural requirements for heparin's antithrombotic effect. We studied a preparation of an unfractionated pig mucosal heparin pure by any accepted criteria (electrophoresis in various systems, conductimetric titration and NMR spectra) and a LMW heparin fraction obtained from the former by fractional precipitation with ethanol. Both heparins completely prevented thrombus formation in an experimental model of stasis-induced venous thrombosis in rats. When administered intravenously to rats, the unfractionated heparin had an ex vivo anti-Xa/APTT ratio of 1.67, versus 6.60 of the LMW heparin fraction. Unexpectedly, both heparins induced a significant prolongation of tail bleeding time, performed by two different techniques, the "transection" (mostly exploring blood clotting) and the "template" (exploring the platelet/vessel wall interactions). This study suggests that, beside anticoagulation, other effects may play a role in both the antithrombotic and haemorrhagic effects of some heparins and LMW heparin fractions.

"Supersulfated" heparin fragments, a new type of low-molecular weight heparin. Physico-chemical and pharmacological properties.

A new type of low-molecular-weight heparin (ss-LMW-H) was prepared (by controlled depolymerization and concurrent sulfation of heparin with a mixture of sulfuric and chlorosulfonic acid), to test the influence of extra-sulfate groups on biological properties of heparin fragments. The fragments had an average molecular weight ranging from 5000 to 10,000, a sulfate-to-carboxyl molar ratio of 2.8-3.1, and electrophoretic mobilities and NMR spectra distinctly different from those of the parent heparins. Depolymerization with oversulfation reduced the anticoagulant activity of heparin (ex vivo, in rats) much more than depolymerization alone, to about 10% of the original APTT and 25-30% of the original a.Xa units. By contrast, the antithrombotic activity (venous stasis model, in rats) was still comparable to that of heparin, and bleeding times were not significantly increased. The lipasemic (lipoprotein-lipase-releasing) activity of ss-LMW-H fragments was more than twice that of heparin. Results are discussed in terms of contribution of charge-density effects to different activities and to different mechanisms for the same activity of heparin.