Normal levels of anticoagulant heparan sulfate are not essential for normal hemostasis

Abstract

Endothelial cell production of anticoagulant heparan sulfate (HSact) is controlled by the Hs3st1 gene, which encodes the rate-limiting enzyme heparan sulfate 3-O-sulfotransferase-1 (3-OST-1). In vitro, HSact dramatically enhances the neutralization of coagulation proteases by antithrombin. The in vivo role of HSact was evaluated by generating Hs3st1–/– knockout mice. Hs3st1–/– animals were devoid of 3-OST-1 enzyme activity in plasma and tissue extracts. Nulls showed dramatic reductions in tissue levels of HSact but maintained wild-type levels of tissue fibrin accumulation under both normoxic and hypoxic conditions. Given that vascular HSact predominantly occurs in the subendothelial matrix, mice were subjected to a carotid artery injury assay in which ferric chloride administration induces de-endothelialization and occlusive thrombosis. Hs3st1–/– and Hs3st1+/+ mice yielded indistinguishable occlusion times and comparable levels of thrombin•antithrombin complexes. Thus, Hs3st1–/– mice did not show an obvious procoagulant phenotype. Instead, Hs3st1–/– mice exhibited genetic background–specific lethality and intrauterine growth retardation, without evidence of a gross coagulopathy. Our results demonstrate that the 3-OST-1 enzyme produces the majority of tissue HSact. Surprisingly, this bulk of HSact is not essential for normal hemostasis in mice. Instead, 3-OST-1–deficient mice exhibited unanticipated phenotypes suggesting that HSact or additional 3-OST-1–derived structures may serve alternate biologic roles

Internalization and degradation of heparin is not required for stimulus of heparan sulfate proteoglycan synthesis

“…Heparan sulfate proteoglycans are ubiquitous components of all tissue‐organized animal life forms (Dietrich et al, 1998; Bernfield et al, 1999; Nader et al, 2004) and are present at the cell surface and associated with the ECM of mammalian cells in culture (Dietrich and De Oca, 1970; Bernfield et al, 1999; Medeiros et al, 2000; Weitz, 2003; Whitelock and Iozzo, 2005; Gallagher, 2006; Taylor and Gallo, 2006; Imberty et al, 2007). Endothelial cells express an HSPG which have an antithrombotic action (Damus et al, 1973; Colburn and Buonassisi, 1982; Marcum and Rosenberg, 1989; HajMohammadi et al, 2003; Weitz, 2003; Liu and Pedersen, 2007). By using an antibody against heparan sulfate, it was confirmed that this effect was at least in part heparan sulfate‐dependent (Colburn and Buonassisi, 1982).…”

“…Among the compounds present on the cell surface and in the extracellular matrix of endothelial cells are heparan sulfate proteoglycans (HSPG). This heparan sulfate has been shown to possess antithrombotic activity in different models (Colburn and Buonassisi, 1982; Marcum and Rosenberg, 1989; Shimada et al, 1991; Shibata et al, 1994; HajMohammadi et al, 2003; Weitz, 2003; Rocha et al, 2005; Liu and Pedersen, 2007).…”

Heparan sulfate: Antithrombotic or not?

“…Despite reduced heparan sulfate activity, the knockouts have a normal phenotype and have the same amount of fibrin deposition in their tissues as wild-type mice under normoxic and hypoxic conditions. Because most of the heparan sulfate is found on the subendothelial matrix, HajMohammadi and colleagues (15) used topical ferric chloride to induce endothelial injury in the carotid arteries, thereby exposing the subendothelium. Despite the reduction in heparan sulfate activity, 3-OST-1 knockout mice failed to show accelerated thrombosis in the injured arteries compared with their wild-type counterparts.…”

The role of heparan sulphate in development: the ectodermal story

“…) and Hs3st1 –/– (HajMohammadi et al . ), and for HS GlcUA C5 epimerase Hsepi −/− (Li et al . ) have also been generated.…”