Endothelialization of Crosslinked Albumin-heparin Gels

Abstract

SummaryCrosslinked gels of albumin as well as heparinized albumin gels, potential sealants of prosthetic vascular grafts, were studied with regard to in vitro stability, binding of basic fibroblast growth factor (bFGF) and cellular interactions. A small percentage of the heparin present in these gels, was released during storage in SDS solution. During storage in cell culture medium at 37° C, heparin release was 21-25 percent. Release of albumin did not occur.Human umbilical vein endothelial cells (HUVECs) rapidly adhered and subsequently spread on (heparinized) albumin gels, but proliferation was only observed if heparin was present in the gel.Binding of 125I-bFGF to heparinized albumin gel was 35 percent higher than to non-heparinized albumin gel. Growth of HUVECs occurred only on heparinized albumin gel loaded with bFGF and not on bFGF-loaded albumin gel.The number of platelets deposited under stationary conditions onto heparinized albumin gel was about twice the number found on nonheparinized albumin gel. Seeding of HUVECs on heparinized albumin gel, significantly reduced the number of platelets adhering to this surface. Moreover, no spreading of platelets was observed on substrates seeded with HUVECs.It can be concluded that crosslinked gels of albumin to which heparin is immobilized, are candidate sealants for prosthetic vascular grafts and suitable substrates for endothelial cell seeding.

The influence of biomaterials on endothelial cell thrombogenicity

“…These studies suggested overall that EC exhibit a relatively non-thrombogenic phenotype on a number of common polymer substrates with or without ECM coatings. Limited platelet adhesion and activation (serotonin release and spreading) occurs on non-stimulated HUVEC cultured on TCPS [175][176][177], fibrillar collagen [178], crosslinked albumin heparin gels with [179] and without heparin [180], thermanox coverslips [181] and fibronectin coated polyethylene [182]. Similar trends were also observed for BAEC cultured on TCPS [183,184], and for sheep pulmonary artery EC cultured on gelatinized polycarbonate or TCPS [185].…”

“…In a different kind of assay measuring fibrin deposition from blood plasma, canine aortic EC on both TCPS and microporous polymer (fluropore filter) with and without a fibronectin coating showed reduced fibrin deposition, that was dependent on the proliferative state of the cells [191]. Moreover in pre-confluent EC cultures platelet adhesion has been observed not just in regions of the exposed underlying matrix but also on the non-confluent EC themselves [176,178,179,183,185] suggesting that the EC are thrombogenic at non-confluent densities.…”

The modulation of platelet and endothelial cell adhesion to vascular graft materials by perlecan

“…Reduced platelet adhesion has been shown on ePTFE coated with laminin compared to fibronectin or plasma [17]. Heparin has also been investigated for graft applications as it inhibits the conversion of prothrombin to thrombin [18] which results in reduced platelet adhesion, however the long-term bioactivity of these coatings is an issue [19].…”

“…Investigations on the role of HS proteoglycans in the promotion of endothelial adhesion and proliferation on vascular graft materials are limited [18], while the benefits of exogenous addition of growth factors are well recognised. In this study, an ovine carotid implantation model was used to determine the extent of endothelialisation and platelet adhesion to endothelial cell-derived perlecan coated ePTFE grafts compared to uncoated controls.…”

Procoagulant phenotype of endothelial cells after coculture with biomaterial‐treated blood cells

“…To improve the functionality of vascular grafts and to better understand the maintenance of the anticoagulant/antiinflammatory cell phenotype, a better understanding of EC/blood/biomaterial interactions is needed. Many studies have focused on blood/biomaterial interactions3, 19–21 and biomaterial/EC interactions4, 22–26 but few on EC/blood/biomaterial interactions. It has been observed that activation of biomaterial adherent PL or leukocytes depends on the material chemistry19; however, leukocyte or PL activation also occurs by transient biomaterial contact, inducing leukocyte and PL microparticle formation,3, 19, 20 PL/leukocyte aggregates formation,19 upregulation of cell adhesion molecules (CAMs),20 and procoagulant activity,19 which is independent of biomaterial surface chemistry 19.…”