Enhancement of capillary and cellular ingrowth in ePTFE implants with a proangiogenic recombinant construct derived from fibronectin

Abstract

Based on our discoveries of a unique, synergistic interplay between vascular endothelial growth factor (VEGF) and specific domains of the matrix protein fibronectin (FN), we used recombinant technology to create a new protein construct derived from the cell-binding and VEGF-binding domains of FN. We wished to test the hypothesis that this prototype recombinant FN (rFN) protein would enhance cellular and capillary ingrowth in vivo into expanded polytetrafluoroethylene (ePTFE) implants. ePTFE disks of high porosity (60 micron internodal distance) were embedded with fibrin gel and heparin, with/without mixtures of VEGF and rFN and were implanted subcutaneously in rats. Control implants embedded with fibrin glue and heparin alone showed an average of 8.5% (±0.51% standard error mean (SEM)) cellular ingrowth. The addition of either VEGF or rFN caused a modest but significant increase in cellular ingrowth (12.7 ± 1% and 11.8 ± 0.98%, respectively, p < 0.004). However, the combination of rFN/VEGF/heparin dramatically increased cellular ingrowth (27.6 ± 1.62%, p < 0.001), compared with all other treatments. Quantification of capillary ingrowth yielded the same pattern. These results suggest that the incorporation of such biological modulators into cardiovascular implants could offer new strategies for the design of a readymade small diameter prosthetic graft with enhanced capacity for neovascularization and endothelialization.

Endothelialization of an ePTFE vessel prosthesis modified with an antithrombogenic fibrin/heparin coating enriched with bound growth factors

“…Several other coating techniques have been developed to cover ePTFE vascular gras with brin, such as the incubation of a gra with brin and thrombin substances, 27 the gelation of brin glue mixtures on ePTFE gras in a vacuum, 36 or the gelation of a brin-thrombin mixture under pressure in occluded gras with the additional removal of excess brin on a surface. 37,38 Unlike other techniques, our method makes it possible to reproducibly coat various types of surfaces, including the inner surface of porous materials, with brin meshes of thickness adjustable from nanometre to micrometre scale without the formation of a bulk brin gel.…”

Dual biofunctional polymer modifications to address endothelialization and smooth muscle cell integration of ePTFE vascular grafts

“…For example, the development of a system that applies a pressure gradient across the graft wall could force or pull hydrogel precursor solution into the pores. Similar mechanisms have been used by others to impregnate ePTFE interstices with fibrin glue . Future work to develop a hydrogel‐loaded ePTFE construct that is more amenable to in vitro cellular analyses could result in an effective in vitro model to study SMC migration, proliferation, and phenotype modulation within ePTFE graft walls.…”

“…Similar mechanisms have been used by others to impregnate ePTFE interstices with fibrin glue. 10,35 Future work to develop a hydrogel-loaded ePTFE construct that is more amenable to in vitro cellular analyses could result in an effective in vitro model to study SMC migration, proliferation, and phenotype modulation within ePTFE graft walls.…”

“…For example, Rotmans and colleagues successfully captured endothelial progenitor cells on ePTFE grafts by immobilizing anti‐CD34 antibodies to the surface . Other groups have used laminin, extracellular matrix (ECM) protein, or cell‐adhesive peptide modification of ePTFE to improve endothelialization . While these strategies have shown some success in adhering and retaining ECs to an ePTFE graft surface, they do not directly address the second issue of IH, and in some cases even enhance intimal thickening …”

“…6 Other groups have used laminin, extracellular matrix (ECM) protein, or cell-adhesive peptide modification of ePTFE to improve endothelialization. [7][8][9][10][11] While these strategies have shown some success in adhering and retaining ECs to an ePTFE graft surface, they do not directly address the second issue of IH, and in some cases even enhance intimal thickening. 6,7 Intimal hyperplasia in ePTFE grafts develops over the course of a few weeks to 2 years, usually at the anastomotic sites.…”