Cholesterol-Modified Polyurethane Valve Cusps Demonstrate Blood Outgrowth Endothelial Cell Adhesion Post-Seeding In Vitro and In Vivo

doi:10.1016/j.athoracsur.2005.07.061

The Annals of Thoracic Surgery

Volume 81, Issue 1, January 2006, Pages 47-55

https://doi.org/10.1016/j.athoracsur.2005.07.061 Get rights and content

Background

The clinical and experimental use of polyurethane heart valve prostheses has been compromised by thrombosis and calcified thrombus. This is caused in part by the lack of an intact endothelium on these implant surfaces. We hypothesize that endothelial seeding of a polyurethane heart valve leaflet with autologous sheep blood outgrowth endothelial cells (BOECs) could be achieved with cholesterol-modified polyurethane (PU-Chol) to promote BOEC adhesion, thereby resulting in an intact, shear-resistant endothelium that would promote resistance to thrombosis.

Methods

Cholesterol-derivatized polyurethane was formulated by bromoalkylation of the urethane nitrogens followed by reactive attachment of mercaptocholesterol. In vitro shear flow studies were carried out comparing BOEC retention on control surfaces versus PU-Chol using forces comparable to those observed in vivo with cardiac valves (75 dyne/cm²). Autologous sheep BOECs were seeded onto PU-Chol before pulmonary leaflet replacement surgery under cardiopulmonary bypass. Studies were terminated at 30 and 90 days followed by retrieval analyses.

Results

Blood outgrowth endothelial cell seeding of PU-Chol surfaces resulted in an endothelial monolayer that was positive for von Willebrand factor. Polyurethane-cholesterol demonstrated significantly greater BOEC adhesion under 75 dyne/cm² shear force in vitro than control polyurethane (75.3% ± 12.3% versus 5.8% ± 3.9%, respectively; p < 0.001). Sheep pulmonary cusp replacements demonstrated retention of seeded BOECs on PU-Chol leaflets with no significant differences in the extent of cellular density comparing unimplanted specimens with explants. Control explants (nonseeded PU-Chol and nonseeded polyurethane) demonstrated no evidence of endothelial recruitment.

Conclusions

Polyurethane-cholesterol represents a polyurethane formulation with very high adhesive properties for BOECs under heart valve level shear forces both in vitro and in vivo.

Section snippets

Polyurethane and Polyurethane-Cholesterol Synthesis

The PU used in these studies, Tecothane TT1074A (Thermedics, Waltham, MA), a polyether polyurethane, was used either unmodified in dimethylacetamide solution, or covalently modified with cholesterol (Chol) by means of bromoalkylation to form PU-Chol as previously published (11) and then dissolved in dimethylacetamide. Polyurethane and PU-Chol dissolved in dimethylacetamide were solvent cast as films as previously described [11]. These films were routinely between 159 and 220 μm thick [11], and

Cholesterol-Modified Polyurethane: Biomechanical Results

Uniaxial stress–strain experiments revealed no significant differences in elastic behaviors in comparisons between PU and PU-Chol (Table 1,Fig 2). The data indicate that between 50% and 200% deformation there were no significant differences noted in the force required to achieve these uniaxial dimensional changes. These deformations are far beyond those that would occur with heart valve leaflet biomechanics under physiologic conditions, and thus indicate that the cholesterol modification does

Comment

The results of these investigations, both in vitro and in vivo, strongly support the hypothesis that PU-Chol has significantly greater BOEC adhesion properties than unmodified PU. The mechanisms responsible for this may depend on a number of factors, including our earlier observations that PU-Chol was markedly different than unmodified PU with regard to a number of material variables, including increased surface energy, a relatively smoother surface by atomic force microscopy results, and a

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Original articleCardiovascularCholesterol-Modified Polyurethane Valve Cusps Demonstrate Blood Outgrowth Endothelial Cell Adhesion Post-Seeding In Vitro and In Vivo

Background

Methods

Results

Conclusions

Section snippets

Polyurethane and Polyurethane-Cholesterol Synthesis

Cholesterol-Modified Polyurethane: Biomechanical Results

Comment

Ann Thorac Surg

Biomaterials

J Thorac Cardiovasc Surg

Blood

FEBS Lett

Trends Cell Biol

Biomaterials

Thoratec VAD system as a bridge to heart transplantation

J Heart Transplant

Biostability of Thoralon left ventricular assist device blood pumping sacs after long-term clinical use

ASAIO J

In vivo and in vitro stability of modified poly(urethaneurea) blood sacs

J Biomater Appl

In vivo evaluation of an intrathoracic ventricular assist device

ASAIO J

Performance of materials in vascular prosthetic devicesheart valves

Bull NY Acad Med

Original article
Cardiovascular
Cholesterol-Modified Polyurethane Valve Cusps Demonstrate Blood Outgrowth Endothelial Cell Adhesion Post-Seeding In Vitro and In Vivo