Porcine aortic wall flexibility. Fresh vs Denacol fixed vs glutaraldehyde fixed.

It has been postulated that, in theory, stentless bioprosthetic heart valves provide improved hemodynamics and durability over their stented counterparts. A number of glutaraldehyde modified porcine stentless valves are currently either on the market or in clinical trials. Polyepoxy compound as an alternative cross-linking reagent to glutaraldehyde for bioprostheses has been reported to mitigate calcification. The present study was to investigate the effect of the fixation methods on porcine aortic wall flexibility. Ring specimens were selected from three groups of porcine roots: fresh, low pressure glutaraldehyde fixed, and low pressure Denacol (polyepoxy compound) fixed. Pulled between two rods on a tensile tester, a ring specimen's load-deformation relationship was recorded and analyzed to numerically compute the tissue modulus at low strains. The results showed that the Young's moduli were 0.113 +/- 0.036, 0.494 +/- 0.113, and 1.320 +/- 0.292 MPa (mean +/- SD, n = 10) for the fresh, Denacol fixed, and glutaraldehyde fixed aortic walls, respectively. The Denacol fixed aortic wall was more flexible than the glutaraldehyde fixed one. It was also found that the Denacol fixed aortic wall maintained most of the natural residual strains, while the glutaraldehyde fixed aortic wall did not.

Accelerated healing of cardiovascular textiles promoted by an RGD peptide.

Polytetrafluoroethylene (PTFE) and polyethylene terephthalate (Dacron polyester) fabrics are used extensively in cardiovascular devices, e.g. heart valve sewing cuffs and vascular prostheses. While devices containing these fabrics are generally successful, it is recognized that fabrics cause complications prior to tissue ingrowth due to their thrombogenic nature. A surface active synthetic peptide, called PepTite Coating (PepTite), which was modeled after the cell attachment domain of human fibronectin has been marketed as a biocompatible coating. This peptide stimulates cell attachment through the arginine-glycine-aspartic acid (RGD) sequence. Modification of medical implants with PepTite has been shown to promote ingrowth of surrounding cells into the material leading to better tissue integration, reduced inflammation and reduced fibrotic encapsulation. In this study, polyester and PTFE textiles were modified with PepTite. The effectiveness of this coating in enhancing wound healing was investigated in a simple vascular and cardiac valve model. Our results indicate that the RGD-containing peptide, PepTite, promoted the formation of an endothelial-like cell layer on both polyester and PTFE vascular patches in the dog model. PepTite was also found to promote the formation of a significantly thinner neointima (pannus) on polyester as compared to that on its uncoated control. These results were corroborated in the cardiac valve model in which a greater amount of thin pannus and less thrombus were seen on coated polyester sewing cuffs than on control uncoated cuffs. This research shows the promising tissue response to RGD coated textiles and the potential role of this peptide in material passivation via accelerated healing.

Enhanced strength of endothelial attachment on polyester elastomer and polytetrafluoroethylene graft surfaces with fibronectin substrate.

Successful development of a vascular prosthesis lined with endothelium may depend on the ability of the attached cells to resist shear forces after implantation. The purpose of this article is to describe a model for measurement of endothelial detachment caused by shear stress and to identify biomaterials that resist loss of attached cells as a result of shear stress. With human umbilical venous endothelium labeled with indium 111-oxine, cellular attachment to uncoated and fibronectin-coated polyester elastomer and expanded polytetrafluoroethylene (e-PTFE) graft surfaces was quantified after an 18-hour incubation. PTFE grafts prepared by immediate seeding were also studied. The relative strength of endothelial attachment was determined by the percentage of the original inoculum remaining after the seeded graft surfaces were subjected to a physiologic shear stress of 15 dynes/cm2 during in vitro perfusion. In polyester elastomer grafts, fibronectin did not significantly increase initial attachment but did increase the percentage of inoculum remaining after perfusion (92.1% vs. 39.74%, p = 0.001). A similar relationship existed between fibronectin-coated e-PTFE and immediately seeded e-PTFE preparations with 61.6% and 25.8%, respectively, of the inoculum remaining after perfusion (p = 0.001). Furthermore, the percentage of inoculum retained on fibronectin-coated polyester elastomer was significantly greater than on fibronectin-coated e-PTFE (p = 0.001). In comparing uncoated grafts, polyester elastomer had 39.7% of the inoculum retained after perfusion whereas only 1.8% was remaining on the e-PTFE grafts (p = 0.0001). We conclude that polyester elastomer permits better endothelial cell attachment than e-PTFE and that fibronectin coating enhances the strength of attachment to both graft materials.