Heparin coating of small-caliber decellularized xenografts reduces macrophage infiltration and intimal hyperplasia

Small-caliber decellularized xenografts with surface heparin coating are known to reduce in vivo thrombogenicity. This study was performed to examine whether heparin coating on the small-caliber decellularized xenografts would reduce macrophage infiltration and intimal hyperplasia. In a rabbit model of bilateral carotid implantation, each of the animals (n = 18) received a heparin-coated decellularized xenograft from a canine carotid artery on one side and a nonheparin-coated one on the other side. These experiments were terminated respectively at 1 week (n = 6), 3 weeks (n = 6), and 12 weeks (n = 6). Results showed that, compared with the nonheparin-coated grafts, the heparin-coated grafts had significantly less macrophage infiltration 1 week after implantation, identified by the mouse antirabbit macrophage antibody (RAM11)-positive cells on the vascular wall, covering all the proximal, middle, and distal parts of the grafts (P < 0.01). Moreover, the heparin-coated grafts also showed less deposition of proliferation cell nuclear antigen (PCNA)-positive cells on the vascular wall, indicating less cell proliferation, which was significant not only at 1 week (P < 0.01) but also at 12 weeks (P < 0.01). Intimal hyperplasia, measured by the intimal : media (I : M) ratio, was found similar in both groups at 1 and 3 weeks. However, the I : M ratio was significantly lower in the heparin-coated group than in the nonheparin-coated group at 12 weeks, especially in the proximal anastomosis area (0.76 +/- 0.12 vs. 0.345 +/- 0.06, P < 0.01). Heparin coating of small-caliber decellularized xenografts is associated with an early reduction of macrophage infiltration and intimal hyperplasia in a rabbit model of bilateral carotid artery implantation for 12 weeks. Thus, heparin coating appears to deliver not only the antithrombogeneity but also the antiproliferative property for small-caliber decellularized xenografts.

Implantation of decellularized small-caliber vascular xenografts with and without surface heparin treatment

Heparin treatment of decellularized xenografts has been reported to reduce graft thrombogenicity. However, little is known about the in vivo comparison of heparin-treated with non-heparin-treated xenografts, especially for small-caliber vascular implants. We implanted either a heparin-treated or a non-heparin-treated canine carotid artery as bilateral carotid xenograft in rabbits (n = 24). Small-caliber xenografts (3 approximately 4 mm) were decellularized by enzymatic and detergent extraction and were further covalently linked with heparin. During implantation, thrombosis rate was 4% in the heparin-treated xenografts and 25% in the non-heparin-treated xenografts after 3 weeks (P < 0.05). After 6 months, it was 8 versus 58%, respectively (P < 0.01). Both heparin-treated and non-heparin-treated xenografts harvested at the end of 3 and 6 months showed a satisfactory cellular reconstruction of either smooth muscle cells or endothelial cells. These results indicate that heparin treatment of the small-caliber decellularized xenograft reduces the in vivo thrombogenicity. Both heparin-treated and non-heparin-treated xenografts seem to undergo a similar cellular remodeling process up to 6 months.

Phosphorylcholine coating of ePTFE reduces platelet deposition and neointimal hyperplasia in arteriovenous grafts

In an attempt to reduce platelet deposition and inhibit neointimal hyperplasia, we evaluated the effect of coating expanded polytetrafluoroethylene (ePTFE) grafts with phosphorylcholine (PC), a lipid found in animal cell membranes, in a dog model of femoral arteriovenous (AV) grafts. Eight mongrel dogs underwent placement of a PC-coated femoral AV graft on one side and an untreated control graft on the contralateral side. Platelet deposition was measured by autologous 111Indium-labeling and scintillation camera imaging analysis. Platelet deposition on the PC-coated grafts at 30 and 90 min. was 9.32 +/- 4.35 x 10(9) and 10.00 +/- 4.38 x 10(9), respectively, as compared with 10.26 +/- 4.36 x 10(9) and 11.64 +/- 5.08 x 10(9) platelet deposition on control grafts (P < 0.05). All grafts were patent at 4 weeks. There was a significant reduction of neointimal area at both arterial (0.07 +/- 0.05 mm2) and venous (0. 18 +/- 0.09 mm2) anastomoses in the treated grafts as compared with arterial (0.15 +/- 0.05 mm2) and venous (0.43 +/- 0.22 mm2) anastomoses in the control grafts (P < 0.05). In addition, neointimal cell proliferation assayed by bromodeoxyuridine (BrdU) incorporation was reduced in both arterial (2.05 +/- 0.81%) and venous (3.25 +/- 0.17%) anastomoses of treated grafts compared with arterial (3.12 +/- 1.23%) and venous (5.36 +/- 1.18%) anastomoses of control grafts (P < 0.05). These data demonstrated that PC coating of ePTFE grafts significantly reduced platelet deposition, anastomotic neointimal hyperplasia, and neointimal cell proliferation in a dog model of AV grafts. This may represent a new strategy for prolonging hemodialysis graft patency.