Smooth muscle cells improve endothelial cell retention on polytetrafluoroethylene grafts in vivo

Objective: We investigated the influence of smooth muscle cells (SMC) on endothelial cell (EC) retention on polytetrafluoroethylene (PTFE) grafts and the effect of SMC seeding on intimal hyperplasia in vivo in a rabbit model. Methods. Fibronectin-coated PTFE grafts (4 mm diameter) were seeded with either EC alone, SMC alone, or SMC followed 24 hours later by EC. The grafts were connected to an extracorporal aortic shunt for I hour or were individually implanted for 1, 30, and 100 days into the infrarenal aorta as an end-to-side bypass graft. The number of retained cells was compared at 1 hour and at I day after implantation. Neointimal thickness was measured 30 and 100 days after implantation. Results. After 1-hour exposure to blood flow, EC retention rate was greater (P < .005) if seeded on top of SMC (98% +/- 2%; n = 8) versus being seeded alone (65 +/- 11%; n = 8). SMC retention rate was 95 +/- 5% (n = 8) when seeded alone. Similar cell retention was obtained I day after implantation. After 30-day implantation the neointima was thicker in grafts seeded with EC and SMC (282 +/- 136 mum; n = 3) than with EC only (52 +/- 45 mum; n = 3; P < .001). However, the neointimal thickness for dual-cell-seeded grafts (126 +/- 60 mum; n = 3) was not significantly different (P = .09) from EC-seeded grafts (79 +/- 48 mum; n = 3) after 100-day implantation. Conclusion: EC retention on PTFE grafts in vivo is improved if seeded over a layer of SMC. Further studies are needed to determine whether overlying EC modulate proliferation of underlying SMC.