The degree of porosity influences the release of growth factors by healing polytetrafluoroethylene (PTFE) grafts

Objectives:The aim of this study was to determine the influence of the degree of porosity on the release of growth factors (PDGF AA, PDGF BB, bFGF) by healing PTFE grafts.Design and setting:Laboratory animal study.Materials:1 cm long segments of non-reinforced PTFE grafts (30 microns fibril length, 2 mm internal diameter, 0.39 mm thick) were placed as an abdominal aortic interposition in Lewis rats. Fifteen grafts served as control (Group A; porous grafts); in eight rats (Group B; non porous grafts) the PTFE graft was completely wrapped by a non-porous plastic envelope. Animals were killed 4 weeks after surgery.Outcome measures:The release of PDGF AA, PDGF BB, and bFGF was assessed by Enzyme Linked Immunosorbent Assay (ELISA).Results:The release of PDGF AA, PDGF BB and bFGF was statistically higher in porous grafts. The only histological difference between the two groups was that porous PTFE grafts were invaded by many tufts of capillaries from the surrounding tissue, whereas this phenomenon was absent in non porous PTFE grafts.Conclusions:The degree of porosity influences the release of growth factors by healing PTFE grafts. This fact may have implication in the endothelisation of PTFE grafts and in myointimal hyperplasia formation as well