Cells in pseudointimal hyperplasia is migrated from extravascular space

The aim of this study was to investigate the origin of the pseudointima (PI) formed in polytetrafluoroethylene (PTFE) tube grafts after implantation into the inferior vena cava (IVC) of rabbits.

A segment of the IVC of rabbits was replaced by PTFE tube graft (3 cm long, 3 mm inner diameter, 30 microns internodal distance, 0.3 mm thickness). The experimental group was divided into two groups as follows: (Group A) non-wrapped, (Group B) wrapped the outer wall of PTFE with impermeable vinyl.

Grafts were harvested at three weeks after implantation and subjected to the following studies: patency, ultrastructural studies by light microscopy (LM) and immunostaining, scanning and transmission electron microscopy (SEM & TEM). The grafts were patient but the lumen of the control group was narrowed by PI. LM and immunostaining studies revealed the presence of thick PI composed of spindle-type cells in Group A, bust almost no PI in Group B. Only few erythrocytes, macrophage and protein-fibrin matrix was found in Group B. Endothelial like cell coverage, judged by SEM, was observed in only Group A. Only some macrophages and platelets were shown in the graft surface in Group B. TEM of PI revealed the presence of VSMCs, myofibroblasts and outer surface of grafts revealed the presence of myofibroblast in Group A.

The formation of PI suppressed by blocking the cellular migration from perigraft space suggest that PI was mainly originated by myofibroblast located in the perigraft space.