Objectives: The aim of this study was to analyze the cellular sources for the neointima and the cell type that is lining the lumen in artificial grafts implanted in pigs.
Materials and methods: We used polytetrafluoroethylene grafts as bypasses from the common to the external iliac arteries. The animals were sacrificed after 1, 4, 7, 14, 21, 30, 60 and 90 days. Morphological, immunohistochemical and electron microscope assessments were made.
Results: After 7 days a circumferential neoadventitia was formed. At day 14 isolated cellular islets of proliferating cells were observed on the luminal side of the graft without connection to the neoadventitia or the adjacent arteries. In the anastomotic regions at day 14 we observed an isolated neointima in contact with the adjacent artery. The cells lining the lumen had characteristics of both smooth muscle cells and endothelial cells.
Conclusions: Our study suggests that in artificial porcine grafts, the perivascular tissue, the blood and the adjacent artery contribute to the formation of the neointima. The luminal surface is covered by a hybrid cell with both smooth muscle cell and endothelial cell properties.