Characterization of neointimal growth for vascular grafts implanted within a baboon model

Within a baboon model (papio cynocephalus) this study investigated the healing properties of three different vascular grafts harvested at one month: reversed autogenous artery, 30 μm ePTFE, 60 μm ePTFE. With H&E staining, we identified minimal neointima within the reversed autogenous arteries. While the 30 μm and the 60 μm ePTFE showed pannus, only the 60 μm ePTFE demonstrated significant intimal thickness at the graft´s midline, characteristic of transmural ingrowth. At the proximal and distal ends, the BRDU index for the top 10% of neointimal area (closest to the flow surface) and lower 90% of neointimal area mirrored each other. At we moved along the axial length of the graft, the BRDU index for the top 10% of neointimal area steadily increased, reaching a maximum at the neointima´s leading edge with a predominance of endothelial cells. Conversely, for the lower 90% of neointimal area, the BRDU index progressively declined to a minimum. These results suggest that localization of proliferating cells within the leading edge´s flow surface strongly influences neointimal progression and allows for continual pseudointimal formation at the already established rate of 0.2 mm/day.