[Optical and scanning electron microscopic observation of a novel small-caliber vascular graft in canine models].

Objective: To observe the histopathological changes of a novel small-caliber vascular graft after implantation in canine theca interna under scanning electron microscope.

Method: A 3 cm segment of the vascular graft (diameter of 4 mm) was implanted in an end-to-end fashion to bridge the severed carotid artery in 19 healthy dogs. Color Doppler sonography was performed 2 weeks after the operation to observe the patency rate of artificial blood vessel. At 1, 8, 12 and 24 week postimplantation, the arteries (4, 4, 6 and 5, respectively) were collected for optical and scanning electron microscopies after angiography to observe the patency of the arteries.

Results: Of the total of 19 arteries, occlusion occurred in 1 at 12 weeks and 1 at 24 weeks. Optical and electron microscopies showed that 1 week after implantation, slight fibroplasias and formation of red thrombus could be seen at the vascular anastomosis without endothelial cell lining. At 8 weeks, the host tissue grew into the lumen of the graft through the pores to form uniform neointima consisting of plenty of collagen fibers, but still without endothelial cells. At 12 weeks, discontinuous endothelial cells were seen to grow on the surface of the neointima. In the middle segment of the vascular graft, immature endothelial cells were found to grow in clusters. The structure of the neointima was loose in comparison with that at the anastomosis, with occasional inflammation cells. Twenty-four weeks after grafting, endothelial cells grew over the entire inner wall of the patent graft, and the surface of the neointima at the anastomosis was lined with continuous endothelial cells.

Conclusion: The vascular graft can be useful for reconstruction of canine carotid artery defect and achieves good endothelialization 24 weeks after implantation.