Age dependency of neointima formation on vascular prostheses in dogs

Neointima formed quickly on vascular prostheses implanted in young dogs but not in aged dogs. Previously, we found that impeding neointima formation o n vascular prostheses occurred more frequently in aged animals. From these observations, we hypothesized that neointima formation was age-dependent in dogs. To test the hypothesis, 26 fabric Dacron vascular prostheses were an alyzed. Half of them were retrieved from aged dogs (more than 13 years old) while the other half were from young ones (less than 1 year old). The graf ts were harvested at 8 weeks and 3 months after implantation. The graft sur faces were photographed and analyzed by computer for the ratio of the areas with and without thrombus. Light and scanning electron microscopic observa tion revealed that most of the thrombus-free areas were lined with endothel ial cells. Then the endothelialized areas were calculated. Using data obtai ned from macroscopic, light microscopic, and scanning electron microscopic observations, the arithmetic means were calculated as the degree of neointi ma formation. In young animals, the degrees at 8 weeks and at 3 months were 89.1 +/- 8.5% (mean +/- SD) and 95.7 +/- 3.3%, respectively. In old animal s, they were 27.9 +/- 5.9% and 31.5 +/- 6.8%, respectively. From these resu lts, we concluded that neointima formation was age-dependent in dogs.