Smooth muscle cell seeding in biodegradable grafts in rats: a new method to enhance the process of arterial wall regeneration

In this study a smooth muscle cell seeding technique was developed and evaluated in biodegradable vascular grafts in rats. Cultured smooth muscle cells (3.5 to 5 X 10(6) in 0.1 ml whole blood) were seeded by means of a one-step preclotting technique in microporous, compliant, biodegradable vascular grafts (internal diameter 1.3 mm, length 1 cm; n = 16). Four seeded grafts as well as four nonseeded preclotted control grafts were histologically evaluated immediately after seeding and on preclotting; the other seeded grafts (n = 12) as well as nonseeded preclotted control grafts (n = 12) were implanted into the abdominal aorta of rats and were evaluated after 2 hours (n = 4), 2 days (n = 4), and 1 week (n = 4) with regard to the process of arterial wall regeneration. All grafts, except one seeded graft harvested at 1 week, were patent. All nonseeded control grafts showed no (at 2 hours and at 2 days) or limited (at 1 week) smooth muscle cell ingrowth. Of the 11 patent seeded grafts three also showed poor or limited neomedia development, probably because of improper preclotting. However, eight of the 11 patent seeded grafts showed fast and uniform noemedia development (clearly discernible at 2 days). Moreover, in two patent 1-week seeded grafts there were neomedia comparable in thickness and architecture (circularly arranged smooth muscle cells) to that of normal rat media, and a neointima had already lined 30% to 40% of the lumen. These results clearly demonstrate that smooth muscle cell seeding in biodegradable grafts is feasible and indicate that this seeding can enhance the process of arterial wall regeneration in these grafts.