Patch augmentation of the pulmonary artery with bioabsorbable polymers andautologous cell seeding

Objective: In recent years bioabsorbable synthetic or biologic materials ha ve been used to augment the pulmonary artery or the right ventricular outfl ow tract. However, each of these polymers has one or more shortcomings. Non e of these patch materials has been seeded with cells. Thus, we have tested a fast-absorbing biopolymer, poly-4-hydroxybutyric acid, with autologous c ell seeding for patch augmentation of the pulmonary artery in a juvenile sh eep model. Methods: Vascular cells were isolated from ovine peripheral veins. (n = 6). Bioabsorbable porous poly-4-hydroxybutyric acid patches (porosity > 95%) w ere seeded on 3 consecutive days with a mixed vascular cell suspension (21. 3 +/- 1.3 x 10(6) cells), Forty-five (+/- 2) days after the vessel harvest, 1 unseeded and 6 autologously seeded control patches were implanted into t he proximal pulmonary artery. The animals received no postoperative anticoa gulation. Follow-up was performed with echocardiography after 1 week and be fore explantation after 1, 7, and 24 weeks (2 animals each) for the seeded control patches and after 20 weeks for the nonseeded control patch. Results: All animals survived the procedure, Postoperative echocardiography of the seeded patches demonstrated a smooth surface without dilatation or stenosis. Macroscopic appearance showed a smooth internal surface with incr easing tissue formation. Histology at 169 days demonstrated a near-complete resorption of the polymer and formation of organized and functional tissue . Biochemical assays revealed increasing cellular and extracellular matrix contents. The control patch showed a slight bulging, indicating a beginning dilatation. Conclusion: This experiment showed that poly-4-hydroxybutyric acid is a fea sible patch material in the pulmonary circulation.