Seeding of vascular smooth muscle cells confers enhanced pharmacological responses to tissue engineered blood vessels in a large animal model

Abstract

These studies evaluated the impact of VSM cell seeding and bioreactor preconditioning on the phenotype and function of tissue engineered blood vessels (TEBV) following 4 months of implantation in vivo. Autologous endothelial progenitor cells (EPC) and vascular smooth muscles cells (VSM) were collected from female sheep and differentiated into mature EC and VSMC in culture. Five TEBV were seeded with both endothelial cells (EC) and VSM, and another 5 grafts seeded with EC only. All grafts were preconditioned to pulsatile flow and physiologic pressure for 2 weeks in a bioreactor. TEBV were implanted in female sheep as an interposition graft of the carotid or femoral artery. The patency rate was 100%, with no aneursymal degeneration or anasomotic stenosis. Vessel wall cells of dual‐seeded grafts had increased immuno‐positive staining to α‐actin (p=0.05) and smooth muscle myosin (p=0.05), as well as increased overall cellularity (p=0.01), when compared to EC only‐seeded grafts. Significantly increased steady‐state maximal contractile responses were observed in the dual‐seeded grafts in response to stimulation with phenylephrine (PE, 10 μM; p=0.01) and 5‐Hydroxytryptamine (5‐HT;10 μM; p=0.01), but not KCl. Maximal contractions to PE and 5‐HT were ≈20% and 15%, respectively, of that observed for the native vessel, respectively. This work represents an important first step toward creation of more native‐like TEBV.