The contraction and relaxation of VSM (vascular smooth muscle) are responsible for the maintenance of vascular tone, which is a major determinant of blood pressure. However, the molecular events leading to the contraction and relaxation of VSM are poorly understood. The development of three-dimensional bioengineered tissues provides an opportunity to investigate the molecular events controlling vascular tone in vitro. In the present study we used fibrin-gel casting to bioengineer functional VSM strips from primary human aortic VSM cells. Our bioengineered VSM strips are functionally similar to VSM in vivo and remained viable in culture for up to 5 weeks. VSM strips demonstrate spontaneous basal tone and can generate an active force (contraction) of up to 85.2 microN on stimulation with phenylephrine. Bioengineered VSM strips exhibited Ca(2+)-dependent contraction and calcium-independent relaxation. The development of functional bioengineered VSM tissue provides a new in vitro model system that can be used to investigate the molecular events controlling vascular tone.