Engineered tissues could form the basis for novel therapies for millions of patients who suffer from the loss of tissue or its function (1 ), and be used for in vitro studies of tissue development and normal and pathological function. One approach to tissue engineering involves seeding of a high density of uniformly distributed cells on three-dimensional (3D) polymeric scaffolds, and cultivating the resulting cell-polymer constructs under conditions that permit the formation of functional tissues (2 ). The scaffold provides a defined structure for cell attachment and tissue development, and the bioreactor provides control over the biochemical and physical factors in the cell environment.