Purpose: This study describes a method of engineering contractile three dimensional cardiac tissue incorporating a vascular pedicle.
Methods: Silicone tubes were filled with a suspension of cardiac myocytes in fibrin gel and placed around the femoral vessels of adult rats. At three weeks, the tissues in the chambers were harvested for in vitro contractility evaluation and histologic analysis.
Results: At three weeks, the chambers had become filled with living tissue. Hematoxylin and eosin staining showed large amounts of muscle tissue situated around the femoral vessels. Electron micrographs revealed well-organized intracellular contractile machinery and a high degree of intercellular connectivity. Immunostaining for von Willebrand factor demonstrated neovascularization throughout the constructs. With electrical stimulation, the constructs were able to generate an average active force of 263 microNewtons with a maximum of 843 microNewtons. Electrical pacing was successful without fatigue at frequencies of 1 to 5 Hz. In addition, the constructs exhibited positive inotropy in response to ionic calcium and positive chronotropy in response to epinephrine.
Conclusions: As engineering of cardiac replacement tissue proceeds, vascularization is an increasingly important component in the development of three-dimensional structures. This study demonstrates the in vivo survival, vascularization, organization and functionality of transplanted myocardial cells