Engineered Cell Sheets
Tissue engineers are on their way over the obstacles posed by the need for blood vessels in larger engineered tissue masses: "Cardiac cells grown in the laboratory as cell sheets can be layered to form myocardial tissue grafts which, when transplanted into animals, will beat like normal cardiac muscle and can survive and function for at least a year ... assessing the growth, morphological development, and functional capacity of the bioengineered tissue the researchers demonstrated its ability to beat in response to electrical stimulation and to form vascular networks, ensuring an adequate blood supply. They confirmed the survival of the pulsatile myocardial tissue at the site of implantation up to one year later." A broad range of regenerative cell therapies and engineered replacement parts for the heart are presently under development; a very good thing, I think.
Link: http://www.genengnews.com/news/bnitem.aspx?name=1205417XSL_NEWSML_TO_NEWSML.xml