Small blood vessel engineering.

Tissue engineering has attracted wide interest as a potential method to alleviate the shortage of transplantable organs (1). To date, almost all of the successfully engineered tissues/organs have relatively thin and/or avascular structures [e.g., skin (2), cartilage (3), and bladder (4)], where postimplantation vascularization from the host (angiogenesis) is sufficient to meet the implant's demand for oxygen and nutrients. Vascularization remains a critical obstacle impeding attempts to engineer thicker, metabolically demanding organs, such as heart and liver. One approach in vascularizing an engineered tissue is to add the cellular components of blood vessels (endothelial and perivascular cells) directly to the tissue-engineered construct. We have shown that coimplanting endothelial cells and perivascular cells in a scaffold in vivo can lead to the formation of a vascular network that anastomoses to the host circulatory system. The engineered vessels are stable and functional, and they persist for more than 1 year in vivo. This approach may potentially lead to the creation of a well-vascularized-engineered tissue.