We may be one step closer to making blood vessal transplants easier. Researchers have successful produced human blood vessals in lab mice from progenitors cells. Progenitors cells are like stem cells but they are only able to "transform" into a limited number of other cells, whereas stem cells can become almost anything.

From Scientific Blogging,

"For the first time, researchers have successfully grown functional human blood vessels in mice using cells from adult human donors — an important step in developing clinical strategies to grow tissue, researchers report in Circulation Research: Journal of the American Heart Association."