Engineered Blood Vessels Developed for Humans

The researchers discovered that they could control the cells' development by growing them on a surface with nanoscale patterning.

Engineered blood vessels could one day be transplanted into tissues such as the kidneys, liver, heart, or any other organs that require large amounts of vascular tissue, which moves nutrients, gases, and waste to and from cells.

"We are very excited about this work,” said Dr. Robert Langer, a professor from the Massachusetts Institute of Technology (MIT; Cambridge, MA, USA; and an author of the study, which was published in the December 2007 online issue of the journal Advanced Materials. "It provides a new way to create nano-based systems with what we hope will provide a novel way to someday engineer tissues in the human body.”

The work focuses on vascular tissue, which includes capillaries, the smallest blood vessels, and is an important component of the circulatory system. The team has created a surface that can be utilized as a template to grow capillary tubes aligned in a specific direction. The researchers built their template using microfabrication machinery at Draper Laboratory (Cambridge, MA, USA). Normally such technology is used to build microscale devices, but the researchers adapted it to create nanoscale patterns on a silicone elastomer substrate. The surface is patterned with ridges and grooves that guide the cells' growth.

"The cells can sense [the patterns], and they end up elongated in the direction of those grooves,” said Christopher Bettinger, MIT graduate student in materials science and engineering and lead author of the study.

The cells, known as endothelial progenitor cells (EPCs), not only elongate in the direction of the grooves, but also align themselves along the grooves. That results in a multicellular structure with defined edges, also called a band structure. Once the band structures form, the researchers apply a commonly used gel that induces cells to form three-dimensional tubes. Unlike cells grown on a flat surface, which form a network of capillary tubes extending in random directions, cells grown on the nano-patterned surface form capillaries aligned in the direction chosen by the researchers.

The researchers believe the technique works best with EPCs because they are relatively immature cells. Earlier attempts with other types of cells, including mature epithelial cells, did not produce band structures. Growing tissue on a patterned surface allows researchers a much greater level of control over the results than the classic tissue engineering technique of mixing cell types with different growth factors and hoping that a useful type of tissue is produced, according to Dr. Bettinger. "With this technique, we can take the guesswork out of it.”

The next step for the investigators is to implant capillary tubes grown in the lab into tissues of living animals and try to integrate them into the tissues.


Related Links:
Massachusetts Institute of Technology