Blood Vessels Grown From Muscle Cells
Engineered Blood Vessel Grafts Could Be Used for Heart Bypass, Kidney Dialysis
Feb. 2, 2011 -- Scientists report that they have successfully grown and tested collagen-based tubes made from human donor tissue that can be used as blood vessel-like grafts in surgical procedures like coronary artery bypass and for creating vascular access points for patients who need kidney dialysis.
What’s more, the tissue-engineered grafts appear to be strong and pliable even after being refrigerated for a year, which means that they could be made ahead of time and kept at the hospital to be used when surgeons need them.
Other researchers have previously reported the ability to develop blood vessels from a patient’s own cells. That process was time consuming, however, requiring six to nine months for harvested cells to multiply and grow a sheet of tissue that could be rolled into a tube and implanted in the body.
"As the authors point out, there is a growing clinical need for replacement arteries and although tissue-engineered blood vessels have been used successfully in the clinic, there is still a need for "off-the-shelf" grafts that can perform as well as autologous small diameter blood vessels without the long production time associated with growing autologous cells to make a graft," says Marsha W. Rolle, PhD, assistant professor in the department of Biomedical Engineering at Worcester Polytechnic Institute in Worcester, Mass.
“I think this is an important study,” says Christopher Breuer, MD, a pediatric surgeon and director of tissue engineering at the Yale School of Medicine in New Haven, Conn., who was not involved in the research.
Bioengineering Blood Vessels
In the new procedure, reported in the Feb. 2 issue of Science Translational Medicine, researchers took smooth muscle cells from cadaver donors and seeded them onto mesh tubes made from the same strong, flexible material used to make dissolvable stitches.
The muscle cells then secreted proteins, primarily collagen, which formed a ring of biosynthetic tissue around the gradually dissolving scaffold, says study researcher Shannon L. M. Dahl, PhD, senior director of scientific operations for Humacyte.
As the collagen was growing, fluid was pumped through the tubes to subject them to stress similar to blood pressure pushing against vessel walls.
In a final step, researchers washed the collagen-based tubes to get rid of any remaining cells, which could trigger immune reactions in a recipient.
Researchers were able to make the tubes in two sizes. One was 6 millimeters, about the diameter of a standard drinking straw.
The others were 3 to 4 millimeters, about the size of cocktail straws.
They then tested the bioengineered blood vessels in two animal models. After six months, about 88% of the larger grafts were still open and trouble free in baboons. After one month, about 83% of the smaller vessels implanted around the hearts of dogs were still open.