It is now possible to stimulate growth of valve-shaped tissue inside an animal’s body, according to a presentation at the annual meeting of the American Heart Association. The process may make it possible to use autologous tissue engineering to make a new valve from an individual’s own cells.

“It’s the first fabrication of an autologous heart valve inside a living body,” said Kyoko Hayashida, MD, lead author of the study and a research fellow at the National Cardiovascular Center Research Institute in Osaka, Japan, and at the Kyoto Prefecture University of Medicine.

“We created an autologous valved-conduit through a simplified and less costly process carried out in living bodies,” she said. “If every body organ could be recreated by using autologous cells, it would solve the current shortage of donated organs available for transplantation and the use of costly and harmful anti-rejection drugs.”

The tissue engineering technique takes advantage of tissue encapsulation, in which cells naturally surround implanted foreign materials. In the current study, Japanese researchers developed plastic molds that included three flap-like leaflets that mimic valve flaps. The leaflets contained a tiny opening, less than one millimeter wide. An elastic-like conduit scaffold, repeatedly pierced by a laser to give it a sponge-like texture, held the leaflets in place.

The entire apparatus is just over a centimeter long with a diameter of less than a centimeter, making it possible to implant up to five molds in a layer of fat on the rabbits’ backs without bothering the rabbits.

The laser-produced holes allowed cells to infiltrate the molds and grow around them. After one month, the researchers removed the molds from the rabbits, removed the outer mold, and left the heart-valve-shaped inner mold intact.

They implanted 10 molds: 5 in the first rabbit, 3 in the second rabbit and 2 in the third. There was a 50 percent success rate overall (5 of 10 attempts): Two of five in the first rabbit, two of three in the second and one of two in the third.

Although the valve conduits did not have the same cell layers as natural heart valves, they functioned in a similar way when researchers performed flow studies in test tubes. Future research will investigate whether the valves can resist the fluid pressures encountered by native heart valves without degradation.

The researchers also plan to further evaluate the engineered valve’s function when implanted in the body, as well as its potential for growth, self-repair and regeneration in the body, Hayashida said.