Researchers Make Test-Tube Blood Vessels
But, she tells WebMD, there has not been much success translating the work to humans: "We can apply the same techniques to human cells and get them to grow, but they don't grow well enough to form vessels." The stumbling block "is a cellular age problem," she says. "The cell doubling rate -- how quickly [the cells] multiply -- is very low in elderly humans." While healthy pig cells quickly multiply in the nutrient medium, harvested human cells "have about 10 doublings before they conk out and die," she says.
The team is working on "optimizing the biochemical environment to get the human cells to grow," but wimpy cells are not the only obstacle, admits Niklason.
Recent discoveries have changed the way scientists look at atherosclerosis, or clogging of the arteries. Rather than being a problem with the blood vessels per se, it is now thought to involve inflammation, genetics, and any number of other as-yet-undetermined factors. A major question, then, is how well engineered vessels will fare when they are made up of cells that have this original problem and then put back into people.
"All of the experiments we've done have been on healthy, non-atherosclerotic animals," says Niklason. "It's really an open question how human vessels will do if we grow them from cells taken from atherosclerotic [vessels]."
Niklason is confident that eventually researchers will devise a way to make bioengineered vessels a reality for human patients. "We'll solve it," she says. "In 4 1/2 years, we've taken the project from absolute ground zero to making it work in animals. ... There's no fundamental reason why this isn't going to work. I think it's just a matter of time."