Feb. 10, 2006 -- What if the tens of thousands of people waiting for organ transplants in the United States didn't have to wait? What if burn victims could replace their scars with skin that was indistinguishable from their own? What if an amputee could replace an entire limb with one that felt, looked and behaved exactly as the original?
In what could be the first step toward human immortality, scientists say they've found a way to do all of these things and more with the use of a technology found in many American homes: an ink-jet printer.
Researchers around the world say that by using the technology, they can actually "print" living human tissue and one day will be able to print entire organs.
"The promise of tissue engineering and the promise of 'organ printing' is very clear: We want to print living, three-dimensional human organs," Dr. Vladimir Mironov said. "That's our goal, and that's our mission."
What's in a Name?
Though the field is young, it already has a multitude of names.
"Some people call this 'bio-printing.' Some people call this 'organ printing.' Some people call this 'computer-aided tissue engineering.' Some people call this 'bio-manufacturing,'" said Mironov, associate professor at the Medical University of South Carolina and one of the leading researchers in the field.
"It looks like every new guy who joins into this field tries to introduce a new term."
The commonly used term is "organ printing" and is simple in concept, but incredibly complex and challenging in its execution.
"What we do is we modify -- it's a regular ink-jet printer -- but we do not use the paper-feed mechanism, so basically we just have a cartridge moving back and forth and where the paper goes we put a petri dish," explained Thomas Boland, an associate professor at Clemson University.
Boland says that there is some liquid in the dish and that in place of ink cartridges are cartridges filled with cells and a "crosslinker."
The crosslinker is a chemical that causes the liquid in the petri dish to gel, giving the printer a soft but solid Jell-O-like surface to print the cells on.
The process can be repeated over and over, adding liquid, gelling it, printing more cells, and building layer upon layer, creating three dimensions.
Limitations and Obstacles
Right now, scientists are limited to a maximum of about 2 inches of thickness. Crossing that threshold presents one of the technique's first big hurdles.
"When you print something very thick, the cells on the inside will die -- there's no nutrients getting in there -- so we need to print channels there and hope that they become blood vessels," Boland said.
In any given human organ, there are blood vessels feeding the organ to keep it alive and working properly. Without the blood vessels, the organ will die and that's the problem facing researchers in building an organ for use in a human: How do you get the printed organ to grow and maintain blood vessels?
Although there are a few competing schools of thought on this, like most things in science, work, ingenuity, and maybe a little money are what researchers say will put printed organs in live humans.
"In the future -- maybe 50 years from now -- we will be able to make very complex organs and bones, and very complex tissues," he said.
And when they can, they won't have to worry about rejection because the replacement part will be catered to the individual receiving it.
"With the printers, we have the ability to tailor the material very well depending on how much crosslinker and so on," Boland said. "So we can actually match the properties of the heart cell [for example] with the properties of the tissue."
The concept behind organ printing is one that's been used in the manufacturing world for years, "rapid prototyping."
"Rapid prototyping is nothing more than layer-by-layer deposition of any materials," explained Mironov. "What is new is that instead of ceramic, instead of polymer, instead of some other nonorganic stuff, we use living tissue and living cells."
Rapid prototyping is the process of quickly turning product designs into actual samples. Using a computer and a rapid prototype machine, one can build almost any object -- limited only by size, complexity and material.
Though we may be half-a-century away from being able to print entire organs, scientists say we're likely much closer to applications that will affect everyone's life.
Boland is working with colleagues at the Medical University of South Carolina to build tissue to repair a heart that's been damaged.
"The problem with heart tissue is that you can't generate your own heart cells anymore," explained Boland. "You're born with a number of heart cells -- maybe a billion or so -- then, that's it."
Mironov said there were researchers working with two-dimensional bio-printed materials for work with drugs and toxicity.
Imagine living patches of skin that could be used to test medicines or even cosmetics.
Indeed as scientists and researchers work to make organ printing a reality, Mironov knows full well the potential implications for all of mankind.
"This could have the same impact as Guttenberg's press," he said.