Within a generation, there may be no limit to the kinds of organs and body parts that can be created from scratch.
Various groups of scientists have recently created thyroid cells in the lab, grown a new ear in the skin a woman's own arm, and won a Nobel Prize for figuring out how to reprogram cells so that they can turn into a variety of cell types.
In the future, there may be no limit to the kinds of organs and body parts that can be created from scratch.
One hope is to make donor organs obsolete, or at least far less necessary, eliminating long waiting lists for transplants. By using a patient's own cells, the new wave of regenerative medicine also circumvents ethical arguments and reduces the chance that recipients will reject their new parts.
"We now have the ability for the first time to create a virtually unlimited supply of all the cell types and building blocks we need to make what we want to make," said stem cell researcher Robert Lanza, chief scientific officer at Advanced Cell Technology, a biotechnology company in Marlborough, Mass. "Now we just have to put it all together."
The concept of growing new organs first cropped up in the scientific literature in the 1930s, said Anthony Atala, director of the Wake Forest Institute for Regenerative Medicine in Winston-Salem, North Carolina. Real-life applications, however, began to appear only more recently.
With bladders grown from the cells of sick children and teenagers, Atala's group was the first to successfully implant lab-grown organs into people, beginning in 1998. In a paper in the Lancet in 2006, the team reported the promising long-term results of those procedures.
According to Atala, researchers have been able to grow and implant three kinds of parts: flat tissues like skin, tubular structures like blood vessels, and hollow organs like stomachs and bladders.
The next frontier includes solid organs, such as hearts, livers and kidneys. These structures are particularly complicated to build because they contain many different kinds of cell types and they require lots of blood vessels to carry fluids in and out.
Around the world, many groups of scientists are working aggressively on a variety of strategies to create these kinds of complex organs.
The process usually begins by extracting cells from the intended recipient. These cells often come from the part of the body that needs help. But in 2006, Shinya Yamanaka of Kyoto University, Japan, announced that he had identified genes that could be used to return mature cells to their embryonic state.
The research earned Yamanaka half of this year's Nobel Prize in Physiology or Medicine and led to an explosion of possibilities in regenerative medicine without requiring the controversial practice of extracting stem cells from embryos.
In recent years, scientists have created sperm, eggs, red blood cells, and a human trachea.
Lanza's group has made retinal cells, and in January, they reported in The Lancet that they used those cells to improve vision in two women with progressive blindness. His team has also created miniature kidneys and little patches of heart tissue that repair the organ like bicycle patches on a tire.
In efforts to create full-sized and functional solid organs, scientists turn to scaffolds that create structure for the infusion of lab-grown cells. Atala's group is working on a three-dimensional printer that uses ink-jet technology to spit out a frame of the desired shape. Another strategy is to remove cells from donor organs and replace them with a patient's own cells.
Progress is so rapid that Lanza expects to see a proliferation of lab-grown organs go mainstream within a generation.
"I would say one day, and it's not science fiction, a doctor will take a skin cell and grow you a new kidney," he said. "It's not that far off. I think, as we master these tricks, we're going to get better and better at this, not only in how to make organs but in how to make them more efficiently."