Between them tissue engineering and prosthetics offer replacement parts for a fair number of organs, but none yet as good as the original. This article somewhat overstates of the case with regard to how far the research and development has progressed, but it is certainly true that both biological and artificial replacement organs as good as or better than the evolved versions lie not so very far in the future:
Growing a human organ is a bit like baking a layer cake, says Dr. Anthony Atala, director of the Wake Forest Institute for Regenerative Medicine. Let's say the "cake" we want is a kidney. After harvesting cells from the patient's kidney and coaxing them to multiply - mixing up the cake batter - Atala's team bastes those cells onto a biodegradable scaffold, one painstaking layer at a time. "Once there's the right amount," he says, "we put it in an oven-like device that has the same conditions as the human body." The kidney "bakes" inside the bioreactor for a couple of weeks, where it's also exercised. Then it's ready for implant. Eventually, the scaffold melts away, leaving the new organ.
A donor kidney was the first organ to be successfully transplanted into a patient, in 1954. Five decades later, we're building new ones from scratch - growing them on scaffolds or printing them with modified desktop printers that shoot cells instead of ink. About 14 years ago, Atala's team implanted bioengineered bladders into patients and, he says, "they've lasted all these years." He and other scientists are moulding jumbles of cells into heart valves, ears, stomachs and skin. They're building advanced prosthetics, including bionic hands and legs, which mimic natural function and can even be controlled by our minds. More and more people will live their lives with these artificial parts integrated into their bodies.
To Atala, human organs fall into one of four categories, ranging from simplest to make to most difficult. First come flat parts, like skin. Then there are tubular organs, including the windpipe and blood vessels. Next are hollow, non-tubular parts, such as the stomach or bladder. The last, and most difficult to create, are solid organs, like the heart, liver, lung and kidneys. "Up to this point, we've implanted the first three types," says Atala. "We have not yet implanted a solid organ." But it can't be all that far off. In his lab, he's growing human fingers.