MADRID—Reaching into a stainless steel tray, Francisco Fernandez-Aviles lifted up a gray, rubbery mass the size of a fat fist.
It was a human cadaver heart that had been bathed in industrial detergents until its original cells had been washed away and all that was left was what scientists call the scaffold.
Next, said Dr. Aviles, "We need to make the heart come alive."
Inside a warren of rooms buried in the basement of Gregorio Marañón hospital here, Dr. Aviles and his team are at the sharpest edge of the bioengineering revolution that has turned the science-fiction dream of building replacement parts for the human body into a reality.
Since a laboratory in North Carolina made a bladder in 1996, scientists have built increasingly more complex organs. There have been five windpipe replacements so far. A London researcher, Alex Seifalian, has transplanted lab-grown tear ducts and an artery into patients. He has made an artificial nose he expects to transplant later this year in a man who lost his nose to skin cancer.
The key to all the lab-built organs are stem cells, found in human bone marrow, fat and elsewhere. Stem cells can be transformed into other tissues of the body, making them the basic building blocks for any organ.
In the case of the nose, stem cells were added to the artist's mold, along with chemicals that control cell development. The stem cells sat inside the pores of the lab-made organ and gradually differentiated into cells that make cartilage.
However, the nose was missing a crucial piece: skin.
This posed a substantial hurdle. No one has made natural human skin from scratch. Dr. Seifalian's idea: to implant the nose under the skin of the patient's forehead in the hope that skin tissue there would automatically sheath the nose.
But the patient objected, and for good reason: The implanted nose would have to sit inside his forehead for weeks or even months. In the end, Dr. Seifalian chose a less obtrusive approach. The bioengineered nose was implanted under the patient's forearm.
The team now is using imaging equipment to keep tabs on whether the necessary blood vessels, skin and cartilage are forming in the right way. "We'll have to also make sure there's no infection," Dr. Seifalian said in late November, on the day of the patient's surgery.
If the skin graft works, surgeons will remove the nose from the arm and attach it to the patient's face. Dr. Seifalian will then apply the right chemicals to convert the man's stem cells into epithelial cells, a common type of tissue found in the nose and in the lining of other organs. The epithelial cells will be inserted into the nose.
As a final step, surgeons will connect blood vessels from the face to the site of the new nose to provide a steady flow of nourishment for the growing cells. "The whole process could take six months," said Dr. Seifalian.
Dr. Seifalian said the new nose could restore some sense of smell to the patient, but its main benefit will be cosmetic. He held up a jar full of early-stage lab-made noses, and another filled with early-stage ears.
"We're actually in the process of making a synthetic face," he said. From a cosmetic point of view, "if you can make the ear and the nose, there's not much left."
Regenerating a nose would be a striking achievement; creating a complex organ like the heart would be historic. A team led by Spain's Dr. Aviles is trying to get there first.
Growing a heart is much harder than, say, growing a windpipe, because the heart is so big and has several types of cells, including those that beat, those that form blood vessels, and those that help conduct electrical signals. For a long time, scientists didn't know how to make all the cells grow in the right place and in the right order.
The problem had been cracked by Dr. Taylor. She said that when human stem cells were put into a heart scaffold in 2010, they seemed to know just where to go. "They organized themselves in a way I didn't believe," said Dr. Taylor, who now works at the Texas Heart Institute but makes regular visits to Madrid to help with the experiments. "It's amazing that the [scaffold] can be as instructional as it is. Maybe we don't need to micromanage every aspect of this."
Mimicking the heart isn't easy. For example, more than a gallon of blood courses through the human heart each minute. The bioreactor will have to be set up so that a similar volume is pumped through it, but gently—to avoid killing the cells.
In addition, the heart cells must be given the right electrical connections.
To model these connections, the Spanish team built a vest with 70 electrical points. Team members wore the vest, which record their hearts' electrical activity. That pattern of signals will have to be replicated for the lab-made heart.
Dr. Aviles concluded:
"We opened the door and showed it was possible, This is no longer science-fiction. It's becoming science."
It's time to start saving those stem cells
You can now prepare for the eventuality of needing stem cells in a variety of different ways, the most commonly know way is by saving the cord blood when a child is born. A new and increasingly popular method, especially for those who missed their opportunity with cord blood is by preserving the dental pulp inside teeth that routinely get removed like baby teeth and wisdom teeth.
Learn more about preserving stem cells from teeth