In the early 1990s, Jim Gleason’s health took a turn for the worse. His heart had been ravaged by an infection, and doctors told him he would need a new one.

Gleason was placed on the organ transplant list. As he waited, he realized he was waiting for death — either his own, or the death of a potential organ donor.

Eventually, Gleason found a match.

The donated heart — from a 38-year-old Brooklyn man named Roberto who had been attacked and was declared brain dead — gave Gleason a second chance at life.

But not everyone who needs it gets that opportunity. Despite advances in modern medicine, not much has changed about organ transplantation since the 1990s. Organs are still removed from donors who have recently died and then given to patients who are often close to death themselves. And by some metrics, patients may be worse off today than they were 25 years ago.

In 1994, Gleason waited five weeks for a match. Today, a typical heart transplant patient waits nine months for a donor organ. Many die waiting.

Technology, such as 3D printing, may offer a solution. “Imagine a world where you can manufacture them, and create substitutes for them,” Gleason, who has since become an advocate for transplant patients, said of organs. “That would be a different world, wouldn’t it?”

Now, scientists at Harvard’s Wyss Institute say they are one step closer to that reality. In lab experiments, they have developed a new technique that uses living human cells to “print” functional heart tissue for an artificial heart — an innovation that could save thousands of lives.

Unlike prior efforts, the new lab-grown heart tissue beats just like a normal human heart and comes equipped with the blood vessels it will need to survive once it is transplanted into a patient.

This technique, called sacrificial writing into functional tissue (or SWIFT), needs to be tested in mice and other animals before it can be used in humans. But if it works for heart tissue, experts say SWIFT could also be used to 3D-print livers, kidneys and other crucial organs.

“It will, I think, be the path forward for bioprinting,” said Jennifer Lewis, a professor of biologically inspired engineering at the Wyss Institute and one of the lead authors of a paper about the technique published Sept. 6 in the journal Science Advances.

Lewis and her colleagues found a way to pack living cells tightly enough together to replicate the density of the human body. At the same time, they carved little tunnels in between the cells to mimic blood vessels that are needed to deliver vital oxygen and other nutrients.

“It’s a very nice technique,” said Anthony Atala, director of the Wake Forest Institute for Regenerative Medicine, who was not involved in the new research. “It’s basically like you’re building a home,” he said. “When you’re putting up the walls, you’re putting in the wiring at the same time.”

Previously, scientists had been able to 3D-print the basic structure of a heart using human stem cells. Separately, scientists had also been able to use ink to create tiny channels that melt away, leaving behind a vascular structure to support living tissue.

SWIFT puts all of these pieces together, successfully creating heart tissue that beats continuously for one week, according to Lewis.

“This is a nifty advance that is a step in the right direction for generating larger tissues,” said Melissa Little, director of the Kidney Research Lab at the Murdoch Children's Research Institute in Melbourne, Australia.

Little noted that the tiny veins in the 3D tissue are not yet coated in a thin layer of protective cells typical of a human vascular system, but added that the new research is “an important stepping stone” to functional artificial tissue.

If the SWIFT technique proves successful in hearts and other organs, it could end the deadly shortage of donor organs. In the United States, there are currently more than 120,000 people waiting for donor organs to become available. On average, 20 people die each day while waiting, according to the U.S. Department of Health and Human Services.

Organs are allocated by weighing geographic proximity and medical need. Hearts and lungs must be transplanted within four to six hours, for example, so they are sent to the nearest donors — even if those donors don’t necessarily have the greatest medical need.

The scarcity of donor organs has created many difficult choices for patients themselves, said bioethicist Daniel Wikler, a professor emeritus of ethics and population health at Harvard.

“If you’re on the list, you can sometimes be offered an organ that’s not the best organ,” Wikler said. “It might be from an older person, or from someone who is not a perfect match with you.”

Accepting a less-than-perfect organ is “a gamble” for those waiting on the transplant list, he added. While it may be a patient’s best shot at a life-saving organ, there’s always a possibility that the donated tissue could lead to other health problems later on.

One of the key benefits of a 3D-printed organ is that it would use the patient’s own cells as the basic building blocks for the new organ, thereby drastically reducing the odds that the tissue will be rejected.

Still, Lewis said it will be years before the SWIFT technique can be used to print fully functional organs that can be safely used in humans.

“It’s exciting,” she said, “but there’s still more work to be done.”

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