Scientists have long warned that the world is running out of donor organs. Traditional transplants rely on a limited supply of human donors and come with risks like rejection and lifelong immunosuppression. These concerns have fueled a new wave of research aimed at creating fully functional human organs through 3D bioprinting according to the Nautilus article “How to Print a Human” by Mary Roach, which describes the early innovations and challenges in the field.
From Ghost Hearts to New Organs
The movement began with a method described in Nautilus called decell and recell. Early photos of a ghost heart showed something that looked like a pale, empty version of a real organ. Detergent had been pumped through its blood vessels to wash out the living cells. What remained was a collagen scaffold that the immune system tolerates well.
The idea was simple but powerful. If you could strip a pig organ of its cells and then refill it with a patient’s own cells, you could create a personalized organ without the danger of rejection. Researcher Adam Feinberg says he was drawn to this idea early in his career. But he adds that turns out that’s very difficult.
The problem is size. Cells are far too large to pass back through the tiny channels left in the decellularized scaffold. Feinberg explains that the difference between molecules and whole cells is like the difference between running a 5K and running around the Earth. So scientists were forced to rethink the entire process.
Building Organs Layer by Layer
Instead of trying to force cells back into old structures, researchers began printing new structures from scratch. This approach is called 3D bioprinting. A printer lays down thin cross sections of collagen and live cells, switching between materials the way an inkjet printer switches colors. The shapes come from MRI scans of actual patients.
But organs are soft and unstable. You cannot build a heart or rectum the same way you print a plastic model. To solve this, Feinberg invented FRESH, a technique where a printer builds the organ inside a gel support bath. His graduate student, Caner Dikyol, demonstrates the method by printing an artery into the gel, which later melts away with heat to leave the printed structure intact.
The collagen ink stays liquid by being acidified, then solidifies when it touches the support gel. Live cell ink cannot be acidified, so Feinberg mimicked the body’s clotting system. The live cell ink contains fibrinogen, which hardens into fibrin when exposed to an enzyme in the support bath.
Printing Real Human Tissue
Researchers can already print liver tumor cells, cartilage-like structures, and sheets of beating heart muscle. But printing tissue is not the same as printing a fully functional organ. Cells need nutrients, oxygen, and waste removal. In nature, this is handled by extremely dense networks of capillaries.
You cannot print these tiny vessels one by one, so scientists hope the printed tissue will grow its own. Growth factors are added to the inks to encourage this process.
One of the hardest tasks is printing muscle tissue in the correct alignment. Maria Stang at Carnegie Mellon prints heart muscle in the helical pattern that lets the organ twist as it pumps. Her printed constructs beat slowly but in a coordinated way, proving that aligned, working heart tissue can be made layer by layer.
At Northeastern University, Guohao Dai and his collaborators designed an elastic hydrogel that allows soft tissues to be printed more easily. After printing, blue light triggers a reaction that turns the soft gel into strong, elastic material without harming the cells. Dai says you can print any geometry. You can print a tube or a blood vessel. Over time, the gel biodegrades as living cells replace it with their own collagen and elastin.
Lessons from Past Attempts
Some labs have already tried early versions of lab-grown organs. In 2006, Wake Forest University implanted engineered bladders into children. One child even carried his engineered bladder into college. But Feinberg’s team notes that these bladders lacked full muscular and nerve function, showing how much more complex real organ engineering must be.
Real Examples of 3D-Printed Structures
Researchers have produced:
- printed arteries and blood vessels
- heart muscle sheets and beating ventricles
- liver cell constructs
- cartilage-like structures
- highly accurate anatomical organ models for surgeons
At the University of Cincinnati, the team behind Meteora3D prints patient-specific replicas of hearts, vessels, and other structures to help surgeons prepare for complex procedures. Their fast-printing technology can produce same-day models that improve surgical planning.
How Close Are We to Human Implants
Feinberg estimates that implantable printed organs are a decade plus away. His colleague Jaci Bliley believes the timeline is two to three decades. Yet both agree the pace of progress is speeding up. Bliley notes that ventricles she printed in 2019 can now survive for months when placed in mice alongside the animals’ natural hearts.
Dai’s team is also advancing toward printed blood vessels that can withstand human pressure. Longer growth periods and faster hydrogel degradation may soon produce strong, functional vessels ready for clinical use.
Scientists describe the field as challenging but deeply motivating. Feinberg compares today’s stage to the earliest days of aviation. We do not want a plane that goes 30 feet, he says. We want a plane that can fly around all day. Bliley adds that every failed experiment simply teaches the team something new. It is never a failure. It is all progress.
Meteora3D’s team says their rapid-printing process is driven by one goal. They want to directly improve patient outcomes by giving surgeons better tools.
The Future of Organ Printing
A future where a failing heart or liver can be replaced with a personalized, printed version made from a patient’s own cells is no longer hard to imagine. Researchers expect that the combination of new materials, improved printing techniques, and continued innovation will bring this future to life. And as several scientists note, what they need most now is time, resources, and support, because every advancement in this field brings the world closer to saving countless lives.
HNZ Editor: We have spoken with a researcher who says that organs can easily be regrown with today’s tech and she does it on a regular basis under lab conditions. But we believe this approach will also be viable. Having more than one way to substitute my failing organs as I get old seems like a really good idea to me.
