Copy, Paste, Print…Kidney?

Surgeons all over the world are facing an organ shortage crisis. In the past century, we have learned how to treat diseases that were previously fatal, and as a result, we are living longer. However, as we age, our organs tend to fail more and must often be repaired or replaced. Right now, the need for spare healthy organs greatly outweighs the supply, and even in cases where replacements are available, the recipients must take a whole regiment of medicines to prevent the body from rejecting the transplanted organ.

What if doctors could grow back a perfect, functioning clone of a patient’s old, damaged organ? In the past decade, researchers in the field of regenerative medicine have brought this idea to life, using living cells as building blocks to grow tissues and certain whole organs outside the body that can later be transplanted into patients. But some researchers are pushing the boundaries even further, hoping to expedite the process through the technology of 3D printing.

Examples of the progress of this field can be seen across the globe and across the many parts of the body. In 2006, Dr. Anthony Atala, Director of the Wake Forest Institute for Regenerative Medicine, and his team of scientists nurtured samples of cells less than the size of a postage stamp to grow into functioning bladders that were implanted into human patients. They are now working on developing kidneys, heart valves, and even livers. In 2010, a team of Yale scientists led by Dr. Laura Niklason, Professor of Anesthesiology and Biomedical Engineering at Yale University, successfully engineered and implanted lung tissue into rats. One year later, Dr. Christopher Breur, a pediatric surgeon at Yale School of Medicine, implanted into a 4-year-old girl a degradable blood vessel scaffold that coaxed her own body into re-growing its own blood vessel. And in Stockholm just last year, a man’s cancerous windpipe was replaced with a lab-grown healthy replica that was grown from stem cells found in his bone marrow.

Biodegradable scaffolds are used to “guide” cells into a proper shape while they grow. Over time, the scaffold degrades and the cells take a particular shape, in this case, a vascular graft. Image courtesy of Sashka Dimitrievska and Dr. Laura Niklason’s Lab.

Tissue engineering: from stem cells to organs

Although the procedure itself is complicated, the principle behind most of all tissue engineering simplifies down to a few basic steps. First, researchers craft a scaffold of the tissue they are trying to reproduce. After the basic framework is created, researchers then flood the scaffold with autologous (patient’s own) stem cells, letting them grow all over the framework. Once the scaffold is coated with the new cells, it is then transplanted into a patient’s body, where the organ is accepted as a natural part of the body itself.

Given the huge benefits of perfecting such a technology, regenerative medicine research is one of the fastest growing fields in science today. “In the past year, our lab has tripled, and most of our efforts are related to this the lung project,” says Sashka Dimitrievska, a third-year graduate student in Niklason’s lab. She explains that in the case of Niklason’s team, they used the fibrous structure of existing lungs as a scaffold to hold anchor cells in their proper places places and helping them communicate with each other. The lung scaffolds were placed in an oven-like device (bioreactor) mimicking the aspects of a fetal lung environment. There, they were “seeded” with rat lung cells from a tissue culture, and after a week, the newly engineered lungs were then surgically implanted into rats. So far, these new lungs have performed acceptably well on very short time frames. Niklason’s team is currently working on trying the same process with human lungs.

However, because scientists still do not fully understand the factors of how stem cells change into other types of cells, growing tissues in a lab is currently a somewhat inefficient technology. “The problem with the vessel grafts this is that you cannot apply this approach in an emergency,” says Dimitrievska, explaining that the growth process of tissues needs to first be made faster. “You cannot just tell a patient, ‘Hold your breath now for a few weeks, while I I culture some cells.’”

The Niklason lab has been hard at work engineering vascular grafts that can be used in bypass surgeries. These images show lab-grown vascular grafts that were implanted into a patient’s heart. Image courtesy of Sashka Dimitrievska and Dr. Laura Niklason’s Lab.

3D Printing: Organ supply closets?

Some researchers, like Atala from Wake Forest University, believe that this growth process of tissues does not just need to be faster—it needs to take only a few hours. Last year, at a Technology Entertainment and Design conference, Atala boasted that one day doctors should be able to “print” out organs by using a device similar to a desktop printer. Instead of ink, he said, the organ would be printed with cells. It would work by culturing a sample of cells taken from a patient’s body, making a blueprint of the existing organ with a CT scan, and then using the cells mixed with a gel as “ink” to literally print out the new organ.

Atala and his team have been successful in printing out bones and are now experimenting with printing out kidneys. Even though these prototype kidneys are non-functional and years away from practical use, the Wake Forest team believes that a similar device, which would print out skin grafts directly onto a burn patient, is much closer to clinical use.

Right now, many researchers — including Dimitrievska — find the idea of a 3D organ printer that can engineer any functioning organ on demand extremely optimistic. In addition to the cell differentiation problem, scientists are still learning how to supply blood to more complex and solid organs. In fact, science has still not even been able to grow liver, nerve, or pancreas cells. Furthermore, the inside of the printer would have to mimic the human body’s conditions in order for the cells to grow properly — and these conditions would have to differ depending the organ.

Although there is much progress to be made before creating a 3D organ printer, Atala and his colleagues remain hopeful. The last several years have seen massive strides in the study of tissue engineering, so perhaps science fiction is not too far from reality. Perhaps one day in the future, doctors may be able to pull ready-made organs off of their supply shelves just as easily as gauze pads.