Written by Catherine Bolgar
Few would have guessed the trajectory from 1970s inkjet printers to 3D printed organs consisting of human cells, yet, that’s where we’re headed.
3D printers apply layers of melted plastic to create complex objects, from the silly to the serious, including personalized prostheses such as eyes, ears or knees. A patient at the University Medical Center Utrecht, the Netherlands, recently was the first to receive a custom 3D printed plastic skull.
A step beyond plastic parts is a biological-synthetic combination. A personalized 3D printed scaffolding is made of synthetic material, on which living cells are placed that will grow around the structure. This technique, which prints the structure but not the cells, is being examined for bone and for skin.
Cells we isolate from fat will stimulate bone formation and blood vessel formation in these structures,” says Stuart K. Williams, director of the bioficial organs program at the University of Louisville, Kentucky. “That is on the cusp of becoming utilized in a more widespread manner.”
The next goal: to use 3D printing techniques with live cells. Tissue made artificially with real human cells is called “bioficial.”
A patch of bone tissue may one day help patients whose vertebrae are damaged by an injury or cancer. Cartilage, which doesn’t regenerate on its own, could be repaired with bioficial tissue created from patients’ own cells. And perhaps, someday, entire organs could be replaced.
Cells are trickier to work with than plastic. The printer itself has to be adjusted—rather than melting at high temperatures, it has to use low temperatures that won’t kill the cells. It has to be sterile. A robot-controlled syringe squeezes out the cells, which are suspended in a gel that can solidify and maintain the desired shape, similar to gelatin desserts. But those desserts melt when they get warm; for the 3D printed tissue not to melt in the heat of the body requires other chemical processes to ensure they retain the desired shape, says Jos Malda, deputy head of orthopedic research at University Medical Center Utrecht.
Not just that, but each cell needs nutrition. When a body part or organ loses its blood supply, it dies. “If you create a larger construct in the lab, keeping that piece alive is a big challenge,” Dr. Malda says.
Finally, “having cells in the right place doesn’t mean an organ will function,” Dr. Malda says. “But never say never.”
These challenges are why Dr. Williams decided to focus on a bioficial heart. “It doesn’t have complex metabolic activities like the liver or kidneys do. A heart is simply a pump. It pushes blood out and allows blood to come back in,” Dr. Williams says.
The artificial heart was one of the first implanted devices made of synthetic materials. Dr. Williams’s team is working to make a bioficial heart, starting by printing individual parts: the valves, the cardiomyocytes (heart muscle cells), the electrical conduction system, the large blood vessels and the small blood vessels.
We have made dramatic steps forward printing the individual parts of the heart,” he says. “We haven’t assembled it yet, but it’s likely to happen in the not too distant future. It won’t be ready for implantation, but we will be able to understand how the heart works in assembled form.”
The first step is to assemble blood vessels to ensure the blood supply. That would allow for building tissue two to four centimeters thick that has its own blood supply.
Back in 1988, Dr. Williams used fat-derived cells to build a blood vessel and put it into the body of a patient. “Fat has the capability of forming all the different cells found in the heart,” he says.
Perhaps we’ll find out it isn’t necessary for a bioficial heart to look exactly like a real heart, or a bioficial kidney to look exactly like a real kidney for them to work well. “Maybe we can make it more simplistic, using a slightly different blueprint,” Dr. Williams says.
Will the first use in a patient be the complete heart or parts of a heart?” he asks. “I think it will be parts: a patch of large and small blood vessels.”
Such a patch, which researchers are trying to make in the lab, could be used in a patient whose blood isn’t reaching part of the heart. Another possibility is pediatric applications, for children whose hearts haven’t formed properly because of a genetic defect.
We’re hoping that one day we’ll be able to treat the patient by repairing parts long before they are in such a condition that we have to replace the entire organ,” Dr. Williams says.
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