3D printed organs a step closer

An unfortunate dichotomy is emerging from breakthroughs in 21st Century medicine. With better medical treatment people are living longer, but with an aging population comes an increase in failing organs. Coupled with unprecedented population growth, the shortage of donor organs is in a critical state.

In the last decade alone the number of patients requiring a replacement organ has doubled, while the number of transplants has barely changed. With around 90% of patients on transplant lists waiting for a kidney, the harsh reality is there are simply not enough available.

Regenerative medicine could address this problem and advances in 3D printing technology have pushed biomaterials research to an all-time high. While 3D printing technology has already been adopted for small scale cell and tissue regeneration, the Holy Grail remains a printable, transplantable, human organ.

"The ultimate goal of regenerative medicine is to develop new therapies to solve the shortage of donor organs available for transplant," says Anthony Atala, director of the Wake Forest Institute for Regenerative Medicine. "We think 3D printing, along with other regenerative medicine treatments, such as cell therapies, may help meet this goal. In addition to organs, we are working on printing tissues such as bone, cartilage and muscle. We expect some of these to be ready for testing in humans within five years or so. But, it will obviously take much longer to develop solid organs such as the kidney and liver."

By its very nature, printing 3D organs raises countless ethical questions. This year Chinese scientists claimed to have developed working printed kidneys, which only survived for four months. But, as the technology matures and if current limitations are overcome, the impact on medicine will be unparalleled.

For larger tissues and organs, the main challenge is to produce the billions of cells required, and to identify the optimum way to supply the structure with oxygen until they can integrate with the body.
To address the oxygenation issue, Atala's team is evaluating several different approaches, including printing channels and other nutrients into the structures that can help with the transfer of oxygen.
Similarly, adding oxygen generating materials to the structures provides a temporary supply of oxygen, while further research is being conducted into printing blood vessels.

"In tissue engineering, the main job of biomaterials is to provide a support structure for cells as they grow and develop," says Atala. "The ideal material must be both biocompatible - so it allows for the normal function of cells and doesn't elicit an immune reaction in the body - as well as biodegradable so that the body's own cells can replace the scaffold and have similar mechanical properties to the native tissue."

Working with a modified desktop inkjet printer, the Wake Institute researchers use cells, instead of ink, and can print a structure in about 40 minutes.

The principle is the same as a normal 3D printer; the head builds a structure layer by layer. So far, a piece of bone has been created using a desktop printer that has been successfully implanted. The next generation of technology is still under development and utilises more sophisticated printers. The overall technology would scan a patient's wound and then the 3D printer would apply cells directly on to the wounded area to repair and rebuild it.

Designing for the human body
Designing materials that can be implanted into the body and last over time has brought several issues to light.

"The challenge is cells, as we could not get enough to grow outside of the body," says Atala. "But, over the last 20 years we've basically tackled that and scientists can now grow many different types of cells, plus we can use stem cells. Even then, though, there are still certain cells that we just can't grow from the patient such as liver, nerve and pancreatic cells. The other challenge we continue to have is vascularity, the actual supply of blood to these organs or tissues to allow them to survive once we regenerate them."

Printing organs
Atala's team is currently experimenting with a technique of weaving and knitting cells to create a tubularised biomaterial; using a patient's own cells to help the regeneration process.

"We had a patient who was presented with a deceased organ and we then created one of these smart biomaterials to replace and repair that patient's structure," says Atala. "We actually used the biomaterial as a bridge so that the cells in the organ could help to close the gap and regenerate the tissue. Six months later the tissue was fully regenerated."

While the printing of major human organs is likely to still be some way off, there is of course another area that 3D medical printing could play a role; cosmetic surgery.

Bioengineers from Weill Cornell Medical College in the US have 3D printed artificial ears using a gel made from living cells which, over a three month period, can grow cartilage that replaces the collagen used to mould them in the first place.

The artificial ears looks and acts like natural ears, and could provide hope for children born with a congenital deformity or in adults that suffer some kind of trama to the ear resulting in disfigurement.

Lead researcher Lawrence Bonassar, associate professor of biomedical engineering at Cornell, says: "This is a win-win for both medicine and basic science, demonstrating what can be achieved."

Replacement ears are traditionally constructed with materials that have 'Styrofoam-like' consistency, or sometimes surgeons build ears from a patient's harvested rib. But this is a challenging and painful procedure, and ears rarely look completely natural or perform well.

To make the ears, a digitised 3D image is used to print and assemble a mould, which is injected with collagen and then cartilage cells. This high density gel is similar to the consistency of jelly when the mould is removed and the collagen acts as a scaffold upon which cartilage can grow. The ear is currently undergoing tests, which could see the first human implant of a Cornell bioengineered ear in as little as three years.

How it works
While 3D printing organs is far more complex than simple structures, the actual process is similar. The printers have cartridges and nozzles that release bio-ink, layer by layer on a platform. To create individual organs, scientists perform CT scans or MRIs on a patient. The results are input into a computer to create a blueprint guide on how cells are positioned in each layer. Once a specimen has been printed, it is put in an incubator to enable cells to fuse and function like a real organ.

Chris Shaw

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Being a possible doner to my 1\2 brother I'm checking up on 3d printed kidneys development & timeline.
Good article.

Comment Roger V. Tranfaglia, 05/10/2014

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