3D Printed Organs: The Future of Organ Transplantation?

Organ donation can be a very sensitive topic. According to the federal Health Resources and Services Administration, more than 100,000 American men, women, and children are on the national transplant waiting list. Unfortunately, 17 people die each day awaiting critically needed transplants.

One of the most promising scientific innovations that could help overcome this issue is three-dimensional (3D) bio-printing. So what is it all about? Could it be the game changer in current medicine? Keep reading to learn more.

What is 3D printing?

Simply put, 3D printing, or additive manufacturing, creates solid, 3D objects from a digital file. The 3D objects are then produced by adding layers of ink. This process can be done using different technologies (different 3D printer types), where ink is deposited, joined, or solidified under computer control. While 3D printing may still seem like something out of science fiction movies, nowadays, it is becoming an irreplaceable innovation in many areas, including the car industry, medicine, robotics, and education.

3D printing for organ transplantation

The main areas where 3D printing can be adopted in medicine are the production of pharmaceuticals and transplants. In the case of artificial organ and tissue production, 3D bioprinters are used instead of typical 3D printers.

The 3D bioprinters differ from conventional 3D printers in the spectrum of the inks that they are able to print. For example, basic 3D printers can only print using synthetic/chemical materials, such as polymers, plastics, ceramics, metals, and composites. However, 3D bioprinters are capable of printing biomaterials — live cells or cellular material, usually mixed in with polymers. This feature allows scientists to artificially create far more realistic tissue/organ structures.

Whole artificial tissue/organ construct production can be divided into three main phases:

1. Computer modeling. Damaged tissues or organs that need to be replaced are layer by layer scanned using computed tomography, magnetic resonance, or other imaging techniques. The digital images are then reconstructed into a 3D model. Finally, the model's data is converted to a digital language called standard tessellation language (STL), which 3D printers can interpret.
2. Printing. Firstly, the desired bio-ink is prepared. For that purpose, cells are isolated from the patient. After isolating them, they are grown in a laboratory in a specially-adapted artificial environment. When the required number of cells have grown, they are mixed with polymers to obtain the suitable bio-ink, which has similar biological properties as the targeted tissue or organ. The bio-ink is then transferred to the printer cartridge, and finally, the previously prepared STL data is used to print out the 3D model.
3. Post-printing processing. Usually, the manufactured products are not directly transplanted into the organism immediately after printing. This is because the printed organ/tissue constructs need to mature to become as similar as possible to the organs or tissues they are meant to replace. Therefore, after printing, the products are placed in a bioreactor where they grow for a month or more to withstand the necessary mechanical forces after transplantation and to perform at least the minimum functions required of the targeted organ/tissue.

The most promising organ/tissue printing projects

Scientists all over the world are actively working to achieve the ultimate goal – to manufacture functional tissue or organ. Below are a few interesting projects in this field:

3D-printed human ear

An ear implant made from a patient's own cartilage cells and polymeric material (collagen hydrogel) was 3D bio-printed and implanted into a 20-year-old woman to replace a small and misshapen right ear. Contrary to the traditional treatment method, in which the ear prosthesis would have been made from the patient's rib cartilage, this treatment is less costly and, most importantly, requires no serious additional intervention with the patient's organism. The clinical study's authors state that this was the first clinical study of a successful medical application of this technology.

3D-printed cornea

The cornea is a transparent, protective eye layer that covers the iris and the pupil. Every year, more than 1.5 million people worldwide suffer from corneal injuries or diseases that may cause permanent damage to the eye and, in some cases, even lead to blindness. Currently, the main treatment for such diseases is corneal transplantation. However, patients often have to wait months before getting donated tissue, and what is even worse — transplantation surgery does not come with a guarantee of success. Therefore, alternatives to biological corneal implants are being created.

One of these alternatives is the “EndoArt” 3D-printed cornea developed by EyeYon. This artificial cornea construct is made from a biocompatible, sterile polymer. It is dome-shaped, around 50 microns thick, with a curvature that resembles the posterior part of the cornea. This cornea implant received the U.S. Food and Drug Administration (FDA) Breakthrough Device Designation for 2020. One more example of a breakthrough in the development of artificial cornea is when Indian scientists produced a 3D bio-printed human cornea. It was made of a bio-ink derived from human donor corneal tissues and synthetic polymer. For that reason, this cornea is very similar to the natural one and is optically and physically suitable for transplantation.

3D-printed skin

The French company Poeitis and its artificial skin model, “Poieskin,“ is best known in the field of artificial skin development. In 2018, the company launched the first bio-printed human full-thickness skin model mimicking dermal and epidermal layers of skin. Poetis' developed skin consists of primary human fibroblasts (cells naturally found in the dermal skin layer) embedded in a collagen I matrix covered with primary human keratinocytes. Various cosmetics companies use this 3D bio-printed skin to test their products.

Moreover, in 2020, Poeitis, together with one French hospital, installed the first bio-printing platform compatible with the regulatory requirements allowing the manufacturing of implantable tissues in patients. They soon hope to finalize the validation of the ”Poieskin” skin manufacturing process and to start clinical trials.

Finally, it is important to note that although much research is being done in this field, there are only a handful of clinical-case studies conducted to date in which printed tissue/organ constructs have been used. Fortunately, 3D bio-printing technologies are improving rapidly, and researchers are getting closer to making artificial organs applicable in today’s medicine and saving lives.