Using 3D printing to create insulin-producing cells

3D printing opens a world of endless possibilities – for both industrial and medical applications. A cross-national project recently created tissue that produces insulin, spelling hope for patients with diabetes.

Gabriel Salg took part in the project. In this MEDICA-tradefair.com interview, he talks about the challenges the team of researchers had to overcome and explains why 3D printed tissue is not the same as 3D printed organs.

Mr. Salg, what was the objective of the Eurostars 3D-PIVOT project?

Gabriel Salg: The aim of the 3D-PIVOT project was to develop and validate a concept for producing functional insulin-producing cells using 3D bioprinting. Although the experimental research was only done in vitro, the idea from the outset was to take a scalable production and application concept for future use in humans into consideration.

Together with our German project partners (ASD Advanced Simulation and Design GmbH in Rostock and INOVA DE GmbH based in Heidelberg), we developed various software modules to evaluate the suitability of a 3D model for bioprinting via complex in silico simulations prior to production. This resulted in a concept for a hybrid insulin-producing device. Our Romanian technology partner LTHD Ltd. from Timisoara developed a new type of 3D bioprinter.

What successes have you had?

Salg: We successfully used a bottom-up tissue engineering approach to create insulin-producing tissue. Insulin-producing cells were embedded in hydrogel and printed with repetitious accuracy using a 3D bioprinter. In the subsequent cell cultivation step, we observed the formation of cell clusters from the original single cells in the gel. This is attributed to the specific 3D hydrogel environment and impossible to achieve in conventional 2D cell culture.

The cell clusters produce insulin, along the lines of islets of Langerhans in the human pancreas. There was experimental evidence of growth, survival, and function of the cell clusters - also via glucose stimulation. Further experiments on fertilized chicken eggs examined the extent to which new vascular networks grow into the 3D bioprinted structures and whether the cells survive over a longer period without a culture medium and nutrients. We detected extensive vascular growth and the formation of new blood vessels, respectively.

The successful results we achieved in the past years must be replicated in vivo - referring to animal experiments - in upcoming projects to make reliable statements based on high- quality science practices.

How does 3D bioprinting of organs work?

Salg: We developed and use a 'building block' approach that creates individual modular components using 3D bioprinting. The idea is to assemble them into a functional organ replacement in the future. In this setting, the function of the organ replacement outweighs its form, meaning the created replacement may not look like its natural counterpart.

You can essentially envision 3D bioprinting as an automated pipetting system that moves with high precision in a three-dimensional space and dispenses specific volumes of bioink at certain points. Bioink is a combination of living cells and a gel component.

What project challenges did you have to overcome?

Salg: It was challenging to establish a method that integrates the highly fragile insulin-producing cells in bioink and prints them without resulting in cell death during this process.

It is crucial to strike a balance between the choice of bioink and the hardening process of the material that is originally in a liquid state. If you use a gel that is too 'thick' or too highly cross-linked or hardened, not enough oxygen and nutrients will reach the cells. If you select a gel that is too permeable or does not harden sufficiently, you lose the effect of the 3D environment, which is important to achieve cell growth. This can have pertinent consequences for the cells and result in a distinct type of cell death. If the gel is too liquid, the 3D printed structure cannot retain the intended shape.

When will this type of artificial pancreas be used to help people?

Salg: The 3D-PIVOT project only pertained to the endocrine component of the organ. More specifically, it attempted to replicate the insulin-producing function of the pancreas. The pancreas is a highly complex organ that performs various functions. There is no scientific consensus on whether a bioprinted organ will ever be used in humans, which means anticipating a time frame amounts to pure unscientific speculation.

When can we expect a comprehensive application of 3D bioprinting technology to create organs?

Salg: Whether we will ever see a comprehensive application of 3D bioprinted organs is speculation. I believe we should always be cautious when it comes to the immediate promise of 3D-printed organs. The technology already plays an important role in tissue engineering applications such as printed scaffolds that are ready for market or are now on the market. However, science still has a long way to go before it can generate functional tissue the size of a whole complete organ such as the pancreas or liver that comes prepared for blood flow. Aside from biological and medical aspects, ethical, legal, and economic challenges are likewise important on the road to 3D printing human organs. The conversation about these issues should already start today.