These almost real conditions are a great advantage when it comes to working out in detail how the tumor manipulates its environment and uses it for itself. The other advantages: The equivalent derived from human tissue can be produced in a standardized way and makes animal experiments replaceable. The journal Biofabrication reports on the promising results.
During the printing process, the Innsbruck researchers placed tumor spheroids (spherical tumor cell aggregates, note) from a neuroblastoma – one of the most common solid tumors in small children – between the cells of the tissue in the new 3D tumor microenvironment model weeks to grow into a microtumor.
“So we were able to observe how this small tumor pulls the capillaries out of the tissue and these then grow into the tumour. The tumor also builds up its own supply structure. This 3D model will help us to better understand the mechanisms of carcinogenesis, i.e. tumor growth, and thus make the tumor microenvironment more usable as a therapeutic target for fighting cancer – and without animal experiments,” emphasizes microbiologist and laboratory head Michael Ausserlechner.
Three-dimensional, animal-free and reproducible
What is new about this development from the 3D bioprinting laboratory at the Medical University of Innsbruck is the combination of complex vascular tissue on a fluidic chip. Although these microfluidic components are already in use in the field of cell cultivation, they usually only have one cell layer. “Our tissue grows into a three-dimensional network up to a thickness of 3 millimeters,” explains microbiologist Ausserlechner.
In a first step, fine channels are lasered into the chips, and a three-dimensional hydrogel with cells is constructed with the bioprinter in such a way that fine channels in the tissue are connected directly to the channels in the chip. Because the tissue needs 2 to 3 weeks to grow and mature, the cells within it have time to organize themselves. This also changes the volume of the tissue and it can detach from the plastic.
“We have therefore developed a special design for interlocking tissue and chip, so that the living tissue remains stable and clear for weeks,” Ausserlechner explains the superiority of the innovative tool.
The Innsbruck researchers also succeeded in cultivating fine, blood vessel-like capillaries so that all cells in this tissue model can be adequately supplied. “The vessels that we generate directly with the bioprinter form the main supply routes in our tissue model and have a diameter of around 0.3 millimeters. So that cells in the tissue that are further away from these channels are also supplied, and fine capillaries are formed. For this we have developed a special bio-ink in which the endothelial cells – they line the inside of the blood vessels – spontaneously organize themselves together with stem cells from 6 to 7 days into a fine capillary network and permeate the entire tissue,” says the biotechnologist Judith Hagenbuchner, who runs and founded the 3D bioprinting laboratory together with Ausserlechner. The process set in motion is similar to natural wound healing.
Broad field of application
The usability of the model is open to many questions. This makes it possible, for example, to test so-called angiogenesis (the formation of new blood vessels, note), a group of drugs that aims to suppress the formation of new blood vessels and thus tumor growth. Also patient-oriented and thus personalized questions can be examined, such as the choice of the appropriate therapy.
The bioprinted tissue model thus also takes a single step in the direction of precision medicine. The Innsbruck development could even prove to be a suitable platform for research into metastasis – a process that significantly reduces the chances of a cure in cancer.
To the people
Michael J. Ausserlechner studied microbiology at the University of Innsbruck, did his doctorate in molecular biology and habilitated in pathophysiology at the Medical University of Innsbruck. Since 2003 he has headed the Molecular Biology Laboratory of Pediatrics I, since 2018 the newly founded 3D bioprinting laboratory together with Judith Hagenbuchner. In his research, he mainly deals with cell death mechanisms in childhood cancer, drug development and 3D bioprinted “organ-on-chip” applications for drug testing.
Judith Hagenbuechner studied biotechnology at the University of Applied Sciences in Wels, received his doctorate in molecular biology from the University of Innsbruck and habilitated in experimental pathophysiology at the Medical University of Innsbruck. They deal with mitochondrial respiration and metabolism as well as the development of bioreactors and bioprinted tissue models for research into cancer and rare diseases.