Researchers from the Human Genome and Stem Cell Research Center (HUG-CELL) at the University of São Paulo in Brazil have successfully 3D bioprinted functional mini livers that are capable of producing vital proteins, storing vitamins and secreting bile, among other things. By using bioprinting technology, the researchers were able to produce the functional hepatic organoids within 90 days.
The research project undertaken at HUG-CELL has relied on a combination of bioengineering processes, such as cell reprogramming and pluripotent stem cell cultivation, with 3D bioprinting. The combination has enabled the team to produce tissues which have multiple hepatic (liver) functions. According to the researchers, their work has resulted in much longer functioning times for the organoids than previous studies. The work is a promising step towards a potentially implantable bioprinted liver.
“More stages have yet to be achieved until we obtain a complete organ, but we’re on the right track to highly promising results,” explained Mayana Zatz, Director of HUG-CELL. In the very near future, instead of waiting for an organ transplant, it may be possible to take cells from the patient and reprogram them to make a new liver in the laboratory. Another important advantage is zero probability of rejection, given that the cells come from the patient.”
An interesting element of the Brazil-based research is that the team found a way to bioprint clusters of cells—also known as spheroids—instead of printing individualized cells. This approach reportedly enabled the printed tissue to remain functional for longer periods of time.
Essentially, printing the cells in little clumps reduced the loss of contact between cells after printing, which is a challenge in most bioprinting efforts. Notably, the differentiation process, in which stem cells are programmed as hepatic tissue cells, took place after the cells had been assembled in spheroid formation.
90-day mini livers
As mentioned, the HUG-CELL research team succeeded in producing the functional mini livers over the course of 90 days, beginning with the collection of the patient’s blood and ending with final maturation.
The first stage of the process consists of reprogramming blood cells to become induced pluripotent stem cells (iPSCs). Once this crucial step is complete, the differentiation can begin, in which the spheroids of iPSCs become liver cells. The cell clumps can then be mixed with a bioink to be 3D bioprinted using CELLINK’s INKREDIBLE machine. The bioprinted structures are then left to mature and culture for 18 days.
“The printing process entails the deposition of spheroids along three axes, which is necessary for the material to gain volume and give the tissue proper support,” said said Ernesto Goulart, a postdoctoral fellow in USP’s Institute of Biosciences and first author of the study. “The gel-like bioink is crosslinked to make the structures more rigid so that they can be manipulated and even sutured.”
“It’s a somewhat traumatic process for the cells, which need time to get used to the environment and acquire functionality,” Goulart added. “At this stage, they aren’t tissue yet because they’re dispersed, but as shown by our study, they already have the capacity to clear the blood of toxins and to produce and secrete albumin [a protein produced only by the liver], for example.”
The resulting “mini livers” showcased a range of liver functionalities as well as superior performance to single-cell dispersed organoids. In future, the process can be scaled up for the production of full-sized organs, which could be implanted.