Researchers from the Human Genome and Stem Cell Study Center (CEGH-CEL), from the Biosciences Institute of the University of São Paulo (IB-USP), developed a technique for the reconstruction and production of liver in the laboratory.
The proof of concept of the method was performed with rat liver. In the next stage of the study, the researchers intend to adapt the technique to produce human livers in the future in order to increase the availability of the organ for transplantation.
The results of the study, supported by FAPESP, were published in the journal Materials Science and Engineering: C.
“The idea is to produce human livers in a laboratory, on a scale, in order to reduce the wait for compatible donors and the risks of rejection of the transplanted organ,” says Luiz Carlos de Caires Júnior, the study’s first author to FAPESP. The researcher holds a post-doctorate at CEGH-CEL – a Research, Innovation and Dissemination Center (CEPID) funded by FAPESP.
The methodology is based on tissue bioengineering techniques developed in recent years for the production of organs for transplantation, called decellularization and recelularization.
The techniques consist of subjecting the organ of a deceased donor – in this case, the liver – to successive washes with detergent solutions or enzymes, in order to remove all cells from the tissue until only the extracellular matrix remains, with the structure and shape originals of the organ. The extracellular matrix is ??recomposed with cells derived from the recipient patient, in order to avoid the risk of immunological reactions and decrease the risk of long-term rejection of the transplanted organ.
“It is as if the recipient received a retreaded liver, which would not be rejected because it was reconstituted using its own cells. It would not even need to take immunosuppressants”, explains Mayana Zatz, coordinator of CEGH-CEL and co-author of the study.
Through these techniques it is also possible to reconstruct organs considered borderline, increasing their availability for patients in the waiting list, explains Caires.
“Many organs available for transplantation are not usable because they come from people who have suffered traffic accidents. Through these techniques it is possible to recover these organs, depending on their condition”, says the researcher.
The decellularization process, however, removes the main components of the organ’s extracellular matrix, such as molecules that signal to the cells that they must proliferate and form vessels. Thus, it compromises tissue recelularization and decreases the adhesion properties of cells to the extracellular matrix.
To solve this obstacle, the CEGH-CEL researchers improved the techniques of decellularization and recelularization, introducing a new stage.
After isolating and decellularizing the liver of rats, they injected into the extracellular matrix a solution rich in molecules, such as Sparc proteins and TGFB1, produced by liver cells grown in the laboratory in a conditioned medium. These proteins signal to liver cells that they must proliferate and form blood vessels – essential functions for the proper functioning of the liver.
“The enrichment of the extracellular matrix with these molecules allows it to become much more similar to that of a healthy liver”, says Caires.
After treating the extracellular matrix of the liver of rats with the solution, hepatocytes, endothelial and mesenchymal cells were introduced into the material – the latter produced from induced pluripotent stem cells (iPS). The method consists of reprogramming adult cells (from the skin or other easily accessible tissue) to make them assume a pluripotency stage similar to that of embryonic stem cells.
“The work showed that it is possible to induce the differentiation of human stem cells into cell lines that are part of a liver and use them to reconstruct the organ so that it is functional. It is the first proof of concept that the technique works “, evaluates Zatz.
With the aid of a syringe pump, liver cells were introduced into the extracellular matrix of rat liver to produce an organ with the characteristics of a human.
The organ grew for five weeks in an incubator that simulates the conditions of a human body. The analyzes indicated that the enrichment of the extracellular matrix with the solution rich in Sparc and TGFB1 proteins greatly improved the recelularization of the produced liver.
“Liver cells grow and function better through this treatment. We now intend to build a bioreactor to decellularize a human liver and evaluate the possibility of producing it in the laboratory and on a scale”, says Caires.
According to the researcher, the technique can also be adapted for laboratory production of other organs, such as lung, heart and skin.
The project is part of one of the research lines of CEGH-CEL, aimed at the manufacture or reconstruction of organs for transplantation using different techniques.
Through a project in partnership with the pharmaceutical company EMS, supported by FAPESP under the Program to Support Research in Partnership for Technological Innovation (PITE), the Center’s researchers intend to modify pig organs, such as the kidney, heart and skin, to transplant them into humans.
As it is not possible to transplant pig liver to humans, the researchers went on to other strategies: decellularization and recelularization and production of the organ by 3D printing.
“These different study fronts are complementary. The expectation is that, in the future, we will have organ plants for transplantation”, says Zatz.