Bioengineered Livers: A New Tool for Drug Testing and a Promising Solution to Meet the Growing Demand for Donor Organs

Abstract

Background: Organ engineering is a new innovative strategy to cope with two problems: the need for physiological models for pharmacological research and donor organs for transplantation. A functional scaffold is generated from explanted organs by removing all cells (decellularization) by perfusing the organ with ionic or nonionic detergents via the vascular system. Subsequently the acellular scaffold is reseeded with organ-specific cells (repopulation) to generate a functional organ. Summary: This review gives an overview of the state of the art describing the decellularization process, the subsequent quality assessment, the repopulation techniques and the functional assessment. It emphasizes the use of scaffolds as matrix for culturing human liver cells for drug testing. Further, it highlights the techniques for transplanting these engineered scaffolds in allogeneic or xenogeneic animals in order to test their biocompatibility and use as organ grafts. Key Messages: The first issue is the so-called decellularization, which is best explored and resulted in a multitude of different protocols. The most promising approach seems to be the combination of pulsatile perfusion of the liver with Triton X-100 and SDS via hepatic artery and portal vein. Widely accepted parameters of quality control include the quantitative assessment of the DNA content and the visualization of eventually remaining nuclei confirmed by HE staining. Investigations regarding the composition of the extracellular matrix focused on histological determination of laminin, collagen, fibronectin and elastin and remained qualitatively. Repopulation is the second issue which is addressed. Selection of the most suitable cell type is a highly controversial topic. Currently, the highest potential is seen for progenitor and stem cells. Cells are infused into the scaffold and cultured under static conditions or in a bioreactor allowing dynamic perfusion of the scaffold. The quality of repopulation is mainly assessed by routine histology and basic functional assays. These promising results prompted to consider the use of a liver scaffold repopulated with human cells for pharmacological research. Transplantation of the (repopulated) scaffold is the third topic which is not yet widely addressed. Few studies report the heterotopic transplantation of repopulated liver tissue without vascular anastomosis. Even fewer studies deal with the heterotopic transplantation of a scaffold or a repopulated liver lobe. However, observation time was still limited to hours, and long-term graft survival has not been reported yet. These exciting results emphasize the potential of this new and promising strategy to create physiological models for pharmacological research and to generate liver grafts for the transplant community to treat organ failure. However, the scientific need for further development in the field of liver engineering is still tremendous.

Decellularized Wharton's jelly extracellular matrix as a promising scaffold for promoting hepatic differentiation of human induced pluripotent stem cells

“…In the case of liver, primary hepatocytes are mainly used to reseed decellularized liver scaffolds; 10,13,20,21 however, utilizing them is challenging because of limited sources, slow growth, and loss of function in vitro. 24 Recently, with increasing knowledge about mechanisms of liver development and the emergence of induced pluripotent stem cells (iPSCs) technology, researchers were encouraged to use these cells for the production of hepatocytes. 24 Recently, with increasing knowledge about mechanisms of liver development and the emergence of induced pluripotent stem cells (iPSCs) technology, researchers were encouraged to use these cells for the production of hepatocytes.…”

Optimization of a Decellularization/Recellularization Strategy for Transplantable Bioengineered Liver

“…Although many studies have been performed in the DLS field for liver tissue engineering [36][37][38][39][40], unfortunately, because of the nDLS being a lack of "active microenvironmental" support in existing ECM components, the optimization of the nDLS biomaterials become an important procedure for improving the skill of liver tissue engineering. Many protocols have been applied to modify the non-bioactive decellularized scaffolds.…”

A Hepatic Scaffold from Decellularized Liver Tissue: Food for Thought

“…The result is down regulation of drug-metabolizing enzymes, thus reducing the relevance of the testing. In order to overcome these limitations, bioengineered livers could be used in the near future for research purposes [57,142,143]. Liver bioscaffolds have been seeded with both mature hepatocytes and stem cells.…”