Availability, Functionality, and Safety as well as Quality Control of Hepatocytes as Seeding Cells in Liver Regenerative Medicine: State of the Art and Challenges

Abstract

Abstract: Hepatic disease is one of the most common causes of death worldwide and has become a global health problem. Liver transplantation is the only effective treatment strategy for patients with hepatic function failure, but the insufficient number of donated healthy livers is the main obstacle limiting this process. To alleviate the demand for donor's livers, alternative approaches are being actively explored using liver tissue engineering principles. Liver tissue engineering consists of three elements, including seeding cells, extracellular matrix, and bioreactors. Among them, seeding cell is the most key factor. In this regard, hepatocyte-based tissue engineering can overcome the above shortages for tissue repair and regeneration in hepatic disorders. Primary human hepatocytes in liver regenerative medicine are the most preferred seeding cells, although limited access to a sufficient number of functional hepatocytes are a major issue due to the difficulties in long-term function maintenance of hepatocyte as well as the lack of availability of healthy donors. Hepatocyte-like cells (HLCs), derived from various stem cells, including non-liver-derived stem cells and liver-derived stem cells, as well as trans-differentiation of other cell types, may provide adequate cell sources and could replace primary human hepatocytes as seeding cells. However, it is still a great difficulty that HLCs generated by stem cell differentiation meet the quality required for clinical therapy. Furthermore, none of the standardized protocols to generate high-quality HLCs is available. Whether primary hepatocytes or HLCs are from various sources, preventing the functional deterioration of hepatocytes or generating fully functional hepatocytes is also a big challenge, respectively. In addition, the adoptions of three-dimensional co-culture systems and some small-molecule compounds contribute to maintaining the hepatic functionality of primary hepatocytes and enhancing the liver-specific functions of HLCs. In short, hepatocyte-based liver regenerative medicine is an attractive alternative strategy for liver diseases, notwithstanding some challenges still exist from bench to bedside. This review summarizes the current status, issues, and challenges in availability, functionality, and safety, as well as quality control of seeding hepatocytes with regard to liver tissue engineering in regenerative medicine for the treatment of liver disorders.