In Vitro Proliferation and Long-Term Preservation of Functional Primary Rat Hepatocytes in Cell Fibers

Primary hepatocytes are essential cellular resource for drug screening and medical transplantation. Since culture systems for them have already succeeded in reconstituting the biomimetic microenvironment, acquiring additional capabilities both to expand primary hepatocytes and to handle them easily would be expected as progress to the next stage. This paper describes a culture system for primary rat hepatocytes that is equipped with scalability and handleability relying on cell fiber technology. Cell fibers are cell-laden core-shell hydrogel microfibers; in the core regions, cells are embedded in extracellular matrix proteins, cultured three-dimensionally, and exposed to soluble growth factors in the culture medium through the hydrogel shells. By encapsulating primary rat hepatocytes within cell fibers, we first demonstrated they increase in number while keeping their viability and their hepatic specific functions for up to thirty days of subsequent culture. Then, we demonstrated the potency of the primary rat hepatocytes that proliferate in cell fibers not only as cell-based sensors to detect drugs that damage hepatic functions and hepatocellular processes but also as transplants to improve the plasma albumin concentrations of congenital analbuminemia. Therefore, our culture system could serve for innovating strategies and promising developments in applying primary hepatocytes to both pharmaceutical and medical fields. ### Competing Interest Statement The authors declare competing financial interests: TO and ST are inventors on intellectual property rights related to the cell fiber technology, and stockholders of Cellfiber Inc, a start-up company based on the cell fiber technology.