Loutherback, Kevin

Abstract Liver cultures may be used for disease modeling, testing therapies, and predicting drug‐induced injury. The complexity of the liver cultures has evolved from hepatocyte monocultures to co‐cultures with non‐parenchymal cells and finally to precision‐cut liver slices. The latter culture format retains liver's native biomolecular and cellular complexity and therefore holds considerable promise for in vitro testing. However, liver slices remain functional for ≈72 h in vitro and display limited utility for some disease modeling and therapy testing applications that require longer culture times. This paper describes a microfluidic device for longer‐term maintenance of functional organotypic liver cultures. This microfluidic culture system is designed to enable direct injection of liver tissue into a culture chamber through a valve‐enabled side port. Liver tissue is embedded in collagen and remained functional for up to 31 days, highlighted by continued production of albumin and urea. These organotypic cultures also express several enzymes involved in xenobiotic metabolism. Conversely, matched liver tissue embedded in collagen in a 96‐well plate loses its phenotype and function within 3–5 days. The microfluidic organotypic liver cultures described here represent a significant advance in liver cultivation and may be used for future modeling of liver diseases or for individualized liver‐directed therapies.

A number of cell culture approaches have been described for maintenance of primary hepatocytes. Forming hepatocytes into three-dimensional (3-D) spheroids is one well-accepted method for extending epithelial phenotype of these cells. Our laboratory has previously observed enhanced function of two-dimensional (2-D, monolayer) hepatocyte cultures in microfluidic devices due to increased production of several hepato-inductive growth factors, including hepatocyte growth factor (HGF). In the present study, we wanted to test a hypothesis that culturing hepatocyte spheroids (3-D) in microfluidic devices will also result in enhanced phenotype and function. To test this hypothesis, we fabricated devices with small and large volumes. Both types of devices included a microstructured floor containing arrays of pyramidal wells to promote assembly of hepatocytes into spheroids with individual diameters of ~100 µm. The hepatocyte spheroids were found to be more functional, as evidenced by higher level of albumin synthesis, bile acid production, and hepatic enzyme expression, in low-volume compared with large-volume devices. Importantly, high functionality of spheroid cultures correlated with elevated levels of HGF secretion. Although decay of hepatic function (albumin secretion) was observed over the course 3 wk, this behavior could be abrogated by inhibiting TGF-β1 signaling. With TGF-β1 inhibitor, microfluidic hepatocyte spheroid cultures maintained high and stable levels of albumin synthesis over the course of 4 wk. To further highlight utility of this culture platform for liver disease modeling, we carried out alcohol injury experiments in microfluidic devices and tested protective effects of interleukin-22: a potential therapy for alcoholic hepatitis.