Benefits, limitations, and validated utility of engineered primary human liver platforms for drug metabolism studies

ModelBenefitsPotential LimitationsDrug Metabolism Applications (Primary Human Liver Cells)
Cellular microarraysCan be used to evaluate the metabolism of many drugs simultaneously in a small footprintPrimarily dependent on imaging-based readouts when using cellsThese arrays have so far been adapted to cancerous hepatic cell lines and application to primary liver cells is pending (Lee et al., 2005, 2008; Yu et al., 2018)
Low novel drug/chemical usageCurrent array configurations are limited in their ability to interrogate responses of adhered cells to molecular gradients
Dual advantage with the ability to evaluate the effects of combinatorial biochemical and biophysical signals on enhancement of liver cell functions.
Conventional cocultures (random distribution)No specialized systems/equipment is needed to create randomly distributed cocultures in standard multiwell culture platesFunction of hepatocytes is highly dependent on the choice of the nonparenchymal support cell typeMeasured activities of NAT2, UGT1A1, SULT, AKR, AO, FMO, CYP1A2, CYP2B6, CYP2C9, CYP2D6, and CYP3A4 after 8 days of culture (Kratochwil et al., 2017)
Part of the randomly distributed cocultures can display morphologic and functional instability due to suboptimal (random) cell-cell contact/interactionsMeasured activities of CYP2D6 and CYP3A4 for 14 days (Novik et al., 2017)
Typically, have lower activities of some drug metabolism enzymes than micropatterned cocultures
Micropatterned cocultures (MPCCs)Controlled homotypic hepatocyte interactions on micropatterned protein domains allow for proper cell polarity and higher/stable liver functions in coculture with fibroblasts for 4–6 weeksSpecialized masks created using lithographic techniques are needed to pattern ECM proteins (e.g., collagen) to enable subsequent clustering of the hepatocytesMeasured activities of NAT2, UGT1A1, SULT, AKR, AO, FMO, CYP1A2, CYP2B6, CYP2C9, CYP2D6, and CYP3A4 after 8 days of culture (Kratochwil et al., 2017)
Available in industry standard multiwell formats (up to 384-well plates)A single configuration containing all major liver cell types is currently lackingMeasured activities of CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2E1, CYP3A4, UGT, and SULT for 30 days (Khetani and Bhatia, 2008; Lin et al., 2016)
Diverse types of liver NPCs can be cultured in MPCCs without significantly affecting the homotypic interactions and polarity of hepatocytes on the micropatterned coloniesUse nonliver fibroblasts for inducing optimal functions in hepatocytesDrug metabolite detection (Wang et al., 2010; Ballard et al., 2016)
Drug clearance prediction (Chan et al., 2013; Lin et al., 2016)
DDIs including P450 induction and inhibition (Khetani and Bhatia, 2008; Lin et al., 2016; Kratochwil et al., 2018)
Transporter, metabolism, and/or P450 induction interplay on drug disposition (Ramsden et al., 2014a; Moore et al., 2016)
Self-assembled SpheroidsMany off-the-shelf plate formats are available for the creation of spheroidsCellular necrosis can occur in the center of spheroids if their diameter exceeds 250–300 µmMeasured activities of CYP1A2, CYP2C8, CYP2C9, CYP2D6, and CYP3A4 for 35 days (Bell et al., 2016, 2018)
Some plate formats can cause large variations in the sizes of the spheroids, which leads to nonuniform viability and function
Single spheroids may not provide enough material for sensitive drug metabolite identification
Heterogeneous cell distribution without any defined architecture
Bioprinted spheroids/organoidsPrinting head allows control over the placement of cells in different locations/compartments (e.g., hepatic, vascular, and other nonparenchymal cell compartments)Microscale printing resolution for control of single cell placement is currently lackingMeasured activity of CYP3A4 for 28 days (Norona et al., 2016)
Software programming allows on-demand 3D architectures to the created with same instrumentation configuration (i.e., expensive masks are not needed as for lithographic techniques)Low-throughput creation of the cultures
The method requires complex and often expensive instrumentation with the need for well-trained technologists
The method requires a larger number of cells than microscale patterning methods using lithography
Printed tissues on the millimeter to centimeter scale can potentially display necrosis in the core of the tissues in the absence of a connected/perfused vasculature
Perfused liver culture/coculture platforms (some are also known as liver-on-a-chip)Enable fluid flow to allow automated nutrient and waste exchange as well as the generation of in vivo-like molecular gradients (e.g., oxygen), which can lead to zonated hepatic phenotypesPerfusion requires specialized fluid pumps and control systemsMeasured activities of CYP2D6 and CYP3A4 for 6 days of culture (Novik et al., 2010)
Many microfluidic perfusion devices are now commercially available for the creation of perfused liver culturesDrugs can potentially bind and be sequestered by the tubing and materials used in the perfusion devicesMeasured activities of CYP2C9, CYP3A4, and UGT for 14 days (Vernetti et al., 2016)
Due to the need for tubing, perfusion devices have a large dead volume, which can necessitate higher quantities of the novel (and often very limited) compounds for treating cell culturesDrug clearance prediction (Dash et al., 2009; Novik et al., 2010)
Most devices are currently low-throughput, allowing up to 12 devices to be perfused at a single timeDrug metabolite identification (Sarkar et al., 2017)
  • AKR, aldo-keto reductase; FMO, flavin monooxygenase; NAT2, N-acetyltransferase 2; SULT, sulfotransferase; UGT1A1, UDP glucuronosyltransferase 1A1.