Background & aims: The truncating mutations in tight junction protein 2 (TJP2) cause progressive cholestasis, liver failure, and hepatocyte carcinogenesis. Due to the lack of effective model systems, there are no targeted medications for the liver pathology with TJP2 deficiency. We leveraged the technologies of patient-specific induced pluripotent stem cells (iPSC) and CRISPR genome-editing, and we aim to establish a disease model which recapitulates phenotypes of patients with TJP2 deficiency.
Methods: We differentiated iPSC to hepatocyte-like cells (iHep) on the Transwell membrane in a polarized monolayer. Immunofluorescent staining of polarity markers was detected by a confocal microscope. The epithelial barrier function and bile acid transport of bile canaliculi were quantified between the two chambers of Transwell. The morphology of bile canaliculi was measured in iHep cultured in the Matrigel sandwich system using a fluorescent probe and live-confocal imaging.
Results: The iHep differentiated from iPSC with TJP2 mutations exhibited intracellular inclusions of disrupted apical membrane structures, distorted canalicular networks, altered distribution of apical and basolateral markers/transporters. The directional bile acid transport of bile canaliculi was compromised in the mutant hepatocytes, resembling the disease phenotypes observed in the liver of patients.
Conclusions: Our iPSC-derived in vitro hepatocyte system revealed canalicular membrane disruption in TJP2 deficient hepatocytes and demonstrated the ability to model cholestatic disease with TJP2 deficiency to serve as a platform for further pathophysiologic study and drug discovery.
Lay summary: We investigated a genetic liver disease, progressive familial intrahepatic cholestasis (PFIC), which causes severe liver disease in newborns and infants due to a lack of gene called TJP2. By using cutting-edge stem cell technology and genome editing methods, we established a novel disease modeling system in cell culture experiments. Our experiments demonstrated that the lack of TJP2 induced abnormal cell polarity and disrupted bile acid transport. These findings will lead to the subsequent investigation to further understand disease mechanisms and develop an effective treatment.
Keywords: ALB, albumin; ASGR2, asialoglycoprotein receptor 2; ATP1a1, ATPases subunit alpha-1; BMP4, bone morphogenetic protein 4; BSA-FAF, bovine serum albumin fatty acid-free; BSEP, bile salt export pump; Bile acid transport; CDFDA, 5-(and-6)-carboxy-2′,7′-dichlorofluorescein; Cellular polarity; DE, definitive endoderm; DILI, drug-induced liver injury; FGF2, fibroblast growth factor 2; GCA, glycocholate; GCDCA, glycochenodeoxycholate; HCM, Hepatocyte Culture Medium; HE, hepatic endodermal; HGF, hepatocyte growth factor; HNF4a, hepatic nuclear factor 4a; MDCKII, Madin–Darby canine kidney II; MRP2, multidrug resistance-associated protein 2; NTCP, Na+-TCA cotransporter; PFIC (progressive familial intrahepatic cholestasis); PFIC, progressive familial intrahepatic cholestasis; PI, propidium iodide; RT-qPCR, quantitative reverse transcription PCR; TCA, taurocholic acid; TCDCA, taurochenodeoxycholate; TEER, transepithelial electrical resistance; TEM, transmission electron microscopy; TJP1, tight junction protein 1; TJP2, tight junction protein 2; iHep, iPSC-derived hepatocytes; iPSC, induced pluripotent stem cell; sgRNA, single-guide RNA; ssODN, single-stranded oligonucleotide-DNA.
© 2022 The Author(s).