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  • Here we report that FH iHeps derived


    Here, we report that FH iHeps derived from patient-specific and genetically engineered FH iPSCs can be used to test the efficacy of two well-known medications for lowering LDL-C, statins and PCSK9 antibodies, not only in vitro but also in vivo, by engrafting FH iHeps into the liver of immunodeficient mice knockout for Ldlr. With these assays, we have confirmed clinical observations of higher potency of PCSK9 A-1210477 cost compared with statins for treating FH (Robinson et al., 2015), indicating the potential of our model for further drug discovery and preclinical testing of experimental therapies.
    Discussion Patient-specific iPSCs can be differentiated into disease-relevant cells, thus providing an unlimited source of human cells for in vitro studies (Grskovic et al., 2011). Using this disease-in-a-dish approach, multiple human conditions including liver diseases have been modeled (Li et al., 2012; Rashid et al., 2010; Zhang et al., 2011). In this study, we have employed patient-specific FH iPSCs and genetically engineered isogenic FH iPSCs to create a platform for in vitro and in vivo drug testing of LDL-C-lowering therapies. Several groups have previously reported FH iPSCs harboring mutations in LDLR and PCSK9 and the ability of the derived iHeps to increase LDL uptake in vitro upon treatment with statins (Cayo et al., 2012; Ramakrishnan et al., 2015; Si-Tayeb et al., 2016). Our work has focused on testing therapies for FH, in particular anti-PCSK9 antibodies, in vitro and in vivo using FH iHeps, although this has been previously studied in vitro using pHH (Zhang et al., 2012). Likewise, FH disease modeling with isogenic iPSCs, which allow healthy versus diseased comparison of iHeps that share the same genetic background, had not been described beforehand. The addition of isogenic iPSCs may overcome the shortcomings of using a small number of patient-specific iPSCs and clones for identifying FH phenotypes in this study. Consistent with previous studies using FH iHeps (Cayo et al., 2012; Ramakrishnan et al., 2015; Si-Tayeb et al., 2016), our in vitro experiments confirm that statins increase LDL uptake in FH iHeps and also demonstrate a concomitant reduction in TC and APOB level. To facilitate the systematic screening of LDL-C-lowering medications with FH iHeps, we designed a 48-well assay based on labeled LDL capture. This assay showed higher efficacy in increasing LDL capture of PCSK9 antibodies compared with statins, and in the future may prove useful for identifying new candidate drugs for treating FH through systematic screening. In this regard, our assay may be adaptable to 96-well plates through further optimization.
    Experimental Procedures
    Author Contributions
    Acknowledgments We thank all members of our laboratories for their support. We also thank Jenny C.Y. Ho for her technical contribution to this work, Sigma-Aldrich for donation of LDLR ZFNs, and Sanofi and Regeneron Pharmaceuticals for providing PCSK9 antibodies (alirocumab). This work was supported by the Hong Kong Research Grant Council Theme Based Research Scheme (T12-705/11), The National Key Research and Development Program of China (2016YFA0100102), the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA01020106), the Hong Kong Government Innovation and Technology Support Program (Tier 3) (ITS/303/12), the Cooperation Program of the Research Grants Council (RGC) of the Hong Kong Special Administrative Region and the National Natural Science Foundation of China (N-HKU 730/12 and 81261160506), the National Natural Science Foundation of China (8157050838 and 31370995), the Guangdong Province Science and Technology Program (2013B050800010, 2014A030312001, and 2016B030229007), the Guangzhou Science and Technology Cooperation Program (201508030027), the Shenzhen Science and Technology Council Basic Research program (JCYJ20150331142757383), the Pearl River Science and Technology Nova Program of Guangzhou (201610010107), and the Youth Innovation Promotion Association of the Chinese Academy of Sciences (2015294). H.-F.T. is the National Coordinator and Investigator of the ODYSSEY OUTCOMES study sponsored by Sanofi and Regeneron Pharmaceuticals.