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Personalized antisense oligonucleotides (ASOs) have achieved positive results in the treatment of rare genetic disease1. As clinical sequencing technologies continue to advance, the ability to identify patients with rare disease harbouring pathogenic genetic variants amenable to this therapeutic strategy will probably improve. Here we describe a scalable platform for generating patient-derived cellular models and demonstrate that these personalized models can be used for preclinical evaluation of patient-specific ASOs. We describe protocols for delivery of ASOs to patient-derived organoid models and confirm reversal of disease-associated phenotypes in cardiac organoids derived from a patient with Duchenne muscular dystrophy (DMD) with a structural deletion in the gene encoding dystrophin (DMD) that is amenable to treatment with existing ASO therapeutics. Furthermore, we designed novel patient-specific ASOs for two additional patients with DMD (siblings) with a deep intronic variant in the DMD gene that gives rise to a novel splice acceptor site, incorporation of a cryptic exon and premature transcript termination. We showed that treatment of patient-derived cardiac organoids with patient-specific ASOs results in restoration of DMD expression and reversal of disease-associated phenotypes. The approach outlined here provides the foundation for an expedited path towards the design and preclinical evaluation of personalized ASO therapeutics for a broad range of rare diseases. A scalable platform for generating patient-specific organoids for testing personalized oligonucleotide therapeutics is described.

There is increasing evidence to suggest that embryonic stem cells (ESCs) are capable of differentiating into hepatocytes in vitro. In this study, we used a combination of cytokines and sodium butyrate in a novel three-step procedure to efficiently direct the differentiation of mouse ESCs into hepatocytes. Mouse ESCs were first differentiated into definitive endoderm cells by 3 days of treatment with Activin A. The definitive endoderm cells were then differentiated into hepatocytes by the addition of acidic fibroblast growth factor (aFGF) and sodium butyrate to the culture medium for 5 days. After 10 days of further in vitro maturation, the morphological and phenotypic markers of hepatocytes were characterized using immunohistochemistry, immunoblotting, and reverse transcription-polymerase chain reaction (RT-PCR). Furthermore, the cells were tested for functions associated with mature hepatocytes, including glycogen storage and indocyanine green uptake and release, and the ratio of hepatic differentiation was determined by counting the percentage of albumin-positive cells. In the presence of medium containing cytokines and sodium butyrate, numerous epithelial cells resembling hepatocytes were observed, and approximately 74% of the cells expressed the hepatic marker, albumin, after 18 days in culture. RT-PCR analysis and immunohistochemistry showed that these cells expressed adult liver cell markers, and had the abilities of glycogen storage and indocyanine green uptake and release. We have developed an efficient method for directing the differentiation of mouse ESCs into cells that exhibit the characteristics of mature hepatocytes. This technique will be useful for research into the molecular mechanisms underlying liver development, and could provide a source of hepatocytes for transplantation therapy and drug screening.