Generation of reporter hESCs by targeting EGFP at the CD144 locus to facilitate the endothelial differentiation

Human Induced Pluripotent Stem Cells as a Screening Platform for Drug-Induced Vascular Toxicity

Evaluation of potential vascular injury is an essential part of the safety study during pharmaceutical development. Vascular liability issues are important causes of drug termination during preclinical investigations. Currently, preclinical assessment of vascular toxicity primarily relies on the use of animal models. However, accumulating evidence indicates a significant discrepancy between animal toxicity and human toxicity, casting doubt on the clinical relevance of animal models for such safety studies. While the causes of this discrepancy are expected to be multifactorial, species differences are likely a key factor. Consequently, a human-based model is a desirable solution to this problem, which has been made possible by the advent of human induced pluripotent stem cells (iPSCs). In particular, recent advances in the field now allow the efficient generation of a variety of vascular cells (e.g., endothelial cells, smooth muscle cells, and pericytes) from iPSCs. Using these cells, different vascular models have been established, ranging from simple 2D cultures to highly sophisticated vascular organoids and microfluidic devices. Toxicity testing using these models can recapitulate key aspects of vascular pathology on molecular (e.g., secretion of proinflammatory cytokines), cellular (e.g., cell apoptosis), and in some cases, tissue (e.g., endothelium barrier dysfunction) levels. These encouraging data provide the rationale for continuing efforts in the exploration, optimization, and validation of the iPSC technology in vascular toxicology.

ssODN-Mediated In-Frame Deletion with CRISPR/Cas9 Restores FVIII Function in Hemophilia A-Patient-Derived iPSCs and ECs

Given that the cDNA of F8 is too large to be packaged into adeno-associated virus (AAV) capsids, gene transfer of some versions of B-domain-deleted F8 (BDD-F8) for hemophilia A (HA) treatment has been attempted with promising results. Here, we describe an efficient gene correction via single-stranded-oligodeoxynucleotide (ssODN)-mediated in-frame deletion within the B domain of F8 with CRISPR/Cas9 in HA-patient-derived induced pluripotent stem cells (HA-iPSCs). The expression and activity of FVIII was restored in corrected HA-iPSC-derived induced endothelial progenitor cells (C-iEPCs) in vitro and in vivo. The bleeding phenotype was rescued in HA mice after C-iEPC infusion. Our results demonstrate an efficient approach for in situ gene correction via introduction of a tiny deletion using ssODN and CRISPR/Cas9 to reframe the F8 transcript and restore FVIII function in HA-iPSC-derived EPCs with potential clinical impact in HA gene therapy. For the first time, we demonstrated in vitro and in vivo the FVIII function that is encoded by the endogenous F8 gene with a partially deleted B domain. This work also suggests an applicable strategy for genetic correction of other gene frameshift mutations.