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Summary: Human embryonic stem cell-derived cardiomyocytes (hESC-CMs) show considerable promise for regenerating injured hearts, and we therefore tested their capacity to stably engraft in a translationally relevant preclinical model, the infarcted pig heart. Transplantation of immature hESC-CMs resulted in substantial myocardial implants within the infarct scar that matured over time, formed vascular networks with the host, and evoked minimal cellular rejection. While arrhythmias were rare in infarcted pigs receiving vehicle alone, hESC-CM recipients experienced frequent monomorphic ventricular tachycardia before reverting back to normal sinus rhythm by 4 weeks post transplantation. Electroanatomical mapping and pacing studies implicated focal mechanisms, rather than macro-reentry, for these graft-related tachyarrhythmias as evidenced by an abnormal centrifugal pattern with earliest electrical activation in histologically confirmed graft tissue. These findings demonstrate the suitability of the pig model for the preclinical development of a hESC-based cardiac therapy and provide new insights into the mechanistic basis of electrical instability following hESC-CM transplantation. : In this article, Laflamme and colleagues show that the transplantation of human embryonic stem cell-derived cardiomyocytes (hESC-CMs) partially remuscularizes the scar of infarcted and appropriately immunosuppressed pigs. hESC-CM recipients exhibited frequent monomorphic ventricular tachycardia before reverting back to normal sinus rhythm by 4 weeks post transplantation. These graft-related tachyarrhythmias were found to be due to focal mechanisms rather than macro-reentry. Keywords: human embryonic stem cell-derived cardiomyocytes, pluripotent stem cells, myocardial infarction, ventricular tachyarrhythmias, electroanatomical mapping, MRI

Chemical and biological (CB) warfare have long been practiced, and although these types of warfare are not acceptable in modern times, this does not prevent them from occurring. This makes it important for societies to be able to appropriately respond to these events, including the best way to decontaminate victims to keep them and emergency responders safe. Decontamination methods such as chemical, physical, wet, and dry methods are discussed, as well as their downsides. Secondary contamination, which played a significant role in the Tokyo sarin attacks, has long been noted by anecdotal evidence, although it has been little studied. Biological agents cause more problems after infection has taken place, and thus preventing the spread of infection is the largest concern. There are many differences between military and civilian populations, and the response to mass casualty attacks differs accordingly. There are several emerging technologies that can make this process easier on all parties, such as bioscavengers, antitoxins, and color changing bleach for visualization. A reliable way to quantify decontamination is also needed, which would allow for better care of victims both in normal hospital situations, as well as during aeromedical transport. In addition, several gaps were identified, such as the lack of scientific basis for 90 percent reduction during decontamination, a way to quantify decontamination, and the lack of studies on toxic industrial chemicals and secondary contamination.

Summary: Human pluripotent stem cells (hPSCs) provide an invaluable tool for modeling diseases and hold promise for regenerative medicine. For understanding pluripotency and lineage differentiation mechanisms, a critical first step involves systematically cataloging essential genes (EGs) that are indispensable for hPSC fitness, defined as cell reproduction in this study. To map essential genetic determinants of hPSC fitness, we performed genome-scale loss-of-function screens in an inducible Cas9 H1 hPSC line cultured on feeder cells and laminin to identify EGs. Among these, we found FOXH1 and VENTX, genes that encode transcription factors previously implicated in stem cell biology, as well as an uncharacterized gene, C22orf43/DRICH1. hPSC EGs are substantially different from other human model cell lines, and EGs in hPSCs are highly context dependent with respect to different growth substrates. Our CRISPR screens establish parameters for genome-wide screens in hPSCs, which will facilitate the characterization of unappreciated genetic regulators of hPSC biology. : Mair et al. establish a robust, inducible CRISPR screening platform for forward genetics in human pluripotent stem cells (hPSCs). Genome-wide proliferation screens identified core essential genes for hPSCs and revealed context-dependent genetic requirements on different substrates. This underlines hPSC plasticity and helps us to understand the genetic wiring of hPSCs. Keywords: human pluripotent stem cells, genome-wide CRISPR screen, functional genomics, essential genes, DRICH1