© Illustration courtesy of Jennifer Doudna/UC Berkeley



This research could produce an alternative sources of organs for transplant. However, there are an array of ethical and technical hurdles to be addressed. According to Nature , a Japanese stem-cell scientist is set to be granted government backing to develop animal embryos that contain human cells. These embryos will then be transplanted into surrogate animals. This follows the rescinding of such a ban earlier in 2019.The study will be led by Hiromitsu Nakauchi (University of Tokyo) with support of scientists from Stanford University in California. The aim is to grow human cells in mouse and rat embryos. The long-term goal is to create animals with organs composed of human cells an for these organs to be capable of being transplanted into people.On being given permission Nakauchi stated : "Finally, we are in a position to start serious studies in this field after 10 years of preparation. We don't expect to create human organs immediately, but this allows us to advance our research based upon the know-how we have gained up to this point. by the government."The basis for the research is human-animal hybrid chimeric embryos made in the U.S. as Digital Journal reported ), but these were never brought to term and the U.S. National Institutes of Health has since imposed a moratorium on funding this type of experimentation.The practice produces several ethical issues, with gene editing standing as a controversial practice, having a balance of supporters and detractors across the science field. The first studies were undertaken in China, where a gene responsible for a blood disorder was edited out. One of the primary concerns is with whether therapy will have "off-target effects", changing other genes. A bioethics measure in place is that if the scientists detect that human cells exceed more than 30 percent of the brains of the rodent embryos, this will lead to the cancellation of the experiment.The first part of the research is a study to create human pancreases in rodents by using human induced pluripotent stem cells. This will involve will creating fertilized eggs of rats and mice without the ability to make pancreases by manipulating genes. The researchers will next place human iPS cells into those fertilized eggs, forming the "animal-human embryos."