• Research: A synthetic embryo opens the door to obtain all kinds of organs

A couple of weeks after presenting the procedure to create synthetic embryos from an adult mouse cell, the Spanish scientist Juan Carlos Izpisúa takes another step in the knowledge of embryonic development and, a little more in the long term, towards different formulas to be able to generate cells, tissues and human organs that can be used for transplantation.

Thanks to an international collaboration, whose results are exposed this Friday in Science , this researcher at the Salk Institute of Biological Studies, in La Jolla (California), has devised a new method that allows monkey embryos to grow in the laboratory for up to 20 days , reaching a state that until now could not be studied in cultivation.

In his words, it is " a first look at the black box of early development , the stages of gastrulation." Embryologist Lewis Wolpert said that "it is not birth, marriage or death, but gastrulation, the most important moment in life ." At that stage of development, by the third week after fertilization, the single-layer embryo (blastocyst or blastula) is transformed into a three-leaf structure (ectoderm, endoderm and mesoderm) from which all the organism

From the first layer will arise the lungs, the gastrointestinal tract and the liver; The middle layer will become the heart, muscles and reproductive organs, and the third layer will be the skin and nervous system. "While we knew a lot about this process in laboratory animal models such as mice or flies, we didn't know the molecular and cellular drivers in primates, including humans."

The method designed by the Izpisúa group, in collaboration with teams from the Primate Biomedical Research Laboratory in Kunmíng (China) and the University of Texas (Dallas), modifies a cell culture protocol to allow cell beams to develop in laboratory conditions up to 20 days.

"The previous protocols had only been able to keep human embryos in culture for less than 14 days," he recalls. This "14-day rule" is a red line drawn by regulatory and legislative institutions that has limited the duration of human embryos in the laboratory for research. It is based on the time of the appearance of the so-called "primitive line" of the embryo, which characterizes the beginning of gastrulation. "Using this system, we could control the cells every day to observe their shape, size and migration patterns, as well as the process by which they transform into different types of cells," all in evolutionary species closer to humans.

In the research that they now describe in Science , they indicate that with these 20-day embryos they have been able to see how the cells followed clear development paths to each layer of the embryo or gastrula. They have even been able to observe some of the molecular details and cellular programs necessary for this growth. Among these processes is, for example, the one that leads to gametes (oocytes and sperm), or the metabolic changes that occur when cells begin to differentiate in the embryo.

In addition, although at work the conditions for this have not been met, the scientist considers it possible from these results to extend the duration of the embryo in culture beyond 20 days and thus better study the differentiation of stem cells and the formation of organs during development.

In short, he synthesizes, "this system provides a basis and a resource to develop better strategies with which to examine early human development in the laboratory", with the implications that this has on the understanding of normal and pathological processes.

This work coincides with another similar study, which is also published by Science , carried out by a team of Chinese scientists headed by Hongmei Wang of the Institute of Zoology of the Chinese Academy of Sciences in Beijing. Izpisúa values ​​that both investigations are published now, "together with other studies that have appeared and will soon be related to this issue," in what it considers a reflection "of the interest and vision of the Chinese government and Chinese scientists that the studies of primates are the key to human health. "

In fact, remember that these types of investigations "are legal in the United States and Europe, only that governments are not providing many funds for it." However, he considers that despite the clear progress in the last 15 years in the process of generating human cells that could be used for transplantation, as well as for the design of models in which to test new drugs, it is obvious that there is still a way To go. "I am convinced that the knowledge of the natural differences that exist between primates and rodents is fundamental, if we want to translate these basic studies into the clinic," he reflects.

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