A set of new technologies allows you to immerse yourself in the body of living beings and explore all your organs cell by cell. It is a cosmological vision of life that until a few years ago was impossible. This set of techniques, known as RNA sequencing of individual cells, is the discovery of the year, according to the prestigious magazine published yesterday. Science.
These techniques, whose use has been universalized since 2013, allow us to know which genes are active in a cell, to know its function, to tag it to follow it throughout its life and to see how it interacts with other cells in a three-dimensional plane. So you can see how an embryo of a few cells gives rise to different organs to generate a healthy individual or unveil the molecular processes that cause cancer and other diseases.
About five years ago these techniques allowed sequencing like many hundreds of cells at a time; now several hundred thousand can be analyzed. This allows to characterize whole organs and even entire organisms. One of the applications of this technology is to find new types of cells in the human body. This year a new class of cells has been discovered from the area of contact of the uterus and placenta that perform a mediation work with the mother's immune system so that the mother recognizes the fetus and does not attack it during the first months of pregnancy. . The same has happened in the brain or respiratory system.
"If before we thought there were about 3,000 different types of cells in the human body, now we believe there are 10 times more," he explains. Holger Heyn, researcher at the National Center for Genomic Analysis, in Barcelona, and one of the coordinators of the Human Cell Atlas project. This initiative, which emerged in 2016 and involves more than 1,000 scientific teams from 58 countries, will provide the first cell map of 10 human organs in 2022. "These techniques are going to give us a Google maps of the complete human body in which we can zoom in each organ and explore it cell by cell. First we will have a reference of a healthy body and then specific profiles of diseases will be added, "he explains.
"We thought there were about 3,000 types of cells in the human body, now we believe there are 10 times more"
Heyn's team focuses on the b-cell atlas of the immune system. "These cells have a key role in the Chronic lymphocytic leukemia and, thanks to this technique, we can know what is wrong with these cells. For example, we will analyze blood from patients who do not respond to the treatments and from others who do not relapse after receiving the drugs. In this way we may be able to predict what is the prognosis of a particular patient and adapt the treatments, for example, to give a very aggressive one or not, "he explains.
From the development of the first human cell atlas, the European project LifeTime aims to analyze the origin and progression of cancer and other diseases at the cellular level. This initiative also competes to obtain funding of 1 billion euros from the European Commission. These types of techniques are used in animal models and human tissues, but can not be applied for now in living people. In any case, the experts emphasize that this does not have to be a limitation in the face of possible medical uses. The team of Nikolaus Rajewsky, one of the coordinators of the European project, develops mini-human organs created from reprogrammed cells of patients to whom the sequencing of individual cells can be applied and see how they change with different drugs. "This technique will be decisive during the next decade, not only in basic science but also in clinical applications," says Rajewsky, who is a researcher at the Max Delbrück Molecular Medicine Center in Germany.
In 1970, a doctoral student named Jaume Baguñà discovered a new species of worm in a pond in Montjuic (Barcelona). If it was cut into ten pieces, each one of them became a new worm, something very similar to immortality. Since then the Schmidtea mediterranea It has become one of the most interesting living beings to study the genes related to the ability to regenerate tissues. This year, Rajewsky's team published a complete cellular atlas of one of these worms. The work connected each type of adult cell with the mother cell that had generated it. "This type of studies can be useful to better understand the regenerative capacity of human beings and know which genes are involved in each step," explains the researcher.
The same type of technology was applied to analyze thousands of cells of the respiratory system of mice and humans, which allowed to discover the pulmonary ionocytes. "These cells account for 0.001% of the respiratory system, but we see that they express a fundamental gene for cystic fibrosis and without this type of technology we would not even have known that they existed," explains Avi Regev, a researcher at Harvard University and project coordinator. Human Cell Atlas.