Parthenon has how many columns

How many cells are there?

According to the textbook, there are around 200 different types of cells in the human body. This information should soon be outdated, says Sarah Teichmann. The bioinformatician from the Wellcome Trust Sanger Institute recently took a close look at the muscle wall of the heart with her team - and discovered over 60 different cell types there alone. “There are so many subtle differences that are important for the function of the organs. If we want to understand how diseases arise, we first have to understand how a healthy cell works, ”says Teichmann in an interview with ORF.

Practical test in the pandemic

If you extrapolate the data obtained from the heart to the whole body, then there are probably 20,000 different cell types that need to be cataloged. At least that is the aim of the “Human Cell Atlas” research project. The project initiated by Teichmann and her colleague Aviv Regev began in 2016 with a “white paper” and a founding congress; 2,000 researchers from all over the world are now involved.

A work that Teichmann published in the journal "Nature Medicine" in April last year shows that collecting the subtle differences in human organs is also of direct benefit.

In it, she and her team demonstrated for the first time where those receptors are located that the coronavirus uses to gain access to the human body. The result of the study, cited more than 700 times, has meanwhile passed into general knowledge: The entry points of the virus are in cells of the nose, eyes and the salivary glands of the mouth. Why masks offer good protection against viral infections - a finding that was not initially obvious last spring.

How the cell comes to its identity

The navigation bridge of the "Human Cell Atlas" is anchored at two institutes, the Wellcome Trust Sanger Institute in Cambridge, Great Britain, and the Broad Institute in the US state of Massachusetts. It is no coincidence that these two research centers are doing pioneering work here. Both institutes played a leading role in the first large-scale cataloging of the human body, the human genome project. Building on the project finalized in 2003, the scientific community is now setting out to understand not only the genetic sequence but also the diverse effects downstream of the genes.

New methods such as “single cell genomics” and “spatial genomics” show when genes become active in tissues, which proteins and metabolic products are created and where the purpose lies in this apparent chaos of molecules, in short: They show how each individual cell becomes theirs Identity comes and “knows” what to do.

The first version of the cell atlas could be ready in five years, says Teichmann. The work on the encyclopedia of the human body will of course not be finished with this. Because the identity of a neuron, an intestinal or heart muscle cell has subtle nuances that only become visible under a molecular magnifying glass - how far this view into the interior of the cell can be sharpened will probably only become apparent in the future. Applications are already possible now. For example in cancer medicine.

Cure cancer, seal of approval for organoids

“The cell atlas data is often used to find out which cell tumors originate from. Comparisons with healthy cells are also important for research into hereditary diseases such as cystic fibrosis, a disease that leads to severe congestion in the lungs. With the help of the data, colleagues from the USA discovered a new cell type that is responsible for these symptoms. ”In both cases, the insights into the origins of the disease also offer starting points for therapies; cystic fibrosis has so far been considered incurable.

A research axis of the “Human Cell Atlas” extends to Vienna. At the Institute for Molecular Biotechnology, Jürgen Knoblich first cultivated miniature brains, so-called organoids, in the Petri dish eight years ago and opened up a completely new field of research with these biotech imitations.

Organoids are now an integral part of basic neurobiological research - and not only there: there are also miniature versions made from stem cells of various other organs, such as the intestine, heart and kidney. However, the unanswered question in all of these experiments was to what extent the model from the Petri dish actually works like its natural counterpart.

This problem could be solved with the help of the cell atlas, says Teichmann. “By comparing it with natural tissues, we could create a seal of approval for organoids, so to speak.” Work on this is already in progress, for example in Christoph Bock's research group at CeMM, the Center for Molecular Medicine in Vienna-Alsergrund. The goal is: If the signature of the molecules in healthy tissue is known, it should in principle also be possible to adapt the imitation more and more to the original. Until it can hardly be distinguished from it.

Robert Czepel, science.ORF.at

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