Mammals like humans lose their ability to smell with age. Researchers have now investigated why this happen. For the analysis, the researchers followed the stem cell development in the brain of mice with so-called confetti reporters.
Disorders of the sense of smell impair the quality of life
A few years ago, researchers from the USA reported on their study, according to which the nose not only contained 10,000 different odors but perceives about a trillion (1,000,000,000,000) odors. However, if the olfactory cells do not work properly, you will lose a lot of quality of life. Disorders of the sense of smell mean a massive restriction in the everyday life of those affected. However, with increasing age, the sense of smell in humans ̵
Stem cell-derived olfactory nerves
In mammals, the formation of nerve cells (neurogenesis) is predominantly restricted to early childhood and occurs in adulthood only in a few regions of the forebrain.  Such an exception are olfactory nerves, which result from several intermediate stages of stem cells.
"The production of these nerve cells is running out with increasing age," explains the head of the working group at the Institute of Computational Biology (ICB) of Helmholtz Zentrum München. Carsten Marr, in a Communication.
"We wanted to clarify in the current work, how it comes to it and what contribution the stem cells have," said the scientist.
To pursue this question, formed Dr. Marr with mathematician Lisa Bast and stem cell researchers Filippo Calzolari (today at the Institute of Physiological Chemistry of the University Medical Center Mainz) and Prof. Dr. med. Jovica Ninkovic is an interdisciplinary team of experts.
"Our approach to the current work works through so-called confetti reporters in mice: we bring individual stem cells and all their progeny – so-called clones – to glow in a specific color," explains Dr. Calzolari.
In this way, the researchers were able to track the development of individual clones and distinguish them as dots of different colors, giving the procedure its name.
"By comparing young and older mice, we wanted to find out in the next step what contribution single stem cells and intermediate stages contribute to the neurogenesis of the finished olfactory cells, "continued Calzolari.
Fewer cells develop into olfactory cells in old age
However, the systematic evaluation of images is hardly manageable for humans: the available data were extreme heterogeneous and a comparison of young and old brains difficult.
Marr and his team to bear. They are specialists in the quantification of single-cell dynamics, ie the question: which and how many cells of a large association are developing further?
Scientists use artificial intelligence, design mathematical models and program algorithms that evaluate the image data for them
"We compared the confetti measurements with several mathematical models of neurogenesis," explains Lisa Bast.
"In this way, we found that, especially in certain intermediate stages – the so-called transit amplifying progenitors – the In addition, the analysis shows that so-called asymmetric cell division in stem cells as well as their resting phases increased in older mice.
"This means that fewer cells develop into olfactory cells and become inactive in the elderly Stem cell pool remain, causing the product According to Jovica Ninkovic,
the work is the first to allow scientists to quantitatively study the behavior of nerve stem cells in the living mammalian brain using a mathematical model. (Ad)