Biological complexity: dying c ells protect living ones (Introduction)

by David Turell , Friday, July 09, 2021, 18:56 (1233 days ago) @ David Turell

Cells are constantly dying and being replaced. The continue=to-live cells are protected by a specific mechanism:

https://phys.org/news/2021-07-dying-cells-neighbors-tissue.html

"To enable tissue renewal, human tissues constantly eliminate millions of cells, without jeopardizing tissue integrity, form and connectivity. The mechanisms involved in maintaining this integrity remain unknown. Scientists from the Institut Pasteur and the CNRS today revealed a new process which allows eliminated cells to temporarily protect their neighbors from cell death, thereby maintaining tissue integrity. This protective mechanism is vital, and if disrupted can lead to a temporary loss of connectivity. The scientists observed that when the mechanism is deactivated, the simultaneous elimination of several neighboring cells compromises tissue integrity. This lack of integrity could be responsible for chronic inflammation.

"Human epithelia are tissues found in several parts of the body (such as the epidermis and internal mucosa). They are composed of layers of contiguous cells that serve as a physical and chemical barrier. This role is constantly being put to the test by both the outside environment and their own renewal. Tissue renewal involves the formation of new cells by cell division and the elimination of dead cells. The mechanisms that regulate the ability of epithelia to maintain their integrity in contexts involving large numbers of eliminated cells remain poorly understood, despite the fact that this situation occurs regularly during embryogenesis or the maintenance of adult tissues.

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"...the research team revealed that when a cell dies, the EGFR-ERK pathway—a cell activation signaling pathway known for its involvement in the regulation of cell survival—is temporarily activated in the neighboring cells. The scientists observed that the activation of the EGFR-ERK pathway protected neighboring cells from cell death for approximately one hour, thereby preventing the simultaneous elimination of a group of cells. "We already knew that this pathway plays a key role in regulating cell survival in epithelial tissue, but we were surprised to observe such protective dynamics between cells," comments Romain Levayer, Head of the Cell Death and Epithelial Homeostasis Unit at the Institut Pasteur and last author of the study.

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"The scientists' observations confirm that tissues need to develop mechanisms preventing the elimination of neighboring groups of cells. "These observations are important as they illustrate the incredible self-organizing ability of biological tissues, a property that enables them to withstand stressful conditions. So there is no need for a conductor to orchestrate where and when the cells should die; everything is based on highly local communications between neighboring cells," adds Romain Levayer.

"This process seems to have been conserved during evolution. The same protective mechanism based on local EGFR-ERK activation was discovered independently in human cell lines by the research group led by Olivier Pertz at the University of Bern in Switzerland. The results of the other study suggest that the protective mechanism is conserved between species separated by hundreds of millions of years, indicating that it is a relatively universal mechanism." (my bold)

Comment: No surprise in my bold. This protective mechanism had to be designed very early in evolution since cells are replaced constantly to keep tissues up-to-date in active metabolism. I imagine, when this mechanism is picked apart it will look highly designed.