Liver regeneration: you can do without stem cells
The liver is one of the few mammalian organs capable of self-regeneration, but the mechanisms of this process are still a biological mystery. Researchers at the University of Copenhagen, working under the guidance of Professor Bo Porse, have identified a protein complex that acts as a molecular switch that triggers a program for restoring liver tissue and simultaneously increases its efficiency. This discovery may shift the direction of research in the field of regenerative medicine from stem cells towards simplifying approaches to repairing damage to organs and tissues.
Specialized cells formed from stem cells during the development of the body, as a rule, lose the ability to divide and form new cells. The task of tissue renewal is performed by stem cells that remain in the body. One of the exceptions are specialized liver cells – hepatocytes. These cells are responsible for the metabolic function of the liver, but they do not lose the ability to give rise to their own kind. For a long time, this ability remained a mystery to specialists.
In experiments on mice, the authors found that the removal of a liver fragment triggers a molecular process that begins with a change in the binding regions of the CEBPA and CEBPB genes encoding proteins of the same name from the group of transcription factors – proteins that bind to specific DNA sites and thereby regulate the process of mRNA synthesis on the DNA matrix (transcription) and, accordingly, the expression of certain genes. Moreover, at different stages of the acute phase of the reaction to damage, three different variants of the temporary binding of these transcription factors were identified.
Liver damage can activate certain genes that enable the division of specialized cells – hepatocytes.
According to the researchers, the observations made are comparable with the patterns identified in the framework of a recent work devoted to the study of the mechanisms of self–renewal of the population of cells of the immune system - macrophages. They believe that these data indicate the existence of a universal self-renewal program used by specialized cells of the body. Further study of the issue can make serious adjustments to the established theory that only stem cells are capable of repairing damage to organs and tissues.
The next stage of the work will be a more detailed study of the molecular mechanisms that trigger and suppress the activity of self-renewal systems of specialized cells.
Article by Janus Schou Jakobsen et al. Temporal mapping of CEBPA and CEBPB binding during liver regeneration reveals dynamic occupation and specific regulatory codes for homeostatic and cell cycle gene batteries is published in the journal Genome Research.
Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on the materials of the University of Copenhagen:
Researchers find molecular switch turning on self-renewal of liver damage.
15.03.2013