The indefinite self-renewal of specialized cells without the need for stem cell intermediates
November 16, 2009 -- PhysOrg.com -- Is the indefinite expansion of adult cells possible without recourse to stem cell intermediates? The team led by Michael Sieweke at the Centre d'immunologie de Marseille Luminy, France has proved that this is the case by achieving the ex vivo regeneration for several months of macrophages, specialized cells in the immune system. Published in Science on November 6, 2009, this discovery could be applied to other cell types.
This research enables a clearer understanding of the mechanisms underlying cell differentiation, but above all raises many hopes for potential therapeutic applications.
The regenerative medicine of the future will be based on replacing damaged cells and repairing deficient organs, notably through the use of stem cells. Indeed, these cells are able not only to proliferate indefinitely but, in theory, to supply all types of cells to the human body. However, the processes that allow the passage from adult (rather than embryonic) cells to stem cells ("reprogramming") are complex and full of risk, as are the processes necessary for the "retransformation" of stem cells into adult cells. The question then arises: might it not be more simple to generate the cells required without passing through the stem cell stage?
The scientists have studied a specific cell type: the macrophages(1). In most cases, when cells have acquired a specialized function (e.g. brain neurons, muscle cells, macrophages for the immune system, etc.) they cease to proliferate and normally remain "blocked" in this state until they die. Thus macrophages, which are key actors in the immune response, are usually incapable of proliferation.
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