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Stem Cells Do What They Do Because They Discriminate

Stem cells are the clean slates of the human body. They're the cells (usually found in bone marrow) that are stored till they have a significant job. Stem cells remain stem cells until they need to differentiate into a specific type of cell i.e  a heart cell, a kidney cell or even a skin cell.

New research goes into the way stem cells differentiate and what goes into the process. The study (conducted by the Institute of Biotechnology and Massachusetts Institute of Technology (MIT)) suggests that asymmetric apportioning of old cellular components during cell division may represent an anti-aging mechanism utilized by stem cells.

They focus on tissue stem cells, that continuously renew our tissues which divide asymmetrically to produce 2 types of daughter cells: one a new stem cell, the second one will become the differentiating cell of a tissue. Stem cells undergo this technique to prevent cellular damage. Extra damage can cause stem cell fatigue and less tissue regeneration and aging.

To follow this method the researches devised a way to follow the different cell organelles; age-selectively during cell division.

"We found that stem cells segregate their old mitochondria to the daughter cell that will differentiate, whereas the new stem cell will receive only young mitochondria" said Pekka Katajisto, a Group leader and Academy research fellow at BI.

Since other types of cell organelles aren't age-specific and only mitochondria are age-specific, especially in stem-cells, also the inhibition of normal mitochondrial quality control pathways stops their age-selective segregation.

"There is a fitness advantage to renewing your mitochondria," says David Sabatini, Professor at MIT and Whitehead Institute. "Stem cells know this and have figured out a way to discard their older components."

Although we still don't know the exact mechanism of how stem cells recognize the age of mitochondria; the forced symmetric apportioning of aged mitochondria resulted in loss of stemness in all of the daughter cells. "This suggests that the age-selective apportioning of old and potentially damaged organelles may be a way to fight stem cell exhaustion and aging," says Katajisto.

Katajisto and his team are now researching how old and new mitochondria compare to each other and whether this phenomenon happens in other types of cells than stem-type cells.


Story Source:
The above story is based on materials provided by University of HelsinkiNote: Materials may be edited for content and length.
Katajisto P, Döhla J, Chaffer C, Pentinmikko N, Marjanovic N, Iqbal S, Zoncu R, Chen W, Weinberg RA, & Sabatini DM (2015). Asymmetric apportioning of aged mitochondria between daughter cells is required for stemness. Science (New York, N.Y.) PMID: 25837514