Method to delay aging of stem cells developed

ScienceDaily (May 24, 2012) Stem cells are essential building blocks for all organisms, from plants to humans. They can divide and renew themselves throughout life, differentiating into the specialized tissues needed during development, as well as cells necessary to repair adult tissue.

Therefore, they can be considered immortal, in that they recreate themselves and regenerate tissues throughout a person's lifetime, but that doesn't mean they don't age. They do, gradually losing their ability to effectively maintain tissues and organs.

Now, researchers at the Salk Institute for Biological Studies have uncovered a series of biological events that implicate the stem cells' surroundings, known as their "niche," as the culprit in loss of stem cells due to aging. Their findings, published May 23rd in Nature, have implications for treatment of age-related diseases and for the effectiveness of regenerative medicine.

"The findings suggest, for example, that putting new or young stem cells into an old environment -- that of an aged patient -- might not lead to the best outcome in tissue regeneration," says the study's senior investigator, Leanne Jones, associate professor in Salk's Laboratory of Genetics.

Stem cells reside within a microenvironment of other cells-the niche-that is known to play a role in stem cell function. For example, after a tissue is injured, the niche signals to stem cells to form new tissue. It is believed that stem cells and their niche send signals to each other to help maintain their potency over a lifetime.

But while the loss of tissue and organ function during aging has been attributed to decreases in stem cell function, it has been unclear how this decline occurs. Jones' lab has been investigating a number of possible scenarios, such as whether the loss of tissue function is due to a decrease in the number of stem cells, to the inability of stem cells to respond to signals from their niche, or to reduced signaling from the niche.

To explore stem cell aging, Jones uses cells found in the testes of the male fruit fly, Drosophila melanogaster, which are remarkably similar to those found in humans.

The researchers show how signals from the niche that act to maintain the vitality of the flies' stem cells are lost over time, leading to a decline in the number of stem cells available to maintain the tissue. They also show that restoring those signals revitalizes the cells.

"Stem cell behavior is similar between flies and humans, so our findings have major implications for breakthroughs in using tissue stem cells to treat age-related tissue decline or regeneration after an injury," says one of the paper's first authors, Hila Toledano, a former Salk investigator who is now at the University of Haifa in Israel.

The Salk researchers discovered that as the stem cell niche ages, the cells produce a microRNA (a molecule that plays a negative role in the production of proteins from RNA) known as let-7. This microRNA is known to exist in a number of species, including humans, and helps time events that occur during development.

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Method to delay aging of stem cells developed