There's a good reason people over 60 are not donor candidates for bone marrow transplantation. The immune system ages and weakens with time, making the elderly prone to life-threatening infection and other maladies, and a UC San Francisco research team now has discovered a reason why.
"We have found the cellular mechanism responsible for the inability of blood-forming cells to maintain blood production over time in an old organism, and have identified molecular defects that could be restored for rejuvenation therapies," said Emmanuelle Passegu, PhD, a professor of medicine and a member of the Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research at UCSF. Passegu, an expert on the stem cells that give rise to the blood and immune system, led a team that published the new findings online July 30, 2014 in the journal Nature.
Blood and immune cells are short-lived, and unlike most tissues, must be constantly replenished. The cells that must keep producing them throughout a lifetime are called "hematopoietic stem cells." Through cycles of cell division these stem cells preserve their own numbers and generate the daughter cells that give rise to replacement blood and immune cells. But the hematopoietic stem cells falter with age, because they lose the ability to replicate their DNA accurately and efficiently during cell division, Passegu's lab team determined.
Especially vulnerable to the breakdown, the researchers discovered in their new study of old mice, are transplanted, aging, blood-forming stem cells, which lack the ability to make B cells of the immune system. These B cells make antibodies to help us fight all sorts of microbial infections, including bacteria that cause pneumonia, a leading killer of the elderly.
In old blood-forming stem cells, the researchers found a scarcity of specific protein components needed to form a molecular machine called the mini-chromosome maintenance helicase, which
|Contact: Jeffrey Norris|
University of California - San Francisco