Article: How old cells can regain youth

• Previous message: Jim McGinn: "Felsenstein: Smoke and Mirrors"
• Messages sorted by: [ date ] [ thread ]

Date: Thu, 17 Feb 2005 16:29:00 -0500 (EST)

How old cells can regain youth
Researchers find a youthful environment invigorates regeneration in old
tissue
By Laura M Hrastar

Old cells may regain a youthful phenotype when exposed to a young cell
environment, say researchers in Nature this week. The results, say the
authors, indicate that aged satellite cells have an intrinsic ability to
regenerate.

"We know old tissue repairs poorly, but it's not because there aren't stem
cells ready to do the repair," coauthor Thomas Rando told The Scientist.
"The problem is, with age, the environment the stem cells hit changes, [and]
it makes them less responsive."

To study how systemic factors affect satellite cell regeneration,
researchers from Stanford University and VA Palo Alto Health Care System in
California created fusions of the circulatory systems of old mice and young
mice-a technique known as parabiosis. The young mice were transgenic,
expressing either green florescent protein or a distinct CD45 allele.

Five days after injuring the mice's hindlimbs, researchers found nucleated
embryonic myosin heavy chain, a specific marker seen in regenerating
myotubes-nascent myofibers-in the old parabiotic animals. Because these
cells did not contain transgenic markers, researchers determined that
activation of resident progenitor cells-not engraftment of younger cells
onto old tissue-was the cause of new growth.

Satellite cells in old parabiotic mice also showed similar upregulation as
young mice controls of Notch ligand Delta, the binding protein necessary to
activate the Notch signaling pathway for cell regeneration. The young
parabiotic mice showed inhibition of Delta when compared with young mouse
controls.

The new findings support the groups' previous work that showed the
diminished expression of Delta related to age decreases Notch signaling,
which reduces stem cell proliferation and impairs cell regeneration.

In the current study, researchers also found that culturing old satellite
cells in young mouse serum restored upregulation of Notch ligand and Notch
activation, whereas adding old mouse serum to young satellite cells
inhibited the effect.

The results were a clear demonstration of how cell environment affects
muscle regeneration, said University of Michigan professor of cell biology
Bruce Carlson, who did not participate in the study. "It [shows] that muscle
has a much greater potential to regenerate than you would think if you just
looked at it in the context of the old animal," Carlson told The Scientist.

Full Text at TheScientist
http://www.biomedcentral.com/news/20050217/01

Posted by
Robert Karl Stonjek

• Previous message: Jim McGinn: "Felsenstein: Smoke and Mirrors"
• Messages sorted by: [ date ] [ thread ]