"Infusions of youthful blood led
older mice to live 6 to 9 percent longer, a new study found.
A team of scientists has extended the lives of old mice by
connecting their blood vessels to young mice. The infusions of youthful blood
led the older animals to live 6 to 9 percent longer, the study found, roughly equivalent to six extra years for
an average human.
While the study does not point to an
anti-aging treatment for people, it does hint that the blood of young mice
contains compounds that promote longevity, the researchers said.
“I would guess it’s a useful
cocktail,” said James White, a cell biologist at the Duke University School of
Medicine and an author of the new study.
Joining animals together, known as
parabiosis, has a long history in science. In the 19th century, French
scientists connected the blood vessels of two rats. To prove that the rats
shared a circulatory system, they injected belladonna, a compound from the
deadly nightshade plant, into one of the animals. The pupils of both rats
dilated.
In the 1950s, Clive McCay of Cornell
University and his colleagues used parabiosis to explore aging. They joined
young and old rats, stitching together their flanks so that the capillaries in
their skin merged. Later, Dr. McCay and his colleagues examined the cartilage
in the old rats and concluded it looked younger.
In the early 2000s, parabiosis went through a renaissance. Researchers used 21st
century techniques to study what happened when animals of different ages shared
the same bloodstream. They found the muscles and brains of old mice were
rejuvenated, while younger mice showed signs of accelerated aging.
Some doctors jumped on these
preliminary results and started offering injections of blood plasma from young
people as a way to treat dementia and other diseases of old age. The Food and
Drug Administration issued a warning against
such treatments in 2019, cautioning that they “have no proven clinical benefits
for the uses for which these clinics are advertising them and are potentially
harmful.”
For several years, Dr. White and his
colleagues have been tweaking parabiosis procedures in mice to better
understand the anti-aging effects. The scientists joined an old and young mouse
together for about three months — twice as long as typical parabiosis
experiments — before carefully detaching them. After the animals recovered, the
scientists observed the animals to see how much longer they lived.
The researchers not only found that
the old mice lived longer, but also that the course of their aging appeared to
change.
After detaching the old mice, the
scientists looked at molecular markers in their blood and liver that act like a
clock for an animal’s biological age. These clocks seemed to have been paused:
Two months later, these molecular markers showed the older animals as “younger”
than untreated mice of the same age.
“We reset the trajectory of aging,”
Dr. White said.
The young mice were also affected by the union. “The young
mice rapidly become older, and when we separate the mice, it goes back,” said
Vadim Gladyshev, an expert on biological clocks at Harvard Medical School and
an author of the new study.
The study was published on Thursday
in the journal Nature Aging.
“It’s a beautiful demonstration — it
really shows that this effect is not transient,” said Tony Wyss-Coray, a
parabiosis expert at Stanford University who was not involved in the study.
But Michael Conboy, a research
scientist at the University of California, Berkeley, cautioned that a similar
experiment published last year
by Ukrainian scientists did not show that old mice lived longer after parabiosis.
“But at least somebody is doing the
experiments, which is brave, because they are not easy,” Dr. Conboy said.
Dr. David Glass, the vice president
for research on age-related disorders at Regeneron, a pharmaceutical company,
noted that the new report used a different strain of mice from the one in last
year’s study. “So one should be cautious in generalizing the findings,” Dr.
Glass said.
Now Dr. White and his colleagues are
following up with experiments to understand what might be slowing down aging in
the old mice. “We’re hunting the hows and whys,” he said.
The long-term effects of the experiment suggest to Dr. White
that the cause can’t be pinned only to cells from the young mice rejuvenating
the old ones. Once the surgeons separated the mice, the old mice lost their
supply of young cells but did not return to their old state.
One possibility is that harmful
compounds in the old animals get diluted by the blood from the young mice. The
young blood may also contain molecules that reprogram cells in the old mice, so
that they kept behaving like younger cells after the animals were detached.
Dr. Gladyshev did not see the new
study as a justification for getting shots of young human serum. For one thing,
he and his colleagues have no idea which factors make up the life-extending
cocktail for mice, let alone people. For another, injections are a far cry from
being joined up to another animal for months.
“To me, it’s just very strange to
think it could work,” Dr. Gladyshev said."
Komentarų nėra:
Rašyti komentarą