Washington: Human stem cells grown in
microgravity generate problematic proteins that may lead to
bone deterioration, a new study has claimed, raising questions
about the viability of long-term human voyages into space.
The study conducted at the Australian Centre for
Astrobiology found that human stem cells grown in a rotating
vessel to simulate microgravity are vastly different from
those developed under normal conditions on earth.
The researchers, who used a NASA-developed bioreactor to
grow cells from a human embryonic stem cell line, discovered
that 64 per cent of the proteins found in the stem cells grown
in simulated microgravity were not in control samples, the
Discovery News reported.
In particular, the bioreactor cells contained several
proteins involved in the breakdown of bone and in the
regulation of calcium, neither type of which were found in
stem cells grown in regular, Earth gravity, the researchers
According to them, these types of cells can develop into
any of the body`s three primary layers -- ectoderm, endoderm
and mesoderm, which in turn form more than the 220 types of
cells found in humans.
"To the best of our knowledge, this is the first study
conducted that has investigated the effect of (simulated
microgravity conditions) on an embryonic stem cell line and
demonstrated a significant alteration in human cell function
as a result of growth in microgravity conditions," said lead
scientist Elizabeth Blaber.
NASA flight surgeons estimate astronauts lose about one
per cent of their bone mineral density every month they are in
In addition to a vigorous daily exercise in orbit,
astronauts are participating in a study to see if taking
bone-building drugs known as bisphosphonates can stave off the
Other well-known impacts of microgravity on the human
body include muscle loss and changes in the cardiovascular and
"The researchers tell us they feel there is some kind of
gene switching at the cellular level that is contributing to
the conditions we see," NASA flight surgeon Mike Duncan told