Cell Growth in Microgravity
307
cells suspended without invoking exces-
sive hydrodynamic shear while providing
abundant mass transfer. The rotating-
wall vessel (RWV) bioreactors developed
at NASA’s Johnson Space Center (Fig. 1)
model some aspects of microgravity and al-
low the extensive analysis of microgravity-
related biological phenomena at the cel-
lular level. We now refer to these culture
vessels as the microgravity analog culture
system (MACS). MACS is based on a pre-
vious clinostat design and consists of a
zero headspace cylindrical culture vessel
that rotates at a slow speed around a hori-
zontal axis. These conditions compensate
the gravity vector by rotation and create a
solid body fluid rotation that can suspend
cells or small particles in a sustained free
fall condition, modeling conditions of mi-
crogravity for cell cultures.
This system provides us with the abil-
ity to assess function at a cellular level,
without the potential confounding influ-
ences of psychoneuroendocrine factors.
Furthermore, the cells are analyzed in
real time while in analog microgravity
in addition to a postflight or postanalog.
Initially, the MACS demonstrated suppres-
sion of lymphocyte locomotion through
c
o
l
l
a
g
e
ni
ng
r
o
u
n
d
-
b
a
s
e
de
x
p
e
r
im
e
n
t
s
.
Subsequent flight experiments conducted
onboard Shuttle missions STS-54 and STS-
56 con±rmed suppression of lymphocyte
locomotion suggested by MACS. This was
Fig. 1
The NASA rotating bioreactor allows for solid body fluid rotation.
The growth medium completely Flls the cylindrical vessel. Rotation of the
vessel along its horizontal axis suspends the cells without stirring,
randomizes orientation to the
g
vector, and renders cells to continuous
fall at terminal velocity through the culture fluid. The cells have less
interaction with inert surfaces and experience greater freedom for
three-dimensional association. Several derivatives of the rotating
bioreactor are available commercially (Synthecon, Inc.). The advantages
lie in the low shear environment and the potential space analog
condition.
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