304
Cell Growth in Microgravity
Microgravity Analog Culture System (MACS)
Refers to the NASA series of bioreactors, including the rotating-wall vessel (RWV), slow
turning lateral vessel (STLV), and the high aspect ratio vessel (HARV).
Modeled Microgravity
Analog paradigms of microgravity such as drop tower, suborbital rockets, MACS,
parabolic flight, and so on.
Three-dimensional Cell Growth
Growth and assembly of cells into deFnite constructs with a third dimension.
T-cell Activation
The process by which T-cell receptor triggering leads to cytokine secretion and cell
proliferation.
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Microgravity affects cells and tissues either through direct response elements within
the cell or by influencing the environment in which the cell lives. Cells respond
to decreased gravity and the reordering of forces by changes in gene expression
and cellular function. This review will address the unique attributes of microgravity
that influence cell growth and function, progressing from ground-based models of
microgravity, the cellular response to microgravity, and experimental results from
cell experiments in microgravity.
1
Introduction
Microgravity is a unique environment
in which cells, tissues, and organisms
undergo
novel
adaptations.
The
adap-
tational responses provide insight into
basic cellular mechanisms and, further-
more, provide opportunities in applied
cell science. Investigations in micrograv-
ity and ground-based model systems have
opened new vistas in tissue engineering,
disease modeling, drug testing, vaccine
production, and space cell biology. In mi-
crogravity, cells no longer sediment to
surfaces, but rather freely associate with
each other, forming large assemblies that
can replicate in three dimensions. No
doubt, the diminution of gravity from the
cell culture setting allows the remaining
forces to be more apparent. The rapid
assembly and three-dimensional growth
afford insight into the nature of physical
forces that affect life at the cellular level
and other new prospects in tissue engi-
neering. Microgravity tissue morphogene-
sis produces functional three-dimensional
constructs that are useful experimental
models and may ultimately be amenable to
transplantation. The reordering of forces
in microgravity is reflected in the profound
shape change, gene expression, differenti-
ation, and metabolic alterations identiFed
in space experiments. Despite the dramatic
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