Microgravity: A Medical Research and Treatment Tool
By Dr. Neal R. Pellis
Manager, Biotechnology Cell Science Program
Johnson Space Center
BIOMEDICAL RESEARCHERS
NATIONWIDE ARE undertaking pioneering studies that may provide new
knowledge and technologies that bring exciting advances in research
and the treatment of disease, by engineering human tissues from
individual cells using the microgravity of space and a unique technology
developed by NASA.
NASA's rotating, cylindrical Bioreactor, relatively new to cell
science, is an application of microgravity that can be used on Earth
as well as in space. The potential for contributions is presently
emerging, and researchers are producing exciting new results by
creating three-dimensional cell cultures that are significantly
more similar to tissues found in the human body.
Much valuable research has been obtained from the traditional
research method used by scientists for more than 100 years—culturing
mammalian cells using dishes in which cells sediment to the bottom
surface, producing a thin sheet of cells—but this has limited
application in modeling functional human tissue. The cells are not
arranged as they are in the body.
The NASA ground-based Bioreactor is a horizontally rotating cylinder
that simulates microgravity. The fluid culture medium filling the
cylinder rotates at the same rate as the cylinder, resulting in
continuous suspension of the cells. Conditions in the Bioreactor
are very conducive to engineering tissues from individual cells
and for simulating microgravity on the ground, where the device
is suitable for the proliferation of small (<0.5 inch) tissue
specimens. The space Bioreactor is substantially more complex than
the ground-based counterpart because it must operate autonomously
and function flawlessly for extended duration in space vehicles.
It is the basis on which more sophisticated units will be designed
for the International Space Station, a setting in which long-duration
experiments are critical to the growth of this science and to its
inevitable application in science and medicine.
The microgravity environment of space flight supports tissue engineering
and may provide the necessary strategy to grow larger tissue specimens.
Cancer cells cultured for five days aboard STS-70 produced results
that clearly showed that cell assembly in microgravity was more
than 10 times the size of the control culture of a ground-based
Bioreactor. In a longer duration study, STS-79 carried cartilage
cells in synthetic scaffolds to be cultured on Mir for more
than 130 days. Tissue in the flight Bioreactor showed some characteristics
that are indicative of microgravity and may be suitable for clinical
and research applications.
Tissue engineering research, using NASA's Bioreactor, can contribute
to reducing costs and developing treatment alternatives. Many of
these areas require both ground-based and space experiments. Microgravity
offers the prospect of advancing research in several critical areas
that can have significant impact in science and medicine. Using
the NASA-developed space and ground-based Bioreactors for growing
human tissues from individual cells, tissues could be developed
for use in medical transplantations to replace defective organs
and tissues. Producing models of human disease could help in the
development of novel drugs for prevention and treatment, strategies
to reengineer defective tissues and new hypotheses for the emergence
of diseases such as cancer.
The unique attribute of simulated and true microgravity, using
the NASA Bioreactor, has begun to produce accomplishments to contribute
to knowledge for improved health care. For example, living cells
from human ovarian and breast tumors are being successfully cultured
and grown into masses that resemble the original tumor to further
understand growth and spreading factors. Ovarian and breast cancers
are among the leading causes of cancer deaths among women. Colon
cancer tumors also are being produced. The Bioreactor also is used
to produce models of human prostate cancer. NASA tissue culture
research has given the medical community a powerful new tool to
study how these cancerous tissues form. Human cartilage is also
being attempted in masses large enough for implant studies. Evaluating
the effects of drugs also is a benefit. Kidney tissue cultured in
the NASA Bioreactor helps evaluate renal drug toxicity, while the
assembly and growth of cardiac muscle tissues grown in the NASA
Bioreactor are used to study the effects of new drugs on muscle
diseases. Cells respond to simulated and true microgravity by making
novel adaptation changes that could in turn give us new insights
to cellular processes and establish a cellular basis to the human
response to microgravity and the space environment.
NASA is confident that the disturbance microgravity invokes on
cells, and the resultant changes to the cell, will lead to new discoveries
in the cell and advance understanding of biological function in
the space environment for use on Earth and in space.
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