Regenerative Processes in Microgravity
The Space Tissue Loss program, a collaboration between NASA and the Department of Defense (DoD), sent 20 sets of experiments into space on 18 shuttle launches since March 1992. It is part of the DoD Space Test Program (STP), which uses cell and tissue cultures in microgravity to study its effects on tissue regeneration and wound healing in space.
Eduardo Almeida, Ph.D., the stem cell regeneration program principal investigator and a scientist at NASA’s Ames Research Center, pointed out to GEN that gravity is important for stem cell health. “In its absence, tissue atrophy occurs, and repair does not occur normally.” He described two experiments aboard space shuttles Atlantis and Discovery.
In one experiment he and his colleagues used a model of stem cell development: mouse embryoid bodies that on earth form a sphere containing patches of differentiated cells such as neurons and muscle cells. “Everything went okay on the ground,” he said of the earth-bound controls, “but failed almost completely in space, as the embryoid body cells did not differentiate, failing to express normally 45 out of 52 differentiated tissue markers from mesoderm, endoderm, and ectoderm lineages, and continued to express stem cell markers such as Sox1 and Sox2.”
In another experiment Dr. Almeida’s team tested the ability of keratinocytes (differentiated from stem cells in space) to migrate correctly. Keratinocytes are key cells that participate in wound closure and healing. In space the cells lost nearly half of their migratory capacity, suggesting one cause of lack of efficient wound healing in microgravity.
“For mammalian cells, microgravity is not replicable on the ground,” Dr. Almeida explained. “The only way to do these experiments is to go up.” The inability to do experiments in space “is frustrating because it’s really inefficient to do space biology experiments on earth with inadequate experimental models. A year of NASA spaceflight research is worth 10 years of ground research because of the wealth of unique insights space provides.”
For space travel, he said, the current research highlights the importance of gravity in promoting stem cell regenerative health. “For medicine on earth, this space research makes clear that forces generated by gravity are required to promote normal tissue regenerative processes and teaches us that sometimes we need to step back from things like gravity that we take for granted to understand their fundamental importance for life on earth.”
Tissue Genesis (TGI) has provided science experiments, hardware/payload integration, and adult stem cells in support of the NASA/DoD research collaboration. Tissue Genesis vp and GM, Thomas F. Cannon, told GEN that the company’s core expertise is in space shuttle cell experimentation.
“We were the science/hardware integrators for three experiments flown on the STS-135 DoD Space Test Program manifested Cell Culture Module (CCM),” he said. The CCM is a hollow fiber-based automated perfusion cell culture payload, originally developed at the Walter Reed Army Institute of Research, Cannon explained. It performs a variety of automated injections, collections, and culture manipulations.
Tissue Genesis also participated in a Telemedicine and Advanced Technology Research Center (TATRC), USAMRMC-sponsored experiment that cultured and grew adipose-derived regenerative cells recovered by the TGI Cell Isolation System.
Back at TGI, Joon Paek, Ph.D., the project PI, evaluated the trophic factors and immunomodulatory response of the cells in the space environment. “We have the cells now back in our lab and they are continuing to pump out growth factors. Hopefully we will have some exciting results to report. The two other investigators—Dr. Almeida, and Dr. Rasha Hammamieh, USAMRMC—are reporting very good preliminary results as well.”