Recently, an experiment with growing brain tissue from stem cells was conducted on the ISS. It showed that they reach maturity faster in space, but don’t show accelerated rates of degradation.
Impact of microgravity on brain cells
Microgravity is known to affect muscles, bones, the immune system, and cognitive processes, but little is known about its specific impact on the brain. To find out how brain cells respond to microgravity, Scripps Research scientists, in collaboration with the New York Stem Cell Foundation, sent tiny clumps of stem cell-derived brain cells called “organoids” to the International Space Station (ISS).
Amazingly, the organoids were still healthy when they returned from orbit a month later, but the cells had matured faster compared to identical organoids grown on Earth, they were closer to becoming adult neurons and were beginning to show signs of specialization. The findings, which may shed light on the potential neurological consequences of space travel, are published in the journal Stem Cells Translational Medicine.
Cell experiments on Earth
While on Earth, the team used stem cells to create organoids composed of cortical or dopaminergic neurons, which are populations of neurons affected in multiple sclerosis and Parkinson’s disease, diseases that Loring has studied for decades. Certain organoids also included microglia, a type of immune cell that lives in the brain, to study the effect of microgravity on inflammation.
Organoids are usually grown in a nutrient-rich liquid medium, which must be changed regularly to ensure the cells have adequate nutrition and to remove waste products. To avoid the necessity of conducting laboratory tests on the ISS, the team developed a method for growing smaller-than-normal-sized organoids in cryovials, small airtight tubes that were originally designed for deep freezing.
The organoids were prepared in laboratories on the Kennedy Space Station and delivered to the ISS in a miniaturized incubator. After a month in orbit, they were returned to Earth, where the team revealed that they were healthy and unharmed.
Cells that mature faster
To investigate how the space environment affects cellular function, the team compared the cells’ RNA expression patterns — a measure of gene activity — to identical “ground control” organoids that remained on Earth. In a surprising result, they found that organoids grown in microgravity had higher levels of maturation-related genes and lower levels of proliferation-related genes compared to the terrestrial control, meaning that cells exposed to microgravity developed faster and replicated less than cells on Earth.
“We discovered that in both types of organoids, the gene expression profile was characteristic of an older stage of development than the ones that were on the ground,” says Loring. “In microgravity, they developed faster, but it’s really important to know these were not adult neurons, so this doesn’t tell us anything about aging.”
The team also noted that, contrary to their hypothesis, organoids grown in microgravity showed less inflammation and lower expression of stress-related genes, but more research is required to find out why this happened.
Loring suggests that microgravity conditions may more closely mirror those of brain cells compared to organoids grown under normal laboratory conditions and in the presence of gravity.
“The characteristics of microgravity are probably also at work in people’s brains, because there’s no convection in microgravity—in other words, things don’t move,” says Loring. “I think that in space, these organoids are more like the brain because they’re not getting flushed with a whole bunch of culture medium or oxygen. They’re very independent; they form something like a brainlet, a microcosm of the brain.”
Prospects for ISS research
The article describes the team’s first space mission, but since then, they have sent four more missions to the ISS. During each one, they replicated the conditions of the first mission and added additional experiments.
“The next thing we plan to do is to study the part of the brain that’s most affected by Alzheimer’s disease,” says Loring. “We also want to know whether there are differences in the way neurons connect with each other in space. With these kinds of studies, you can’t rely on earlier work to predict what the result would be because there is no earlier work. We’re on the ground floor, so to speak; in the sky, but on the ground floor.”
Provided by phys.org
