Nichols is particularly interested in the role of pneumocytes, which are cells that line lung cavities. Type 1 pneumocytes facilitate gas exchange — “We want to make sure we keep it very healthy,” Nichols remarked — while Type 2 pneumocytes secrete a substance called a surfactant to decrease surface tension. Type 2 cells can replace Type 1 cells as the Type 1 cells naturally die off, but they only do it in low numbers. There’s also another complication: gravity cues the body as to which type of cell is which.
“In space, [the cells] don’t [touch] as much, so it might be bad for astronauts on long-term spaceflight,” Nichols said. “For me, I hope to gain an understanding into how our lungs heal, which maybe would provide me with a plan or therapeutics. In the case of COPD or lost lung function, perhaps we would be able to replace the missing cells.”
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For the experiment, Nichols’ team created 60 tiny human lung scaffold pieces (just 0.5 mm cubed) to support the growth of bioengineered lung tissue — including, specifically, Type 2 cells. The samples were carefully checked for possible contamination before flight. After getting the all-clear, the samples were rocketed to space on a Dragon spacecraft and curated in a science glovebox on the ISS during Expeditions 51 and 52. Then they were brought back to Earth on Sept. 17, also on a Dragon.
Nichols has just started her analysis, but she already sees some differences between the lung tissue samples she grew as a control on Earth and the ones that flew in space.
“They don’t have the same structures of the little ovular spaces,” she said.
In future months, she’ll examine things such as the amount of surfactant the Type 2 cells produced. Once she has preliminary results, she plans to write another proposal to NASA to try to land another investigation on the space station in a couple of years.
In the distant future, Nichols said it could be useful to grow pure stem cells in microgravity and then transfer them to a scaffold here on Earth, in order to grow an entire lung. This could make it easier to achieve lung transplants for patients. But such a goal, she cautioned, is many years away.
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