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‘Accidental’ discovery during NASA mission could transform the future of cardiac cell therapy
In a nutshell
- Heart cells sent to space showed major molecular changes that may help them survive stress, including boosted activity in genes and proteins linked to metabolism, cell growth, and resilience.
- These space-exposed cells kept beating normally but developed adaptations similar to those seen in cancer cells, which are known for thriving in harsh environments—a potentially useful trait for heart therapies.
- The study suggests that understanding how microgravity strengthens cells could lead to better treatments on Earth, especially for improving the survival of transplanted heart cells in damaged tissue.
ATLANTA — What happens when you send heart cells to space? They come back transformed. Scientists discovered that after just eight days aboard the International Space Station, human heart cells underwent hundreds of molecular changes linked to stress response, metabolism, and survival. This accidental discovery might solve one of cardiology’s biggest challenges: keeping transplanted heart cells alive.
This matters because heart disease is the number one killer of Americans, responsible for the deaths of one in five adults. When heart tissue is damaged, it becomes scarred and cannot regenerate naturally. While heart transplants offer hope for some patients with end-stage heart failure, donor hearts are scarce. Cell therapy—transplanting healthy heart cells into damaged areas—represents a promising alternative, but faces two critical challenges: producing enough cells and ensuring they survive after transplantation.
Treating a single patient requires about a billion heart cells. Even more problematic, many transplanted cells die quickly in the harsh environment of an injured heart.
A team from Emory University, Georgia Tech, and BioServe Space Technologies wondered if the unique conditions of space might trigger useful adaptations in heart cells. The study, published in Biomaterials, tested whether the stress of microgravity might force the cells to become more resilient in ways that could be useful for medicine back on Earth.
Heart Cells in Space
The inspiration for this research came from an unexpected source: cancer studies. Scientists had previously observed that cancer cells grow faster in space and develop stronger survival mechanisms—a dangerous combination for cancer patients. However, for heart cells used in regenerative medicine, these same properties could be beneficial.
Scientists created three-dimensional clusters of heart cells (called spheroids) from special stem cells that were originally adult human cells, reprogrammed to act like embryonic ones. These cells can differentiate into many cell types, including heart muscle cells, making them valuable for regenerative medicine.
Before sending cells to the ISS, researchers conducted ground studies using simulated microgravity. Those early tests showed that cells in simulated microgravity grew 1.5 times faster than in normal 3D cultures and four times faster than in standard 2D cultures. The space-grown cells also displayed greater purity and maturity—both essential for successful therapies.
To test their idea, Some of these heart cell clusters traveled to the International Space Station on SpaceX’s Crew-8 mission in March 2024, while identical control samples stayed behind on Earth.
For eight days, NASA astronauts Jasmin Moghbeli and Andreas Mogensen maintained the cell cultures in space. This included changing the growth medium and recording videos showing the heart cells beating normally in microgravity. When the cells returned to Earth, the researchers compared them to the earthbound control samples.
The space-exposed heart cells looked and functioned normally. They still beat with proper rhythm and showed normal calcium signals (essential for heart function). But when the researchers dug deeper, examining proteins and gene expression, they found remarkable differences.
Molecular Changes for Survival
Space had changed these cells at the molecular level. Compared to the identical Earth-bound cells, they showed altered expression of 698 proteins and 160 genes. Many of these changes involved pathways related to stress response, cell survival mechanisms, and metabolism.
For example, space exposure increased proteins that protect against oxidative stress and others that help cells survive harsh conditions by preventing cell death. The cells also ramped up the expression of proteins involved in cell growth.
The space environment triggered what scientists call “metabolic remodeling,” changes in how cells produce and use energy. Many of these adaptations resembled those seen in cancer cells, which are notorious for their ability to survive in difficult environments.
Researchers discovered the heart cells also showed increased activity in pathways related to mitochondria, the tiny power plants within cells that generate energy. Since mitochondria control energy production and play critical roles in cell survival, these changes might explain how the cells adapted to space stress.
The analysis showed that many of the same metabolic pathways found in cancer cell proliferation and survival were also activated in the cardiac cells exposed to space. Incredibly, the microgravity environment appeared to trigger stress response mechanisms that helped the heart cells adapt and become more resilient.
Still, questions remain. “How exactly is mitochondrial function changing? How are the metabolites changing?” asks Chunhui Xu, a professor at Emory University, in a statement. “Additional studies will eventually put the pieces of the puzzle together and give us the details needed to find a new way to produce better heart cells.”
From Space to Earth-Based Medicine
This isn’t the first hint that space affects cells in potentially useful ways. Previous studies have shown that cardiovascular progenitor cells, early-stage cells that can develop into heart and blood vessel tissues, grow and move better after a month on the ISS. Human mesenchymal stem cells, versatile cells that can reduce inflammation and help repair tissues, develop enhanced immunosuppressive properties (helpful for treatments) after two weeks in space. But this study provides new details about exactly what happens to heart cells at the molecular level.
The researchers think these changes might hint at ways to make transplanted heart cells more likely to survive. By understanding how space naturally triggers protective adaptations, scientists might find ways to create tougher cardiac cells without the need for a rocket ride.
One interesting technical achievement from this study was the method used to transport the cells safely to space. The team developed techniques to freeze the 3D cardiac spheroids and thaw them later, which allowed them to prepare cells well in advance of the unpredictable space launch schedule. This approach could prove useful not just for future space experiments but also for medical applications on Earth, where freezing cell therapies would allow more thorough testing before use in patients.
What This Means for the Future
Understanding how microgravity affects heart cells becomes increasingly important for astronaut health. But the bigger impact might be here on Earth, where these insights could lead to better treatments for heart disease.
By figuring out how to make heart cells more resistant to stress—whether through genetic modifications, drugs, or other methods that mimic space-induced changes—doctors might eventually improve the success rate of cardiac cell therapies. This could transform treatment options for millions of heart disease patients worldwide.
“The space environment provides an amazing opportunity for us to study cells in new ways,” says Xu. “Our research on the ISS could allow us to develop a new strategy to generate cardiac cells more efficiently with improved survival when transplanted into damaged heart tissue, which would greatly benefit patients on Earth.”
Paper Summary
Methodology
Scientists created ball-shaped clusters of heart cells from human stem cells that had been reprogrammed from adult cells. They first froze these heart cell clusters, then thawed them before sending them to space. After testing to confirm the cells were healthy and pure, researchers placed them in special culture chambers called BioCells that allowed for changing the growth liquid while keeping cells suspended. These chambers went into temperature-controlled containers and traveled to the International Space Station on the SpaceX Crew-8 mission launched March 3, 2024. Astronauts refreshed the growth liquid on day 4 and recorded video of the beating heart clusters on day 5. The cells spent 8 days in microgravity before returning to Earth. Identical cell clusters stayed on Earth as a comparison group. After returning, researchers used 3D imaging to examine cell function, including contraction and calcium movement. They also performed comprehensive analysis of all proteins and gene expression patterns to identify differences between the space-exposed cells and Earth-bound controls.
Results
The heart cells that traveled to space showed significant molecular changes while keeping their normal function intact. Using advanced 3D imaging, researchers found that space-exposed heart clusters maintained normal contraction patterns and calcium movements—both essential for proper heart function. However, protein analysis identified 698 upregulated proteins in the space samples compared to Earth controls. Many of these proteins help cells survive stress, respond to challenging conditions, maintain efficient metabolism, and support cell growth. For example, proteins like UGT2A3, ADH1A, CEBPD, and EEF2K—all involved in cellular stress response and survival—showed significant increases. Researchers also found 62 upregulated proteins associated with mitochondria (the cell’s power plants) and 90 proteins connected to metabolic pathways. Gene sequencing identified 160 upregulated genes, including those involved in heart development, structure, and metabolism. Particularly noteworthy was the increase in genes associated with lipid metabolism pathways critical for cell survival under stress. In essence, spaceflight reprogrammed the heart cells to become more resilient while maintaining their normal beating function.
Limitations
The research had several constraints worth noting. The study involved relatively brief exposure to microgravity (8 days), while longer periods might produce different effects. Researchers used 3D heart cell clusters from just one cell line, potentially limiting how broadly the findings apply across different genetic backgrounds or cell arrangements. Though molecular changes were observed, the study didn’t directly test whether these alterations actually improved survival under stress conditions that mimic heart transplantation. The experiment included only three samples per group—though this is typical for space-based research due to practical constraints. Also, other space environmental factors besides microgravity (such as radiation) might have contributed to the observed changes. The research team acknowledges that additional studies should examine metabolic profiles, directly test survival benefits, and compare responses between heart cells and other cell types.
Funding and Disclosures
This research received support from the National Science Foundation CBET 1926387 and the Center for the Advancement of Science in Space, sponsored by the International Space Station National Laboratory under grant agreement UA-2019-0921. Additional funding came from NIH R01AA028527, NIH R35GM124846, and NSF BIO2145235. The Emory NPRC Genomics Core received partial support from NIH P51 OD011132. The authors declared no competing financial interests or personal relationships that might have influenced their work. The researchers thanked NASA astronauts Jasmin Moghbeli and Andreas Mogensen for conducting ISS procedures, Trisha Joseph at Kennedy Space Center for pre-flight support, the Emory NPRC Genomics Core for RNA sequencing services, and Drs. Kristin Kopperud and John Catechis from the ISS National Laboratory for guidance throughout the study.
Publication Information
The research paper “Spaceflight alters protein levels and gene expression associated with stress response and metabolic characteristics in human cardiac spheroids” appeared in Biomaterials (volume 317, 2025, article 123080) and became available online January 6, 2025. A multidisciplinary team led by Chunhui Xu from Emory University School of Medicine and Children’s Healthcare of Atlanta authored the paper, with collaborators from Georgia Institute of Technology, Emory University, and BioServe Space Technologies. The manuscript was received December 17, 2024, and accepted December 30, 2024.
