Space Travel Speeds Up Aging of Blood Stem Cells, Study Finds

New research has uncovered yet another way that spaceflight affects the human body. Scientists have discovered that traveling to space can speed up the aging of blood-forming stem cells, which are essential for maintaining healthy blood and a strong immune system. These findings come from a NASA-funded study that analyzed stem cells sent to the International Space Station (ISS) on four SpaceX resupply missions.

Study Design and Method

The research involved stem cell samples flown on four different SpaceX resupply missions to the ISS, specifically in December 2021, July 2022, November 2022, and March 2023. To understand the effects of spaceflight, the scientists carefully monitored stem cells from the bone marrow of individual donors in real-time during these missions. The changes observed in space were compared with samples that remained on Earth from the same donors.

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By studying these samples, researchers were able to track exactly how space conditions affected the stem cells over periods of 30 to 45 days. This allowed them to see direct changes caused by microgravity, radiation, and other spaceflight factors, rather than relying on indirect observations.

Key Findings: How Spaceflight Affects Stem Cells

The results of the study showed several important changes in the stem cells after their time in space:

1. Reduced Ability to Form New Cells:
   The cells that traveled to space lost some of their capacity to produce healthy new blood cells. This reduction in regenerative ability means the body may struggle to replace old or damaged blood cells efficiently.

2. Increased DNA Damage:
   Spaceflight exposed the stem cells to higher levels of DNA damage. DNA is the genetic material in cells, and damage to it can lead to diseases like cancer or interfere with the cells’ ability to function correctly.

3. Accelerated Aging:
   The ends of the chromosomes in the stem cells, called telomeres, showed signs of faster aging. Telomeres protect genetic information during cell division, and their shortening is a hallmark of cellular aging.

The scientists concluded that these changes were primarily caused by the combination of microgravity—the weightlessness experienced in space—and the increased radiation exposure astronauts face outside the Earth’s protective atmosphere.

What Are Stem Cells and Why Are They Important?

Stem cells are unique cells in the body that can develop into different types of cells. The specific stem cells studied here are called hematopoietic stem and progenitor cells, which are found in the bone marrow inside our bones. These cells are responsible for producing all types of blood cells:

• Red blood cells that carry oxygen throughout the body

• White blood cells that fight infections and protect the body from diseases

• Platelets that help the blood clot when injuries occur

If these cells stop functioning properly, it can have serious effects on overall health. For example, the body may struggle to repair tissue damage, fight infections, or detect and eliminate cancer cells. Over time, this can even affect a person’s lifespan.

How Space Affects Stem Cells

During space missions, the stem cells showed signs of becoming overactive. Normally, stem cells have periods of rest that allow them to regenerate and maintain their ability to create new cells over time. In space, however, they depleted their reserves too quickly, reducing their long-term regenerative potential.

The cells also showed increased stress and inflammation in their mitochondria. Mitochondria are the structures in cells that produce energy, and when they are stressed, the cell cannot function as efficiently. Additionally, parts of the genome usually kept silent, known as the “dark genome,” became active, which can lead to instability and further cell stress.

Interestingly, the study found differences in how stem cells from different donors responded to spaceflight. According to Dr. Catriona Jamieson, senior author of the study and a professor of medicine at the University of California San Diego, some individuals’ stem cells showed natural resilience and were able to withstand space stress better than others. This variability suggests that certain anti-aging factors might be present in some people’s cells but not in others.

Radiation and Microgravity: The Main Culprits

On Earth, we are protected from cosmic radiation by the planet’s atmosphere and magnetic field. In space, this protection is gone. Astronauts are exposed to high-energy radiation that can damage DNA and increase risks for:

• Cancer

• Neurodegenerative diseases like Alzheimer’s

• Cardiovascular problems

• Immune system disorders

In addition to radiation, the microgravity environment in space leads to other health issues such as:

• Loss of bone density

• Muscle atrophy

• Changes in blood flow and organ function

These combined factors create a unique challenge for the human body, especially during long-duration missions such as trips to Mars or extended stays on the ISS.

Implications for Astronaut Health

Understanding how spaceflight affects blood-forming stem cells is crucial for keeping astronauts healthy during long missions. These findings may help scientists develop strategies to protect astronauts from the harmful effects of space travel. This could include targeted treatments to strengthen stem cells, protect DNA, or reduce stress in mitochondria during missions.

Dr. Jamieson emphasized that studying these stem cell changes not only helps space medicine but also provides insights into human aging and diseases on Earth, including cancer. By observing how space accelerates certain cellular processes, researchers can better understand how aging and cellular stress affect everyone.

Future Research

The researchers are continuing to study stem cell responses during ongoing SpaceX resupply missions to the ISS. They aim to identify key resilience factors that could be enhanced before, during, and after space travel to improve human health in space and on Earth.

This ongoing research may one day allow astronauts to maintain healthier blood and immune systems during long journeys, while also offering new insights into how to slow aging and improve stem cell function on Earth.

This study clearly shows that spaceflight has profound effects on the human body at the cellular level. Blood-forming stem cells, which are essential for health and immunity, age faster and become more stressed in space. While these findings are particularly important for astronauts, they may also help scientists develop new treatments for age-related diseases and improve human health on Earth. The work underscores the challenges of human space travel and the importance of continued research into protecting the body in extreme environments.