The Beauty of Accelerated Aging: Using Tissue Chips to Explore Age-Related Muscle Loss in Microgravity

August 29, 2024 • By Amelia Williamson Smith, Upward Managing Editor and ISS National Lab Science Communications Manager

Contrary to Bob Dylan’s famous song, it’s not possible to “stay forever young,” and aging is inevitable. As we get older, many things change, and while we may gain wisdom, we often lose muscle.

At age 30, people begin to lose three to five percent of their muscle mass per decade, and the loss speeds up in a person’s 60s. The World Health Organization estimates that more than 50 million people worldwide have sarcopenia, an age-related condition causing loss of muscle mass, strength, and function, and the condition will affect more than 200 million people within the next 40 years.

But sarcopenia isn’t just about weakened muscles. People with sarcopenia have a higher risk of falling, which can lead to fractured bones, loss of mobility, long hospital stays, and significant healthcare costs. A study published in the Journal of Frailty and Aging in 2019 found that the total annual cost of hospitalization for Americans with sarcopenia is more than $40 billion.

Right now, there are no treatments for sarcopenia other than exercise. To find new therapies, researchers need a better understanding of how muscles change at the tissue level as we age. However, studying age-related change is difficult because studies must last decades, and it can be hard to see changes that occur slowly over time.

But what if there were a way to accelerate the muscle aging process? A University of Florida research team led by Siobhan Malany found a place where this is possible: the International Space Station (ISSInternational Space Station).

In an investigation funded by the National Institutes of Health (NIH) and sponsored by the ISS National Laboratory®, Malany and her team sent skeletal muscle tissue chips to space to help people with muscle loss on Earth. The team created a tissue chipA tissue chip, or organ-on-a-chip or microphysiological system, is a small engineered device containing human cells and growth media to model the structure and function of human tissues and/or organs. Using tissue chips in microgravity, researchers can study the mechanisms behind disease and test new treatments for patients on Earth. The National Institutes of Health (NIH) has a multiyear partnership with the ISS National Laboratory® to fund tissue chip research on the space station. system that grows bundles of human skeletal muscle called myobundles. By sending the tissue chips to the microgravityThe condition of perceived weightlessness created when an object is in free fall, for example when an object is in orbital motion. Microgravity alters many observable phenomena within the physical and life sciences, allowing scientists to study things in ways not possible on Earth. The International Space Station provides access to a persistent microgravity environment. environment of the ISS, where muscle loss is accelerated, the researchers hoped to study age-related muscle deterioration in ways not possible in ground-based labs.

“Our system can study human muscle responses under disease conditions for which there are not a lot of therapeutics, mainly because there hasn’t been a way to look at what’s happening at the tissue level,” said Malany, an associate professor in the College of Pharmacy at the University of Florida. “There are mechanisms you don’t pick up on in studies in the whole animal, but you can see at the human tissue level.”

Malany and her team knew that microgravity induces muscle loss, but does it mimic muscle loss specifically related to aging? To answer that question, the team launched three experiments to the space station, each using tissue chips created using skeletal muscle cells from two groups of donors: young active adults and older sedentary adults.

Upon return to Earth, gene expression analysis of the space-flown tissue chips revealed several microgravity-induced gene changes that mimic aspects of muscle aging and stress, including changes in muscle differentiation, decreased muscle contraction, a shift in muscle fiber type, and metabolic alterations. The team also found differences in gene expression between the young and old age groups and published the initial findings in npj Microgravity.

“Through insight we gather from microgravity, we can understand not just the end result of the disease, but really look at the progressive change in young and old cells to see what happens as cells age,” Malany said. “We don’t get that on the ground because aging occurs over so many years, but in space, we can see the snapshots of how these cells are changing by monitoring tissue structure, contraction magnitude, and gene expression.”

Building a Microgravity Muscle Tissue Model

To better understand the mechanisms behind age-related muscle loss, Malany and her team created a microfluidic device that grows three-dimensional muscle tissue and circulates fluids through the tissue, recapitulating the growth and function of muscle tissue in the body. The goal is for these tissue chips to replace animal models to more accurately test potential new drugs for treating sarcopenia.

On Earth, muscles constantly work against gravity, but in space, where gravity is removed, muscles don’t have to work as hard and weaken quickly. Malany and her team hypothesized that microgravity would speed up age-related changes to muscle physiology, making it possible to study muscle cell aging on a much quicker timescale.

The team collaborated with AdventHealth, Micro-gRx, Micro Aerospace Solutions, and Space Tango for the investigation. To develop the tissue chips, AdventHealth provided donor cells from two groups: people younger than 40 who exercise several times a week and people older than 60 who are sedentary.

“A unique aspect of this work is the use of human muscle cells derived from muscle biopsies performed on our study volunteers,” said Paul Coen, associate investigator at the AdventHealth Translational Research Institute. “Results from these experiments are highly relevant to skeletal muscle health, and our participants get a kick out of knowing their muscle cells may take a trip to the ISS.”

The muscle cells for each group were acquired from six to eight donors and pooled to create “young” and “old” sets of tissue chips. The cells retain their age-related characteristics in culture as they mature into muscle tissue on the chips, explained Maddalena Parafati, a pharmacodynamics research assistant professor at the University of Florida.

“We have a micro-engineered chip, and we model the muscle tissue in our body at the smallest acceptable biological scale,” Parafati said. “Donor-derived younger and older myoblasts are seeded on the chips and then proliferate, migrate, align, and fuse to form a functional construct.”

Going From Ground to Space

Creating the tissue chips was only half the puzzle—the team also had to design the experiments to work in space, a process Malany said was done in partnership with the ISS National Lab and Commercial Service ProviderImplementation Partners that own and operate commercial facilities for the support of research on the ISS or are developing future facilities. Space Tango.

“The ISS National Lab is beneficial because it already has the implementation processes and the technology to tap into,” she said. “There is a framework in place that has continually become more efficient and less expensive to take your research to space and bring it back.”

Space Tango worked closely with Malany and her team on the experiments, said Shelby Giza, director of scientific business strategy at Space Tango. Before joining Space Tango, Giza was a researcher on Malany’s team at the University of Florida, giving her a unique perspective on both sides of the process.

“From the beginning, Space Tango works with investigators on their science requirements and translates those needs into a hardware solution to make sure their research is successful,” Giza said. “As a Commercial Service Provider, we can see around corners because we have so much experience with microgravity research and can help ensure success.”

The team’s experiments were hosted in a novel Space Tango CubeLab, a standardized, modular system that can house a variety of payloads on the ISS. With a ground control CubeLab remaining on Earth, a flight CubeLab would be installed into a Space Tango Powered Ascent Utility Locker (PAUL) facility that provides power and environmental control during all phases of flight. Designed specifically to host the team’s tissue chips, the CubeLab is equipped with a camera and microscope system to record muscle movement, and data could be sent to the research team in near real time, allowing the team to check on the experiment and make adjustments if needed. Lastly, a key feature of the platform is that it runs autonomously.

“Automation is really important for reliability and reproducibility, and being able to run experiments autonomously in space enables better data and research,” Giza said.

For Malany, having the old and young sets of tissue chips together in the same automated platform was crucial because it allowed the team to compare the two age groups directly.

“Because the tissue chips were all in the same CubeLab with the same spaceflight conditions and the same automated flow rate, any changes we see should be directly comparable,” Malany said. “So, we can gain insight into the process by which the muscle cells are responding to microgravity, and then we can look at potential countermeasures.”

Iteration on Station

The team’s first experiment launched on SpaceX’s 21st Commercial Resupply Services (CRS) mission in December 2020. Knowing that doing automated experiments in space is challenging, the main goal of this mission was to validate the tissue chip system. The team sent 16 tissue chips to the ISS, half created using young cells and half using older cells. In space, myobundles grew on the chips for 15 days and then were preserved, frozen, and returned to Earth for analysis. While there were operational issues, the overall mission was a success in demonstrating the technology, and the team learned a lot about the system’s camera operation, temperature control, and fluid flow and how to improve them.

“The key things that came out of that first flight were the generation of myobundles and demonstrating the end-to-end processing with the tissue chips in an autonomous closed system,” Malany said. “It was complex biology and a complex system, and even though we had some operational issues, the 3D-engineered tissue was robust. We obtained good-quality RNA for gene expression studies, and that was a big accomplishment for the team.”

Building on lessons learned, Malany and her team worked with Space Tango to overcome the challenges from the first flight and improve the integrated system for its second flight on SpaceX CRS-25 in 2022. This time, when the tissue chips were returned to Earth, gene expression analysis revealed something big: in microgravity, the cells from the young active adults had many more gene expression changes than those from the older sedentary adults.

The team also compared the differences between the young and old cells grown in space to the differences between the young and old cells grown in the same CubeLab on the ground. When they looked specifically at 957 muscle tissue genes associated with human aging, Malany and her team found something really exciting. Several genes upregulated in aging muscle cells on Earth were upregulated in the young muscle cells in space.

“We have lacked the data to prove the concept of accelerated aging in microgravity, and I think our data starts to speak to that,” Malany said. “We found that microgravity induces changes in the expression of specific aging genes in muscle tissue chips in space, and that is an exciting result.”

Additionally, this time, the team embedded electrodes in half the tissue chips to examine contraction in the myobundles. Understanding contraction is important because it can be used to assess muscle performance. The CubeLab delivered electrical stimulation to the chips through the electrodes and captured video of the muscle bundle contraction.

“I think this was probably the first time muscle cells have been electrically stimulated in space in a tissue engineering product, so that’s a big takeaway,” Malany said.

To analyze myobundle contraction, the researchers use “digital image correlation.” With the help of software, the team can identify small changes in the myobundles based on the movement of pixels in the video, and this data can be converted into micrometers of contraction, Parafati explained. Although the team is still analyzing the data, there appears to be less contraction in the spaceflight tissue chips than in ground controls, indicating decreased muscle function in microgravity.

The team’s third flight, which launched on SpaceX CRS-26 later in 2022, took the experiment one step further and used the tissue chips to test a potential muscle loss drug—an anti-atrophy compound derived from the skin of green tomatoes. This analysis is also ongoing, but initial results show differences in contraction response between young and old tissue chips treated with the drug in space versus those on the ground and those untreated, which is promising.

Making the Leap From Concept to Commercialization

The success of these experiments underscores the value of conducting fundamental research in microgravity, said Danilo Tagle, director of the Office of Special Initiatives at NIH’s National Center for Advancing Translational Sciences (NCATS). “Studies through the ISS National Lab that leverage the unique stressor of microgravity have provided opportunities for NCATS-funded research to identify some of the hallmarks of accelerated aging,” he said. “Dr. Malany’s findings will provide crucial clues toward developing new treatments for patients on Earth with muscle loss.”

According to Malany, the priority now is getting the team’s results out to the scientific community, and her team is planning to submit multiple papers for publication. Malany also started a consortium of faculty labs across multiple disciplines for space-based research at the University of Florida, called the In-Space Biomanufacturing Innovation Hub, which received a $1.5 million investment from the university.

“We have made substantial progress from the exposure and the experience we’ve gained through our ISS National Lab research,” she said. “Now that we have validated this technology, we can continue to improve both the tissue chip and CubeLab integration to make the system more standardized, higher throughput, and adaptable to operate over several months in orbit, which will be important to test potential therapeutics.”

Continued research on the ISS is critical for the team’s work, she says. Validation studies are needed to gather enough statistical data to advance the tissue chips beyond proof of concept and entice pharmaceutical companies to invest in them over animal models to study disease progression and test drugs.

Parafati says she feels many emotions when she thinks about the opportunity to take her research to space and what it could one day mean for sarcopenia patients on Earth.

“Conducting research on the ISS is exciting because it allows us to do experiments that are not possible anywhere else,” Parafati said. “It enables innovative research that, hopefully at the end of the day, can help us identify biomarkers to treat different types of muscle disease.”