Health

The frustrating reality of slower muscle healing with age may stem from a surprising cellular adaptation, according to new research from UCLA. A study published in the journal Science reveals that aging muscle stem cells accumulate a protective protein that prioritizes survival over rapid repair, suggesting that the decline in tissue regeneration isn’t simply deterioration, but a fundamental shift in cellular strategy.

Researchers discovered that this protein, called NDRG1, increases significantly with age, acting as a brake on the muscle stem cells’ ability to activate and mend damaged tissue. While this slowdown hinders repair, it simultaneously bolsters the cells’ resilience in the challenging environment of aging muscle. This finding challenges conventional thinking about aging and opens new avenues for developing therapies that balance function and longevity.

The Role of NDRG1 in Muscle Aging

The research team, led by postdoctoral scholars Jengmin Kang and Daniel Benjamin, compared muscle stem cells from young and old mice. They found that levels of NDRG1 were 3.5 times higher in older cells compared to their younger counterparts. NDRG1 works by suppressing the mTOR signaling pathway, a crucial regulator of cell growth, activation and tissue repair. Essentially, the protein puts the brakes on the processes needed for quick healing. To confirm NDRG1’s role, scientists allowed mice to age to approximately 75 human years and then blocked the protein’s activity. The results were striking: older muscle stem cells, with NDRG1 inhibited, began to behave like those of young mice, activating more quickly and accelerating muscle repair.

A Trade-Off Between Repair and Survival

However, this rejuvenation came at a cost. Blocking NDRG1 led to a decrease in the overall survival rate of muscle stem cells over time. The muscle’s capacity to regenerate after repeated injuries was diminished. “Think of it like a marathon runner versus a sprinter,” explained Dr. Thomas Rando, senior author of the study and director of the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research at UCLA, who is similarly a professor of neurology at the David Geffen School of Medicine at UCLA. “The stem cells in young animals are hyper-functioning – really good at what they do, namely sprinting, but they’re not good for the long term. They can make it through the 100-yard dash, but they can’t make it even halfway through the marathon. By contrast, aged stem cells are like marathon runners – slower to respond, but better equipped for the long haul. However, what makes them so proficient over long distances is exactly what renders them poor at sprinting.”

The team consistently observed this pattern across multiple experiments, both in lab dishes and within living tissue. Higher NDRG1 levels correlated with slower activation and repair, but also with enhanced long-term cell survival. This led them to propose the concept of a “cellular survivorship bias,” where stem cells that don’t produce enough NDRG1 are more likely to die off, leaving behind a population of cells that are slower to act but more resilient.

Implications for Future Therapies

Dr. Rando suggests that some age-related changes previously considered purely detrimental may, in fact, be necessary compromises to prevent the complete depletion of the stem cell pool. He draws a parallel to survival strategies observed in nature, where animals prioritize resilience over reproduction during times of extreme stress, such as droughts or famines. Similarly, aging stem cells appear to shift their focus from rapid cell production to survival mechanisms as they cope with the challenges of aging. UCLA Newsroom details this shift in cellular priorities.

These findings have significant implications for the development of therapies aimed at boosting muscle regeneration in older adults. However, Dr. Rando cautions that simply enhancing stem cell performance without addressing the survival aspect could have unintended consequences. “There’s no free lunch. People can improve the function of aged cells for a period of time, for certain tissues, but every time we do this, there’s going to be a potential cost and a potential downside.”

The research team is now focused on unraveling the molecular mechanisms that control this delicate balance between survival and regeneration. “This gene is almost like our doorway that we’ve opened into understanding what controls these trade-offs that are so critical, not only for evolution of species but also for the aging of tissues within an individual,” Dr. Rando stated. Further research, funded by the National Institutes of Health, the NOMIS Foundation, the Milky Way Research Foundation, the Hevolution Foundation and the National Research Foundation of Korea, will be crucial to translating these findings into effective interventions.

Disclaimer: This article provides information for general knowledge and informational purposes only, and does not constitute medical advice. It is essential to consult with a qualified healthcare professional for any health concerns or before making any decisions related to your health or treatment.

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