Researchers at the Icahn School of Medicine at Mount Sinai have found a way to make old blood stem cells behave young again, a discovery that could reshape treatment for age-related disorders and regenerative medicine. The team identified and corrected a critical malfunction in cellular recycling centers called lysosomes, restoring stem cell vigor in aging mice.
The work, published in Cell Stem Cell, shows that lysosomes in aged blood-forming stem cells become overactive, excessively acidic, and damaged. These breakdowns disrupt the cells' metabolic balance and genetic stability, accelerating the decline of immune function that comes with age. By blocking this excessive lysosomal activity with a targeted inhibitor, the researchers reversed these damage patterns and rejuvenated the stem cells.
Hematopoietic stem cells are rare, long-lasting cells in bone marrow that generate all blood and immune cells throughout life. As people age, these cells lose their regenerative power, weakening immune defenses and contributing to increased infection risk in older adults. The decline is also linked to clonal hematopoiesis, an asymptomatic condition that raises the risk of blood cancers and inflammatory diseases, becoming much more common with advancing age.
The treated stem cells showed dramatic functional improvement. They regained the ability to produce balanced blood and immune cells, generate additional healthy stem cells, and showed improved metabolism and mitochondrial performance. The cells also displayed healthier genetic patterns and reduced inflammation. In tests using cells removed from the body, treated in the lab, and returned to living animals, the old stem cells showed a more than eightfold increase in blood-forming ability.
Dr. Saghi Ghaffari, who led the research, described the finding as fundamentally challenging assumptions about aging. "Our findings reveal that aging in blood stem cells is not an irreversible fate," Ghaffari said. "Old blood stem cells have the capacity to revert to a youthful state; they can bounce back." By targeting the lysosomal hyperactivity, the team was able to reset aged stem cells to a younger state and significantly boost their regenerative capacity.
The mechanism behind the improvement involves healthier lysosomes better processing mitochondrial DNA and lowering activation of immune signaling pathways that drive inflammation and aging. This correction reduced damaging inflammatory signals that accumulate with age and damage tissues throughout the body.
The clinical implications could be substantial. The findings may lead to new treatments for age-related blood disorders, improve stem cell transplantation outcomes in older patients, and enhance therapies that rely on healthy stem cells. The researchers are already investigating whether lysosomal dysfunction in aging stem cells connects to leukemic stem cell development, potentially linking normal aging processes to cancer formation.
Lysosomes function as cells' internal recycling centers, breaking down proteins and other molecules while storing nutrients for use when needed. Their role in maintaining cellular metabolism makes them essential for both breaking down complex molecules and building new ones. The Mount Sinai team's discovery positions lysosomal dysfunction as a central driver of stem cell aging, opening a new target for anti-aging interventions.
Author Jessica Williams: "This research reframes an entire category of cellular decline as potentially reversible, which should energize both the aging and regenerative medicine fields."
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