The study, published in Blood, reveals that levels of platelet factor 4 (PF4) – a protein that helps regulate the proliferation of blood stem cells – decrease with age, leading to dysfunction in the body’s ability to produce healthy blood and immune cells.  

Hematopoietic stem cells, which reside in the bone marrow, are responsible for generating all blood and immune cells. In youth, these stem cells can flexibly produce both myeloid cells (including certain immune cells and red blood cells) and lymphoid cells (such as T and B cells). With age, however, they become biased toward the myeloid lineage, reducing immune resilience and increasing susceptibility to disease.  

Led by Associate Professor Sandra Pinho of the Department of Pharmacology and Regenerative Medicine, the UIC team found that platelet factor 4 acts as a molecular signal telling blood stem cells to stop dividing once they have produced enough progeny. As PF4 levels fall with age, these cells proliferate more frequently, accumulating mutations that can contribute to inflammation, blood cancers, and cardiovascular disease.  

When the researchers supplied platelet factor 4 to older mice, they observed a reversal of these ageing effects: the animals’ blood and immune cells began to resemble those of much younger counterparts. The same rejuvenating effect was seen in aged human bone marrow samples treated with PF4 in the lab.  

“It rejuvenated the ageing of the blood system,” said Pinho. “It’s clear evidence that it’s possible to reverse, intrinsically, certain age-associated disorders.” While PF4 alone is unlikely to serve as a universal anti-ageing therapy, Pinho noted that it could become an important component in broader rejuvenation strategies aimed at preventing or treating age-related diseases of the blood and immune system.