Blood stem cells age, but their successors do not

The bone marrow houses stem cells responsible for producing all blood cells: red blood cells, white blood cells and platelets. With age, hematopoietic stem cells (HSCs) lose their regenerative capacity. This contributes to a weakened immune system and increased clotting risk in later life. But the researchers found that not every layer of this system ages equally.

Between stem cells and fully specialised blood cells lies a group of intermediate cells called multipotent progenitors (MPPs). The study, published in Stem Cell Reports, showed that young and old MPPs perform nearly identically. They had the same capacity to replenish blood cells, comparable gene activity, similar cell division rates and equal mitochondrial capacity, the energy-producing machinery inside cells.

A buffer in the bone marrow

The researchers propose that these progenitor cells act as a buffer. Even as the stem cells at the top of the hierarchy decline, MPPs may sustain blood production. This could explain why blood output in older individuals remains more intact than expected based on stem cell decline alone.

Implications for therapy

It is too early to know what this means for clinical applications. Treatments targeting the blood system have so far focused on stem cells as the key factor. But if MPPs play a major compensatory role, therapies may need to address this intermediate layer as well. The researchers describe three potential mechanisms by which MPPs maintain blood system integrity, while noting that further research is needed to confirm them. For longevity researchers, the question is now: which level offers the most therapeutic leverage?

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