Getting comfortable: clonal haematopoiesis creates a senescent niche for expansion.

Clonal haematopoiesis (CH) is characterized by the age-associated expansion of mutant haematopoietic clones. How these clones expand, interact with the niche, and maintain a competitive advantage remains poorly understood. In a recent study published in Nature Cell Biology, Mistry and colleagues uncover that senescence in the bone marrow stromal microenvironment is a key contributor to the clonal growth of haematopoietic stem and progenitor cells (HSPCs) carrying CH mutations. Using mouse models and primary human samples, they show that mutant haematopoietic cells induce MSC senescence through contact-independent, cytokine-mediated signalling involving TNF-α, IL-6 and STAT3. Senescent MSCs preferentially support mutant haematopoietic stem and progenitor cells (HSPCs) over wild-type cells. Moreover, genetic or pharmacological depletion of senescent non-haematopoietic cells reduces CH burden and delays progression towards myeloid neoplasia in mice. By demonstrating that the premalignant niche is actively remodelled to favor mutant haematopoiesis, this study identifies MSC senescence as a relevant mechanism regulating CH evolution and a potential target for early disease intervention.