Megakaryocyte progenitor cell function is enhanced upon aging despite the functional decline of aged hematopoietic stem cells

Summary Age-related morbidity is associated with a decline in hematopoietic stem cell (HSC) function, but the mechanisms of HSC aging remain unclear. We performed heterochronic HSC transplants followed by quantitative analysis of cell reconstitution. Although young HSCs outperformed old HSCs in young recipients, young HSCs unexpectedly failed to outcompete the old HSCs of aged recipients. Interestingly, despite substantial enrichment of megakaryocyte progenitors (MkPs) in old mice in situ and reported platelet (Plt) priming with age, transplanted old HSCs were deficient in reconstitution of all lineages, including MkPs and Plts. We therefore performed functional analysis of young and old MkPs. Surprisingly, old MkPs displayed unmistakably greater regenerative capacity compared with young MkPs. Transcriptome analysis revealed putative molecular regulators of old MkP expansion. Collectively, these data demonstrated that aging affects HSCs and megakaryopoiesis in fundamentally different ways: whereas old HSCs functionally decline, MkPs gain expansion capacity upon aging.
Graphical abstract
Highlights • Reconstitution deficit by old HSCs was observed by chimerism and absolute cell numbers • Young HSCs did not outcompete resident HSCs in aged recipient mice • Old MkPs display remarkable capacity to engraft, expand, and reconstitute platelets • Aging is associated with changes in MkP genome-wide expression signatures
Poscablo et al. explored age-related changes to hematopoietic stem cell and megakaryocyte progenitor (MkP) function. They found an unexpected gain of in vitro expansion and in vivo reconstitution potential of MkPs upon aging. These functional changes were accompanied by differences in transcriptome profiles between young and old MkPs, suggesting progenitor cell mechanisms contributing to hematopoietic aging.