Paradoxic enhancement of mitochondrial capacity in aging-specific megakaryopoiesis from hematopoietic stem cells

Abstract

Aging leads to quantitative and qualitative changes in platelet (Plt) production, with increased risk for thrombosis and other adverse cardiovascular events. Recent reports showed that aging promotes the emergence of non-canonical (nc) megakaryocyte progenitors (MkPs) directly from hematopoietic stem cells (HSCs), leading to the production of hyperactive Plts. The higher engraftment potential of ncMkPs compared to both young and old canonical (c)MkPs, contrasts with the functional decline of old HSCs. Emerging reports suggest that mitochondrial function critically regulates lineage commitment and cellular functionality, but how mitochondrial activity affects aging megakaryopoiesis is unknown. Here, we demonstrate that aged MkPs sustain unique mitochondrial activity, characterized by higher mitochondrial membrane potential, higher ATP content, and lower ROS levels compared to their younger counterparts. This contrasts with the dysfunctional mitochondrial state observed in old HSCs, suggesting lineage-specific organelle adaptations upon aging. Notably, we observed that the elevated mitochondrial capacity in aged MkPs is driven selectively by the age-specific ncMkPs. Paradoxically, in vivo pharmacological enhancement of mitochondrial activity in old mice reduced in situ Plt production, but increased Plt reconstitution by transplanted HSCs. These discoveries link uniquely regulated mitochondrial capacity to the intrinsic properties of age-specific MkPs, raising the possibility of therapeutic targeting to prevent aging-induced megakaryopoiesis.