Homeostasis of megakaryocytes: balancing tissue residency and consumptive platelet production

Megakaryocytes (MKs) release platelets through a terminal event that results in the complete consumption of their cytoplasm. Once viewed as end-stage conductors of platelet biogenesis, MKs are now recognized as multifunctional regulators of the bone-marrow (BM) niche, supporting hematopoietic stem cell (HSC) maintenance, immune regulation, and extracellular matrix (ECM) remodeling. This multiple identity raises a fundamental question: how is MK homeostasis orchestrated to preserve a functional BM MK pool despite consumptive platelet production? Herein we review recent mechanistic insights into the biology of diverse MK functions, MK lineage development, and homeostatic regulation of megakaryopoiesis. Beyond classical systemic regulation, which maintains platelet counts within a physiological range by sensing the circulating platelet pool, we highlight BM tissue-level homeostatic circuits that treat the MK itself as the primary regulated variable.