Integrin β3 dysregulation impairs megakaryopoiesis and microparticle production via disrupting Rho-associated protein kinase-dependent cytoskeletal dynamics.

BACKGROUND: Megakaryocyte (MK) fragmentation into proplatelets (PPTs) and microparticles (megakaryocyte-derived microparticles [MKMPs]) is well established, yet the mechanisms underlying MKMP generation remain unclear.

OBJECTIVES: This study aimed to investigate the role of integrin β3 and cytoskeletal dynamics during megakaryopoiesis and explore potential therapeutic targets for thrombocytopenia.

METHODS: Proplatelet formation and MKMP release were evaluated both in vivo and in vitro under integrin β3 receptor-impaired environment. The integrin activation and RhoA-associated kinase triggered signaling were analyzed.

RESULTS: In human MK cultures, we demonstrated that the anti-β3 antibody SZ21 hyperactivated RhoA‒Rho-associated protein kinase (ROCK) signaling, stabilizing F-actin polymerization via LIM kinase/myosin light chain 2 phosphorylation and impairing both PPT and MKMP release. MKMP release depends on actin depolymerization, whereas PPT formation requires microtubule assembly and actomyosin contraction, revealing differential cytoskeletal regulation among megakaryocytic byproducts. Pharmacologic ROCK inhibition with Y27632 rescued these defects in vitro and accelerated platelet recovery in thrombocytopenic mice without compromising hemostasis.

CONCLUSIONS: Our study reveals a novel dysregulation of the integrin β3-ROCK axis in immune-mediated MK dysfunction and suggests that targeting ROCK signaling or cytoskeletal dynamics may represent promising therapeutic strategies for thrombocytopenia and other disorders affecting platelet production.