A systems herbal-to-molecule and transcriptomic strategy identifies emodin as an ESR1-targeting phytochemical driving thrombopoiesis.

Radiation-induced thrombocytopenia (RIT) is a major dose-limiting toxicity of radiotherapy, for which effective pharmacological interventions remain limited. Rhei Radix et Rhizoma (RR) is widely used in traditional medicine, yet its thrombopoietic activity and molecular basis have not been systematically defined. Here, we investigated the effects of RR on thrombopoiesis using an integrated herbal-to-molecule and transcriptomic strategy. RR extract and representative phytochemicals were screened for megakaryocyte (MK) differentiation in Meg-01, K562, and murine haematopoietic stem and progenitor cells (HSPCs), followed by validation in a mouse RIT model. Network pharmacology and transcriptomic analyses indicated that RR regulates thrombopoiesis through coordinated multi-pathway modulation. Emodin was identified as the principal bioactive constituent mediating these effects. Functionally, emodin promoted MK maturation and polyploidization in vitro, accelerated megakaryopoiesis and platelet recovery in irradiated mice. Integrated target prediction and experimental validation identified ESR1 as a direct functional target of emodin, supported by molecular docking, molecular dynamics simulations, CETSA, and DARTS assays. Mechanistically, emodin activated ESR1-dependent PI3K/AKT and JAK2/STAT3 signaling, leading to induction of lineage-specific transcription factors and enhanced platelet biogenesis. Collectively, these findings identify emodin as a key thrombopoietic constituent of RR and reveal an ESR1-centered regulatory axis in megakaryopoiesis, supporting its therapeutic potential for RIT.