Minoxidil ameliorates myelodysplastic syndrome by targeting Wnt4 while sparing normal hematopoiesis

Hematopoietic stem cells (HSCs) maintain blood production via tightly regulated differentiation. Disruptions at this level can lead to myelodysplastic syndromes (MDS), characterized by ineffective hematopoiesis and marrow failure. Despite its clinical use, the antihypertensive and hair-growth agent minoxidil has been linked to hematologic side effects, yet its mechanism remains unknown. Compounds affecting hematopoiesis were identified by a small-molecule screen using Tg(mpl:eGFP) zebrafish embryos and validated by immunofluorescent antibody staining. The impact of minoxidil on different blood cell types was determined by whole-mount in situ hybridization. HSPCs proliferation and apoptosis were assessed in Tg(cd41:eGFP) embryos using bromodeoxyuridine (BrdU) incorporation and TUNEL assays. Gene expression changes were profiled by RNA sequencing. Functional relevance of wnt4 was assessed through overexpression and F0 knockout experiments. At suitable concentrations that avoided notable developmental delay, minoxidil demonstrated its dual effects—therapeutic efficacy and hematopoietic toxicity—across larval and adult MDS-like zebrafish and in wild-type mice, and further exerted antiproliferative effects in human malignant hematopoietic cells in vitro. Minoxidil significantly reduced hematopoietic stem and progenitor cell numbers in zebrafish embryos, leading to broad suppression of multiple blood lineages. Transcriptomic profiling revealed that minoxidil downregulated wnt4 expression. Functional validation demonstrated that wnt4 directly modulates HSPC abundance: knockout of wnt4 recapitulated the hematopoietic suppression seen with minoxidil, while overexpression restored HSPC levels. In c-mybhyper MDS-like zebrafish, minoxidil treatment alleviated myeloid hyperplasia at appropriate doses without impairing lymphoid or erythroid lineages. Consistently, minoxidil showed inhibitory effects on human malignant hematopoietic cells in vitro, supporting its conserved suppressive effect on myeloid and progenitor expansion. In both adult zebrafish and wild-type mice, low or intermittent minoxidil dosing preserved hematopoietic integrity, whereas continuous high-dose treatment resulted in multilineage cytopenia. Our findings demonstrate that minoxidil modulates hematopoiesis through wnt4 downregulation, resulting in both HSPC suppression and therapeutic alleviation of MDS-like phenotypes. At optimized dosing, minoxidil exhibits hematologic safety in vivo. This study identifies wnt4 as a regulatory node linking pharmacologic intervention to HSPC homeostasis and highlights its therapeutic potential in MDS.