Platelet-derived TGF-β1 induced functional reprogramming of MDSCs in active-ITP mice through Smad2/Smad3. (A) AAV-DJ-SMAD2-GFP-miR30-shRNA, AAV-DJ-SMAD3-GFP-miR30-shRNA with CD11b as the specific promoter, and control AAV were injected into SCID mice through tail vein. Four weeks later, the active model of ITP was established. Platelet counts were detected once a week. (B) Percentage of MDSCs in bone marrow nucleated cells. The proportion of GFP⁺ cells in MDSCs was 40% to 50%. (C) MDSCs of mice from Control-NC, Romi-NC, Romi-Smad2^–, and Romi-Smad3^– groups were individually transferred to the new active-ITP murine model. Platelet counts were detected once a week. (D) Percentage of CD4⁺ cells in G0 stage. (E) Percentage of CD19⁺ cells in G0 stage. Percentage of Th1 (F) and Tregs (G) in CD4⁺ cells. (H) Percentage of FasL⁺ CTLs. (I) Percentage of CD138⁺ B cells. SCID, severe combined immune deficiency.