Histopathological characterization and flow cytometric analysis of BM and spleen of Jak2V617F knock-in mice treated with placebo or vorinostat. (A) Peripheral blood smears show normalization of RBCs and reticulocytes in vorinostat-treated Jak2V617F knock-in mice. Arrows indicate reticulocyte and immature nucleated RBCs. H&E staining of BM (B) and spleen (C) sections from placebo-treated Jak2V617F knock-in mice show hypercellularity with trilineage hyperplasia, which was markedly reduced by vorinostat treatment. (D) Percentage of erythroid precursors, determined by Ter119⁺ and CD71⁺ cells, was significantly reduced in both the BM and spleens of Jak2V617F knock-in mice treated with vorinostat compared with those of placebo-treated mice. Results shown represent means ± SEM from 7 mice in each group.