Megakaryocyte adhesion assay. Megakaryocytes were differentiated from CD34⁺ hematopoietic progenitor cells derived from control HSs or patients with PMF. Because possible oxidation of extracellular residues by secreted LOX would take place during cellular development, it was important to add the LOX inhibitor during this process. At day 2 of differentiation, cells were treated or not with 100 µm of LOX inhibitor BAPN until the end of culturing. BAPN concentration was selected based on consideration of the incubation time, so as to inhibit LOX but avoid effects on cell number (confirmed). At day 13, megakaryocytes were collected and counted, and equal numbers of HS and PMF megakaryocytes were plated on PSCI-coated glass coverslips for 3 hours. Adherent megakaryocytes were fixed and stained with anti-β1 tubulin antibody (green) and counterstained with Hoechst (blue). (A) Adherent HS- and PMF-derived megakaryocytes (Mks) were counted and expressed as number (n) of β1 tubulin⁺ megakaryocytes per field. Data are expressed as mean ± standard deviation of 5 samples from patients with PMF and 3 HS samples. *P < .05. Ctrl, control. (B) Images of adhering cells; scale bar, 50 µm. See supplemental Methods for additional details on cell culturing, cell isolation, and other procedures and statistics.