Coculture of huMkMPs and muHSPCs promotes murine megakaryopoiesis. Sixty thousand muHSPCs were cocultured for 5 days with huMkMPs only, with 50 ng/mL TPO, or without any supplements (vehicle control). Cells were harvested and fixed at day 5 and (A) stained for expression of VWF, TUBB1, and nucleus (DAPI), via confocal microscopy along with bright-field imaging. Some cells were analyzed by flow cytometry to count Mk cells (B) or to measure the percentage of Mk cells (C) in the various ploidy classes. The bar represents 10 μm; error bars represent the SEM (n = 4).