Coculture of huMkMPs and muHSPCs in vitro. muHSPCs were cocultured for up to 5 hours with huMkMPs stained with CFSE and PKH26. The cells were examined by confocal microscopy at 3 (A) and 5 (B) hours after the start of coculture, and fluorescence images were taken at different confocal planes. The numbers represent the specific slice (Z-stack) number (left)/total number of slices (right). Red arrows indicate huMkMPs binding to muHSPCs; white arrows indicate huMkMPs that have been internalized by muHSPCs.