Fig. 1

Identification and morphology of OP9 cells and hESCs before co-culture. A Immunophenotype of OP9 cells. Immunofluorescence staining of Calponin and CD34 in the OP9. Original magnification: × 40. B The morphology of hESCs (HN14) before co-culture (bar = 100 μm). hESCs monolayers at 80% confluence and co-cultured with OP9 cells. C The morphology of OP9 cells in the control group. OP9 cells reached confluence for culturing for 4 days at a seeding number of 3.1 × 10⁴ cells/cm² in 6-well plates (bar = 100 μm). D The morphology of OP9 cells in the experimental group. OP9 cells were cultured for 1 day with six different seeding numbers in 6-well plates: a to f show the morphology of different seeding densities, i.e. 3.1 × 10⁴ cells, 5.2 × 10⁴ cells, 7.3 × 10⁴ cells, 10.4 × 10⁴ cells, 13.5 × 10⁴ cells, and 16.6 × 10⁴ cells per square centimeter, respectively (bar = 100 μm). When the seeding number of OP9 cells could reach 16.6 × 10⁴cells/cm², the cultures reached confluence