Fig. 4.

Expanding OP9 cells and preparing them for differentiation studies. (a) The day after passing OP9 cells. (b) Cells at ~80% confluency and are either ready for mESCs to be seeded on them for differentiation studies, or they need to be passed. (c) When cells become too confluent, they start to differentiate into adipocytes and deposit lipid droplets in their cytoplasm. At this stage, they will no longer support the maintenance and differentiation of hematopoietic cells and they should no longer be used for differentiation studies. (d) OP9 cells (orange cells) are grown in a T25 flask until about 80% confluent (Fig. 4b). At this stage, the OP9 cells need to be passed into a T25 flask for expansion (left) and/or into a 12-well plate for differentiation studies (right)