The dissociation process was controlled to ensure that the dispersed cells mainly consisted of 3–5 cells in each aggregate. The CEHs were collected by centrifugation (200 g, 6 min) and filtrated through a 150 μM mesh. After washing three times with fresh medium 199 the cell number was counted by a hemacytometer.
Cell viability was always over 90% as determined by trypan blue exclusion test.