(続き)
STAP cells could not be efficiently maintained for additional passages in conventional LIF+FBS-containing medium or 2i medium20 (most STAP cells died in 2i medium within 7 days; Extended Data Fig. 8a). Notably, an adrenocorticotropic hormone (ACTH)+LIF-containing medium (hereafter called ACTH medium) known to facilitate clonal expansion of ES cells36 supported outgrowth of STAP cell colonies. When cultured in this medium on a MEF feeder or gelatin, a portion of STAP cell clusters started to grow (Fig. 5a, bottom; such outgrowth was typically found in 10–20% of wells in single cluster culture using 96-well plates and in >75% when 12 clusters were plated per well). These growing colonies looked similar to those of mouse ES cells and expressed a high level of Oct4-GFP.
