GES-1 versus hybrids. GES-1 (A) and CM-MSCs (C) were stained using PKH26 (B) and CFSE (D) separately. At day 1 after in vivo cell fusion and cell sorting, most cells expressed both PKH26 and CFSE (E–G), and the hybrids began growing colonies at day 5 (H). H&E staining showed that the morphologies of GES-1 (I) and fusion cells (J) were oval, spindle or polygonal, and CK-18 IF results showed that CK-18 was expressed in the cytoplasm in both GES-1 (K) and fusion cells (L). Magnification: 400×, Scale bar A-J = 25 μm; K-L = 20 μm.