Sphere cultures from representative tissues were washed twice with Hank’s balanced salt solution (Gibco). Under a microscope, 2000 spheres, each containing *1000 cells, were collected using a glass pipette and placed in a 50mL tube. Hank’s balanced salt solution (20mL) was added to each tube and subsequently centrifuged at 800rpm for 3min. The supernatant was discarded and the pellet was resuspended in 50mL of DMEM with 10% fetal bovine serum. This solution was seeded onto a sheet 3x3x1mm, composed of a nonwoven mesh of polyglycolic acid ﬁbers, 200mm in diameter, and implanted subcutaneously into the dorsal ﬂanks of a 4-week-old NOD/SCID mice (Jackson Laboratory).