Human AMSCs were obtained from normal postpartum placenta.
At first, the amnion and villus layer were bluntly separated, and
repeatedly washed with D-Hank’s solution including double resistant
(100 U/ml penicillin, 100 μg/ml streptomycin). After rinsing, amnion
was cut into several 1 mm×1 mm pieces with ophthalmic scissors and
digested at 37°C water bath for about 30 min with the action of 2.5 g/L
trypsin (Gibco). The digestion of amnion was terminated by DMEM
containing 5% calf serum and filtered through 200 mesh cell sieve. The
filtered productions of amnion were digested again in a 37°C water
bath for about 0.5 h with the addition of 1.0 g/L collagens II (Sigma).
Subsequent termination and filtrations were done as the described
above. Finally, harvested cell suspensions were centrifuged at 1000 rpm
for 5 min and the cell pellet was resuspended in low-glucose Dulbecco’s
modified Eagle’s medium (L-DMEM; Hyclone) supplemented with
10% fetal bovine serum (FBS; Hyclone), 1% penicillin-streptomycin
(Invitrogen, USA). They were then plated in 25-cm2 culture flasks at
a density of 106 cells per ml and incubated at 37°C with 5% carbon
dioxide. Medium was changed every 2 days. When the established
adherent cell colonies reached 70% confluence, they were detached
with 2.5 g/L trypsin and replated at a ratio of 1:2 in 25 cm2 flasks.