Evaluation for the formation of ovarian cell aggregates according to cultured ovarian cell populations. (A) Schematic representation of experimental procedures. Two different cell populations from 20 to 40% layers and top to 50% layers after Percoll density gradient centrifugation were compared for ovarian cell aggregate formation after culture for 7 days. (B) Pictures showing two different forms of ovarian cell aggregates. Aggregates were formed in two different ways; large single aggregate and small multiple aggregates. Scale bar = 100 μm. (C) Frequencies of replicates in which different aggregate forms appeared. Ten independent experiments were performed.