Ovarian tissues of normal pigs, on day 15 of their estrous cycle, were collected from a local slaughterhouse at Pyeong-Nong, Pyeongtaek, Korea. The samples were placed into an LN2 freezer box and were transported to the laboratory within 2 hours. The ovarian tissues of miniature pigs, on day 15 of estrous cycle (luteal phase), were obtained via laparotomy under general anesthesia from Medi Kinetics Co., Ltd. (Pyeongtaek, Korea). This study was carried out in strict accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health. The protocol was approved by the Committee on the Ethics of Animal Experiments of the Hankyong National University (Permit Number: 2012-1). All surgery was performed under sodium pentobarbital anesthesia, and all efforts were made to minimize suffering.