Apoptosis inhibition by insulin-like growth factor (IGF)-I during in vitro maturation of bovine oocytes

• Published in: Journal of Reproduction and Development Vol. 53; no. 2; pp. 419 - 426
• Main Authors: Wasielak, M.(Polish Academy of Sciences, Olsztyn (Poland)), Bogacki, M
• Format: Journal Article
• Language: English
• Published: Japan THE SOCIETY FOR REPRODUCTION AND DEVELOPMENT 01.04.2007
• Subjects: Animals; APOPTOSE; APOPTOSIS; Apoptosis - drug effects; Bovine; Caspase Inhibitors; Caspases - metabolism; Cattle; Cells, Cultured; COWS; CULTIVO IN VITRO; CULTURE IN VITRO; Cysteine Proteinase Inhibitors - pharmacology; FACTEUR DE CROISSANCE IGF; FACTOR DE CRECIMIENTO IGF; Female; In Situ Nick-End Labeling; IN VITRO CULTURE; In vitro maturation (IVM); INSULIN-LIKE GROWTH FACTOR; Insulin-like growth factor (IGF)-I; Insulin-Like Growth Factor I - pharmacology; MADURACION; MATURATION; Oocyte; Oocytes - cytology; Oocytes - drug effects; Oocytes - physiology; Oogenesis; OVA; OVULE; OVULO; VACA; VACHE
• ISSN: 0916-8818; 1348-4400
• DOI: 10.1262/jrd.18076

Recently, significant progress has been achieved in improving the yield of good quality embryos in vitro. However, efforts are still required to recognize the factors and understand the mechanisms of oocyte maturation, which are essential for subsequent embryo development. The aims of the present study were to determine the frequency of apoptosis in oocytes recovered from slaughterhouse ovaries and to investigate whether insulin-1ike growth factor (IGF)-I action during oocyte maturation in vitro may withhold apoptosis and improve oocyte quality. Only oocytes of proper morphology with homogenous ooplasm and compact cumulus cells were selected for this study. All oocytes recovered from the slaughterhouse ovaries were divided into two groups. One group of oocytes, chosen for apoptosis detection, was examined immediately after recovery. The other group of oocytes was maturated in vitro. Oocytes were maturated with IGF-I supplementation (100 ng/ml). Oocytes without supplementation were used as a control. Apoptosis in oocytes was determined by positive results of TUNEL assay and active caspase labeling. The percentage of apoptotic oocytes detected by TUNEL fell to zero when the maturation medium was supplemented with IGF-I in comparison to the control matured oocytes (0 vs. 9.87%; P0.05). However, active caspase labeling was only slightly decreased in the IGF-I matured oocytes compared with the control matured oocytes (1.13 vs. 2.08%; P0.05). The results indicate that IGF-I may serve as an antiapoptotic factor during oocyte maturation. We suggest that IGF-I may inhibit apoptosis in oocytes at the stage of caspase activation and may prevent further advancement of oocyte apoptosis.