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RESEARCH |
Institute of Cell Biology, University of Edinburgh, The Darwin Building, Kings Buildings, Mayfield Road, Edinburgh EH9 3JR, UK, 1 Division of Reproductive Medicine, School of Human Development, Queens Medical Centre, University of Nottingham, Nottingham NG7 2UH, UK and 2 Division of Integrative Biology, Roslin Institute (Edinburgh), Roslin, Midlothian EH25 9PS, UK
Correspondence should be addressed to E E Telfer; Email: evelyn.telfer{at}ed.ac.uk
The aim of this study was to determine the effect of regulation of IGF-I bioavailability on preantral follicle development in vitro. Bovine preantral follicles were cultured for 6 days in serum-free medium with increasing doses of Long R3 (LR3) IGF-I (an analog with low affinity for IGF-binding proteins (IGFBPs)), or human recombinant IGF-I (hrIGF-I). Follicle diameter and estradiol production were measured every second day. On day 6, ratios of oocyte/follicle diameter and oocyte morphology were assessed by histological examination, and IGFBP-2 and -3 were detected by immunocytochemistry and in situ hybridization respectively. Both types of IGF-I increased follicle diameter in a dose-dependent manner (P < 0.05) and increased estradiol production over control levels (P < 0.05). However, follicles treated with LR3 IGF-I and the highest concentration of hrIGF-I (1000 ng/ml) had smaller oocyte/follicle ratios, and increased oocyte degeneration, compared with controls or follicles treated with physiological concentrations of hrIGF-I (P < 0.05). IGFBPs were detected in cultured preantral follicles, indicating a requirement for regulation of IGF bioavailability during the early stages of follicular development. Specifically, IGFBP-3 mRNA was found to be expressed in oocytes, and IGFBP-2 immunoreactivity was detected in oocytes and granulosa cells of cultured follicles. In summary, the regulation of IGF-I bioavailability by IGFBPs is necessary for the co-ordination of oocyte and follicle development in vitro.
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E. E. Telfer, M. McLaughlin, C. Ding, and K. J. Thong A two-step serum-free culture system supports development of human oocytes from primordial follicles in the presence of activin Hum. Reprod., May 1, 2008; 23(5): 1151 - 1158. [Abstract] [Full Text] [PDF] |
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