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|Title:||Comparison of oocyte factors and transforming growth factor-b in the regulation of DNA synthesis in bovine granulosa cells|
|Citation:||Molecular and Cellular Endocrinology, 2003; 201(1-2):87-95|
|Publisher:||Elsevier Sci Ireland Ltd|
|R. B. Gilchrist, M. P. Morrissey, L. J. Ritter and D. T. Armstrong|
|Abstract:||Oocytes are powerful local modulators of follicular cell functions and many of the activities of oocytes are attributed to members of the transforming growth factor-β (TGF-β) superfamily. Whilst in the mouse it is known that members of this family are able to mimic many of the effects of oocytes on follicular cells, the relative importance of any of these factors is unknown in bovine follicles. The objectives of this study were to determine if bovine oocytes express and secrete TGF-β and to compare oocyte-secreted factor(s) to TGF-β in terms of their capacities to stimulate mural granulosa cell (MGC) DNA synthesis. Bovine ovaries were collected from an abattoir and RNA was extracted from isolated MGC, cumulus cells, cumulus-oocyte complexes and denuded oocytes (DO). Using RT-PCR, all cell types were found to express TGF-β1 and TGF-β2 mRNA transcripts. However, no TGF-β bioactivity could be detected from DO using a sensitive (40 pg/ml) and specific mink lung fibroblast cell bioassay. MGC were cultured with various combinations and doses of TGF-β2 and DO for 18 h, followed by a 6-h pulse of [3H]-thymidine as an indicator of cellular DNA synthesis. MGC DNA synthesis was stimulated by both TGF-β2 and DO. However in response to increasing doses of TGF-β2, [3H]-thymidine levels plateaued at <2-fold above control levels, whereas levels continued to increase over the dose range of DO tested (up to 3.4-fold). Addition of a TGF-β pan-specific neutralising antibody to MGC cultures eliminated the TGF-β2-stimulatory effects on DNA synthesis and the TGF-β2-suppressive effects on progesterone production, but the antibody was unable to neutralise the same responses when induced by DO. These results support a role for TGF-β1, TGF-β2 and DO in paracrine/autocrine regulation of bovine granulosa cell function, but indicate that neither TGF-β1 nor TGF-β2 can account for the actions of bovine oocytes on granulosa cells.|
|Keywords:||Oocyte-secreted factor(s); Transforming growth factor-β; Mural granulosa cell; Oocyte; Cumulus-oocyte complex|
|Rights:||© 2002 Published by Elsevier Science Ireland Ltd.|
|Appears in Collections:||Obstetrics and Gynaecology publications|
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