Growth Factors and Components for Extracellular Proteolysis Are Differentially Expressed during In Vitro Maturation of Bovine Cumulus-Oocyte Complexes¹

^a Institute of Physiology, Technical University München-Weihenstephan, 85350 Freising, Germany ^b Institute of Molecular Animal Breeding and Genetics, Ludwig-Maximilian-University München,85764 Oberschleissheim, Germany

In the present study, the time-dependent collagenolytic potential and mRNA transcription of extracellular matrix (ECM)-degrading components, transforming growth factor ß1 (TGFß1), and both basic fibroblast growth factor (bFGF) and FGF receptors (FGFR) in bovine cumulus-oocyte complexes (COCs) were investigated during 24 h of in vitro maturation (IVM). COCs were collected from 2- to 6-mm follicles, cultured in maturation medium, and sequentially removed at 3-h intervals for analysis. From 285 oocytes matured under these conditions, 114 (40.0%) developed to blastocysts on Day 9 after fertilization. Gelatin zymograms revealed protease activity at about 55 kDa for COCs matured for at least 3 h and two additional proteolytic zones at about 70 kDa after at least 9 h of IVM. The mRNAs of ECM-degrading components urokinase-type plasminogen activator (uPA), plasminogen activator inhibitor 1 (PAI1), matrix metalloproteinase 1 (MMP1), and tissue inhibitor of metalloproteinases 1 (TIMP1), as well as TGFß1, bFGF, and FGFR, were detected during IVM in a factor-specific pattern: all transcript levels found at COC 0 generally increased after 3 h of maturation and either remained high or decreased thereafter. On the basis of the chosen reverse transcription-polymerase chain reaction technique, one could suggest relative higher mRNA concentrations for TIMP1, PAI1, and both growth factors compared to uPA, MMP1, and FGFR.

Our results suggest a finely tuned extracellular proteolysis during IVM of bovine COCs, for which the concerted action of modulating growth factors like bFGF and TGFß1 may be essential.

¹ This study was funded by a grant from the Deutsche Forschungsgemeinschaft (Ei 296/4–2) and by the Bayerische Forschungsstiftung (76/93).

² Correspondence: Ralf Einspanier, Institute of Physiology, FML Weihenstephan, Voettingerstr. 45, D-85350 Freising, Germany. FAX: (49) 8161–714204; einspani{at}pollux.edv.agrar.tu-muenchen.de

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