title: Mitochondrial distribution and adenosine triphosphate content of bovine oocytes before and after in vitro maturation: correlation with morphological criteria and developmental capacity after in vitro fertilization and culture.
abstract: In this study, we evaluated mitochondrial distribution and ATP content of individual bovine oocytes before and after in vitro maturation (IVM). Cumulus-oocyte complexes were classified according to morphological criteria: category 1, homogeneous oocyte cytoplasm, compact multilayered cumulus oophorus; category 2, cytoplasm with small inhomogeneous areas, more than five layers of compact cumulus; category 3, heterogeneous/vacuolated cytoplasm, three to five layers of cumulus including small areas of denuded zona pellucida; category 4, heterogeneous cytoplasm, completely or in great part denuded. In immature oocytes, staining with MitoTracker green revealed mitochondrial clumps in the periphery of the cytoplasm, with a strong homogenous signal in category 1 oocytes, a weaker staining in category 2 oocytes, allocation of mitochondria around vacuoles in category 3 oocytes, and poor staining of mitochondria in category 4 oocytes. After IVM, mitochondrial clumps were allocated more toward the center, became larger, and stained more intensive in category 1 and 2 oocytes. This was also true for category 3 oocytes; however, mitochondria maintained their perivacuolar distribution. No mitochondrial reorganization was seen for category 4 oocytes. Before IVM, the average ATP content of category 1 oocytes (1.8 pmol) tended to be higher than that of category 2 oocytes (1.6 pmol) and was significantly (P < 0.01) higher than in category 3 (1.4 pmol) and 4 oocytes (0.9 pmol). The IVM resulted in a significant (P < 0.01) increase in the average ATP content of all oocyte categories, with no difference between oocytes extruding versus nonextruding a polar body. After in vitro fertilization (IVF) and culture, significantly (P < 0.05) more category 1 and 2 than category 3 and 4 oocytes developed to the morula or blastocyst stage (determined 168 h after IVF). Total cell numbers of expanded blastocysts derived from category 1 and 2 oocytes were significantly (P < 0.05) higher than of those originating from category 3 and 4 oocytes. These data indicate that mitochondrial reorganization and ATP levels are different between morphologically good and poor oocytes and may be responsible for their different developmental capacity after IVF.
authors.affiliation: Department of Molecular Animal Breeding and Genetics, University of Munich, D-85764 Oberschleissheim, Germany. m.stojkovic@gen.vetmed.uni-muenchen.de
authors.forename: M
authors.initials: M
authors.lastname: Stojkovic
authors.forename: S A
authors.initials: SA
authors.lastname: Machado
authors.forename: P
authors.initials: P
authors.lastname: Stojkovic
authors.forename: V
authors.initials: V
authors.lastname: Zakhartchenko
authors.forename: P
authors.initials: P
authors.lastname: Hutzler
authors.forename: P B
authors.initials: PB
authors.lastname: Gonçalves
authors.forename: E
authors.initials: E
authors.lastname: Wolf
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism / Q000502:physiology*; D000447:Aldehydes / Q000737:chemistry; D000818:Animals; D001755:Blastocyst / Q000166:cytology / Q000502:physiology; D002417:Cattle / Q000502:physiology*; D002452:Cell Count; D004734:Energy Metabolism; D005260:Female; D005307:Fertilization in Vitro / Q000662:veterinary*; D005456:Fluorescent Dyes / Q000737:chemistry; D008297:Male; D008856:Microscopy, Fluorescence / Q000662:veterinary; D008928:Mitochondria / Q000378:metabolism / Q000502:physiology*; D009865:Oocytes / Q000166:cytology / Q000378:metabolism / Q000502:physiology*
chemical_list: D000447:Aldehydes; D005456:Fluorescent Dyes; C111472:mitotracker green FM; D000255:Adenosine Triphosphate