Effect of follicle cells and steroidogenesis on maturation and fertilization in vitro of pig oocytes.
Follicle cell numbers, steroidogenesis, and culture conditions were manipulated in a series of experiments designed to identify their effect during in vitro maturation of pig oocytes upon meiotic cycle progression, sperm penetration and male pronuclear formation. In Experiment 1 a static culture system was used to determine the effect of follicle cell numbers on maturation. When the follicle cell number was 3.5 x 10(3) cells per complex or less, cell cycle progression to metaphase II (M-II) and male pronuclear formation were both low (< 30%). Increasing follicle cell numbers to 15 x 10(3) per complex significantly enhanced both meiotic maturation (93%) and male pronuclear formation (83%). A further 10-fold increase in follicle cell numbers (150 x 10(3)), however, reduced subsequent male pronuclear formation (33%). The purpose of Experiment 2 was to determine whether the observed follicle cell effects were influenced by the type of culture system used for oocyte maturation. Comparisons were made between both static and non-static forms of culture. Meiotic progression was significantly depressed when non-static culture systems were used for the maturation of oocyte-cumulus complexes containing low numbers of somatic cells (< 15 x 10(3) cells). However, the addition of somatic cells (follicle shells) to non-static, but not static, culture systems significantly enhanced male pronuclear formation in all groups irrespective of the number of cumulus cells in the oocyte complex. Experiment 3 investigated the effects of the steroid environment on maturation and male pronuclear formation.(ABSTRACT TRUNCATED AT 250 WORDS)
Nagai
T
T
Department of Molecular Embryology, Institute of Animal Physiology and Genetics Research, Babraham, Cambridge, England.
Ding
J
J
Moor
R M
RM
D000818:Animals; D002452:Cell Count; D002467:Cell Nucleus; D002478:Cells, Cultured; D005260:Female; D005306:Fertilization / Q000502:physiology*; D005307:Fertilization in Vitro; D008297:Male; D008540:Meiosis; D009865:Oocytes / Q000502:physiology*; D009866:Oogenesis / Q000502:physiology*; D006080:Ovarian Follicle / Q000502:physiology*; D011374:Progesterone / Q000494:pharmacology; D013256:Steroids / Q000096:biosynthesis / Q000502:physiology*; D013552:Swine
D013256:Steroids; D011374:Progesterone