EFFECTS OF CUMULUS CELL-DENSITY DURING IN-VITRO MATURATION ON THE DEVELOPMENTAL COMPETENCE OF BOVINE OOCYTES (VOL 48, PG 1451, 1998)

To determine the role of cumulus cells in oocyte maturation, we carrie d out an investigation on the effects of addition of cumulus cells to the maturation medium on the developmental competence of corona-enclos ed oocytes and oocytes denuded from their somatic cells. The addition of cumulus cell (1.6 x 10(6) cells/mL) improved the development of bov ine corona-enclosed oocytes, however, addition of a similar number of cumulus cells as cumulus-oocyte-complexes (COCs, cumulus cell density: 4.2 x 10(6) cells/mL) had no effect on the development of oocytes den uded from their somatic cells. To determine if corona-enclosed oocytes can obtain developmental competence without the addition of extra cum ulus cells, the effects of cell density during in vitro maturation on the developmental competence were studied. A density of 1.6 to 3.2 x 1 06 cumulus cells/mL was the most effective for in vitro maturation of oocytes with intact gap junctions. The effects of the medium condition ed by COCs on the developmental competence of oocytes was also examine d. It was demonstrated that COG-conditioned medium improved the develo pment of bovine oocytes to the blastocyst stage. These data suggest th at the developmental competence of bovine oocytes surrounded with coro na cells is supported in a cell density-dependent manner in the matura tion medium. In addition, the data indicate that cumulus cells benefit bovine oocyte development either by secreting soluble factors which i nduce developmental competence or by removing an embryo development-su ppressive component from the medium. (C) 1998 by Elsevier Science Inc.