BENEFICIAL INFLUENCE OF VERO CELLS ON IN-VITRO MATURATION AND FERTILIZATION OF BOVINE OOCYTES

The aim of this study was to examine the effects of Vero cells and oth er somatic cells on in vitro maturation of bovine oocytes. Both denude d oocytes and oocytes with intact cumuli (COCs) were cultured on monol ayer of Vero cells, cumulus cells and granulosa cells. The effect of g onadotropins was investigated after the addition of gonadotropins to t he culture medium. The evaluation using analysis of variance revealed that removal of cumulus cells generally reduced the percentage of oocy tes completing their maturation in vitro and that this effect could no t be overcome by the addition of gonadotropins to the culture medium. However, in individual experiments, when oocytes were co-cultured with different monolayers of somatic cells, Vero cells were able significa ntly support the maturation of denuded oocytes, and their beneficial e ffect was further enhanced by the addition of gonadotropins (76 vs 80. 9 %). We did not observe a similar effect after the co-culture of oocy tes with a monolayer of cumulus cells (65.3 and 53 %, respectively). G ranulosa cell monolayer delayed maturation in the both COCs and denude d oocytes (10.5 and 16.5 %, respectively). In vitro fertilization was successful in most of the experimental groups. However, when denuded o ocytes were cultured without any somatic cell support, they did not de condense the penetrated sperm head after in vitro fertilization. This study demonstrates that 1) Vero cells beneficially affect the in vitro maturation of bovine oocytes; 2) cumulus cells in the form of monolay er lose their beneficial influence on in vitro maturation of bovine oo cytes; and 3) granulosa cells and FSH and LH alone (without somatic ce lls) do not show positive effects on in vitro maturation of bovine ooc ytes.