Objective

The aim of the study was investigate whether cumulus cells have an effect on meiosis of domestic cat oocyte in vitro.

Material & Methods

Quantity of layers of cumulus cell were used to classify oocytes cumulus complexes (COCs) into 4 groups (>5 layers, 2-5 layers, 1 layers, None). All group were cultured in 75 µl droplets of IVM medium that comprised DMEM (Gibco BRL., Grand Island, NY, U.S.A.) supplemented with 1 mM pyruvate, 1 mM lactate, 0.4% BSA 1 µg/ml LH 1 µg/ml FSH, 1 µg/ml, Estradiol , 100 IU/ml penicillin, 100 IU/ml streptomycin (Sigma Co)and incubated in a 5%CO₂ incubator at 39 °C with high humidity for 34-36 hours. Oocyte were cultured in 2 conditions, with and without granulosa cell. After 34-36 hours, cumulus cells were removed by incubations with 1% hyaluronidase and mechanical aspiration. Oocytes were observed under stereomicroscope to examined parthenogenesis and maturation (metaphase II) and finally staining with Hoechst 33258 and observed by fluorescent microscope.

Results

The result showed that the percentage of parthenogenesis and degeneration of nuded oocytes (absent of cumulus cell) was significantly higher (P<0.05) than oocyte with 5 layers of cumulus cells. In contrast the highest maturation rate was found in 5 layers COCs while the lowest maturation rate was found in nude oocytes.

Conclusion

The present study showed that the cumulus cell had an effect on meiosis of the domestic cat oocyte. Cumulus cells more than 2-layers were able to increased normal meiosis and inhibited parthenogenesis of the domestic cat oocyte.

* layer of cumulus cell

a-c Values with different superscripts show significant difference among groups of COCs (rows) (P<0.05)

Supported by Faculty of Veterinary Science, Mahidol University.