Germinal vesicle chromatin configuration and meiotic competence is related to the oocyte source in canine

• Published in: Animal reproduction science Vol. 103; no. 3; pp. 336 - 347
• Main Authors: Lee, H.S., Yin, X.J., Jin, Y.X., Kim, N.H., Cho, S.G., Bae, I.H., Kong, I.K.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 30-01-2008
• Subjects: Animals; Canine oocyte; Cells, Cultured; Chromatin - genetics; Chromatin - ultrastructure; Dogs - genetics; Dogs - physiology; Estrous Cycle - physiology; Estrous phase; Female; Germinal vesicle configuration; In vitro maturation; Luteal Phase - physiology; Meiosis; Oocyte diameter; Oocytes - cytology; Oocytes - physiology; Zona Pellucida - physiology; Oocyte diameter; Germinal vesicle configuration; Canine oocyte; In vitro maturation; Estrous phase
• ISSN: 0378-4320; 1873-2232
• DOI: 10.1016/j.anireprosci.2006.12.016

This study investigated the effect of deriving oocytes from different stages of the estrous cycle on oocyte diameter, germinal vesicle (GV) chromatin configuration, and in vitro meiotic competence in canine oocytes. Cumulus oocyte complexes (COCs) were recovered from both ovaries during anestrous, follicular, and luteal phases and in vivo ovulated oocytes. The diameter of canine oocyte was compared with or without the zona pellucida (ZP) before in vitro maturation (IVM). Also, GV chromatin configuration was evaluated before (0
h) or 72
h after IVM by fixation with 3.7% formaldehyde supplemented with 10
μg/ml Hoechst 33342 for 30
min. COCs were matured in TCM199 supplemented with 10% fetal bovine serum (FBS), 0.6
mM cysteine, 0.2
mM pyruvic acid, 50
μg/ml gentamycin sulfate, and 20
μg/ml 17β-estradiol (E
2) at 39
°C and 5% CO
2 in air for 72
h. The diameter of in vivo ovulated oocytes with the ZP (167.5
±
12.7
μm) or without ZP (133.9
±
5.3
μm) was significantly greater (
p
<
0.05) than those of anestrous, follicular, and luteal oocytes (with ZP, 151.2
±
7.4, 153.1
±
8.8 and 152.8
±
5.4
μm, respectively; without ZP, 115.3
±
7.6, 122.1
±
4.9 and 114.3
±
6.6
μm, respectively). At 0
h, the GV-II configuration was more prevalent in oocytes from anestrual ovaries than from follicular or luteal ovaries or in vivo ovulated oocytes (63.6% versus 14.8%, 33.0%, and 0.0%;
p
<
0.05), whereas the proportion of oocytes with the GV-V configuration was higher in follicular phase and ovulated oocytes than in oocytes from anestrus and luteal phase (57.4% and 100% versus 2.0% and 22.7%;
p
<
0.05). However, oocytes in luteal phase exhibited diverse GV configurations (10.3%, 33.0%, 16.5%, 13.4%, and 22.7% in GV-I, GV-II, GV-III, GV-IV, and GV-V, respectively). After 72
h post-IVM, a greater percentage of in vivo ovulated oocytes progressed to MII than those oocytes collected during anestrous, follicular, and luteal phases (50.0% versus 5.5%, 11.5%, and 9.1%;
p
<
0.05). In conclusion, the oocyte diameter, GV chromatin configuration, and meiotic maturation of canine COCs are related to the oocyte source. These results indicated that the oocyte source could be critical to nuclear progression to MII stage in canines.