Role of cumulus cells and serum on the in vitro maturation, fertilization, and subsequent development of rat oocytes.
Immature oocytes were collected from immature female rats (60-65 g) 40 h after injection with 6 IU pregnant mare's serum gonadotropin (PMSG). Oocytes were matured cumulus-intact (CI) or cumulus-free (CF) in medium supplemented with 0.5% bovine serum albumin (BSA) or 5-20% serum for periods of up to 24 h. After assessment for nuclear maturation, the oocytes were exposed to epididymal sperm for fertilization in vitro. In vitro-matured and ovulated oocytes undergoing fertilization were transferred to unilaterally pregnant recipients for embryonic and fetal development. The presence of cumulus cells and serum shortened (by 2 h) the time required for polar body emission by in vitro-matured oocytes and also helped to increase significantly the penetrability of the oocytes by spermatozoa. A high proportion (45.6%) of fertilized oocytes showed evidence of abnormal fertilization following maturation in the absence of cumulus cells. Oocytes matured CI before fertilization were able to develop to viable fetuses (57.8%) in proportions similar to ovulated oocytes (55.0%) after in vitro fertilization. These findings indicate an essential role for cumulus cells in promoting normal cytoplasmic maturation of oocytes necessary for pronuclear formation and subsequent developmental capability.
Vanderhyden
B C
BC
Department of Physiology, University of Western Ontario, London, Canada.
Armstrong
D T
DT
D000818:Animals; D001769:Blood; D002467:Cell Nucleus / Q000502:physiology; D002970:Cleavage Stage, Ovum; D004624:Embryo Transfer; D005314:Embryonic and Fetal Development; D005260:Female; D005307:Fertilization in Vitro; D008297:Male; D009865:Oocytes / Q000502:physiology* / Q000648:ultrastructure; D006080:Ovarian Follicle / Q000166:cytology / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D013084:Sperm-Ovum Interactions