Effect of follicle-stimulating hormone on nuclear and cytoplasmic maturation of sow oocytes in vitro

Abstract A series of experiments were conducted to evaluate the effects of FSH supplementation during IVM on porcine oocyte nuclear maturation, and subsequent fertilization, cleavage and embryo development. Cumulus–oocyte complexes (COCs) were cultured 40 h without FSH (control), 40 h with FSH (FSH 0–40 h), or 20 h with FSH followed by a 20-h culture period without FSH (FSH 0–20 h). Nuclear stage of oocytes was assessed at intervals from 12 to 40 h of IVM. Furthermore, oocytes were in vitro fertilized, fixed and stained to determine normally fertilized and polyspermic oocytes. Additionally, COCs were matured with FSH, fertilized and zygotes cultured in NCSU-23. The percentage of cleaved embryos and blastocysts were determined and the number of nuclei was counted. The presence of FSH during the first 20 h of IVM retarded germinal vesicle breakdown. After 40 h of culture 84, 67 and 58% MII oocytes were observed in the FSH 0–20 h, FSH 0–40 h and control groups, respectively. After IVF, penetration rates were similar at 27, 26 and 29%, while the proportion of polyspermic oocytes was 7, 19 and 11% of penetrated oocytes for control, FSH 0–40 and FSH 0–20 h groups, respectively. Cleavage and blastocyst rates differed among treatments (21, 29 and 38%, and 7, 15 and 20% for control, FSH 0–40 and FSH 0–20 h groups, respectively). No differences in blastocyst cell number were found among groups. Blastocyst rates, based on number of cleaved embryos, were 51 and 52% for the FSH 0–40 and FSH 0–20 h groups, which differed significantly from the control group (31%). The results indicate that FSH has a stimulatory effect on nuclear and cytoplasmic maturation of sow oocytes. Addition of FSH for the first 20 h of culture was most beneficial, based on cleavage and blastocyst development rates.