title: Heat shock decreases the embryonic quality of frozen-thawed bovine blastocysts produced in vitro.
abstract: In this study, the effect of heat shock on frozen-thawed blastocysts was evaluated using in vitro-produced (IVP) bovine embryos. In experiment 1, the effects of 6 h of heat shock at 41.0 C on fresh blastocysts were evaluated. HSPA1A expression as a reflection of stress was increased by heat shock (P < 0.05), but the expressions of the quality markers IFNT and POU5F1 were not affected. In experiment 2, frozen-thawed blastocysts were incubated at 38.5 C for 6 h (cryo-con) or exposed to heat shock at 41.0 C for 6 h (cryo-HS). Then, blastocysts were cultured at 38.5 C until 48 h after thawing (both conditions). Cryo-HS blastocysts exhibited a decreased recovery rate: HSPA1A expression was dramatically increased compared with that in fresh or cryo-con blastocysts at 6 h, and IFNT expression was decreased compared with that in cryo-con blastocysts at 6 h (both P < 0.05). Cryo-con blastocysts at 6 h also exhibited higher HSPA1A expression than fresh blastocysts (P < 0.05). At 48 h after thawing, the number of hatched blastocysts and blastocyst diameter were lower in cryo-HS blastocysts (P < 0.05). Cryo-con blastocysts showed lower POU5F1 levels at 48 h than fresh, cryo-con or cryo-HS blastocysts at 6 h (P < 0.05), but their POU5F1 levels were not different from those of cryo-HS blastocysts at 48 h. These results indicated that application of heat shock to frozen-thawed blastocysts was highly damaging. The increase in damage by the interaction of freezing-thawing and heat shock might be one reason for the low conception rate in frozen-thawed embryo transfer in summer.
authors.affiliation: Fukuoka Agriculture and Forestry Research Center, Fukuoka 818-8549, Japan.
authors.forename: Miyuki
authors.initials: M
authors.lastname: Mori
authors.forename: Takeshi
authors.initials: T
authors.lastname: Hayashi
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Isozaki
authors.forename: Naoki
authors.initials: N
authors.lastname: Takenouchi
authors.forename: Miki
authors.initials: M
authors.lastname: Sakatani
mesh_terms: D000003:Abattoirs; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D001755:Blastocyst / Q000166:cytology* / Q000378:metabolism; D002417:Cattle; D002470:Cell Survival; D015925:Cryopreservation / Q000662:veterinary*; D004477:Ectogenesis; D046149:Embryo Culture Techniques / Q000662:veterinary; D005260:Female; D005307:Fertilization in Vitro / Q000662:veterinary; D018507:Gene Expression Regulation, Developmental; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D006358:Hot Temperature / Q000009:adverse effects; D007370:Interferon Type I / Q000235:genetics / Q000378:metabolism; D008297:Male; D050814:Octamer Transcription Factor-3 / Q000235:genetics / Q000378:metabolism; D011257:Pregnancy Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D015415:Biomarkers; D018840:HSP70 Heat-Shock Proteins; D007370:Interferon Type I; D050814:Octamer Transcription Factor-3; D011257:Pregnancy Proteins; C020947:interferon tau