Heat shock decreases the embryonic quality of frozen-thawed bovine blastocysts produced
in vitro |
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Authors: | Miyuki MORI Takeshi HAYASHI Yoshihiro ISOZAKI Naoki TAKENOUCHI Miki SAKATANI |
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Institution: | 1)Fukuoka Agriculture and Forestry Research Center, Fukuoka 818-8549, Japan;2)Livestock and Grassland Research Division, Kyushu Okinawa Agricultural Research Center, National Agriculture and Food Research Organization (NARO), Kumamoto 861-1192, Japan |
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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. |
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Keywords: | Blastocysts Cryopreservation Heat shock IVF |
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