HSP90 Inhibitor, 17-AAG, Affects Meiotic Maturation and Preimplantation Embryos Development in Pigs.

Heat Shock Protein 90 (HSP90) is ATPase-directed molecular chaperon and affects survival of cancer cell. Inhibitory effect of HSP90 by inducing cell cycle arrest and apoptosis in the cancer cell was found. However, its role during oocyte maturation and early embryo development is very insufficient. Therefore, in the present study, we examined the roles of a HSP90 inhibitor (17-AAG) on meiotic maturation and early embryonic development in pigs, as well on the expression of HSP90-, cell cycle-, and apoptosis-related genes. Porcine oocytes were cultured in the NCSU-23 medium with or without 17-allylamino-17-demethoxygeldanamycin (17-AAG) for 44 hr and then cultured in fresh maturation medium without hormones for an additional 22 hr. In vitro fertilization was performed in the modified Tris-buffered medium with fresh ejaculated spermatozoa, and fertilized embryos were cultured in PZM3 medium. Meiotic maturation in porcine oocytes was examined in the presence of concentrations of 17-AAG (2 µM). After IVM, a lower proportion of 17-AAG treated compared with untreated oocytes was in MII (71.0 vs 27.9%, P < 0.05). Expression patterns of apoptosis related genes (Bax and Bcl-xl), HSP90 complex genes (HSP90, HSP70 and p23) and cell cycle genes (cdc2 and cdc25c) were significantly changed by using RT-PCR analysis. In addition, the frequency of penetration decreased in 17-AAG treated oocytes (35.6%) compared with control (68.2%), furthermore the rate of blastocyst formation decreased (P<0.05). Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) showed that the number of containing fragmented DNA at the blastocyst stage increased in the 17-AAG-treated group compared with control (8.8 vs. 6.6, respectively). In conclusion, HSP90 appears to play a direct role in porcine oocyte maturation by enhancing blastocyst development and survival.

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