Alteration of Constitutive Heat Shock Protein 70 (HSC70) Production by in vitro Culture of Porcine Preimplanted Embryos

Defined media optimization for in vitro culture of bovine somatic cell nuclear transfer (SCNT) embryos

The objective was to establish an efficient defined culture medium for bovine somatic cell nuclear transfer (SCNT) embryos. In this study, modified synthetic oviductal fluid (mSOF) without bovine serum albumin (BSA) was used as the basic culture medium (BCM), whereas the control medium was BCM with BSA. In Experiment 1, adding polyvinyl alcohol (PVA) to BCM supported development of SCNT embryos to blastocyst stage, but blastocyst formation rate and blastocyst cell number were both lower (P < 0.05) compared to the undefined group (6.1 vs. 32.6% and 67.3 ± 3.4 vs. 109.3 ± 4.5, respectively). In Experiment 2, myo-inositol, a combination of insulin, transferrin and selenium (ITS), and epidermal growth factor (EGF) were added separately to PVA-supplemented BCM. The blastocyst formation rate and blastocyst cell number of those three groups were dramatically improved compared with that of PVA-supplemented group in Experiment 1 (18.5, 23.0, 24.1 vs. 6.1% and 82.7 ± 2.0, 84.3 ± 4.2, 95.3 ± 3.8 vs. 67.3 ± 3.4, respectively, P < 0.05), but were still lower compared with that of undefined group (33.7% and 113.8 ± 3.4, P < 0.05). In Experiment 3, when a combination of myo-inositol, ITS and EGF were added to PVA-supplemented BCM, blastocyst formation rate and blastocyst cell number were similar to that of undefined group (30.4 vs. 31.1% and 109.3 ± 4.4 vs. 112.0 ± 3.6, P > 0.05). In Experiment 4, when blastocysts were cryopreserved and subsequently thawed, there were no significant differences between the optimized defined group (Experiment 3) and undefined group in survival rate and 24 and 48 h hatching blastocyst rates. Furthermore, there were no significant differences in expression levels of H19, HSP70 and BAX in blastocysts derived from optimized defined medium and undefined medium, although the relative expression abundance of IGF-2 was significantly decreased in the former. In conclusion, a defined culture medium containing PVA, myo-inositol, ITS, and EGF supported in vitro development of bovine SCNT embryos.

Different preferences of IVF and SCNT bovine embryos for culture media

The preference of fertilized (IVF) and somatic cell nuclear transfer (SCNT) presumptive zygotes for different media when cultured in vitro to the blastocyst stage was evaluated in this study. The experiment comprised two zygote production methods (IVF and SCNT) × two culture media (mSOF and G1.5/G2.5) factorial design in which culture droplets that contained approximate 30 presumptive zygotes formed the experimental plots for the assessment of cleavage and blastocyst development. There were 15 to 20 replicates (culture droplets) per treatment combination. Sub-samples 30 to 41 of the blastocysts produced were assessed for cell number and cell apoptosis. A further 10 blastocysts per treatment combination were used for quantitative real-time polymerase chain reaction (RT-PCR) to evaluate the relative abundance of Hsp70 and Bax mRNA. Presumptive zygotes produced by IVF were developmentally more competent than SCNT zygotes in terms of cleavage rate (66.9 vs. 57.0%; P < 0.05) and blastocyst development rates (blastocysts of presumptive zygotes 29.7 vs. 24.8%; blastocysts of cleaved zygotes 44.4 vs. 36.6%; P < 0.05). Over both zygote production systems, however, the results were similar whether culture was in mSOF or in G1.5/G2.5 media for cleavage rate (63.2 vs. 62.4%; P > 0.05) and blastocyst development rate (blastocysts of presumptive zygotes 26.4 vs. 25.7%; P > 0.05; blastocysts of cleaved zygotes 41.8 vs. 41.2%; P > 0.05). There was, however, a significant interaction between the method of zygote production and culture medium for the apoptotic index of blastocysts. The interaction was such that IVF-produced zygotes cultured in mSOF had a lower apoptotic index compared with those cultured in G1.5/G2.5 (4.7 ± 1.2% vs. 9.8 ± 0.9%; P < 0.05) whereas SCNT zygotes had a higher apoptotic index when cultured in mSOF compared with those cultured in G1.5/G2.5 (11.9 ± 1.5% vs. 4.5 ± 1.2%; P < 0.05). Moreover, RT-PCR analysis showed that embryos from IVF-produced zygotes cultured in mSOF had a lower expression level of stress-related and apoptosis genes (Hsp70 and Bax) than those cells cultured in G1.5/G2.5 medium, while SCNT-derived embryos cultured in mSOF had a higher expression level of these genes than those embryos cultured in G1.5/G2.5 medium. The results of this study show that bovine IVF- and SCNT-produced presumptive zygotes have different nutrient requirements for in vitro culture to the blastocyst stage of development. IVF-derived zygotes have a preference for mSOF as the culture medium whereas the G1.5/G2.5 medium is more suitable for the culture of bovine SCNT-derived zygotes.

Expression and characterization of constitutive heat shock protein 70.1 (HSPA-1A) gene in in vitro produced and in vivo-derived buffalo (Bubalus bubalis) embryos

Cells are blessed with a group of stress protector molecules known as heat shock proteins (HSPs), amongst them HSP70, encoded by HSPA-1A gene, is most abundant and highly conserved protein. Variety of stresses hampers the developmental competence of embryos under in vivo and in vitro conditions. Present work was designed to study the quantitative expression of HSPA-1A mRNA in immature oocytes (IMO), matured oocytes (MO), in vitro produced (IVP) and in vivo-derived (IVD) buffalo embryos to assess the level of stress to which embryos are exposed under in vivo and in vitro culture conditions. Further, HSPA-1A gene sequence was analysed to determine its homology with other mammalian sequences. The mRNA expression analysis was carried out on 72 oocytes (40 IMO; 32 MO), 76 IVP and 55 IVD buffalo embryos. Expression of HSPA-1A was found in oocytes and throughout the developmental stages of embryos examined irrespective of the embryo source; however, higher (p < 0.05) expression was observed in 8-16 cell, morula and blastocyst stages of IVP embryos as compared to IVD embryos. Phylogenetic analysis of bubaline HSPA-1A revealed that it shares 91-98% identity with other mammalian sequences. It can be concluded that higher level of HSPA-1A mRNA in IVP embryos in comparison with in vivo-derived embryos is an indicator of cellular stress in IVP system. This study suggests need for further optimization of in vitro culture system in which HSPA-1A gene could be used as a stress biomarker during pre-implantation development.