Dose-Dependent Effects of Heat Shock Cognate 70 on Viability and Apoptosis-Related Gene Expression in In Vitro–Produced Bovine Embryos

Endogenous heat shock cognate 73 kDa protein (HSC70) has an important role in early embryonic development. We assessed the effects of exogenous HSC70 on bovine embryo development and the expression of genes associated with apoptosis. Expression analyses of HSPA1A, HSPA8, BCL-2, and BAX genes were performed in bovine embryos in vivo on day 7 of development. The expression of HSPA1A and HSPA8 was associated with apop-totic gene (BCL-2 and BAX) expression in cultured bovine embryos in vitro that were sup-plemented with various concentrations (500 ng/mL or 1000 ng/ mL) of HSC70. The results indicated that the control group of in vitro embryos exhibited higher expression of the HSPA8, BAX, and BCL-2 genes compared with in vivo embryos (p ≤ 0.001). In vitro-produced embryos supplemented with 500 or 1000 ng/mL of HSC70 exhibited high-er expression of HSPA1A, HSPA8, BCL-2, and BAX genes compared with the control group (p ≤ 0.01). Embryos supplemented with 1000 ng/mL showed higher expression of the HSPA8 gene compared with the control group and the group supplemented with 500 ng/mL. However, embryos supplemented with 500 ng/mL exhibited more favorable char-acteristics (i.e., development stage and quality) compared with the control and 1000 ng/mL-treated groups. In conclusion, supplementation of bovine embryo culture media with 500 ng/mL recombinant HSC70 protein increased the expression of the HSPA1A and BCL-2 anti-apoptotic genes, resulting in an increase of the number of blastocysts produced in vitro.