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) plays a role in early embryonic development and cellular stress regulation. This study evaluated the effects of exogenous recombinant HSC70 supplementation on bovine embryo development and the expression of apoptosis-related genes under in vitro conditions. Expression analyses of HSPA1A, HSPA8, BCL-2, and BAX were performed on Day 7 bovine embryos produced in vivo and in vitro. In vitro embryos exhibited higher basal expressions of HSPA8, BAX and BCL-2 compared with in vivo embryos (p ≤ 0.001). Supplementation with 500 or 1000 ng/mL HSC70 was associated with increased expression of HSPA1A, HSPA8, BCL-2, and BAX relative to control embryos (p ≤ 0.01). The 1000 ng/mL group showed significantly higher HSPA8 expression compared with both the control and 500 ng/mL groups. Morphological evaluation indicated that embryos supplemented with 500 ng/mL were associated with improved blastocyst yield and quality compared with control and 1000 ng/mL groups.In conclusion, supplementation with 500 ng/mL recombinant HSC70 was associated with modulation of apoptosis-related gene expression and improved morphological developmental parameters under in vitro conditions. These findings indicate dose-dependent regulatory effects of HSC70 on apoptosis-related signaling pathways; however, as apoptosis was assessed at the transcriptional level, the results should be interpreted as molecular associations rather than direct confirmation of altered apoptotic activity.