The NF-κB signaling system is required for blastocyst hatching in the golden hamster: Mediated by the expression of hatching-promoting cathepsins

Background

Blastocyst hatching is a prerequisite for successful implantation. Knowledge on this phenomenon is scarce in humans and the available information stems from studies on rodents. In hamsters, we earlier showed that embryo-derived cathepsin (Cat) proteases (Cat-L, -B and -P) are involved in blastocyst hatching and it is governed by a few molecular regulators. Here, we assessed the involvement of NF-κB signaling in blastocyst development and hatching.

Methods

Hamster embryos, recovered from super-ovulated hamsters, were cultured in the absence or presence of NF-κB inhibitors (BAY-11-7082 or JSH-23). Development through peri-hatching stages and hatching rates were scored. Embryonic mRNA and protein expressions analyzed for NF-κB and Cats (-L, -B, -P); their levels correlated with hatching rates; their cellular immuno-localizations were examined.

Results

Transcript and protein expression of NF-κB components (IKK, Rel-A and IκB-b) were observed in 8-cell embryos through hatched-blastocysts. The NF-κB inhibitors (BAY-11-7082 and JSH-23) inhibited blastocyst hatching in a dose-dependent manner; percentages being 37.8 ± 3% and 36.5 ± 2.8%, respectively; >90% hatching in untreated-controls. NF-κB inhibition lead to a peri-hatching inflated-state of blastocysts, in contrast to deflated-state observed with control blastocysts. Also, NF-κB signaling inhibition-mediated reduction in hatching rates were accompanied by significant reductions in transcript and protein levels of Cat-L, -B and -P.

Conclusion

We conclude that NF-κB signaling components are expressed during peri-hatching blastocyst development and that it is important for blastocyst hatching. Our results provide the first evidence for the involvement of NF-κB transcription-factor in mammalian blastocyst hatching phenomenon.