Possible involvement of Wnt/β-catenin signaling pathway in hatching and trophectoderm differentiation of pig blastocysts.

The Wnt/β-catenin signaling pathway plays essential roles in the regulation of cell fate and polarity during embryonic development of many animal species. This study investigated the possible involvement of Wnt/β-catenin signaling pathway during hatching and trophectoderm (TE) development in pig blastocysts. Results showed that β-catenin and DVL3, the key mediators of Wnt/β-catenin signaling, disappeared from the nucleus after blastocyst hatching. Specific inhibition of Wnt/β-catenin signaling pathway, by Dickkopf-1, increased the rate of blastocyst hatching, total nuclear number per blastocyst, and reduced the ratio of inner cell mass (ICM):TE (P < 0.05). In contrast, specific activation of the Wnt/β-catenin signaling pathway, by lithium chloride, reduced the rate of blastocyst hatching, total nuclear number per blastocyst, and increased the ratio of ICM:TE (P < 0.05). The change in the ICM:TE ratio was associated with the change in the number of TE cells but not the ICM cells. Activation or inhibition of Wnt/β-catenin signaling and β-catenin nuclear accumulation, by lithium chloride or Dickkopf-1, also altered the expression of CDX2. These data therefore, suggest the possible involvement of Wnt/β-catenin signaling in regulating hatching and TE fate during the development of pig blastocyst.