Prevention of quality decline and delivery of siRNA using exogenous TCTP translocation across the zona pellucida in mouse oocytes.

The delivery of exogenous molecules into mammalian oocytes or embryos has been a challenge because of the existence of the protective zona pellucida (ZP) surrounding the oocyte membrane. Here we show that exogenous translationally controlled tumor protein (TCTP) is able to translocate into oocytes across the ZP and prevents quality deterioration during in vitro culture. Recombinant TCTP-mCherry added to culture media were incorporated into oocytes after passing through the ZP. After internalization, recombinant TCTP-mCherry were enriched at the cortex with wide distribution within the cytoplasm. This translocation capacity of TCTP is dependent on its N-terminal protein transduction domain (PTD). Moreover, translocated recombinant TCTP-mCherry reduced quality deterioration of oocytes during prolonged in vitro culture, which in turn improved fertilization and early embryo development. Furthermore, conjugates between PTD of TCTP and cyclin B1 siRNAs internalized into the cytoplasm of oocytes and downregulated cyclin B1 level. Therefore, our results are the first to show that TCTP has the ability to translocate into oocyte cytoplasm penetrating through the ZP, providing the possibility for preserving oocyte quality during extended in vitro culture and for delivering siRNAs into mouse oocytes.