Tricostatin A-treated round spermatid enhances preimplantation embryo developmental competency following round spermatid injection in mice

It has been documented that the inefficacy of round spermatid injection (ROSI) might be caused by abnormal epigenetic modifications. Therefore, this study aimed to evaluate the effect of trichostatin A (TSA) as an epigenetic modifier of preimplantation embryo development in activated ROSI oocytes. Matured oocytes were collected from superovulated female mice. Testes were placed in human tubal fluid medium and masses were then cut into small pieces to disperse spermatogenic cells. Round spermatids were treated with TSA and subsequently injected into oocytes. The expression level of the development-related genes including Oct4, Sox2, Nanog, Dnmt and Hdac transcripts were evaluated using qRT-PCR. Immunohistochemistry was performed to confirm the presence of Oct-4 protein at the blastocyst stage. There was no statistically significant difference in fertilization rate following ROSI/+TSA compared with the non-treated ROSI and intracytoplasmic sperm injection (ICSI) groups. Importantly, TSA treatment increased blastocyst formation from 38% in non-treated ROSI to 68%. The relative expression level of developmentally related genes increased and Dnmt transcripts decreased in ROSI/+TSA-derived embryos, similar to the expression levels observed in the ICSI-derived embryos. In conclusion, our results indicate that spermatid treatment with TSA prior to ROSI would increase the success rate of development to the blastocyst stage and proportion of pluripotent cells.