Safety of embryo cryopreservation: insights from mid-term placental transcriptional changes.

BACKGROUND: In recent years, with benefits from the continuous improvement of clinical technology and the advantage of fertility preservation, the application of embryo cryopreservation has been growing rapidly worldwide. However, amidst this growth, concerns about its safety persist. Numerous studies have highlighted the elevated risk of perinatal complications linked to frozen embryo transfer (FET), such as large for gestational age (LGA) and hypertensive disorders during pregnancy. Thus, it is imperative to explore the potential risk of embryo cryopreservation and its related mechanisms. METHODS: Given the strict ethical constraints on clinical samples, we employed mouse models in this study. Three experimental groups were established: the naturally conceived (NC) group, the fresh embryo transfer (Fresh-ET) group, and the FET group. Blastocyst formation rates and implantation rates were calculated post-embryo cryopreservation. The impact of FET on fetal growth was evaluated upon fetal and placental weight. Placental RNA-seq was conducted, encompassing comprehensive analyses of various comparisons (Fresh-ET vs. NC, FET vs. NC, and FET vs. Fresh-ET). RESULTS: Reduced rates of blastocyst formation and implantation were observed post-embryo cryopreservation. Fresh-ET resulted in a significant decrease in fetal weight compared to NC group, whereas FET reversed this decline. RNA-seq analysis indicated that the majority of the expression changes in FET were inherited from Fresh-ET, and alterations solely attributed to embryo cryopreservation were moderate. Unexpectedly, certain genes that showed alterations in Fresh-ET tended to be restored in FET. Further analysis suggested that this regression may underlie the improvement of fetal growth restriction in FET. The expression of imprinted genes was disrupted in both FET and Fresh-ET groups. CONCLUSION: Based on our experimental data on mouse models, the impact of embryo cryopreservation is less pronounced than other in vitro manipulations in Fresh-ET. However, the impairment of the embryonic developmental potential and the gene alterations in placenta still suggested it to be a risky operation.

Gestational diabetes mellitus suppresses fetal testis development in mice†.

The prevalence of gestational diabetes mellitus (GDM) is increasing rapidly. In addition to the metabolic disease risks, GDM might increase the risks of cryptorchidism in children. However, its mechanism involved in abnormalities of the male reproductive system is still unclear. The purpose of this study was to study the effects of GDM on the development of mouse fetal Leydig cells (FLCs) and Sertoli cells (SCs). Pregnant mice were treated on gestational days 6.5 and 12.5 with streptozotocin (100 mg/kg) or vehicle (sodium citrate buffer). Leydig cell and SC development and functions were evaluated by investigating serum testosterone levels, cell number and distribution, genes, and protein expression. GDM decreased serum testosterone levels, the anogenital distance, and the level of desert hedgehog in SCs of testes of male offspring. FLC number was also decreased in testes of GDM offspring by delaying the commitment of stem Leydig cells into the Leydig cell lineage. RNA-seq showed that FOXL2, RSPO1/ß-catenin signaling was activated and Gsk3ß signaling was inhibited in GDM offspring testis. In conclusion, GDM disrupted reproductive tract and testis development in mouse male offspring via altering genes related to development.