Comparison of DNA methylation profiles of human embryos cultured in either uninterrupted or interrupted incubators

PURPOSE: We aimed to compare the DNA methylation profiles of human embryos cultured in uninterrupted or interrupted incubators. METHODS: This study included 9 women, ≤ 30 years old (range: 20-30 years), without a history of genetic diseases or smoking, undergoing ICSI treatment, and each woman donated one oocyte. Embryos were randomly assigned to culture in either time-lapse imaging or standard incubators after ICSI. We compared the DNA methylation profiles of human eight-cell embryos cultured in uninterrupted condition using time-lapse imaging (TLI) incubator (EmbryoScope) to those cultured in interrupted culture model using standard incubators (SI, G185 K-System). Nine single-cell whole-genome bisulfite sequencing (WGBS) datasets were analyzed, including four SI-cultured embryos and five TLI-cultured embryos at the eight-cell stage. RESULTS: A total of 581,140,020 and 732,348,182 clean reads were generated from the TLI and SI groups, respectively. TLI-cultured embryos had similar genome-wide methylation patterns to SI-cultured embryos. There were no significant differences in the methylation and transcription levels of transposable elements and imprinted control regions. Although a total of 198 differentially methylated genes (DMGs) were identified, only five DMGs had significantly different transcription levels between the two groups. CONCLUSIONS: This is the first study to compare the DNA methylation profiles of embryos cultured in TLI and SI and will provide a foundation for evaluating the safety of TLI application in assisted reproductive technologies. However, further study with a larger cohort of samples was needed for the data validation.