The addition of antibiotics to embryo culture media caused altered expression of genes in pathways governing DNA integrity in mouse blastocysts

Abstract

Antibiotics are common components of embryo culture media and minimize the risk of microbial contamination and infection during assisted reproductive technology procedures (ART). The effects of two aminoglycoside antibiotics (gentamicin, streptomycin) and penicillin on the global profiles of gene expression (DE) were assessed by RNA-seq of individual mouse blastocysts. Zygotes were cultured in an optimized defined medium formulation (KSOM) to which a dose range of each antibiotic was added. A dose-dependent retardation of the rate of zygote development to morphologically normal blastocyst was observed and this was accompanied by a reduction in the number of cells present within the resulting blastocysts. The lowest dose of each antibiotic tested (similar to the concentrations used in clinical grade media) caused significant differential expression of approximately 1800 genes. In most cases antibiotic treatment caused a reduction in gene expression and gene ontology analysis showed that down regulated genes were enriched for several biological processes related to the maintenance of genomic integrity. All three antibiotics caused the downregulation of Brca2, Blm, Rad51c and Rad54l, genes involved DNA homologous recombination pathways and also several p53-dependent genes. Immunolocalization studies showed that each antibiotic also reduced level of BRCA2 and RAD51C detected within blastocysts. The present study shows that the supplementing embryo culture media with antibiotics is associated with wide ranging alterations in gene expression in a manner that could potentially compromise the genomic integrity of the resulting embryos.