Effects of intrauterine extracellular vesicle microRNAs on embryonic gene expression in low‐fertility cows

• Published in: The FASEB journal 2024-10, Vol.38 (20), p.e70116-n/a
• Main Authors: Ichikawa, Rei, Kimura, Koji, Nakamura, Sho, Ohkura, Satoshi, Matsuyama, Shuichi
• Format: Article
• Language: English
• Subjects: Animals; Blastocyst - metabolism; Cattle; cow; Embryo, Mammalian - metabolism; Embryonic Development - genetics; extracellular vesicle; Extracellular Vesicles - metabolism; Female; Fertility - genetics; Gene Expression Regulation, Developmental; low‐fertility; microRNA; MicroRNAs - genetics; MicroRNAs - metabolism; Pregnancy; Pregnancy Proteins - genetics; Pregnancy Proteins - metabolism; uterus; Uterus - metabolism
• ISSN: 0892-6638; 1530-6860; 1530-6860
• DOI: 10.1096/fj.202401728R

Embryo survival and pre‐implantation development depend on uterine luminal fluid, which is believed to play a role in early embryonic death and infertility in cows. Extracellular vesicles (EVs) in the uterine luminal fluid contain microRNAs (miRNAs), crucial mediators of intercellular communication. miRNAs regulate conceptus–maternal interactions and participate in embryonic development by suppressing gene expression. Therefore, we hypothesized that miRNAs in the intrauterine EVs of low‐fertility cows would hinder embryonic survival and development. EVs were collected from the bovine uterine luminal fluid of both normal‐ and low‐fertility cows 7 days post‐estrus. Small RNA‐sequencing analysis of miRNAs isolated from these EVs identified eight miRNAs that were highly expressed in normal‐fertility cows (normal‐fertility miRNAs) and eight with elevated expression in low‐fertility cows (low‐fertility miRNAs). These two sets of miRNAs were transfected into hatched blastocysts via lipofection. RNA‐seq following lipofection with low‐fertility miRNAs identified 424 differentially expressed genes (DEGs) relative to the control; in contrast, following lipofection with normal‐fertility miRNAs, seven DEGs were identified. Pathway analysis of the DEGs identified following lipofection with low‐fertility miRNAs revealed substantial enrichment of mitogen‐activated protein kinase (MAPK) signaling. Expression of activator protein 1 (AP1) and interferon‐tau (IFNT) mRNA was significantly lower in the low‐fertility miRNA transfection group than in the control. IFNT is essential for maternal pregnancy recognition. Therefore, miRNAs in intrauterine EVs from low‐fertility cows at 7 days post‐estrus may inhibit embryo development and suppress IFNT expression by altering MAPK signaling. Eight microRNAs were highly expressed in the intrauterine extracellular vesicles (EVs) of low‐fertility cows 7 days post‐estrus. Transfection of the 8 miRNAs into hatched blastocysts significantly altered the expression including mitogen‐activated protein kinase signaling‐related genes and interferon tau (IFNT) gene. These results suggest that miRNAs in intrauterine EVs of low‐fertility cows inhibit embryonic development by altering MAPK signaling and suppress IFNT gene expression, thereby reducing fertility.