102 SUPPLEMENTATION WITH ESTRADIOL CYPIONATE AT THE ONSET OF A SYNCHRONIZED PROESTRUS ALTERS THE UTERINE GENE EXPRESSION OF SUCKLED ANESTROUS BEEF COWS

Abstract

The present study evaluated the effect of oestradiol cypionate (ECP) supplementation at the onset of a proestrus [i.e. at progesterone (P4) device removal of the synchronization of ovulation protocol] on the global endometrial gene expression of suckled anestrous beef cows. A total of 12 suckled cows presenting absence of corpus luteum detected by ultrasound received 2 mg of oestradiol benzoate IM and an intravaginal P4 device. Eight days later, P4 devices were removed, and the cows received 500 mg of sodium cloprostenol IM. Cows were blocked according to body condition score and diameter of largest follicle (LF) at P4 device removal and were randomly assigned to receive an IM treatment with 1 mg of ECP (ECP, n = 6) or not (CON, n = 6) at the P4 device removal. All cows received 10 μg of buserelin acetate 48 h after P4 device removal and were timed AI immediately after. Cows presenting a new corpus luteum formed 6 days after the gonadotropin-releasing hormone treatment had an endometrial fragment collected by transcervical biopsy. RNA-Seq analysis was performed and the transcriptome profile was obtained. The significance of differential gene expression was assessed with the package DESEqn 2 v.1.2.10 and the differential expression estimation was based on the GLM followed by the Wald test. The significance threshold was established as an FDR- Benjamini-Hochberg-adjusted P-value of <0.1. The integrated analysis was performed using DAVID database. In total, 135 transcripts were differentially expressed between ECP and CON groups, of which 73 genes were up-regulated by ECP supplementation and 62 genes were up-regulated in the CON cows. Two pathways were overrepresented by the ECP-induced transcripts: pathways in cancer (n = 5 genes) and small cell lung cancer (n = 3 genes). On the other hand, ECP-inhibited transcripts indicated the enrichment of 3 pathways: Parkinson's disease (n = 3 genes), oxidative phosphorylation (n = 3 genes), and Alzheimer's disease (n = 3 genes). More specifically, ECP-induced transcripts associated with pathways in cancer [gene symbol (fold change); respectively] were LAMC3 (1.55), PTCH1 (1.51), PTCH2 (1.52), PIK3R3 (1.22), and PIAS1 (1.18), whereas ECP-inhibited transcripts associated with oxidative phosphorylation were ATP5F1 (1.18), ATP5J (1.24), and NDUFB3 (1.37). Therefore, ECP supplementation at onset of the synchronized proestrous slightly alters the uterine transcriptome. The enriched pathways affected by the ECP supplementation described in this work need to be studied more but these results show candidate pathways that can be associated with uterine environment and receptivity and with possible regulation by oestradiol supplementation given at the onset of the proestrous.