Impact of hormonal modulation of proestrus on uterine gene expression associated with cell proliferation of suckled anestrous beef cows

Previous studies demonstrated that estradiol cypionate (ECP) supplementation at the onset of proestrus alters uterine transcriptome of anestrous suckled beef cows (Sa Filho et al., IETS, 2015. p. 102 – abstract). Enriched pathways affected by the ECP supplementation described in this previous work identified genes associated with cell proliferation, suggesting a relationship with the modulation of uterine receptivity. Thus, the aim of the present study was to evaluate the impact of ECP and/or equine chorionic gonadotropin (eCG) supplementation at the onset of synchronized proestrus on endometrial expression of candidate genes associated with cell proliferation, in suckled anestrous beef cows. Evaluated genes were: progesterone receptor (PGR), oestrogen receptor 1 (ESR1), oestrogen receptor 2 (ESR2), epidermal growth factor receptor (EGFR), heparin-binding EGF-like growth factor (HB-EGF), collagen, type IV, alpha 1 (COL4A1), patched homolog 2 (PTCH2) and integrin, beta 3 (ITGB3). A total of 46 suckled cows was treated with 2 mg of intramuscular estradiol benzoate and received a P4 intravaginal device. Eight days later, P4 devices were removed, and cows received an intramuscular administration of 500 mg of cloprostenol. Cows were blocked by body condition score and diameter of largest follicle (LF) at the time of progesterone (P4) device removal. Simultaneously, animals were randomly assigned to one of the following groups: control (CON; n=11), ECP (1mg; n=11), eCG (400IU; n=12) and ECP+eCG (1mg and 400IU, respectively; n=11). At 48 h after the P4 device removal, all cows received 10 μg of buserelin acetate and were immediately artificially inseminated at fixed time. Six days after GnRH treatment, cows that presented a recently formed corpus luteum had uterine tissue collected by transcervical biopsy. The P values 0.10) between ECP and eCG on the expression of the evaluated transcripts. ECP treatment induced greater endometrial abundance of PTCH2 (P=0.07) and COL4A1 (P=0.02) genes, whereas suppressed EGFR (P=0.09) gene expression. ECP treatment did not affect the gene expression of ESR1 (P=0.90), ESR2 (P=0.61), HBEGF (P=0.80) and ITGB3 (P=0.57). On the other hand, eCG treatment induced greater endometrial abundance of HB-EGF (P=0.06), ESR2 (P=0.09), and ITGB3 (P=0.05) genes, whereas reduced the gene expression of ESR1 (P=0.05). eCG supplementation did not alter the expression of EGFR (P=0.34), PTCH2 (P=0.31) and COL4A1 (P=0.19). Additionally, the expression of PGR was not altered by either ECP (P=0.51) or eCG (P=0.25) treatments. Therefore, the present results support the hypothesis that supplementation with ECP or eCG at onset of the proestrous in suckled anestrous beef cows acts on the endometrial tissue to alter the abundance of genes associated with cell proliferation during early diestrus