Effect of cytobrush technique in mares

Abstract

Several studies have been done correlating transcervical techniques or mechanical manipulation on the endometrium and its effect on the equine estrous cycle length in mares. However, the effect of the endometrial cytobrush technique on the estrous cycle and its use for the study of endometrial-ovarian relationships is still unknown. The aim of this study was to evaluate the usage of the endometrial cytobrush technique for study of the role of endometrial receptors and genes involved in the luteolytic mechanism. The study was divided in three groups: single endometrial cytobrush (CBS), endometrial samples collected in different animals on days 12, 14, and 16 (n = 5 /day); endometrial samples collect multiple times (CBM) in the same animal on days 12, 14, and 16 (n = 5/day); no endometrial samples collection (CSN). Blood samples were collected daily from ovulation to subsequent ovulation on the three groups to evaluate progesterone (P4) concentration. Additionally, on Day 12, blood samples were collected at h0 (just before cytobrush collection), 15 min, 30 min, h1, h2, and h4 to evaluate concentrations of P4 and a metabolite of prostaglandin F2α (PGFM). The gene expression was compared among the preluteolytic, luteolytic, and postluteolytic periods. The day before P4 concentration decreased by 20% from the previous day with an uninterrupteddecrease thereafter was defined as the beginning of luteolysis (luteolytic period), and the first day P4 concentration decreased to < 1.0 ng/mL was defined as the end of luteolysis (postluteolytic period). The interovulatory length, beginning of luteolysis, and concentrations of P4 and PGFM did not differ among the groups (P > 0.05). Three animals in the CBM group developed 5 ± 2 mm of endometrial fluid after the second cytobrush collection. However, these animals did not have endometrial fluid after ovulation. According to endometrial gene expression, in the CBM group, the prostaglandin-endoperoxide synthase 2 (PTGS2) was upregulated during luteolysis (P < 0.05), PGF transporter (SLCO2A1) was upregulated after luteolysis, and 15-hydroxyprostaglandin dehydrogenase (HPGD) was downregulated during luteolysis. In the CBS group, oxytocin receptor (OXTR), prostaglandin F2 receptor (PTGFS), and (HPGD) were upregulated during luteolysis (P < 0.05). SLCO2A1 was upregulated during and after luteolysis (P < 0.05). These results suggest that endometrial cytobrush technique does not influence the length of the cycle and is a viable method for studying endometrial gene expression of genes associated with luteolysis in a single sample collection in mares.