Abstract
During the periovulatory period, the cervix relaxes in response to changes in circulating concentrations of reproductive hormones. The present study investigated the role of gonadotrophins in cervical function by examining the expression of cyclooxygenase-2 (COX2) and COX2 mRNA and the concentration of hyaluronan (HA) in the cervix, after intracervical treatment with either FSH or LH. Eighteen ewes were assigned to four groups. They were then treated with commercial intravaginal progestagen sponges and eCG to synchronize their estrous cycles. Intracervical treatments were given 24 hours after removal of the sponges as follows: group 1: FSH, 2 mg; group 2: LH, 2 mg; group 3: vehicle; and group 4: control. Cervices were collected 54 hours after sponge removal and then divided into three regions. The expression of COX2 and COX2 mRNA was determined by immunohistochemistry and in situ hybridization and those of HA by ELISA. The levels of expression of COX2, COX2 mRNA, and HA were compared in six tissue layers (luminal epithelium, subepithelial stroma, circular, longitudinal and transverse muscle, and serosa) and in three cervical regions (vaginal, mid, and uterine). The results showed that both FSH and LH significantly increased the levels the COX2 mRNA and COX2 in the cervix, but the effects of the gonadotrophins were selective. The effects of both FSH and LH were most evident at the vaginal end of the cervix and least at the uterine end of the cervix. Furthermore, their effects were confined to the stroma and smooth muscle layers of the cervix in the case of FSH and to smooth muscle only in the case of LH. Neither FSH nor LH affected the concentration of HA in the cervix although FSH but not LH reduced the concentration of HA in cervical mucus. These findings suggest that the gonadotrophins regulate the expression of COX2 in the cervix and that they may have a role facilitating relaxation of the cervix during estrus in the ewe.
Highlights
One of the main purposes of artificial insemination in sheep breeding is to increase the rate of genetic improvement for a particular trait or group of traits
The expression of COX2 mRNA in the cervix of ewes treated with intra-cervical follicle stimulating hormone (FSH) was significantly greater than those treated with vehicle (P = 0.003) or the untreated control group
The expression of COX2 mRNA in the cervix of ewes treated with intra-cervical luteinizing hormone (LH) was significantly greater than those treated with vehicle (P = 0.007) or the untreated control group (P =0.006; Figure 1)
Summary
One of the main purposes of artificial insemination in sheep breeding is to increase the rate of genetic improvement for a particular trait or group of traits. Conventional cervical insemination in sheep gives poor fertility if the semen used has been frozen and thawed (F-T), mainly because of the unusual anatomy of the sheep cervix. The ovine cervix is a long, fibrous and convoluted tubular organ that prevents easy passage of an insemination pipette along the cervical lumen [1, 2]. Semen is normally deposited at the entrance to the cervix and the spermatozoa have to traverse the cervix to enter the uterus and eventually, the site of fertilization in the oviducts. A practical, low cost and effective technique for intrauterine insemination would be a valuable aid to sheep breeding
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