Formation of ovarian follicular cysts and corpora lutea after treatment with antihistamine or indomethacin in prepubertal gilts

Atretic preovulatory follicles could be precursors of ovarian lutein cysts in the pig

Ovarian cysts contribute to reduced reproductive performance in pigs. Unfortunately, the mechanism of lutein cysts formation remains unknown. Here, we compared the endocrine and molecular milieus of intact, healthy preovulatory follicles (PF), gonadotropin (eCG/hCG)-induced healthy and atretic-like PF, as well as gonadotropin-provoked and spontaneous ovarian cysts in gilts. Several endocrine and molecular indicators and microRNA were compared in walls of PF and cysts. Intact and healthy PF, showed high estradiol/androstendione and low progesterone levels associated with CYP17A1, HSD17B1, and CYP19A1 elevation and reduced StAR/HSD3B1 protein expression. In contrast, low estradiol/androstendione and high progesterone concentrations, accompanied by decreased CYP17A1, HSD17B1, CYP19A1 and increased HSD3B1 protein abundance, appeared in atretic-like PF, gonadotropin-induced and spontaneous cysts. High progesterone receptor (PGR) protein abundance was maintained in intact and healthy PF, while it dropped in atretic-like PF, gonadotropins-induced and spontaneous cysts. The atretic PF showed high level of TNFα compared to healthy PF. In conclusion, follicular lutein cysts could be recruited from atretic-like PF with lost estrogenic milieu and inability to ovulate. Ovulatory cascade was presumably disrupted by a low PGR and high TNFα levels associated with earlier luteinization of follicular walls. These results suggest a novel mechanism of lutein ovarian cysts development in pigs and, perhaps, other species.

Concentrations of tissue-type plasminogen activator and relaxin in normal and induced-cystic follicles of gilts

Manipulation of one ovary in prepubertal gilts treated with pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG) results in cysts on the manipulated ovary and corpora lutea (CL) on the non-manipulated (control) ovary. Because tissue-type plasminogen activator (tPA) might play a role in follicular rupture and because relaxin might increase tPA production, concentrations of tPA and relaxin in manipulated and control follicles were measured at different stages of development. Prepubertal gilts were treated with 1000 IU PMSG followed by 750 IU hCG at 72 hr later. Follicles on one ovary in each gilt were manipulated at laparotomy 48 hr after PMSG administration. Gilts were ovariectomized at 72, 90, 108, 114, 144, and 216 hr after PMSG. Concentrations of tPA and relaxin were determined for follicular fluid from follicles dissected free of ovarian stroma and snap frozen in liquid nitrogen and media from follicles cultured for 48 hr. Relaxin did not differ between treatment groups (manipulated and control) at any time (P > 0.05); whereas, tPA was greater in control follicles at 114 hr after PMSG than in manipulated follicles (P < 0.01). The effect of pyrilamine, a histamine-1 receptor antagonist, on tPA concentrations was determined in manipulated and control follicles collected at 3, 12, 24, 42, and 66 hr after manipulation. Concentrations of tPA were similar in control and manipulated follicles for gilts treated with pyrilamine, but again control follicles had greater (P < 0.05) tPA concentrations at 114 hr after PMSG. Thus, tPA seems to be involved in ovulation, and blockage of ovulation and subsequent cyst formation results from inadequate tPA activity in manipulated follicles.

Effect of ovarian antral follicle cauterization on the interestrus interval of the gilt

The objective of the present study was to determine if destruction of ovarian antral follicles by laser-cauterization affects CL lifespan during the estrous cycle of the gilt. Cyclic gilts were randomly assigned to either SHAM, laser (L) or laser-estradiol (L-E2) treatment groups, with the L-E2 group receiving a 5-mg intramuscular (i.m.) injection of estradiol-17beta cypionate at the time of the first surgery. Ovarian antral follicles were laser-cauterized on either Days 12 and 14 (L12) or Days 14 and 17 (L14) of the estrous cycle. In the L12-E2 group, 3 of 4 gilts had extended mean interestrus intervals of more than 22 days compared with 0 of 4, 0 of 6, 0 of 7 and 1 of 5 gilts in the SHAM, L12, L14 and L14-E2 groups, respectively. The L12-E2 gilts had a longer (P<0.05) mean interestrus interval (23.5+/-1.3 days) than the L12 (20.0+/-1.1 days), L14 (20.7+/-1.0 days) and SHAM (20.5+/-1.3 days). The mean interestrus interval of L14-E2 gilts (21.8+/-1.2 days) did not differ from those of the L12-E2 group or the L12, L14 and SHAM group gilts. Six additional gilts were injected with 5 mg estradiol cypionate-17beta to serve as nonsurgical controls for E2 treatment. Gilts (3 of 3) given an E2 injection on Day 12 had extended mean interestrus interval (26.0+/-2.6 days), while 2 of 3 gilts injected with E2 on day 14 had extended mean interestrus intervals (27.7+/-2.1 days). These results indicate that in cyclic gilts destruction of ovarian follicles by laser-cauterization did not affect CL lifespan, and that luteolysis is not dependent on the presence of antral follicles.

Factors contributing to the formation of experimentally-induced ovarian cysts in prepubertal gilts

Manipulation of an ovary during the follicular phase in cycling gilts or prepubertal gilts treated with PMSG and hCG results in formation of cysts on manipulated ovaries and corpora lutea (CL) of normal appearance on nonmanipulated ovaries. In contrast, cysts did not form after manipulation in luteal phase gilts. In the present experiment, daily administration of 50 mg progesterone to prepubertal gilts treated with PMSG and hCG established luteal phase concentrations of progesterone but did not lessen the incidence of manipulated-induced cysts. Number of cysts formed was associated with the number of follicles > or = 5 mm at manipulation, which was inversely related to serum concentrations of progesterone. Number of receptors for LH/hCG in follicular tissues did not differ between manipulated and nonmanipulated ovaries but was greater in granulosa (P < .05) and theca (P < .08) from follicles with diameters > or = 7 mm compared to 5 and 6 mm. Contents of estradiol, androstenedione, testosterone, progesterone and prostaglandins E2 and F2 alpha in follicular fluid, granulosa and theca were not different between follicles > or = 5 mm destined to form cysts. Profiles of progesterone and estradiol in peripheral serum and duration of luteal phase concentrations of progesterone were not different for gilts with induced cysts and gilts with CL. In conclusion, manipulation of follicles resulted in a failure to ovulate. Subsequent formation of cysts did not result from or result in a loss of steroidogenic function or the ability to bind LH to follicular receptors. These results demonstrate that the mechanism for ovulation is independent of other follicular processes, since ovulation can be disrupted without altering follicular steriodogenesis or subsequent luteinization.