Ultrasonographic characteristics of ovulatory follicles and associated endocrine changes in cyclic ewes treated with medroxyprogesterone acetate (MAP)-releasing intravaginal sponges and equine chorionic gonadotropin (eCG)

Production of Mare Chorionic Girdle Organoids That Secrete Equine Chorionic Gonadotropin

The equine chorionic girdle is comprised of specialized invasive trophoblast cells that begin formation approximately 25 days after ovulation (day 0) and invade the endometrium to become endometrial cups. These specialized trophoblast cells transition from uninucleate to differentiated binucleate trophoblast cells that secrete the glycoprotein hormone equine chorionic gonadotropin (eCG; formerly known as pregnant mare serum gonadotropin or PMSG). This eCG has LH-like activity in the horse but variable LH- and FSH-like activity in other species and has been utilized for these properties both in vivo and in vitro. To produce eCG commercially, large volumes of whole blood must be collected from pregnant mares, which negatively impacts equine welfare due to repeated blood collections and the birth of an unwanted foal. Attempts to produce eCG in vitro using long-term culture of chorionic girdle explants have not been successful beyond 180 days, with peak eCG production at 30 days of culture. Organoids are three-dimensional cell clusters that self-organize and can remain genetically and phenotypically stable throughout long-term culture (i.e., months). Human trophoblast organoids have been reported to successfully produce human chorionic gonadotropin (hCG) and proliferate long-term (>1 year). The objective of this study was to evaluate whether organoids derived from equine chorionic girdle maintain physiological functionality. Here we show generation of chorionic girdle organoids for the first time and demonstrate in vitro production of eCG for up to 6 weeks in culture. Therefore, equine chorionic girdle organoids provide a physiologically representative 3D in vitro model for chorionic girdle development of early equine pregnancy.

Equine chorionic gonadotropin administration after insemination affects luteal function and pregnancy establishment in postpartum anestrous beef cows

Two experiments were conducted with the aim of determining the effect of equine chorionic gonadotropin (eCG) administration on day 14 after insemination on ovarian response and pregnancy establishment in postpartum anestrous beef cows. In both experiments, cows were subjected to a progesterone- and estradiol-based treatment for fixed-time artificial insemination (FTAI) and were randomly allocated into 4 groups to receive or not receive eCG (400 IU) at the time of device removal and/or at 14 d after FTAI. In experiment 1, from day 14 to 22, daily ultrasonographic determinations were performed to monitor ovarian dynamics, and blood was collected to determine hormone concentrations in 60 cows. In experiment 2, confirmation of pregnancy was performed at 30 and 60 d after FTAI in 1,060 anestrous cows assigned to the same experimental design. Cows that received eCG on day 14 after FTAI showed increases in corpus luteum area (P < 0.01), follicle diameter (P < 0.05), serum progesterone concentrations (P < 0.01), and estradiol-17β concentrations (P < 0.01), compared with cows that did not receive eCG on day 14. Pregnancy rate on day 30 was greater in those cows that received both eCG treatments (ie, at device removal and 14 d after insemination) than in those that did not receive eCG treatment (P < 0.05). In conclusion, eCG administered on day 14 after FTAI increases serum progesterone concentrations during the critical period of pregnancy in anestrous cows, and this second eCG treatment seems to have a positive effect on achieving pregnancy.

Use of B-mode ultrasound and grey-scale analysis to study uterine echogenicity in the pig

This study was conducted to determine uterine echogenicity by grey-scale analysis (GSA) and transcutaneous ultrasonography in pregnant sows (P-sows; n=16) and gilts (P-gilts; n=13) vs. cyclic gilts (C-gilts; n=9) between days 8 and 16 post ovulation (po) with the aims of testing for feasibility of uterine GSA and of gathering reference data. Estruses and ovulations were hormonally synchronized and the animals artificially inseminated. Ovulation was monitored by ultrasound. The equipment used was a HS 2000 ultrasound unit and a 5 MHz linear probe. Unit settings were standardized for all GSA scanning sessions and the animals crated during scanning. For GSA, cross-sections of the uterine horns were imaged, entirely defined as regions of interest, and pixel analyses done. A total of 342 scanning sessions were performed, 341 GSA accomplished, and 1-13 cross-sections analyzed per session. Comparison of coefficients of variation suggests that analysis of two cross-sections per session is sufficient for a reliable GSA per animal. P-sows and P-gilts were similar in their echogenicity course, but differed from C-gilts. Most noticeable, echogenicity declined in pregnant animals on day 12 po, while it increased in cyclic gilts. In conclusion, the study demonstrates that GSA using transcutaneous ultrasound is a feasible procedure for the determination of uterine echogenicity in the pig, and that pregnant and cyclic pigs differ in the uterine echogenicity, particularly during the time when maternal recognition of pregnancy occurs.

Evaluation of the ultrasound image attributes of developing ovarian follicles in the four follicular waves of the interovulatory interval in ewes

Computer-assisted quantitative echotextural analysis was applied to ultrasound images of antral follicles in the follicular waves of an interovulatory interval in sheep. The ewe has three or four waves per cycle. Seven healthy, cyclic Western White Face ewes (Ovis aris) underwent daily, transrectal, ovarian ultrasonography for an interovulatory interval. Follicles in the third wave of the ovulatory interval had a longer static phase than that of those in Waves 1 and 2 (P<0.05). The numeric pixel value for the wall of anovulatory follicles emerging in the third wave of the cycle was significantly higher than that for Waves 1 and 2 at the time of emergence (156.7+/-8.09, 101.6+/-3.72, and 116.5+/-13.93, respectively), and it decreased as follicles in Wave 3 reached maximum follicular diameter (P<0.05). The numeric pixel value of the antrum in the ovulatory follicles decreased as follicular diameter increased to > or =5mm in diameter (P<0.05). The pixel heterogeneity of the follicular antrum in Wave 1 increased from the end of the growth phase to the end of the regression phase for follicles in that wave (P<0.05). The total area for the wall and antrum of the follicles studied were correlated with follicular diameter in all follicular waves (r=0.938, P<0.01 and r=0.941, P<0.01 for the wall and antrum, respectively). Changes in image attributes of the follicular wall and antrum indicate potential morphologic and functional differences among antral follicles emerging at different stages of the interovulatory interval in cyclic ewes.

Relationships of changes in ultrasonographic image attributes to ovulatory and steroidogenic capacity of large antral follicles in sheep

Ovarian steroidogenesis and antral follicular development in ewes, following the treatment with medroxyprogesterone acetate (MAP) and equine chorionic gonadotrophin (eCG), are affected by the reproductive season. The objective of this study was to compare the ultrasonographic attributes of large antral follicles between cyclic (December) and seasonally anovular (June-July) ewes, after a 12-day treatment with MAP-soaked intravaginal sponges, with or without the administration of 500IU of eCG at sponge removal, and to determine whether there is a correlation between the ultrasonographic attributes of the follicular wall and serum concentrations of oestradiol. Digital images of ovulatory follicles from cyclic ewes and eCG-treated anoestrous ewes (n=34 follicles), and of anovulatory follicles attaining > or =5mm in control anoestrous ewes (n=8 follicles), were analysed using the spot and line techniques designed to determine the echotextural characteristics of the follicular antrum (central and peripheral), follicular wall and perifollicular ovarian stroma. The mean diameter of ovulatory follicles was greater (P<0.001) in cyclic than anoestrous ewes, with or without the eCG treatment. The mean pixel heterogeneity (SD of numerical pixel values) of the follicular antrum (P<0.05), as well as mean pixel intensity and heterogeneity of the peripheral antrum, follicular wall proper and perifollicular ovarian stroma (P<0.05), were consistently greater in anoestrous than cyclic ewes at the time of sponge removal and 24h after the treatment with MAP sponges or MAP/eCG. Mean oestradiol concentrations were greater (P<0.05) in cyclic compared to anoestrous ewes in both MAP- and MAP/eCG-treated animals, from 1 to 2 days after sponge withdrawal. There was a moderate negative correlation (r(2)=0.12, P<0.05; Pearson's Product Moment and r(2)=0.23, P<0.05; ANCOVA) between mean pixel heterogeneity (standard deviation of mean pixel values) of the follicular wall proper (all follicles > or =5mm in diameter) and serum concentrations of oestradiol after sponge withdrawal. Our results indicate that large antral follicles from cyclic and seasonally anovular ewes exhibit distinctive ultrasonographic characteristics. The differences in follicular echotexture appear to be related mainly to seasonal variations in ovarian follicular morphology and oestradiol production.