Animal reproduction science2009; 116(3-4); 291-307; doi: 10.1016/j.anireprosci.2009.01.013

The efficacy of recombinant equine follicle stimulating hormone (reFSH) to promote follicular growth in mares using a follicular suppression model.

Jennings, MW
·
Boime, I
·
Daphna-Iken, D
·
Jablonka-Shariff, A
·
Conley, AJ
·
Colgin, M
·
Bidstrup, LA
·
Meyers-Brown, GA
·
Famula, TR
·
Roser, JF

Abstract: The efficacy of a recently engineered single chain recombinant equine follicle stimulating hormone (reFSH) was investigated in estrous cycling mares whose gonadotropins and follicular activity had been suppressed by concurrent treatment with progesterone and estradiol (P&E). Time of estrus was synchronized in 15 estrous cycling mares during the breeding season with prostaglandins F(2alpha) (PGF(2alpha)). The day after ovulation, mares were treated once daily with P&E for 14 days. Mares received a second injection of PGF(2alpha) on day 6 of the synchronized estrous cycle to induce luteolysis. On day 8 post-ovulation mares were randomly assigned to three groups: small dose reFSH-treatment group (0.5mg reFSH IV, twice daily); large dose reFSH-treatment group (0.85mg reFSH IV twice daily); control group (saline IV, twice daily). reFSH treatment occurred concurrently with the last week of P&E treatment. After a follicle or cohort of follicles reached 35mm in diameter, mares were injected with 0.75mg of recombinant equine luteinizing hormone (reLH) to induce ovulation. Post-treatment ovulation was assessed. Daily blood samples were collected for analysis of FSH, LH, estradiol, progesterone, and inhibin by radioimmunoassay (RIA). On the first day of reFSH/saline treatment, blood samples were collected periodically from 1h prior to treatment to 6h post-injection via an indwelling jugular catheter to determine acute changes in FSH concentrations. Monitoring of follicular activity, estrus, and ovulation was performed daily by utilizing a stallion and transrectal ultrasonography. A difference (p<or=0.05) between the largest diameter follicle in the reFSH-treatment groups compared to controls occurred on day 14 post-ovulation, the day treatments ended, and the difference continued until day 21 post-ovulation. reFSH-treatment groups had larger (por=35mm follicles (days 16-21) than controls. Mares treated with reFSH, at either dose, took less time (average: 2.95+/-0.42 days) to develop 2-3 times more pre-ovulatory follicles than control mares (7.8+/-0.51 days) (p<or=0.05). The number of ovulations between treated mares and controls were similar due to a greater incidence of ovulation failure in reFSH-treated mares. During reFSH treatment, concentrations of plasma FSH, inhibin and estradiol were greater (p<or=0.05) compared to control concentrations. Plasma LH concentrations in reFSH-treated mares were suppressed and did not exhibit the ovulatory surge of controls (p<or=0.05). Plasma progesterone concentrations were not different across groups. These findings demonstrate the specific effects of reFSH to increase number of total follicles including pre-ovulatory follicles in mares with endogenous pituitary gonadotropins and follicular growth suppressed by a regimen of P&E.

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Publication Date: 2009-01-31 PubMed ID: 19237253DOI: 10.1016/j.anireprosci.2009.01.013Google Scholar: Lookup

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Randomized Controlled Trial
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Non-U.S. Gov't

Summary

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This study examines the effects of a new single chain recombinant equine follicle stimulating hormone (reFSH) in stimulating follicle growth in mares, taking into account estrus syncing and hormonal suppression conditions.

Methodology

The research involved 15 mares in breeding season. Their estrus cycles were synched using prostaglandin F(2alpha) or PGF(2alpha).
Starting the day after ovulation, the mares were treated daily with progesterone and estradiol (P&E) for two weeks.
PGF(2alpha) was re-administered on day 6 of the synced estrus cycle to induce luteolysis (the degradation of the corpus luteum, a structure that develops in the ovary after ovulation).
The mares were then divided into three groups and began treatment on the eighth day after ovulation.
Two groups were given small or large doses of reFSH, while the control group received saline. All treatments were administered intravenously twice a day concurrently with the final week of P&E treatment.
When a follicle or group of follicles reached 35mm in diameter, the mares were given recombinant equine luteinizing hormone (reLH) to stimulate ovulation.

Measurements and Observations

Blood was sampled each day to measure for FSH, LH, estradiol, progesterone, and inhibin using a method called a radioimmunoassay (RIA).
On the first day of reFSH or saline treatment, periodic blood samples were collected for six hours post-injection to check for changes in FSH concentration.
Ultrasonography and a stallion were utilized to monitor daily follicular activity, estrus, and ovulation.

Results

A significant increase was observed in the diameter of the largest follicle in reFSH-treated mares compared to controls, from treatment end day till day 21 post-ovulation.
reFSH-treated mares developed more follicles of sizes within the ranges of 20-29mm, 30-34mm, and above or equal to 35mm.
Mares receiving reFSH treatment generated 2-3 times more pre-ovulatory follicles in a shorter time than control mares.
Despite reFSH treatment resulting in more follicular growth, the number of successful ovulations in treated and control mares remained similar due to increased incidence of ovulation failure in the treated group.
Mares treated with reFSH showed higher concentrations of plasma FSH, inhibin, and estradiol compared to controls. Meanwhile, their plasma LH concentrations were suppressed and did not exhibit the ovulatory surge of controls.

Conclusion

The study proved that using the novel reFSH increases the number of total and pre-ovulatory follicles in mares where natural pituitary gonadotropins are suppressed.
The use of reFSH was found to be efficacious in promoting the development of more pre-ovulatory follicles, even when the mares were undergoing a regimen of P&E that suppressed follicular growth.

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APA

Jennings MW, Boime I, Daphna-Iken D, Jablonka-Shariff A, Conley AJ, Colgin M, Bidstrup LA, Meyers-Brown GA, Famula TR, Roser JF. (2009). The efficacy of recombinant equine follicle stimulating hormone (reFSH) to promote follicular growth in mares using a follicular suppression model. Anim Reprod Sci, 116(3-4), 291-307. https://doi.org/10.1016/j.anireprosci.2009.01.013