Effects of FSH treatment and withdrawal during proestrus on uterine proliferation and steroid hormone receptor expression in beef heifers

Abstract

To determine the effects of Follicle Stimulating Hormone (FSH) treatment and subsequent withdrawal on uterine proliferation and estrogen receptor (ESR), Brahman crossbred heifers (n = 12) were twice daily injected with FSH (4, 3, and 2 mg/injection) on Days 17–19 of the estrous cycle (FSH 3 days) and (4 and 3 mg/injection) on Days 17–18 (FSH 2 days) and withdrawal with saline on Day 19 and (4 mg/injection) on Day 17 (FSH 1 day) and withdrawal with saline on Days 18–19. Uterine tissue was subjectively collected on Day 20 and microscopically classified to four regions: endometrial stroma (ES), surface endometrial gland (EG), deep endometrial gland (DG), and myometrium (Myo). The cell proliferation marker, Ki‐67, was quantified as labeling index (LI) in uterine regions, and tissues were immunostained to detect ESR2 followed by image analysis. The LI of ES, EG, and DG was greater (P = 0.0018, P = 0.0005, and P = 0.0103; respectively) in heifers received FSH for 3 days. The expression of ESR2 protein on ES and EG was greatest (P < 0.0001 and P = 0.0036, respectively) in FSH 3 days‐treated group. Thus, FSH administration during proestrus stimulates uterine cell proliferation, and ESR2 expressions are affected by FSH during proestrus and differentially distributed in the uterine regions.

Quantitative Histomorphometry of Pre-ovulatory Follicles and Uterine Glands of Ongole-grade Heifer in Response to the Low Doses of PMSG Administration

“…During the follicular phase (proestrus-estrus), it was reported an increase in the number of estradiol receptors α (ERα) in three parts of the uterus (Zeng et al, 2017;Perry et al, 2021). The increase in plasma E2 concentrations in the circulation and the increasing existence of Erα will cause the lengthening of uterine glands, followed by the production of estrus mucus by ciliated epithelial cells of the endometrium and secretory cells (Bunma et al, 2021). The increase in the thickness of the stratum functional and the activity of the other uterine glands during the estrus phase is a direct effect of the high increase in E2 synthesis in the GC.…”

Impact of age and FSH treatment on follicular environment, folliculogenesis and endometrial histomorphometry in prepubertal gilts

“…Expression of the FSHR is detected in gonadal tissues (specifically, granulosa and Sertoli cells); however, FSHR can also be found in extra-gonadal tissues of reproductive tract [21][22][23]. In this context, it has been demonstrated that in ruminant and human species, FSH affects uterine functions by changes in endometrium transcriptome, vascular density and endometrial morphology [24][25][26][27][28]. In pigs, the presence of FSH receptor in endometrium of prepubertal gilts was recently described [22,29], evidencing an extra-gonadal action of FSH in this specie.…”