Effect of age on follicle stimulating hormone receptor expression in ovine endometrium

Follicle stimulating hormone receptors (FSHR) are present predominately in granulosa cells of secondary and preovulatory follicles. In addition, FSHR are present within ovine endometrium. 1 In humans, ovarian FSHR expression decreased with age. 2 Objective of this study was to compare endometrial FSHR expression among ewes < 9 months of age (prepubertal/peripubertal; n = 6), 1.5 - 2 years of age (mature; n = 4), and > 3 years of age (aged; n = 4). We hypothesized that similar to human ovary, ovine endometrial FSHR expression would decrease over time. Intracaruncular endometrial samples were collected from crossbred ewes (n =14) at slaughter. Age of ewe was determined by dental eruption and wear. Ovine ovary served as positive control. Samples were fixed in 10% formalin, embedded in paraffin, and sectioned (5 μm) onto charged slides. Sections were deparaffinized in xylene and rehydrated in graded ethanol series. Heat-induced antigen retrieval was performed with sodium citrate. Endogenous peroxidases were blocked with 3% hydrogen peroxide and nonspecific binding was blocked with a serum-free protein block. Rabbit antihuman FSHR (F-3929, Sigma Aldrich) was applied to tissues at 1:200 dilution and universal rabbit negative agent was applied to an adjacent tissue section to serve as control. Horseradish peroxidase-conjugated polymer antirabbit IgG was used as secondary antibody, followed by treatment with NovaRED TM peroxidase substrate, and counterstained with hematoxylin. Slides were dehydrated in graded ethanol series, passed through 3 xylene solutions, and then coverslipped. Slides were evaluated by a blinded observer (HH) at 400 x magnification with a Leica DM4000B microscope. Intensity of FSHR expression was quantified from no staining (score of 0) to very strong staining (score of 4) for various endometrium compartments from 3 randomly selected fields per ewe. 1 Data on FSHR expression between age groups were analyzed with one-way ANOVA. Significance was defined as p < 0.05. Although FSHR was expressed in endometrial luminal epithelium, superficial and deep glandular epithelium, superficial and deep blood vessels, and superficial and deep stroma in both age groups, there were no differences (p > 0.05) in expression among age groups. It is not clear what role FSHR plays in ovine endometrium, but it may regulate mucin-1 expression that is involved in early pregnancy establishment.3 

Keywords: Immunohistochemistry, intracaruncular, sheep, uterus

References

1. Grazul-Bilska AT, Reyaz A, Valkov V, et al: Acta Histochem 2018;120:420-428.
2. Brodowska A, Laszczynska M, Brodowski J, et al: Histol Histopathol 2012;27:241-248.
3. Constantinou PE, Morgado M, & Carson DD: Adv Anat Embryol Cell Biol 2015;216:51-68.

This manuscript was originally published in the journal Clinical Theriogenology Vol 12(3) Sept 2020.  Clinical Theriogenology is the official journal of the Society for Theriogenology (SFT) and the American College of Theriogenologists (ACT).  This content has been reproduced on the IVIS website with the explicit permission of the SFT/ACT.