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The Induction of SPP1 in Ovine Endometrial Glandular Epithelium and Stroma Requires Progesterone, but is Augmented to Maximal Production by Conceptus Attachment

KM Reed1, KA Dunlap1, FJ White1, JL Farmer2, RC Burghardt1, TE Spencer2, GA Johnson1
Departments of Veterinary Integrative Biosciences1 and Animal Science2, Texas A&M University, College Station, TX 77843-4458

AbstractKristy pic

Objective: determine the regulation of SPP1 in endometrial stroma and GE of sheep.

Animals Used: adult virgin control ewes, Uterine Gland Knockout (UGKO) ewes and unilaterally pregnant ewes

Procedure: During seasonal anestrus, adult virgin control and UGKO ewes were hemi-ovariohysterectomized (Day 0) and then received daily injections of progesterone.  On Day 60, the remaining uterine horn was recovered.  SPP1 expression in unilaterally pregnant sheep in which one uterine horn was ligated and the ipsilateral ovary removed was also examined.  The sheep were mated to rams and then hysterectomized on Days 40, 80 or 120 of pregnancy.

Results: In control sheep, SPP1 mRNA was induced in uterine glands and stroma whereas in UGKO ewes SPP1 mRNA was induced in stroma in both caruncular and intercaruncular regions.  SPP1 mRNA was detected in GE of both gravid and non-gravid horns, and SPP1 protein was present on luminal epithelium in both horns.  Gravid horns exhibited extensive stromal SPP1 expression as early as Day 40, whereas SPP1 was much lower in the non-gravid horns through Day 80.  By Day 120 of pregnancy expression between gravid and non-gravid horns became equal.  SPP1 expression directly correlated with increased vascularization of the stratum compactum stroma.

Conclusion: Collectively, these studies suggest that pregnancy levels of progesterone are sufficient to induce SPP1 mRNA and protein expression by endometrial GE and stroma, but it is paracrine and/or physical effects from the conceptus that up-regulate developmental changes in endometrial GE and stroma essential for maximal production of SPP1.