PARENT SESSION
IMPLANTATION AND PREGNANCY - B

Tuesday, August 3, 2004
10:30 AM–12:30 PM
Buchanan Courtyard

(517) CONCEPTUS SECRETORY FACTORS, OTHER THAN ESTROGEN, INCREASE EXPRESSION OF INTERFERON-STIMULATED GENES IN THE PORCINE ENDOMETRIUM DURING PREGNANCY.

Joyce, Margaret¹, Burghardt, Robert¹, Spencer, Thomas², Johnson, Greg¹, ¹ Texas A&M University, College Station, TX² Texas A&M University, College Station, TX

ABSTRACT- Maternal recognition of pregnancy in ruminants involves conceptus secretion of the Type I interferon tau (IFN), while this process in pigs involves conceptus secretion of estrogen. Despite the differences in hormones used for pregnancy recognition, IFN-stimulated genes (ISGs), including IFN regulatory factor-1 (IRF-1), signal transducer and activator of transcription 1 (STAT1), STAT2, major histocompatibility complex class I (MHCI), and 2-microglobulin (2MG) increase in the uterus during early pregnancy in both species. However, the temporal and spatial expression pattern of these ISGs in the pig is unknown. Also, it is unclear what factor(s) up-regulate ISG expression in pigs. Therefore, Study One examined uterine ISG mRNA expression throughout the estrous cycle and pregnancy, while Study Two determined if ISGs are regulated by estrogen in the pig uterus. For Study One, gilts were hysterectomized on Days 5, 9, 12, or 15 of the cycle or Days 9, 10, 12, 13, 14, 15, 20, 25, 30, 35, 40, 60, or 85 of pregnancy. In Study Two, cyclic gilts were treated daily (Days 11-14) with 5 mg estradiol benzoate (i.m.) or corn oil vehicle, and then were hysterectomized on Day 15. Steady-state levels of ISG mRNAs increased in the endometrium during pregnancy as compared to the cycle, and were highest between Days 13 and 25. In situ hybridization indicated that the pregnancy-associated increase in ISG mRNAs was localized to regions of the stratum compactum stroma in close proximity to the conceptus, but not in endometrium away from the conceptus. Therefore, ISG expression in the porcine endometrium is regulated by a paracrine factor(s) from the conceptus. In Study Two, no effect of estrogen was detected on uterine endometrial ISG mRNA levels. Given that ISG mRNAs increase in regions of the endometrium around the conceptus, we hypothesize that other conceptus secretory factor(s), possibly IFN and/or IFN, are required for this induction. Because ISGs increase during pregnancy in ruminants and pigs, as well as primates and rodents, this phenomenon appears to be a universal uterine stromal response important for successful pregnancy.

KEY WORDS: pregnancy, interferon-stimulated genes, uterus, porcine