PARENT SESSION
BIOLOGY OF THE FEMALE REPRODUCTIVE TRACT
Harborside C
7:30 AM-10:00 AM

(555) DISTRIBUTION OF INTEGRIN SUBUNITS, MUC-1, AND OSTEOPONTIN IN EQUINE UTERINE EPITHELIUM AND CONCEPTUSES DURING EARLY PREGNANCY.

Al-Ramadan, Saeed¹, Johnson, Greg³, Jaeger, Laurie¹, Brinsko, Steven², Burghardt, Robert¹, ¹ Department of Veterinary Anatomy & Public Health and Center for Animal Biotechnology and Genomics, College Station, TX³ Department of Animal & Veterinary Science and Center of Reproductive Biology, Moscow, ID² Department of Veterinary Large Animal Medicine and Surgery, College Sation, TX

ABSTRACT- MUC-1, osteopontin (OPN), and the integrin subunits ₄, ₅, _v, ₁ and ₃ have been proposed to be involved in a cascade of events that leads to successful conceptus implantation and placentation in sheep and pigs. This study examined the expression of these proteins by indirect immunofluorescence in cryosectioned equine uterine biopsies from both gravid and non-gravid uterine horns (Days 14, 17, 21, 27, 37), and in snap-frozen conceptuses recovered on the same Days of pregnancy. MUC-1 was uniformly and constitutively expressed at the apical surfaces of glandular and luminal epithelium, however, the intensity of MUC-1 staining appeared to be greater in the gravid horn than non-gravid horn with exception of Day 37 when the intensity staining was comparable in both horns. Integrin subunits _v and ₃ were constitutively expressed at low levels on uterine epithelium whereas the intensity of staining was greater at the apical surface of the trophectoderm. In addition, the integrin subunits ₄, ₅ and ₁ were present in uterine epithelium and conceptus tissues. These integrins could form a number of potential integrin heterodimers capable of binding OPN that may be present in histotroph. OPN immunoreactivity was detectable on the apical surfaces of the luminal and glandular epithelium of pregnant mares as well as trophectoderm. The intensity of OPN staining in endometrium was greater on Days 21 and 27 of pregnancy than other days examined. These results are consistent with a potential role for OPN as a potential mediator of implantation in the mare as a bridge between integrin heterodimers expressed by trophectoderm and uterine luminal epithelium responsible for adhesion and initial conceptus attachment. (Supported in part by USDA-NRICGP 98-35203-6223 and by TAMU CVM Signature Program).

KEY WORDS: integrin, MUC-1, osteopontin, equine