SPATIAL AND TEMPORAL ANALYSES OF INTEGRIN AND MUC-1 EXPRESSION IN PORCINE UTERINE EPITHELIUM AND TROPHECTODERM IN-VIVO

The spatial and temporal expressions of Muc-1, selected integrin subun its, and extracellular matrix components in porcine uterine epithelium from estrous (Days 0, 4, 8, 10-15) and early pregnant (Days 10-15 of pregnancy) gilts and from steroid-treated ovariectomized gilts were an alyzed using indirect immunofluorescence analyses on cryosectioned tis sues to identify potential components of uterine receptivity. Integrin subunit and extracellular matrix expressions were also examined in Da y 11-15 conceptuses. Intense Muc-1 staining was detected on apical ute rine epithelium on Day 0 but was absent by Day 10 in both cyclic and p regnant gilts. The result of estrogen treatment (E(2); 100 mu g/day fo r 10 days) was similar to that of the corn oil vehicle control, while treatment with progesterone (P-4; 200 mg/day for 10 days) or E(2)+P-4 decreased Muc-1 staining in ovariectomized gilts. Immunostaining perfo rmed with antibodies directed against integrin subunits (alpha(1), alp ha(3), alpha(4), alpha(5), alpha(v), beta(1), and beta(3)) in uterine epithelium revealed low (integrin subunits alpha(1) and alpha(3)), hig h (integrin subunits alpha(v) and beta(3)), or modulated (integrin sub units alpha(4), alpha(5), and beta(1)) expression, with the lowest exp ression on Day 0 and maximum expression by Days 10-15. Additionally, n o differences due to pregnancy status were detected in staining of ute rine epithelium on Days 10-15. Uterine epithelium from steroid-treated ovariectomized gilts had low expression of alpha(4), alpha(5), and be ta(1) subunits in the presence of E(2) that increased in response to P -4 and E(2)+P-4 treatments. The expression of integrin subunits alpha( 3), alpha(v), and beta(3) was not affected by sex steroids. Trophectod erm also expressed alpha(1), alpha(4), alpha(5), alpha(v), beta(1), an d beta(3) integrin subunits. Extracellular matrix constituents (fibron ectin, vitronectin, laminin, and collagen type IV) were also examined. Fibronectin and vitronectin were present on trophectoderm, but only v itronectin was detected on uterine epithelium. The alpha(4), alpha(5), alpha(v), beta(1), and beta(3) integrin subunits, vitronectin, and fi bronectin were detected at sites of attachment between uterine epithel ial cells and trophectoderm on Days 12-15 of pregnancy. These studies indicate that down-regulation of Muc-1 coincides with the transition o f the prereceptive uterus to the receptive uterus. Additionally, the e xpression of alpha(4), alpha(5), alpha(v), beta(1), and beta(3) integr in subunits along with the extracellular matrix components of fibronec tin and vitronectin correlates with the time of implantation in swine.