Johnson Greg A, Burghardt Robert C, Joyce Margaret M, Spencer Thomas E, Bazer Fuller W, Gray C Allison, Pfarrer Christiane
Center for Animal Biotechnology and Genomics, Texas A&M University, College Station, Texas 77843, USA.
Biol Reprod. 2003 Jul;69(1):92-8. doi: 10.1095/biolreprod.102.013573. Epub 2003 Jan 8.
Osteopontin (OPN) is a phosphorylated and glycosylated, secreted protein that is present in various epithelial cells and biological fluids. On freezing and thawing or treatment with proteases, the native 70-kDa protein gives rise to 45- and 24-kDa fragments. Secreted OPN functions as an extracellular matrix (ECM) protein that binds cell surface receptors to mediate cell-cell adhesion, cell-ECM communication, and cell migration. In sheep and humans, OPN is proposed to be a secretory product of uterine glandular epithelium (GE) that binds to uterine luminal epithelium (LE) and conceptus trophectoderm to mediate conceptus attachment, which is essential to maintain pregnancy through the peri-implantation period. Cell-cell adhesion, communication, and migration likely are important at the interface between uterus and placenta throughout pregnancy, but to our knowledge, endometrial and/or placental expression of OPN beyond the peri-implantation period has not been documented in sheep. Therefore, the present study determined temporal and spatial alterations in OPN mRNA and protein expression in the ovine uterus between Days 25 and 120 of pregnancy. The OPN mRNA in total ovine endometrium increased 30-fold between Days 40 and 80 of gestation. In situ hybridization and immunofluorescence analyses revealed that the predominant source of OPN mRNA and protein throughout pregnancy was the uterine GE. Interestingly, the 45-kDa form of OPN was detected exclusively, continuously, and abundantly along the apical surface of LE, on conceptus trophectoderm, and along the uterine-placental interface of both interplacentomal and placentomal regions through Day 120 of pregnancy. The 45-kDa OPN is a proteolytic cleavage fragment of the native 70-kDa OPN, and it is the most abundant form in uterine flushes during early pregnancy. The 45-kDa OPN is more stimulatory to cell attachment and cell migration than the native 70-kDa protein. Collectively, the present results support the hypothesis that ovine OPN is a component of histotroph secreted by the uterine GE that accumulates at the uterine-placental interface to influence maternal-fetal interactions throughout gestation in sheep.
骨桥蛋白（OPN）是一种磷酸化和糖基化的分泌蛋白，存在于各种上皮细胞和生物体液中。在冻融或用蛋白酶处理时，天然的70 kDa蛋白会产生45 kDa和24 kDa的片段。分泌的OPN作为一种细胞外基质（ECM）蛋白，与细胞表面受体结合，介导细胞间粘附、细胞与ECM通讯以及细胞迁移。在绵羊和人类中，OPN被认为是子宫腺上皮（GE）的一种分泌产物，它与子宫腔上皮（LE）和孕体滋养外胚层结合，介导孕体附着，这对于在植入前期维持妊娠至关重要。在整个妊娠期间，细胞间粘附、通讯和迁移可能在子宫与胎盘的界面处很重要，但据我们所知，绵羊在植入前期之后子宫内膜和/或胎盘的OPN表达尚未见报道。因此，本研究确定了妊娠第25天至120天绵羊子宫中OPN mRNA和蛋白表达的时空变化。妊娠第40天至80天期间，绵羊子宫内膜中总的OPN mRNA增加了30倍。原位杂交和免疫荧光分析显示，整个妊娠期间OPN mRNA和蛋白的主要来源是子宫GE。有趣的是，在妊娠第120天之前，仅在LE的顶端表面、孕体滋养外胚层以及胎盘间区域和胎盘区域的子宫-胎盘界面持续大量检测到45 kDa形式的OPN。45 kDa的OPN是天然70 kDa OPN的蛋白水解裂解片段，并且是妊娠早期子宫冲洗液中最丰富的形式。与天然的70 kDa蛋白相比，45 kDa的OPN对细胞附着和细胞迁移的刺激作用更强。总的来说，目前的结果支持这样的假设，即绵羊OPN是子宫GE分泌的组织营养物质的一个组成部分，它在子宫-胎盘界面积累，以影响绵羊整个妊娠期的母胎相互作用。
