HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 69/1/92    most recent biolreprod.102.013573v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Johnson, G. A. Articles by Pfarrer, C. Search for Related Content PubMed PubMed Citation Articles by Johnson, G. A. Articles by Pfarrer, C. Agricola Articles by Johnson, G. A. Articles by Pfarrer, C.

Osteopontin Is Synthesized by Uterine Glands and a 45-kDa Cleavage Fragment Is Localized at the Uterine-Placental Interface Throughout Ovine Pregnancy¹

Center for Animal Biotechnology and Genomics,³ Department of Veterinary Anatomy and Public Health,⁴ College of Veterinary Medicine, Department of Animal Science,⁵ College of Agriculture and Life Sciences, Texas A&M University, College Station, Texas 77843 Department of Veterinary Anatomy, Histology and Embryology,⁶ Justus-Liebig-University, 35392 Giessen, Germany

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.

¹ The microscopy and imaging facilities in the College of Veterinary Medicine Image Analysis Laboratory are supported, in part, by NIH grant P30 ES 09106.

² Correspondence: Greg A. Johnson, Department of Veterinary Anatomy and Public Health, College of Veterinary Medicine, Texas A&M University, College Station, TX 77843-4458. FAX: 979 845 7249; gjohnson{at}cvm.tamu.edu