ORIGINAL ARTICLESProtein S deposition at placenta: a possible role of protein S other than anticoagulationMatsumoto, Makikoa; Tachibana, Daisukea; Nobeyama, Hiroyukia; Nakano, Akemia; Nakai, Yuichiroa; Nakayama, Masahirob; Ishiko, Osamua Author Information aDepartment of Obstetrics and Gynecology, Osaka City University Graduate School of Medicine, Japan bOsaka Medical Center and Research Institute for Maternal and Child Health, Osaka, Japan Received 13 August, 2007 Revised 7 March, 2008 Accepted 7 March, 2008 Correspondence to Makiko Matsumoto, MD, Department of Obstetrics and Gynecology, Osaka City University Graduate School of Medicine, 1-4-3, Asahi-machi, Abeno-ku, Osaka, 545-8585, Japan E-mail: [email protected] Blood Coagulation & Fibrinolysis 19(7):p 653-656, October 2008. | DOI: 10.1097/MBC.0b013e3283001d1f Buy Metrics Abstract Protein S is an antithrombotic cofactor for protein C that also has multifunctional anti-inflammatory, cellular protective, apoptotic and mitogenic properties. Protein S levels are thought to decrease during pregnancy, but the underlying mechanism remains unknown. We compared protein S concentrations throughout normal pregnancy with those of nonpregnant women and measured plasma C4b-binding protein levels in nonpregnant women and in pregnant women at the 40th gestational week. We also examined protein S and C4b-binding protein in the placenta by immunohistochemical staining at early (20th gestational week) and late (40th gestational week) stages of pregnancy. Plasma protein S activity and free protein S-antigen levels significantly decreased from the 10th gestational week and total protein S antigen decreased from the 20th. C4b-binding protein levels between pregnant and nonpregnant women did not significantly differ. The stainable portion of protein S was located at the fetomaternal interface, particularly at degenerative villi. C4b-binding protein was weakly stained at the same areas as protein S. Neither protein S nor C4b-binding protein were stained at normal villi. These results indicated that protein S can protect or restore damaged villi via a physiological effect in addition to its anticoagulation properties. © 2008 Lippincott Williams & Wilkins, Inc.