Immunolocalization of integrins and fibronectin in tubal pregnancy

Integrins are a large family of cell adhesion molecules that serve as receptors involved in cell-to-cell and cell-to-matrix interactions during implantation. We studied immunohistochemical staining of integrins ( α3, αV, β1, and α2 β1) and fibronectin in ectopic tubal pregnancy. Thirty fallopian tube samples with ectopic pregnancies and five normal tubal segments were obtained during ligation operations; the latter specimens served as controls in the study. Formalin-fixed paraffin-embedded tissue sections were stained with hematoxylin–eosin or primary antibodies against α3, β1, αV, and α2 β1 integrins and fibronectin, using the avidin–biotin–peroxidase method. A semi-quantitative grading system was used to compare staining intensities. In the control samples, immunostaining of all integrins was found in a single layer of tall columnar epithelial cells, the lamina propria (Lp) and the muscular layer. Fibronectin staining was detected in the Lp and the muscular layer. Staining intensities of α3 and β1 integrins and fibronectin were increased in the normal part of fallopian tubes with ectopic pregnancies. Staining of β1 integrin was more intense than staining of α3 and fibronectin, whereas there was no difference in αV and α2 β1 integrin expression between normal tubal tissue in the ectopic pregnancy group and control tubal tissue. In the tubal pregnancy group at the site of implantation, staining intensity of α3 and β1 integrins and fibronectin was strong in decidual cells, supporting tissue and placental villi, whereas αV and α2 β1 staining was mild. We concluded that integrins, especially β1 and α3, and fibronectin may play a role in progression of tubal implantation. Although the role of integrins has not yet been clearly defined, these molecules may function as markers of normal and abnormal states of receptivity. We like to suggest that integrins and fibronectin, which are needed in utero implantation, are expressed in tubal tissues during ectopic pregnancy and are involved in ectopic implantation.