Membrane cytoskeleton-linking proteins radixin and its activated form phospho-radixin show phase specific expression in human endometrium

Abstract

Radixin is a protein playing a role in cell adhesion, migration and organization of cell surface structures. We examined immuno-reactive radixin (ir-radixin) expression and activation (phospho-radixin; ir-p-radixin) throughout the menstrual cycle and correlated its localization and activation to cytological changes. Endometrial tissues from reproductive age women (mean age 35 ± 13 years) were obtained from endometrial biopsies and human uteri after hysterectomy conducted for benign diseases other than endometrial disease following institutional review board approval. A total of eighteen endometrial samples were studied. The phase of each endometrial sample was assessed and confirmed blindly by a single pathologist. Early proliferative (n = 3), mid proliferative (n = 3), late proliferative (n = 3), early secretory (n = 3), mid secretory (n = 3) and late secretory phase (n = 3) endometrial samples were analyzed for ir-radixin and ir-p-radixin expression by immunohistochemical analysis. The H-score values were analyzed by one-way ANOVA and Student's t-test where appropriate. Statistical significance was defined as P<0.05. The intensity and location of both ir-radixin and ir-p-radixin varied throughout the menstrual cycle. Both radixin and p-radixin were localized beneath the lateral specializations. A dense immunohistochemical staining of the apical surfaces including microvilli of epithelial cells especially during the mid to late secretory phases was observed. Radixin was present in the glandular secretions as well. Stromal cells were heavily stained with radixin and p-radixin reaching the highest expression levels during mid and late secretory phases. Radixin is an important protein in human endometrium. Expression of radixin and p-radixin on apical surfaces of luminal and glandular epithelium, microvilli, luminal secretions and dense staining of stromal cells during the mid and late secretory phases may have functional implications for endometrial receptivity.