Characterization of cyclin D2 expression in human endometrium

Objective: This study was undertaken to investigate cyclin D2 mRNA and protein expression in human endometrium during the menstrual cycle. Methods: Endometrial samples were obtained from 15 premenopausal nonpregnant women who had hysterectomies for benign gynecologic reasons. They were divided into the following five groups according to histologic dating: early proliferative (n = 3), mid to late proliferative (n = 3), early secretory (n = 3), mid secretory (n = 3), and late secretory (n = 3). Cyclin D2 mRNA and protein expression were analyzed using reverse transcriptase-polymerase chain reaction, Western blotting, and immunohistochemistry. Results: Cyclin D2 mRNA and protein were expressed in human endometrial tissue throughout the menstrual cycle. Cyclin D2 mRNA and protein expression of proliferative phase endometrium were significantly higher than those of secretory phase endometrium (P < .05). The staining intensity of cyclin D2 in proliferative phase endometrium was higher than that in secretory phase (P < .05). Cyclin D2 mRNA level showed good correlation with cyclin D2 protein level (R = 0.579, P < .03), and cyclin D2 protein also showed good correlation with immunohistochemical staining intensity (R = 0.562, P < .03). Conclusion: Cyclin D2 was expressed in human endometrium throughout the menstrual cycle. Cyclin D2 mRNA and protein were expressed at high levels in proliferative phase endometrium, especially in the early proliferative phase, and then decreased in the secretory phase.