Immunohistochemical staining of von Willebrand factor in human endometrium during normal menstrual cycle

Endometrial biopsies were obtained from 73 normal women throughoutthe menstrual cycle. Using a polyclonal antibody and a streptavidin–biotin–peroxidasemethod, formalinfixed paraffin sections of the tissue were stainedfor von Willebrand factor (vWF). Both subjective scoring andobjective quantitative colour image analysis were used to assessthe staining intensity, and the results obtained by the twomethods were in concordance with each other. Positive stainingwas observed at all stages of the menstrual cycle. Specificstaining was confined to the vascular endothelium and showedcyclical changes. The staining intensity was the weakest duringthe menstrual phase and was significantly (P < 0.02) reducedfrom all other stages of the cycle, except late secretory phase.This was followed by a rapid increase in the early proliferativephase to reach a peak in the mid cycle before gradually fallingoff towards the end of the cycle. The staining intensity inthe late secretory phase was significantly reduced (P < 0.05)from other stages except menstrual, early proliferative andmid secretory phase. Vascular staining for vWF was heterogeneouswith some vessels devoid of any positive staining.