Glycans as biochemical markers of human endometrial secretory differentiation

Uterine fluid contains a mixture of glycoprotein components the quantity and composition of which vary during the menstrual cycle. Their analysis may give clues to the involvement of maternally derived components in modulating the state of the peri-implantation blastocyst and aid in assessing the differentiation of the endometrium in preparation for implantation. Endometrial epithelium also exhibits an apical glycocalyx, the composition of which varies with the state of tissue differentiation. Evidence from animal systems suggests that glycans may be involved in molecular recognition between the embryo and maternal surface at implantation. Lectins and monoclonal antibodies to glycan epitopes have been used as sensitive and specific probes to examine the carbohydrates associated with endometrial epithelium as a function of the ovarian cycle. Numerous glycan structures are detected specifically in epithelial cells. Hitherto unsuspected biosynthetic heterogeneity is present in the glands. A secretory sialokeratan sulphate epitope is described, the occurrence of which coincides with the implantation phase of the cycle.