Detection of receptors for sulfated polysaccharides in human placenta by biotinylated probes

Histochemical detection of binding sites for sulfated polysaccharides believed to be important mediators within recognitive interactions was carried out by application of biotinylated probes such as heparin, native and desulfated fucoidan, dermatan sulfate, and two types of carrageenans. The probes were derivatized by mild cyanogen bromide activation and subsequent aminoalkylation to allow incorporation of biotin, inserted with an epsilon-aminocaproic acid spacer to reduce charge-related and steric impediments. Specific labeling could be detected in different cell types of human placenta, dependent on the developmental stage. Sulfated polysaccharides bound predominantly to leucocytes in full-term placenta, whereas demonstration of specific binding sites in decidua, syncytiotrophoblasts, and cytotrophoblasts was restricted primarily to heparin and, less intensely, fucoidan, although not desulfated fucoidan. Heparin binding in the placenta after 8 weeks of gestation was reduced for epithelia that, at this stage of development, revealed carrageenan binding sites. Fucoidan binding was at this developmental stage measurable only for leucocytes. These results provide definite histochemical evidence for the presence and developmental regulation of expression of receptors for sulfated polysaccharides in different cell types of human placenta.