Lower expression of the alpha2,3-sialylated fibronectin glycoform and appearance of the asialo-fibronectin glycoform are associated with high concentrations of fibronectin in human seminal plasma with abnormal semen parameters.

BACKGROUND: Sialic acid isoforms expressed on glycoconjugates are known to be involved in different biological functions. The aim of this study was to compare alpha2,3- and/or alpha2,6-linked sialic acid expression on fibronectin in the seminal plasma of male partners from infertile couples. The data obtained were analyzed in relation to normal and abnormal semen parameters, as well as to fibronectin concentrations. METHODS: Fibronectin concentrations were determined by ELISA using a specific monoclonal antibody. The relative degree of sialic acid linked to fibronectin glycans either by alpha2,3 or alpha2,6 isomeric linkage was estimated by lectin-fibronectin ELISA utilizing lectins from Maackia amurensis and Sambucus nigra, respectively. RESULTS: High seminal fibronectin concentration was more frequently associated with abnormal semen parameters. The glycans of seminal plasma fibronectin, in contrast to blood plasma fibronectin, contained sialic acid more frequently attached by alpha2,3 than by alpha2,6 isomeric linkage. The relative amounts of both alpha2,3- and alpha2,6-linked sialic acid fibronectin isoforms were lower in the seminal plasma of men suspected of infertility. CONCLUSIONS: Seminal fibronectin showed an oncofetal type of sialylation and the distribution of hypo- and asialylated fibronectin glycoforms were associated with abnormal semen parameters and with high concentrations of fibronectin.