Heart failure is caused by various factors, making the underlying pathogenic mechanisms difficult to identify. Since cardiovascular disease tends to worsen over time, early diagnosis is key for treatment. In addition, understanding the qualitative changes in the heart associated with aging, where information on the direct influences of aging on cardiovascular disease is limited, would also be useful for treatment and diagnosis. To fill these research gaps, the focus of our study was to detect the structural and functional molecular changes associated with the heart over time, with a focus on glycans, which reflect the type and state of cells.
METHODS: We investigated glycan localization in the cardiac tissue of normal mice and their alterations during aging, using evanescent-field fluorescence-assisted lectin microarray, a technique based on lectin-glycan interaction, and lectin staining.
RESULTS: The glycan profiles in the left ventricle showed differences between the luminal side (medial) and wall side (lateral) regions. The medial region was characterized by the presence of sialic acid residues. Moreover, age-related changes in glycan profiles were observed at a younger age in the medial region. The difference in the age-related decrease in the level of α-galactose stained with Griffonia simplicifolia lectin-IB4 in different regions of the left ventricle suggests spatiotemporal changes in the number of microvessels.
CONCLUSIONS: The glycan profile, which retains diverse glycan structures, is supported by many cell populations, and maintains cardiac function. With further research, glycan localization and changes have the potential to be developed as a marker of the signs of heart failure.

The presence of α2,6-sialic acids on the Fc N-glycan provides anti-inflammatory properties to the IgGs through a mechanism that remains unclear. Fc-sialylated IgGs are rare in humans as well as in industrial host cell lines such as Chinese hamster ovary (CHO) cells. Facilitated access to well-characterized α2,6-sialylated IgGs would help elucidate the mechanism of this intriguing IgG\'s effector function. This study presents a method for the efficient Fc glycan α2,6-sialylation of a wild-type and a F243A IgG1 mutant by transient co-expression with the human α2,6-sialyltransferase 1 (ST6) and β1,4-galactosyltransferase 1 (GT) in CHO cells. Overexpression of ST6 alone only had a moderate effect on the glycoprofiles, whereas GT alone greatly enhanced Fc-galactosylation, but not sialylation. Overexpression of both GT and ST6 was necessary to obtain a glycoprofile dominated by α2,6-sialylated glycans in both antibodies. The wild-type was composed of the G2FS(6)1 glycan (38%) with remaining unsialylated glycans, while the mutant glycoprofile was essentially composed of G2FS(6)1 (25%), G2FS(3,6)2 (16%) and G2FS(6,6)2 (37%). The α2,6-linked sialic acids represented over 85% of all sialic acids in both antibodies. We discuss how the limited sialylation level in the wild-type IgG1 expressed alone or with GT results from the glycan interaction with Fc\'s amino acid residues or from intrinsic galactosyl- and sialyl-transferases substrate specificities.