Site-Specific N- and O-Glycosylation Analysis of Human Plasma Fibronectin

Human plasma fibronectin is an adhesive protein that plays a crucial role in wound healing. Many studies had indicated that glycans might mediate the expression and functions of fibronectin, yet a comprehensive understanding of its glycosylation is still missing. Here, we performed a comprehensive N- and O-glycosylation mapping of human plasma fibronectin and quantified the occurrence of each glycoform in a site-specific manner. Intact N-glycopeptides were enriched by zwitterionic hydrophilic interaction chromatography, and N-glycosite sites were localized by the 18O-labeling method. O-glycopeptide enrichment and O-glycosite identification were achieved by an enzyme-assisted site-specific extraction method. An RP–LC–MS/MS system functionalized with collision-induced dissociation and stepped normalized collision energy (sNCE)-HCD tandem mass was applied to analyze the glycoforms of fibronectin. A total of 6 N-glycosites and 53 O-glycosites were identified, which were occupied by 38 N-glycoforms and 16 O-glycoforms, respectively. Furthermore, 77.31% of N-glycans were sialylated, and O-glycosylation was dominated by the sialyl-T antigen. These site-specific glycosylation patterns on human fibronectin can facilitate functional analyses of fibronectin and therapeutics development.

Comparison of fetal and plasma fibronectin concentrations in diagnosis of Preterm: delivery A cross sectional, descriptive-analytical study

Background Preterm delivery is amongst the main reasons for child mortality. Therefore, its prediction can reduce a large number of its complications. The present study aimed to compare fetal and plasma fibronectin concentrations in diagnosis of preterm delivery. Methods Serum samples were obtained from 105 women at 24-36 weeks of gestation. However, only 40 women gave permission for taking vaginal samples. Fibronectin concentration was measured using ELISA technique. Then, plasma and fetal fibronectin levels were compared in term and preterm deliveries. Results Out of the 105 participants, 28 experienced preterm delivery (26.7%). The mean gestational age at the time of sampling was 28.11 + 2.98 weeks. The mean plasma fibronectin level was 6226.43+7174.97 ng/ml among the mothers with term infants and 7724.01 + 1143.82 ng/ml among those with preterm infants. Although the mean plasma fibronectin level was higher in preterm delivery, the difference was not statistically significant (p=0.667). The mean fetal fibronectin level was 156.61 + 126.42 ng/ml among the mothers with term infants and 127.71 + 43.14 ng/ml among those with preterm infants, but the difference was not statistically significant (p=0.241). The cut-off point of plasma fibronectin level was 1750 ng/ml with the sensitivity of 80.25% and specificity of 85.17%. Additionally, the cut-off point of fetal fibronectin level was 158.98 ng/ml with the sensitivity of 94.62% and specificity of 22.08%. Conclusion Plasma fibronectin testing had lower sensitivity and higher specificity compared to fetal fibronectin testing. This implies that plasma testing has lower false positive cases and can identify a larger number of true positive cases of preterm delivery.