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7: Identification and characterization of proteomic biomarkers in amniotic fluid that are differentially expressed before and after antenatal corticosteroid administration

      Objective

      Antenatal corticosteroid therapy decreases the incidence of neonatal complications in preterm infants. To better understand the effects on the developing fetus, proteomic analysis of amniotic fluid(AF) was performed before and after steroid administration.

      Study Design

      AF was collected by amniocentesis for threatened PTB<34 weeks both before and in the same subject within 7 days of steroid administration(n=12). There was no evidence of intraamniotic infection/inflammation. Proteomic analysis was performed by SELDI-TOF(surface-enhanced laser desorption/ionization time-of-flight) mass spectrometry. Proteomic biomarkers before and after steroid administration were isolated, characterized and quantified.

      Results

      Five biomarkers differentially expressed in the AF before and after antenatal corticosteroid therapy were identified by proteomic analysis, all of which were significantly decreased. These were designated peaks A(6, 879 Da), B(13, 756 Da), C(22, 206 Da), D(12, 454 Da) and E(44, 450 Da). Fractions containing the biomarkers of interest were then separated by FPLC and subjected to SDS-PAGE gel electrophoresis, in-gel tryptic digestion, immunodepletion assays, ELISA and MS/MS. Peaks A and B were identified as isoforms of transthyretin; peaks C, D and E were identified as triple-charged albumin, prothrombin fragment 2 and lumican, respectively. ELISA confirmed a significant decrease in AF concentrations of albumin and prothrombin following antenatal corticosteroid therapy, but the differences in transthyretin and lumican measurements did not achieve statistical significance.

      Conclusion

      This study uses proteomic technology to identify for the first time protein biomarkers in the AF before and after antenatal corticosteroid therapy. The biomarkers were identified as transthyretin, albumin, prothrombin and lumican. A better understanding of the molecular and cellular mechanisms by which antenatal steroids prevent neonatal complications will facilitate the development of new and innovative interventions to improve perinatal outcome in infants destined to deliver preterm.