Protease, Amylase, and Secretory Phospholipase A2 Levels in Human Amniotic Fluid of Fetuses with Open Spina Bifida.

INTRODUCTION

We previously demonstrated elevated levels of secretory Phospholipase A2 (sPLA2) and Amylase in the amniotic fluid (AF) of a fetal rat Retinoic Acid (RA) Induced Open Spina Bifida (OSB) model. Our objective was to determine whether these enzymes, as well as protease, were elevated in the AF of human fetuses with OSB.

METHODS

AF was collected at the time of diagnosis (Early 21-22 weeks, n=9) or during fetoscopic repair (Late 26-27 weeks, n=12). Controls (21-22 weeks, n=3) were amniocentesis samples collected for advanced maternal age. Activity levels of amylase, protease, and PLA2 in these samples were measured, and we compared enzymatic activity in the control vs. early groups and the early vs. late groups.

RESULTS

In comparison to the control group, the activities of Amylase (p=0.003), sPLA2 (p=0.014), and Protease (p=0.012) were increased in the early OSB samples. No significant differences were seen in the activities of these enzymes between the early OSB and late OSB groups.

DISCUSSION: Protease, amylase, and sPLA2 levels were increased in the AF of human OSB fetuses but did not appear to increase further during the late second trimester. These neurotoxic enzymes may contribute to the "second hit" of OSB, the timing of which appears to be during the first half of the pregnancy. It is important to note that the assays used measure enzyme activity rather than absolute enzyme concentration, and findings should be interpreted accordingly. Direct extrapolation should be made cautiously given differences in study design and species-specific developmental timing (see Discussion).