Altered Amniotic Fluid Levels of Hyaluronic Acid in Fetal Rats with Myelomeningocele: Understanding Spinal Cord Injury

Myelomeningocele (MMC) is a devastating congenital neural tube defect that results in the exposure of spinal cord to the intrauterine environment, leading to secondary spinal cord injury and severe impairment. Although the mechanisms underlying the secondary pathogenesis are clinically relevant, the exact cause of in utero–acquired spinal cord damage remains unclear. The objective of this study was to determine whether the hyaluronic acid (HA) concentration in amniotic fluid (AF) in the retinoic acid-induced model of MMC is different from that in normal controls and whether these differences could have an impact on the viscosity of AF. Our data shows that the concentration of HA in AF samples from fetuses with MMC (MMC-AF) and normal control samples (Norm-AF) were not significantly different at embryonic day 18 (E18) and E20. Thereafter, the HA concentration significantly increased in Norm-AF but not in MMC-AF. Compared with Norm-AF, the concentration of HA in MMC-AF and the viscosity of MMC-AF were significantly lower at E21. Agarose gel electrophoresis confirmed a significant reduction in the HA level of MMC-AF compared with Norm-AF at E21. No HA-degrading activity was detected in MMC-AF. In summary, we identified a deficiency in the AF level of HA and the viscosity of AF in fetal rats with MMC. These data are discussed in relation to a potential role the reduction in the AF viscosity due to the low level of HA may play in the exacerbating effects of mechanical trauma on spinal cord damage at the MMC lesion site.