Assistant Professor UCSF San Francisco, California, United States
Disclosure(s):
Sze Chun Winson Ho, MD: No financial relationships to disclose
Introduction: Neonatal IVH and post-hemorrhagic hydrocephalus (PHH) is a leading cause of neurologic morbidity and mortality in preterm infants. Hemoglobin and iron-mediated cellular injury has been theorized but not well-delineated as a causal mechanism in the pathophysiology of PHH. There is a need for a model that closely simulates neonatal IVH - occurring in the early postnatal period - and reproduces both phenotypic and radiographic features of PHH. Our study’s objective was to establish a reliable pre-clinical model of IVH and severe PHH to uncover the underlying players that mediate ependymal cell dysfunction and subsequent hydrocephalus and develop targeted therapies to prevent PHH.
Methods: Lysed red blood cells (RBC) 60μL (n=41), sterile saline 20μL (n=19), hemoglobin 7.5mg (n=9), or iron (FeCl3) 50μg (n=16) were stereotactically injected bilaterally into the lateral ventricles of postnatal day 3 Sprague Dawley rat pups. Ventricular volumes were assessed at postnatal days 4, 12, 19 and 26 with 11.7T MRI. Clinical and behavioral manifestations of hydrocephalus were monitored. Ventricular ependyma and choroid plexus morphology were characterized by SEM. Ependymal and choroid plexus iron deposition were evaluated with immunohistochemistry/PERL staining.
Results: Lysed RBCs and iron intraventricular injections resulted in severe hydrocephalus characterized by severe ventriculomegaly, domed cranium, and neurobehavioral deficits (rotarod and negative geotaxis). Hb-injected and control (saline) pups did not demonstrate significant ventricular enlargement. Ventriculomegaly was most severe in iron-injected pups. Ventricular volumes at 26 days were severely enlarged in iron- and lysed RBC-injected rat pups compared to saline- and hemoglobin-injected rat pups (p < 0.0001). Iron deposition (PERL stain) was markedly increased in iron- and lysed RBC-injected pups. SEM revealed denudation of the ependymal cilia and morphologic changes in the choroid plexus of iron- and lysed RBC-injected pups with hydrocephalus.
Conclusion : Intraventricular free iron is critical to the development of PHH following IVH. Though we have observed elevated intraventricular hemoglobin in human CSF in prior clinical studies following severe IVH, this study shows that its degradation product, iron, is the pathologic component in the development of PHH.
