Restoration of ependymal integrity reduces posthemorrhagic hydrocephalus in preterm neonates

Abstract About 27% of premature infants weighing less than 1500 g develop intraventricular hemorrhage (IVH). These infants suffer from post-hemorrhagic hydrocephalus, cerebral palsy, and cognitive deficits. No optimal therapy exists to prevent or minimize post-IVH hydrocephalus. IVH damages the multiciliated ependyma in the cerebral

ventricles and aqueduct disrupting the cilia-driven CSF flow. Moreover, this inflames the choroid plexus (ChP) and periventricular regions, increasing CSF production and contributing to hydrocephalus. The cerebral ventricle in fetuses is lined by pseudostratified epithelium consisting of radial glia and other neural progenitors. As the

brain matures, the radial glia differentiates into multiciliated ependymal cells (E1) and quiescent neural stem cells (B1). This multiciliated differentiation program is regulated by MCIDAS>p73>FOXJ1 signaling pathway that regulates the specification of radial glia into multiciliated ependyma. Indeed, human infants with FoxJ1 or

MCIDAS mutation and FoxJ1 knock-out mice display defective multiciliated ependyma and hydrocephalus. IVH injures the ependyma and ChP, reduces the proliferation of progenitors in the ventricular (VZ) and subventricular zone (SVZ), and downregulates Sonic hedgehog (Shh) expression in the periventricular regions. Conversely,

Shh overexpression promotes the proliferation of progenitors in VZ and SVZ, reduces inflammation, and upregulates FoxJ1, p73, and Rfx3 transcription factors, likely promoting repair of the damaged ependyma and CSF flow. Our preliminary data show that IVH reduces the number of E1 and B1 cells. Additionally, the Shh

activation increases the population of E1 and B1 cells and reduces the ventricular volume in the rabbit model of IVH. We hypothesize that a) IVH results in apoptosis, reduction, and arrested maturation of multiciliated ependymal cells in preterm rabbits and humans, and b) activation of Shh/MCIDAS > FoxJ1 signaling reverses

the damage to the ciliated ependyma and reduces hydrocephalus in kits with IVH. Our well-established rabbit model of IVH (E29 kits) and autopsy samples from human preterm infants will be used to test these hypotheses. In Aim 1, we will evaluate the effect of IVH on the proliferation and maturation of the ependyma development in

premature rabbit kits (E29) at postnatal D3, 7, and 14 by immunohistochemistry and electron microscopy. Also, the planar polarity of cilia in immunostained sections, ciliary movement, and ependymal transcriptomic changes by scRNA-seq will be assessed. Autopsy samples from human fetuses and premature infants (20-40 weeks) will

be analyzed to assess the impact of gestational age and IVH on the ciliated ependyma development. In Aim 2, we will determine if Shh activation by Ad-Shh or Smo-agonist treatment reverses IVH-induced ependymal damage, ciliary loss, hydrocephalus, and behavioral deficits by increasing FoxJ1 expression. In Aim 3, we will

modulate MCIDAS>p73>FoxJ1 signaling to reverse the ependymal injury, reduce hydrocephalus, and assess its impact on Shh-signaling. These studies should hasten the development of new therapies for hydrocephalus and expand our understanding of ependymal plasticity in premature newborns.