(1016) Histopathological Findings of In-Utero Ventriculosubgaleal Shunt Placement in a Fetal Lamb Model of Induced Hydrocephalus

Objective:
To evaluate the histopathological changes which accompany in-utero ventriculosubgaleal shunt (VSGS) placement in a fetal lamb model of experimentally induced hydrocephalus.

Study Design:
Hydrocephalus was induced in fetal lambs via cisterna magna injection of BioGlueⓇ. At 13-15 days, VSGS were placed in utero. Near term, surviving fetal lambs were delivered, and brains were assessed by gross exam, postmortem MRI, and GFAP/Iba1 immunostaining. Shunt patency was tested by injecting saline into the distal end.

Results:
Of n=14 fetuses that underwent hydrocephalus induction, 7 survived to near term and underwent gross and histopathological evaluation. All exhibited ventriculomegaly, denuded ependyma, and disruption of the corpus callosum (Fig 1A). Shunt patency was confirmed in 4 of 7 lambs (Fig 1B) and in the remaining there was notableobstructed by tissue debris and fibrin. Western blot revealed consistent decreases in N-cadherin and Beta-4 tubulin expression, most pronounced in severe cases, correlating with ependymal denudation and loss of ciliated neuroepithelium. GFAP levels increased with hydrocephalus severity, indicating progressive astrocyte activation. In contrast, Iba1 expression remained unchanged or decreased, possibly reflecting limitations in detecting activated microglia. qPCR showed about 0.5-fold reduction in GFAP.  IBA1 and N-cadherin levels were similar across groups, while Beta-4 tubulin decreased progressively with increasing severity.

Conclusion:
In-utero VSGS placement is technically feasible and maintains CSF flow in some cases. Despite this, hydrocephalus led to ventriculomegaly, ependymal denudation, and corpus callosum disruption. Severity correlated with loss of cilia-related proteins and increased astrocyte activation, while microglial response appeared limited. Cerebral histopathology will be an important focus of study with subsequent fetal hydrocephalus treatments.