Intracisternal BioGlue injection in the fetal lamb: a novel model for creation of obstructive congenital hydrocephalus without additional chemically induced neuroinflammation

Abstract

OBJECTIVEThe authors hypothesized that new agents such as BioGlue would be as efficacious as kaolin in the induction of hydrocephalus in fetal sheep.METHODSThis study was performed in 34 fetal lambs randomly divided into 2 studies. In the first study, fetuses received kaolin, BioGlue (2.0 mL), or Onyx injected into the cisterna magna, or no injection (control group) between E85 and E90. In the second study, fetuses received 2.0-mL or 2.5-mL injections of BioGlue into the cisterna magna between E85 and E90. Fetuses were monitored using ultrasound to assess lateral ventricle size and progression of hydrocephalus. The fetuses were delivered (E120–E125) and euthanized for histological analysis. Selected brain sections were stained for ionized calcium binding adaptor 1 (Iba1) and glial fibrillary acidic protein (GFAP) to assess the presence and activation of microglia and astroglia, respectively. Statistical comparisons were performed with Student’s t-test for 2 determinations and ANOVA 1-way and 2-way repeated measures for multiple determinations.RESULTSAt 30 days after injection, the lateral ventricles were larger in all 3 groups that had undergone injection than in controls (mean diameter in controls 3.76 ± 0.05 mm, n = 5). However, dilatation was greater in the fetuses injected with 2 mL of BioGlue (11.34 ± 4.76 mm, n = 11) than in those injected with kaolin (6.4 ± 0.98 mm, n = 7) or Onyx (5.7 ± 0.31 mm, n = 6) (ANOVA, *p ≤ 0.0001). Fetuses injected with 2.0 mL or 2.5 mL of BioGlue showed the same ventricle dilatation but it appeared earlier (at 10 days postinjection) in those injected with 2.5 mL. The critical threshold of ventricle dilatation was 0.1 for all the groups, and only the BioGlue 2.0 mL and BioGlue 2.5 mL groups exceeded this critical value (at 30 days and 18 days after injection, respectively) (ANOVA, *p ≤ 0.0001). Moderate to severe hydrocephalus with corpus callosum disruption was observed in all experimental groups. All experimental groups showed ventriculomegaly with significant microgliosis and astrogliosis in the subventricular zone around the lateral ventricles. Only kaolin resulted in significant microgliosis in the fourth ventricle area (ANOVA, *p ≤ 0.005).CONCLUSIONSThe results of these studies demonstrate that BioGlue is more effective than Onyx or kaolin for inducing hydrocephalus in the fetal lamb and results in a volume-related response by obstructive space-occupancy without local neuroinflammatory reaction. This novel use of BioGlue generates a model with potential for new insights into hydrocephalus pathology and the development of therapeutics in obstructive hydrocephalus. In addition, this model allows for the study of acute and chronic obstructive hydrocephalus by using different BioGlue volumes for intracisternal injection.