Inhibition of Fibrinogen Reduces Brain Injury and Hydrocephalus in Premature Neonates with Intraventricular Hemorrhage

About This Grant

ABSTRACT The occurrence of intraventricular hemorrhage (IVH) leads to posthemorrhagic white matter injury (WMI) and hydrocephalus. No optimal therapeutic strategy exists to minimize these complications of IVH. The occurrence of IVH results in the formation of fibrin clots in the ventricle and extravasation of blood in the periventricular brain parenchyma. Fibrin accumulation in the brain triggers inflammation, promotes scarring, and inhibits the maturation of oligodendrocyte precursor cells, leading to WMI. Furthermore, fibrin clots block the intraventricular CSF pathways, meningeal lymphatics, villi, and perineural routes, contributing to both obstructive and communicating hydrocephalus. Therefore, the degradation or inhibition of fibrinogen is expected to alleviate both hydrocephalus and WMI in IVH. We will employ two strategies to minimize post-hemorrhagic hydrocephalus and WMI. First, we will administer a tissue-plasminogen activator (t-PA) to lyse the clot in the ventricles and in the routes of CSF exit to reduce hydrocephalus. Moreover, t-PA is a neuroprotectant and has been shown to protect against WMI in models of traumatic brain injury and hypoxia-ischemia. To enhance efficacy and minimize adverse effects, we will employ thrombus-targeted delivery of t-PA, encapsulating it in lipid nanovesicles for selective and gradual release at the site of the clot. Second, we will inhibit the binding of fibrinogen γ chain (γ377- 395) to CD11B-CD18 integrin receptor using either fibrin-derived γ377-395 peptide or 5B8 monoclonal antibody to prevent microglial activation, reduce inflammation, and thereby minimize WMI and hydrocephalus. Indeed, fibrin-targeted immunotherapy reduces inflammation, oxidative stress, and neurological dysfunction in animal models of several neurological diseases. Despite the powerful premises, the role of fibrinogen in IVH-induced brain injury remains obscure. We hypothesize that a) extravasation of fibrinogen in the brain parenchyma and formation of ventricular clots induce WMI and hydrocephalus and b) these pathologies can be rescued by administering t-PA nanovesicle or inhibiting fibrinogen γ chain (γ377-395). Our approach is to employ our IVH model in preterm (E29) rabbits, which recapitulates the post-hemorrhagic WMI and hydrocephalus observed in IVH survivors. In Aim 1, we will administer t-PA nano-vesicles in the ventricle and subarachnoid space and evaluate ventricle volume, inflammation, myelination, and motor behavior in t-PA vs. vehicle-treated animals. To elucidate the mechanisms, we will determine how t-PA treatment impacts microglial and oligodendrocyte transcriptome by performing RNAseq. In Aim 2, we will inhibit the fibrin γ chain by peptide or antibody and assess inflammation, transcriptomic changes in microglia, oligodendrocyte maturation, myelination, ventricle size, and neurobehavior in peptide- and antibody-treated kits compared to controls. We will also test if fibrin γ chain inhibition is mediated by CD11b/18>NADPH oxidase>ROS pathway. These studies will define the role of fibrin in inducing post-IVH WMI and hydrocephalus and hasten the development of new therapies for these disorders in IVH survivors.