A Role of Complement in the Pathogenic Sequelae of Mouse Neonatal Germinal Matrix Hemorrhage

Abstract

Germinal matrix hemorrhage (GMH) is a devastating disease of infancy that results in intraventricular hemorrhage, post-hemorrhagic hydrocephalus (PHH), periventricular leukomalacia, and neurocognitive deficits. There are no curative treatments and limited surgical options. We developed and characterized a mouse model of GMH based on the injection of collagenase into the subventricular zone of post-natal pups and utilized the model to investigate the role of complement in PHH development. The site-targeted complement inhibitor CR2Crry, which binds deposited C3 complement activation products, localized specifically in the brain following its systemic administration after GMH. Compared to vehicle, CR2Crry treatment reduced PHH and lesion size, which was accompanied by decreased perilesional complement deposition, decreased astrocytosis and microgliosis, and the preservation of dendritic and neuronal density. Complement inhibition also improved survival and weight gain, and it improved motor performance and cognitive outcomes measured in adolescence. The progression to PHH, neuronal loss, and associated behavioral deficits was linked to the microglial phagocytosis of complement opsonized neurons, which was reversed with CR2Crry treatment. Thus, complement plays an important role in the pathological sequelae of GMH, and complement inhibition represents a novel therapeutic approach to reduce the disease progression of a condition for which there is currently no treatment outside of surgical intervention.

Rare variants in complement system genes associate with endothelial damage after pediatric allogeneic hematopoietic stem cell transplantation

“…Our patient with the MASP-1 variant Ala544Thr had severe and persistent diffuse gastrointestinal bleeding leading to ICU-admission twice and ending up being lethal. Massive haemorrhage is thought to be a possible trigger of complement activation ( 47 , 48 ) and activated complement could contribute to tissue damage seen at the site of the haemorrhage ( 49 , 50 ). We speculate that the MASP-1 variant rs1712360640 with severe GI-bleeding could lead to a more vigorous activation of the complement and coagulation cascade, leading to endothelium-related complications.…”

Complement Drives Chronic Inflammation and Progressive Hydrocephalus in Murine Neonatal Germinal Matrix Hemorrhage

“…In a previous study, we demonstrated that complement inhibition reduced C3-dependent microglial phagocytosis of neurons and reduced inflammation at early timepoints after GMH [ 29 ]. Here we have followed outcomes chronically and show a role for the terminal complement activation product, the MAC, in early GMH pathogenesis and which appears to impact chronic pathology.…”

“…Animal breeders and litters were randomly assigned to each of the three groups. A single individual performed all surgeries and treatments, and all GMH injuries were performed by guided injection of collagenase into the subventricular zone (SVZ) on postnatal day 4 (P4), as previously described [ 29 ]. Testing and scoring were blinded to group randomization for the duration of the study.…”

“…The complement inhibitory activity of the recombinant protein was verified using a zymosan assay, as previously described [ 30 , 54 ]. CR2-Crry treatment was carried out at 10 mg/kg, a dose previously optimized for adult brain injury [ 30 ] and as used by us previously in a GMH model [ 29 ]. IP treatments with CR2-Crry or PBS were performed at 1 h after GMH injury, then every 3 days until P13, then every 7 days until either P45 or P90.…”

“…Free Hb is further oxidized into met-Hemoglobin (metHb) which has been correlated with an increase in activation of proinflammatory mediators such as TNFα and TLR-4 [ 22 ]. In a therapeutic paradigm using the complement inhibitor CR2-Crry, we previously demonstrated that complement activation contributes to an acute/subacute proinflammatory response that leads to PHH following GMH [ 29 ]. CR2-Crry is a previously characterized inhibitor that binds at sites of C3 activation (C3d deposition) and inhibits the central C3 activation step of all complement pathways [ 30 ].…”