Complement Inhibition Reduces Post-Hemorrhagic Hydrocephalus in Mouse Neonatal Germinal Matrix Hemorrhage

IntroductionGerminal 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 a novel mouse model of GMH and investigated the role of complement in PHH development.MethodsWe utilized a neonatal mouse model of GMH involving injection of collagenase into the subventricular zone of post-natal day four (P4) pups. Animals were randomized into four experimental arms: Naïve, sham injured, injured and vehicle (PBS) treated, and injured and CR2Crry-treated (a pan-complement inhibitor). Histopathologic and immunofluorescence analyses were performed at P14 with a focus on parameters of neuroinflammation and neuroprotection. Survival was monitored through day 45, prior to which cognitive and motor function was analyzed.ResultsThe complement inhibitor CR2Crry, which binds C3 complement activation products, localized specifically in the brain following systemic administration after GMH. Compared to vehicle treatment, 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. Progression to PHH and neuronal loss was linked to microglial phagocytosis of complement opsonized neurons, which was reversed with CR2Crry treatment. Complement inhibition also improved survival and weight gain, and improved motor performance and cognitive outcomes measured in adolescent GMH mice. ConclusionComplement plays an important role in the pathological sequelae of GMH. Complement inhibition represents a novel therapeutic approach to reduce disease progression in neonatal GMH and PHH, for which there is currently no treatment outside of surgical intervention.

White matter injury but not germinal matrix hemorrhage induces elevated osteopontin expression in human preterm brains

Osteopontin (OPN) is a matricellular protein that mediates various physiological functions and is implicated in neuroinflammation, myelination, and perinatal brain injury. However, its expression in association with brain injury in preterm infants is unexplored. Here we examined the expression of OPN in postmortem brains of preterm infants and explored how this expression is affected in brain injury. We analyzed brain sections from cases with white matter injury (WMI) and cases with germinal matrix hemorrhage (GMH) and compared them to control cases having no brain injury. WMI cases displayed moderate to severe tissue injury in the periventricular and deep white matter that was accompanied by an increase of microglia with amoeboid morphology. Apart from visible hemorrhage in the germinal matrix, GMH cases displayed diffuse white matter injury in the periventricular and deep white matter. In non-injured preterm brains, OPN was expressed at low levels in microglia, astrocytes, and oligodendrocytes. OPN expression was significantly increased in regions with white matter injury in both WMI cases and GMH cases. The main cellular source of OPN in white matter injury areas was amoeboid microglia, although a significant increase was also observed in astrocytes in WMI cases. OPN was not expressed in the germinal matrix of any case, regardless of whether there was hemorrhage. In conclusion, preterm brain injury induces elevated OPN expression in microglia and astrocytes, and this increase is found in sites closely related to injury in the white matter regions but not with the hemorrhage site in the germinal matrix. Thus, it appears that OPN takes part in the inflammatory process in white matter injury in preterm infants, and these findings facilitate our understanding of OPN’s role under both physiological and pathological conditions in the human brain that may lead to greater elucidation of disease mechanisms and potentially better treatment strategies.

Technical Nuances in Neuroendoscopic Lavage for Germinal Matrix Hemorrhage in Preterm Infants: Twenty Tips and Pearls after More than One Hundred Procedures

<b><i>Introduction:</i></b> Posthemorrhagic hydrocephalus in preterm infants is a serious entity related to high mortality and morbidity. Neuroendoscopic lavage (NEL) is a suitable alternative for the management of this pathology. However, as with every endoscopic technique, it requires some experience and several cases to master. <b><i>Methods:</i></b> We present a descriptive study of some technical nuances, tips, and tricks that have been learned in the last 8 years with over a hundred NELs performed in preterm infants. These variations are classified into 3 categories according to their temporal relationship with the surgical procedure: preoperative stage, intraoperative stage, and postoperative stage. We include a brief description of each one and the reasons why they are included in our current clinical practice. <b><i>Results:</i></b> Twenty tips and pearls were described in detail and are reported here. Preoperative, intraoperative, and postoperative variations were exposed and related to the most frequent complications of this procedure: infection, cerebrospinal fluid leak, and rebleeding. <b><i>Conclusions:</i></b> NEL is a useful technique for the management of germinal matrix hemorrhage in preterm infants. These technical nuances have improved the results of our technique and helped us to prevent complications related to the procedure.

A Model of Germinal Matrix Hemorrhage in Preterm Rat Pups

Germinal matrix hemorrhage (GMH) is a serious complication in extremely preterm infants associated with neurological deficits and mortality. The purpose of the present study was to develop and characterize a grade III and IV GMH model in postnatal day 5 (P5) rats, the equivalent of preterm human brain maturation. P5 Wistar rats were exposed to unilateral GMH through intracranial injection into the striatum close to the germinal matrix with 0.1, 0.2, or 0.3 U of collagenase VII. During 10 days following GMH induction, motor functions and body weight were assessed and brain tissue collected at P16. Animals were tested for anxiety, motor coordination and motor asymmetry on P22–26 and P36–40. Using immunohistochemical staining and neuropathological scoring we found that a collagenase dose of 0.3 U induced GMH. Neuropathological assessment revealed that the brain injury in the collagenase group was characterized by dilation of the ipsilateral ventricle combined with mild to severe cellular necrosis as well as mild to moderate atrophy at the levels of striatum and subcortical white matter, and to a lesser extent, hippocampus and cortex. Within 0.5 h post-collagenase injection there was clear bleeding at the site of injury, with progressive increase in iron and infiltration of neutrophils in the first 24 h, together with focal microglia activation. By P16, blood was no longer observed, although significant gray and white matter brain infarction persisted. Astrogliosis was also detected at this time-point. Animals exposed to GMH performed worse than controls in the negative geotaxis test and also opened their eyes with latency compared to control animals. At P40, GMH rats spent more time in the center of open field box and moved at higher speed compared to the controls, and continued to show ipsilateral injury in striatum and subcortical white matter. We have established a P5 rat model of collagenase-induced GMH for the study of preterm brain injury. Our results show that P5 rat pups exposed to GMH develop moderate brain injury affecting both gray and white matter associated with delayed eye opening and abnormal motor functions. These animals develop hyperactivity and show reduced anxiety in the juvenile stage.

NT-4 attenuates neuroinflammation via TrkB/PI3K/FoxO1 pathway after germinal matrix hemorrhage in neonatal rats

Background Neuroinflammation plays an important role in pathogenesis of germinal matrix hemorrhage (GMH). Neurotrophin-4 (NT-4) is a member of the neurotrophin family and interacts with the tropomyosin receptor kinase B (TrkB). NT-4 has been shown to confer neuroprotective effects following cerebral ischemia. We aimed to investigate the neuroprotective function of NT-4-TrkB signaling, as well as its downstream signaling cascade phosphatidylinositol-3-kinases (PI3K)/protein kinase B (Akt)/forkhead box protein O1 (FoxO1), following GMH in neonatal rats. Methods GMH was induced by intraparenchymal injection of bacterial collagenase (0.3 U) in P7 rat pups. A total of 163 pups were used in this study. Recombinant human NT-4 was administered intranasally at 1 h after the collagenase injection. The selective TrkB antagonist ANA-12, selective PI3K inhibitor LY294002, and FoxO1 activating CRISPR were administered intracerebroventricularly at 24 h prior to NT-4 treatment to investigate the underlying mechanism. Short-term and long-term neurobehavioral assessments, immunofluorescence staining, Nissl’s staining, and Western blot were performed. Results Expression of phosphorylated TrkB increased after GMH, reaching the peak level at day 3 after hemorrhage. TrkB receptors were observed on neurons, microglia, and astrocytes. The administration of rh-NT-4 induced phosphorylation of TrkB, expression of PI3K, and phosphorylation of Akt. Meanwhile, it decreased FoxO1 and IL-6 levels. Selective inhibition of TrkB/PI3K/Akt signaling in microglia increased the expression levels of FoxO1 and pro-inflammatory cytokines. FoxO1 activating CRISPR increased the expression of IL-6, suggesting that FoxO1 might be a potential inducer of pro-inflammatory factors. These results suggested that PI3K/Akt/FoxO1 signaling may be the downstream pathway of activation of TrkB. The rat pups treated with rh-NT-4 performed better than vehicle-treated animals in both short-term and long-term behavioral tests. Conclusion These data showed that rh-NT-4 reduced the expression levels of pro-inflammatory cytokines, improved neurological function, attenuated neuroinflammation, and thereby mitigated post-hemorrhagic hydrocephalus after GMH by TrkB/PI3K/Akt/FoxO1 pathway. These results indicated that rh-NT-4 could be a promising therapeutic strategy to ameliorate neuroinflammation and hydrocephalus after GMH or other similar brain injuries.

Rh-relaxin-2 Attenuates Degranulation of mast cells by Inhibiting NF-κB through PI3K-AKT/TNFAIP3 Pathway in an Experimental Germinal Matrix Hemorrhage Rat Model

Background: Mast cells play an important role in early immune reactions in the brain by inducing degranulation and releasing inflammatory mediators. Our aim of the study is to investigate the effects of rh-relaxin-2 on mast cells and the underlying mechanisms in a GMH rat model. Methods: One hundred and sixty-four P7 rat pups were subjected to germinal matrix hemorrhage (GMH) by an intraparenchymal injection of bacterial collagenase. Clodronate liposome was administered through intracerebroventricular (i.c.v.) injections 24 hours prior to GMH to inhibit microglia. Rh-relaxin-2 was administered intraperitoneally at 1 hour and 12 hours after GMH. Small interfering RNA of RXFP1 and PI3K inhibitor LY294002 were given by i.c.v. injections. Post-GMH evaluation included neurobehavioral function, Western blot analysis, immunofluorescence, Nissl staining, and Toluidine staining. Results: Our results demonstrated that endogenous relaxin-2 was downregulated and that RXFP1 level peaked on the first day after GMH. Administration of rh-relaxin-2 improved neurological functions, attenuated degranulation of mast cells and neuroinflammation, and ameliorated post-hemorrhagic hydrocephalus after GMH. These effects were associated with RXFP1 activation, increased expression of PI3K, phosphorylated AKT and TNFAIP3, and decreased levels of phosphorylated NF-κB, tryptase, chymase, IL-6 and TNF-α. However, knockdown of RXFP1 and PI3K abolished the protective effects of rh-relaxin-2. Conclusions: Our findings showed that rh-relaxin-2 attenuated degranulation of mast cells and neuroinflammation, improved neurological outcomes and ameliorated hydrocephalus after GMH through RXFP1/PI3K-AKT/TNFAIP3/NF-κB signaling pathway.