Posthemorrhagic ventricular dilation in the neonate: development and characterization of a rat model

The Role of Oxidative Stress in the Progression of Secondary Brain Injury Following Germinal Matrix Hemorrhage

Germinal matrix hemorrhage (GMH) can be a fatal condition responsible for the death of 1.7% of all neonates in the USA. The majority of GMH survivors develop long-term sequalae with debilitating comorbidities. Higher grade GMH is associated with higher mortality rates and higher prevalence of comorbidities. The pathophysiology of GMH can be broken down into two main titles: faulty hemodynamic autoregulation and structural weakness at the level of tissues and cells. Prematurity is the most significant risk factor for GMH, and it predisposes to both major pathophysiological mechanisms of the condition. Secondary brain injury is an important determinant of survival and comorbidities following GMH. Mechanisms of brain injury secondary to GMH include apoptosis, necrosis, neuroinflammation, and oxidative stress. This review will have a special focus on the mechanisms of oxidative stress following GMH, including but not limited to inflammation, mitochondrial reactive oxygen species, glutamate toxicity, and hemoglobin metabolic products. In addition, this review will explore treatment options of GMH, especially targeted therapy.

Posttraumatic hydrocephalus: Recent advances and new therapeutic strategies

Background

Hydrocephalus or ventriculomegaly is a condition brought on by an overabundance of cerebrospinal fluid (CSF) in the ventricular system. The major contributor to posttraumatic hydrocephalus (PTH) is traumatic brain injuries (TBIs), especially in individuals with occupations set in industrial settings. A variety of criteria have been employed for the diagnosis of PTH, including the combination of neurological symptoms like nerve deficits and headache, as well as an initial improvement followed by a worsened relapse of altered consciousness and neurological deterioration, which is detected by computed tomography-brain imaging that reveals gradual ventriculomegaly.

Aim

In this article, we discuss and summarize briefly the current understandings and advancements in the management of PTH.

Methods

The available literature for this review was searched on various bibliographic databases using an individually verified, prespecified approach. The level of evidence of the included studies was considered as per the Centre for Evidence-Based Medicine recommendations.

Results

The commonly practiced current treatment modality involves shunting CSF but is often associated with complications and recurrence. The lack of a definitive management strategy for PTH warrants the utilization of novel and innovative modalities such as stem cell transplantations and antioxidative stress therapies.

Conclusion

One of the worst complications of a TBI is PTH, which has a high morbidity and mortality rate. Even though there hasn't been a successful method in stopping PTH from happening, hemorrhage-derived blood, and its metabolic by-products, like iron, hemoglobin, free radicals, thrombin, and red blood cells, may be potential targets for PTH hindrance and management. Also, using stem cell transplantations in animal models and antioxidative stress therapies in future studies can lower PTH occurrence and improve its outcome. Moreover, the integration of clinical trials and theoretical knowledge should be encouraged in future research projects to establish effective and updated management guidelines for PTH.

Deferoxamine Prevents Neonatal Posthemorrhagic Hydrocephalus Through Choroid Plexus-Mediated Iron Clearance

Posthemorrhagic hydrocephalus occurs in up to 30% of infants with high-grade intraventricular hemorrhage and is associated with the worst neurocognitive outcomes in preterm infants. The mechanisms of posthemorrhagic hydrocephalus after intraventricular hemorrhage are unknown; however, CSF levels of iron metabolic pathway proteins including hemoglobin have been implicated in its pathogenesis. Here, we develop an animal model of intraventricular hemorrhage using intraventricular injection of hemoglobin at post-natal day 4 that results in acute and chronic hydrocephalus, pathologic choroid plexus iron accumulation, and subsequent choroid plexus injury at post-natal days 5, 7, and 15. This model also results in increased expression of aquaporin-1, Na+/K+/Cl- cotransporter 1, and Na+/K+/ATPase on the apical surface of the choroid plexus 24 h post-intraventricular hemorrhage. We use this model to evaluate a clinically relevant treatment strategy for the prevention of neurological sequelae after intraventricular hemorrhage using intraventricular administration of the iron chelator deferoxamine at the time of hemorrhage. Deferoxamine treatment prevented posthemorrhagic hydrocephalus for up to 11 days after intraventricular hemorrhage and prevented the development of sensorimotor gating deficits. In addition, deferoxamine treatment facilitated acute iron clearance through the choroid plexus and subsequently reduced choroid plexus iron levels at 24 h with reversal of hemoglobin-induced aquaporin-1 upregulation on the apical surface of the choroid plexus. Intraventricular administration of deferoxamine at the time of intraventricular hemorrhage may be a clinically relevant treatment strategy for preventing posthemorrhagic hydrocephalus and likely acts through promoting iron clearance through the choroid plexus to prevent hemoglobin-induced injury.

Stem cells for neonatal brain injury - Lessons from the bench

Neonatal brain injury resulting from various intractable disorders including intraventricular hemorrhage and hypoxic ischemic encephalopathy still remains a major cause of mortality and morbidities with few effective treatments. Recent preclinical research results showing the pleiotropic neuroprotective effects of stem cell therapy, specifically mesenchymal stem cells (MSCs), suggest that MSCs transplantation might be a promising new therapeutic modality for neuroprotection against the currently intractable and devastating neonatal brain injury with complex multifactorial etiology. This review summarizes recent advances in preclinical stem cell research for treating neonatal brain injury with a focus on the important issues including the mechanism of neuroprotection, and determining the ideal cell source, route, timing and dose of MSCs transplantation.

Impact of intraventricular hemorrhage symmetry on endoscopic third ventriculostomy with choroid plexus cauterization for posthemorrhagic hydrocephalus: an institutional experience of 50 cases

OBJECTIVE

The success rate of endoscopic third ventriculostomy with choroid plexus cauterization (ETV/CPC) in the management of posthemorrhagic hydrocephalus (PHH) following intraventricular hemorrhage (IVH) in infants is not well defined. Furthermore, parameters of IVH at initial presentation have not been tested for predictive associations of ETV/CPC success in this setting. The authors sought to summarize their institutional outcomes to identify possible predictors of ETV/CPC success within this niche.

METHODS

A retrospective review was conducted of all ETV/CPC procedures performed at the authors' institution for PHH between 2011 and 2021. Patients were screened against a set of selection criteria including follow-up time of at least 6 months. Associations with ETV/CPC failure were evaluated using regression and Kaplan-Meier analyses.

RESULTS

A total of 50 patients satisfied all criteria. There were 32 (64%) male and 18 (36%) female patients with a mean gestational birth age of 26 weeks. The presenting IVH was symmetric in 30 (60%) and asymmetric in 20 (40%) patients, and the maximum IVH grade was IV in 30 (60%) patients overall. Six months after the procedure, ETV/CPC success was seen in 18 (36%) patients and failure in 32 (64%) patients. The median overall follow-up was 42 months, at which point ETV/CPC success was observed in 11 (22%) patients and ETV/CPC failure in 39 (78%) patients. Regression analyses indicated that radiological IVH symmetry was a statistically significant predictor of ETV/CPC failure at 6 months (OR 3.46, p = 0.04) and overall (OR 5.33, p = 0.03). Overall rates of failure were 89% versus 62% (p = 0.02) when comparing symmetric versus asymmetric IVH patients, and time to failure occurred at median times of 1.4 versus 6.5 months (p = 0.03) after the initial procedure. Higher maximum IVH grade and younger age at initial ETV/CPC only trended toward increased failure rates. When the etiology component of the ETV Success Score was adjusted such that symmetric IVH was scored 0, the area under the curve for failure at 6 months increased from 0.58 to 0.69.

CONCLUSIONS

Overall, approximately 1 in 5 infants with PHH can expect to not require further intervention following ETV/CPC. The authors demonstrate that IVH symmetry is statistically predictive of ETV/CPC failure in this setting independent of all other parameters, where PHH infants with symmetric IVH are more likely to experience failure, and sooner, than PHH infants with asymmetric IVH. When discussing possible success rates of ETV/CPC for PHH, IVH symmetry should be considered.

Emerging therapies for brain recovery after IVH in neonates: Cord blood derived Mesenchymal Stem Cells (MSC) and Unrestricted Somatic Stem Cells (USSC)

In this report, we summarize evidence on mechanisms of injury after intraventricular hemorrhage resulting in post-hemorrhagic white matter injury and hydrocephalus and correlate that with the possibility of cellular therapy. We describe how two stem cell lines (MSC & USSC) acting in a paracrine fashion offer promise for attenuating the magnitude of injury in animal models and for improved functional recovery by: lowering the magnitude of apoptosis and neuronal cell death, reducing inflammation, and thus, mitigating white matter injury that culminates in improved motor and neurocognitive outcomes. Animal models of IVH are analyzed for their similarity to the human condition and we discuss merits of each approach. Studies on stem cell therapy for IVH in human neonates is described. Lastly, we offer suggestions on what future studies are needed to better understand mechanisms of injury and recovery and argue that human trials need to be expanded in parallel to animal research.

Adiponectin Ameliorates GMH-Induced Brain Injury by Regulating Microglia M1/M2 Polarization Via AdipoR1/APPL1/AMPK/PPARγ Signaling Pathway in Neonatal Rats

Adiponectin (APN), a fat-derived plasma hormone, is a classic anti-inflammatory agent. Multiple studies have demonstrated the beneficial role of APN in acute brain injury, but the effect of APN in germinal matrix hemorrhage (GMH) is unclear, and the underlying molecular mechanisms remain largely undefined. In the current study, we used a GMH rat model with rh-APN treatment, and we observed that APN demonstrated a protective effect on neurological function and an inhibitory effect on neuroinflammation after GMH. To further explore the underlying mechanisms of these effects, we found that the expression of Adiponectin receptor 1 (AdipoR1) primarily colocalized with microglia and neurons in the brain. Moreover, AdiopR1, but not AdipoR2, was largely increased in GMH rats. Meanwhile, further investigation showed that APN treatment promoted AdipoR1/APPL1-mediated AMPK phosphorylation, further increased peroxisome proliferator-activated receptor gamma (PPARγ) expression, and induced microglial M2 polarization to reduce the neuroinflammation and enhance hematoma resolution in GMH rats. Importantly, either knockdown of AdipoR1, APPL1, or LKB1, or specific inhibition of AMPK/PPARγ signaling in microglia abrogated the protective effect of APN after GMH in rats. In all, we propose that APN works as a potential therapeutic agent to ameliorate the inflammatory response following GMH by enhancing the M2 polarization of microglia via AdipoR1/APPL1/AMPK/PPARγ signaling pathway, ultimately attenuating inflammatory brain injury induced by hemorrhage.

Pericyte dynamics in the mouse germinal matrix angiogenesis

Germinal matrix-intraventricular hemorrhage (GM-IVH) is the most devastating neurological complication in premature infants. GM-IVH usually begins in the GM, a highly vascularized region of the developing brain where glial and neuronal precursors reside underneath the lateral ventricular ependyma. Previous studies using human fetal tissue have suggested increased angiogenesis and paucity of pericytes as key factors contributing to GM-IVH pathogenesis. Yet, despite its relevance, the mechanisms underlying the GM vasculature's susceptibility to hemorrhage remain poorly understood. To gain better understanding on the vascular dynamics of the GM, we performed a comprehensive analysis of the mouse GM vascular endothelium and pericytes during development. We hypothesize that vascular development of the mouse GM will provide a good model for studies of human GM vascularization and provide insights into the role of pericytes in GM-IVH pathogenesis. Our findings show that the mouse GM presents significantly greater vascular area and vascular branching compared to the developing cortex (CTX). Analysis of pericyte coverage showed abundance in PDGFRβ-positive and NG2-positive pericyte coverage in the GM similar to the developing CTX. However, we found a paucity in Desmin-positive pericyte coverage of the GM vasculature. Our results underscore the highly angiogenic nature of the GM and reveal that pericytes in the developing mouse GM exhibit distinct phenotypical and likely functional characteristics compared to other brain regions which might contribute to the high susceptibility of the GM vasculature to hemorrhage.

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

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.

Proteomics and functional study reveal kallikrein-6 enhances communicating hydrocephalus

Background

Communicating hydrocephalus (CH) is a common neurological disorder caused by a blockage of cerebrospinal fluid. In this study, we aimed to explore the potential molecular mechanism underlying CH development.

Methods

Quantitative proteomic analysis was performed to screen the differentially expressed proteins (DEPs) between patients with and without CH. A CH rat model was verified by Hoechst staining, and the co-localization of the target protein and neuron was detected using immunofluorescence staining. Loss-of-function experiments were performed to examine the effect of KLK6 on the synapse structure.

Results

A total of 11 DEPs were identified, and kallikrein 6 (KLK6) expression was found to be significantly upregulated in patients with CH compared with that in patients without CH. The CH rat model was successfully constructed, and KLK6 was found to be co-localized with neuronal nuclei in brain tissue. The expression level of IL-1β, TNF-α, and KLK6 in the CH group was higher than that in the control group. After knockdown of KLK6 expression using small-interfering RNA (siRNA), the expression levels of synapsin-1 and PSD95 in neuronal cells were increased, and the length, number, and structure of synapses were significantly improved. Following siRNA interference KLK6 expression, 5681 differentially expressed genes (DEGs) were identified in transcriptome profile. The upregulated DEGs of Appl2, Nav2, and Nrn1 may be involved in the recovery of synaptic structures after the interference of KLK6 expression.

Conclusions

Collectively, KLK6 participates in the development of CH and might provide a new target for CH treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12014-021-09335-9.

Intracerebral haemorrhage: from clinical settings to animal models

Spontaneous intracerebral haemorrhage (ICH) is a devastating type of stroke with high mortality and morbidity and for which no effective treatments are available to date. Much experimental and clinical research have been performed to explore its mechanisms regard the subsequent inflammatory cascade and to seek the potential therapeutic strategies. The aim of this review is to discuss insights from clinical settings that have led to the development of numerous animal models of ICH. Some of the current and future challenges for clinicians to understand ICH are also surveyed.

Germinal Matrix-Intraventricular Hemorrhage of the Preterm Newborn and Preclinical Models: Inflammatory Considerations

The germinal matrix-intraventricular hemorrhage (GM-IVH) is one of the most important complications of the preterm newborn. Since these children are born at a critical time in brain development, they can develop short and long term neurological, sensory, cognitive and motor disabilities depending on the severity of the GM-IVH. In addition, hemorrhage triggers a microglia-mediated inflammatory response that damages the tissue adjacent to the injury. Nevertheless, a neuroprotective and neuroreparative role of the microglia has also been described, suggesting that neonatal microglia may have unique functions. While the implication of the inflammatory process in GM-IVH is well established, the difficulty to access a very delicate population has lead to the development of animal models that resemble the pathological features of GM-IVH. Genetically modified models and lesions induced by local administration of glycerol, collagenase or blood have been used to study associated inflammatory mechanisms as well as therapeutic targets. In the present study we review the GM-IVH complications, with special interest in inflammatory response and the role of microglia, both in patients and animal models, and we analyze specific proteins and cytokines that are currently under study as feasible predictors of GM-IVH evolution and prognosis.

Impaired hippocampal development and outcomes in very preterm infants with perinatal brain injury

Preterm infants are at high risk for brain injury during the perinatal period. Intraventricular hemorrhage and periventricular leukomalacia, the two most common patterns of brain injury in prematurely-born children, are associated with poor neurodevelopmental outcomes. The hippocampus is known to be critical for learning and memory; however, it remains unknown how these forms of brain injury affect hippocampal growth and how the resulting alterations in hippocampal development relate to childhood outcomes. To investigate these relationships, hippocampal segmentations were performed on term equivalent MRI scans from 55 full-term infants, 85 very preterm infants (born ≤32 weeks gestation) with no to mild brain injury and 73 very preterm infants with brain injury (e.g., grade III/IV intraventricular hemorrhage, post-hemorrhagic hydrocephalus, cystic periventricular leukomalacia). Infants then underwent standardized neurodevelopmental testing using the Bayley Scales of Infant and Toddler Development, 3rd edition at age 2 years, corrected for prematurity. To delineate the effects of brain injury on early hippocampal development, hippocampal volumes were compared across groups and associations between neonatal volumes and neurodevelopmental outcomes at age 2 years were explored. Very preterm infants with brain injury had smaller hippocampal volumes at term equivalent age compared to term and very preterm infants with no to mild injury, with the smallest hippocampi among those with grade III/IV intraventricular hemorrhage and post-hemorrhagic hydrocephalus. Further, larger ventricle size was associated with smaller hippocampal size. Smaller hippocampal volumes were related to worse motor performance at age 2 years across all groups. In addition, smaller hippocampal volumes in infants with brain injury were correlated with impaired cognitive scores at age 2 years, a relationship specific to this group. Consistent with our preclinical findings, these findings demonstrate that perinatal brain injury is associated with hippocampal size in preterm infants, with smaller volumes related to domain-specific neurodevelopmental impairments in this high-risk clinical population.

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Perinatal brain injury is related to smaller hippocampal volumes in preterm infants

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Infants with high-grade intraventricular hemorrhage have smallest hippocampi

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Larger ventricular size is related to smaller hippocampal volumes in hydrocephalus

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Smaller hippocampi are related to worse cognitive outcomes in brain injured infants

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Smaller hippocampal volumes associated with worse motor performance across groups

Brain endothelial cell junctions after cerebral hemorrhage: Changes, mechanisms and therapeutic targets

Vascular disruption is the underlying cause of cerebral hemorrhage, including intracerebral, subarachnoid and intraventricular hemorrhage. The disease etiology also involves cerebral hemorrhage-induced blood-brain barrier (BBB) disruption, which contributes an important component to brain injury after the initial cerebral hemorrhage. BBB loss drives vasogenic edema, allows leukocyte extravasation and may lead to the entry of potentially neurotoxic and vasoactive compounds into brain. This review summarizes current information on changes in brain endothelial junction proteins in response to cerebral hemorrhage (and clot-related factors), the mechanisms underlying junction modification and potential therapeutic targets to limit BBB disruption and, potentially, hemorrhage occurrence. It also addresses advances in the tools that are now available for assessing changes in junctions after cerebral hemorrhage and the potential importance of such junction changes. Recent studies suggest post-translational modification, conformational change and intracellular trafficking of junctional proteins may alter barrier properties. Understanding how cerebral hemorrhage alters BBB properties beyond changes in tight junction protein loss may provide important therapeutic insights to prevent BBB dysfunction and restore normal function.

Challenges for intraventricular hemorrhage research and emerging therapeutic targets

INTRODUCTION

Intraventricular hemorrhage (IVH) affects both premature infants and adults. In both demographics, it has high mortality and morbidity. There is no FDA approved therapy that improves neurological outcome in either population highlighting the need for additional focus on therapeutic targets and treatments emerging from preclinical studies. Areas covered: IVH induces both initial injury linked to the physical effects of the blood (mass effect) and secondary injury linked to the brain response to the hemorrhage. Preclinical studies have identified multiple secondary injury mechanisms following IVH, and particularly the role of blood components (e.g. hemoglobin, iron, thrombin). This review, with an emphasis on pre-clinical IVH research, highlights therapeutic targets and treatments that may be of use in prevention, acute care, or repair of damage. Expert opinion: An IVH is a potentially devastating event. Progress has been made in elucidating injury mechanisms, but this has still to translate to the clinic. Some pathways involved in injury also have beneficial effects (coagulation cascade/inflammation). A greater understanding of the downstream pathways involved in those pathways may allow therapeutic development. Iron chelation (deferoxamine) is in clinical trial for intracerebral hemorrhage and preclinical data suggest it may be a potential treatment for IVH.

Mesenchymal Stem Cells: The Magic Cure for Intraventricular Hemorrhage?

Severe intraventricular hemorrhage (IVH) remains a major cause of mortality and long-term neurologic morbidities in premature infants, despite recent advances in neonatal intensive care medicine. Several preclinical studies have demonstrated the beneficial effects of mesenchymal stem cell (MSC) transplantation in attenuating brain injuries resulting from severe IVH. Because there currently exists no effective intervention for severe IVH, the therapeutic potential of MSC transplantation in this intractable and devastating disease is creating excitement in this field. This review summarizes recent progress in stem cell research for treating neonatal brain injury due to severe IVH, with a particular focus on preclinical data concerning important issues, such as mechanism of protective action and determining optimal source, route, timing, and dose of MSC transplantation, and on the translation of these preclinical study results to a clinical trial.

Combination of endogenous neural stem cell mobilization and lithium chloride treatment for hydrocephalus following intraventricular hemorrhage

As there are multiple factors causing hydrocephalus subsequent to intraventricular hemorrhage (IVH), it is difficult to achieve the best treatment effect using a single drug alone. In the present study, the protective effect of combination treatment with granulocyte-colony stimulating factor (G-CSF) and lithium chloride against hydrocephalus after IVH was investigated. A total of 130 adult male Sprague-Dawley rats were divided into five groups, including the IVH control, G-CSF treatment, lithium chloride treatment, combination treatment and sham surgery groups. An IVH rat model was established in order to examine the effect of combination treatment on hydrocephalus incidence. A TUNEL assay was performed to detect neuronal apoptosis in the five groups. In addition, the protein expression levels of B-cell lymphoma 2 (Bcl-2) and Bcl-2-associated X protein (Bax) were detected by western blot analysis. The differentiation of nerve cells in the brain tissue obtained from the five rat groups was also determined with double immunofluorescence staining. The results demonstrated that administration of G-CSF or lithium chloride alone was able to only partly relieve the incidence of hydrocephalus after IVH. By contrast, combination treatment with G-CSF and lithium chloride significantly attenuated the development of hydrocephalus following IVH. TUNEL assay showed that neuronal apoptosis was significantly reduced by the combination treatment with G-CSF and lithium chloride. Furthermore, the expression of Bcl-2 was upregulated, whereas Bax expression was downregulated in the combination treatment group. The results also detected the highest expression of BrdU/GFAP, BrdU/NeuN and BrdU/PSA-NCAM in the combination treatment group. In conclusion, the combination of endogenous neural stem cell mobilization (using G-CSF) and lithium chloride treatment resulted in highly reduced incidence of hydrocephalus after IVH by inhibiting neuronal apoptosis.

Role of hemoglobin and iron in hydrocephalus after neonatal intraventricular hemorrhage

BACKGROUND

Neonatal germinal matrix hemorrhage/intraventricular hemorrhage is common and often results in hydrocephalus. The pathogenesis of posthemorrhagic hydrocephalus is not fully understood.

OBJECTIVE

To explore the potential role of hemoglobin and iron released after hemorrhage.

METHODS

Artificial cerebrospinal fluid (aCSF), hemoglobin, or iron was injected into the right lateral ventricle of postnatal day-7 Sprague Dawley rats. Ventricle size, heme oxygenase-1 (HO-1) expression, and the presence of iron were evaluated 24 and 72 hours after injection. A subset of animals was treated with an iron chelator (deferoxamine) or vehicle for 24 hours after hemoglobin injection, and ventricle size and cell death were evaluated.

RESULTS

Intraventricular injection of hemoglobin and iron resulted in ventricular enlargement at 24 hours compared with the injection of aCSF. Protoporphyrin IX, the iron-deficient immediate heme precursor, did not result in ventricular enlargement after injection into the ventricle. HO-1, the enzyme that releases iron from heme, was increased in the hippocampus and cortex of hemoglobin-injected animals at 24 hours compared with aCSF-injected controls. Treatment with an iron chelator, deferoxamine, decreased hemoglobin-induced ventricular enlargement and cell death.

CONCLUSION

Intraventricular injection of hemoglobin and iron can induce hydrocephalus. Treatment with an iron chelator reduced hemoglobin-induced ventricular enlargement. This has implications for the pathogenesis and treatment of posthemorrhagic hydrocephalus.

ABBREVIATIONS

aCSF, artificial cerebrospinal fluidDAB, 3,3'-diaminobenzidine-4HClGMH-IVH, germinal matrix hemorrhage/intraventricular hemorrhageHO-1, heme oxygenase-1ICH, intracerebral hemorrhagePBS, phosphate-buffered salineSVZ, subventricular zoneTBST, tris-buffered saline with Tween 20.

Mesenchymal stem cells transplantation for neuroprotection in preterm infants with severe intraventricular hemorrhage

Severe intraventricular hemorrhaging (IVH) in premature infants and subsequent posthemorrhagic hydrocephalus (PHH) causes significant mortality and life-long neurological complications, including seizures, cerebral palsy, and developmental retardation. However, there are currently no effective therapies for neonatal IVH. The pathogenesis of PHH has been mainly explained by inflammation within the subarachnoid spaces due to the hemolysis of extravasated blood after IVH. Obliterative arachnoiditis, induced by inflammatory responses, impairs cerebrospinal fluid (CSF) resorption and subsequently leads to the development of PHH with ensuing brain damage. Increasing evidence has demonstrated potent immunomodulating abilities of mesenchymal stem cells (MSCs) in various brain injury models. Recent reports of MSC transplantation in an IVH model of newborn rats demonstrated that intraventricular transplantation of MSCs downregulated the inflammatory cytokines in CSF and attenuated progressive PHH. In addition, MSC transplantation mitigated the brain damages that ensue after IVH and PHH, including reactive gliosis, cell death, delayed myelination, and impaired behavioral functions. These findings suggest that MSCs are promising therapeutic agents for neuroprotection in preterm infants with severe IVH.

Perinatal biomarkers in prematurity: early identification of neurologic injury

Over the past few decades, biomarkers have become increasingly utilized as non-invasive tools in the early diagnosis and management of various clinical conditions. In perinatal medicine, the improved survival of extremely premature infants who are at high risk for adverse neurologic outcomes has increased the demand for the discovery of biomarkers in detecting and predicting the prognosis of infants with neonatal brain injury. By enabling the clinician to recognize potential brain damage early, biomarkers could allow clinicians to intervene at the early stages of disease, and to monitor the efficacy of those interventions. This review will first examine the potential perinatal biomarkers for neurologic complications of prematurity, specifically, intraventricular hemorrhage (IVH), periventricular leukomalacia (PVL) and posthemorrhagic hydrocephalus (PHH). It will also evaluate knowledge gained from animal models regarding the pathogenesis of perinatal brain injury in prematurity.

Structure and function of the ependymal barrier and diseases associated with ependyma disruption

The neuroepithelium is a germinal epithelium containing progenitor cells that produce almost all of the central nervous system cells, including the ependyma. The neuroepithelium and ependyma constitute barriers containing polarized cells covering the embryonic or mature brain ventricles, respectively; therefore, they separate the cerebrospinal fluid that fills cavities from the developing or mature brain parenchyma. As barriers, the neuroepithelium and ependyma play key roles in the central nervous system development processes and physiology. These roles depend on mechanisms related to cell polarity, sensory primary cilia, motile cilia, tight junctions, adherens junctions and gap junctions, machinery for endocytosis and molecule secretion, and water channels. Here, the role of both barriers related to the development of diseases, such as neural tube defects, ciliary dyskinesia, and hydrocephalus, is reviewed.

Mechanisms of hydrocephalus after neonatal and adult intraventricular hemorrhage

Intraventricular hemorrhage (IVH) is a cause of significant morbidity and mortality and is an independent predictor of a worse outcome in intracerebral hemorrhage (ICH) and germinal matrix hemorrhage (GMH). IVH may result in both injuries to the brain as well as hydrocephalus. This paper reviews evidence on the mechanisms and potential treatments for IVH-induced hydrocephalus. One frequently cited theory to explain hydrocephalus after IVH involves obliteration of the arachnoid villi by microthrombi with subsequent inflammation and fibrosis causing CSF outflow obstruction. Although there is some evidence to support this theory, there may be other mechanisms involved, which contribute to the development of hydrocephalus. It is also unclear whether the causes of acute and chronic hydrocephalus after hemorrhage occur via different mechanisms; mechanical obstruction by blood in the former, and inflammation and fibrosis in the latter. Management of IVH and strategies for prevention of brain injury and hydrocephalus are areas requiring further study. A better understanding of the pathogenesis of hydrocephalus after IVH, may lead to improved strategies to prevent and treat post-hemorrhagic hydrocephalus.

Systemic inflammation, intraventricular hemorrhage, and white matter injury

To see if the systemic inflammation profile of 123 infants born before the 28th week of gestation who had intraventricular hemorrhage without white matter injury differed from that of 68 peers who had both lesions, we compared both groups to 677 peers who had neither. Cranial ultrasound scans were read independently by multiple readers until concordance. The concentrations of 25 proteins were measured with multiplex arrays using an electrochemiluminescence system. Infants who had both hemorrhage and white matter injury were more likely than others to have elevated concentrations of C-reactive protein and interleukin 8 on days 1, 7, and 14, and elevated concentrations of serum amyloid A and tumor necrosis factor-α on 2 of these days. Intraventricular hemorrhage should probably be viewed as 2 entities: hemorrhage alone and hemorrhage with white matter injury. Each entity is associated with inflammation, but the combination has a stronger inflammatory signal than hemorrhage alone.

Mesenchymal stem cells prevent hydrocephalus after severe intraventricular hemorrhage

BACKGROUND AND PURPOSE

Severe intraventricular hemorrhage (IVH) in premature infants and the ensuing posthemorrhagic hydrocephalus cause significant mortality and neurological disabilities, and there are currently no effective therapies. This study determined whether intraventricular transplantation of human umbilical cord blood-derived mesenchymal stem cells prevents posthemorrhagic hydrocephalus development and attenuates brain damage after severe IVH in newborn rats.

METHODS

To induce severe IVH, 100 μL of blood was injected into each lateral ventricle of postnatal day 4 (P4) Sprague-Dawley rats. Human umbilical cord blood-derived mesenchymal stem cells or fibroblasts (1 × 10(5)) were transplanted intraventricularly under stereotaxic guidance at P6. Serial brain MRI and behavioral function tests, such as the negative geotaxis test and rotarod test, were performed. At P32, brain tissue and cerebrospinal fluid were obtained for histological and biochemical analyses.

RESULTS

Intraventricular transplantation of umbilical cord blood-derived mesenchymal stem cells, but not fibroblasts, prevented posthemorrhagic hydrocephalus development and significantly attenuated impairment on behavioral tests; the increased terminal deoxynycleotidyltransferase-mediated deoxyuridine triphosphate nick end labeling-positive cells; increased expression of inflammatory cytokines, such as interleukin-1α, interleukin-1β, interleukin-6, and tumor necrosis factor-α; increased astrogliosis; and reduced corpus callosal thickness and myelin basic protein expression after inducing severe IVH.

CONCLUSIONS

Intraventricular transplantation of umbilical cord blood-derived mesenchymal stem cells significantly attenuated the posthemorrhagic hydrocephalus and brain injury after IVH. This neuroprotective mechanism appears to be mediated by the anti-inflammatory effects of these cells.

Neonatal seizures: controversies and challenges in translating new therapies from the lab to the isolette

Neonatal seizures have unique properties that have proved challenging for both clinicians and basic science researchers. Clinical therapies aimed at neonatal seizures have proven only partially effective and new therapies are slow to develop. This article will discuss neonatal seizures within the framework of the barriers that exist to the development of new therapies, and the challenges inherent in bringing new therapies from the bench to the bedside. With the European Union and USA creating national collaborative project infrastructure, improved collaborative resources should advance clinical research on urgently needed new therapies for this disorder.

Rodent neonatal germinal matrix hemorrhage mimics the human brain injury, neurological consequences, and post-hemorrhagic hydrocephalus

Germinal matrix hemorrhage (GMH) is the most common neurological disease of premature newborns. GMH causes neurological sequelae such as cerebral palsy, post-hemorrhagic hydrocephalus, and mental retardation. Despite this, there is no standardized animal model of spontaneous GMH using newborn rats to depict the condition. We asked whether stereotactic injection of collagenase type VII (0.3 U) into the ganglionic eminence of neonatal rats would reproduce the acute brain injury, gliosis, hydrocephalus, periventricular leukomalacia, and attendant neurological consequences found in humans. To test this hypothesis, we used our neonatal rat model of collagenase-induced GMH in P7 pups, and found that the levels of free-radical adducts (nitrotyrosine and 4-hyroxynonenal), proliferation (mammalian target of rapamycin), inflammation (COX-2), blood components (hemoglobin and thrombin), and gliosis (vitronectin and GFAP) were higher in the forebrain of GMH pups, than in controls. Neurobehavioral testing showed that pups with GMH had developmental delay, and the juvenile animals had significant cognitive and motor disability, suggesting clinical relevance of the model. There was also evidence of white-matter reduction, ventricular dilation, and brain atrophy in the GMH animals. This study highlights an instructive animal model of the neurological consequences after germinal matrix hemorrhage, with evidence of brain injuries that can be used to evaluate strategies in the prevention and treatment of post-hemorrhagic complications.

High-frequency ultrasound in the evaluation of cerebral intraventricular haemorrhage in preterm rabbit pups

Cerebral intraventricular haemorrhage (IVH) is the most common cause of severe neurologic impairment following preterm birth in human infants. Ideally, an animal model for cerebral IVH should allow for reliable noninvasive evaluation of haemorrhagic extension and of subsequent development of posthaemorrhagic ventricular dilatation (PHVD). The aim of this study was to evaluate the use of high-frequency ultrasound (HFU) in premature rabbit pups with cerebral IVH induced by IP glycerol injection. Serial examinations using HFU enabled an accurate description of haemorrhagic extension and measurement of progressive PHVD over 72 h. The coefficient of variation for inter- and intraobserver variability in two measurements of ventricular size was less than 8.8% and 9.3%, respectively. Repeated ultrasound-guided intraventricular injection and sampling could be performed in vivo excluding requirement of stereotactic procedures and sedation. Application of HFU is a powerful tool for the evaluation of mechanisms involved in cerebral IVH and PHVD in the preterm rabbit pup model.

Lysophosphatidic acid signaling may initiate fetal hydrocephalus

Fetal hydrocephalus (FH), characterized by the accumulation of cerebrospinal fluid, an enlarged head, and neurological dysfunction, is one of the most common neurological disorders of newborns. Although the etiology of FH remains unclear, it is associated with intracranial hemorrhage. Here, we report that lysophosphatidic acid (LPA), a blood-borne lipid that activates signaling through heterotrimeric guanosine 5'-triphosphate-binding protein (G protein)-coupled receptors, provides a molecular explanation for FH associated with hemorrhage. A mouse model of intracranial hemorrhage in which the brains of mouse embryos were exposed to blood or LPA resulted in development of FH. FH development was dependent on the expression of the LPA(1) receptor by neural progenitor cells. Administration of an LPA(1) receptor antagonist blocked development of FH. These findings implicate the LPA signaling pathway in the etiology of FH and suggest new potential targets for developing new treatments for FH.

Neonatal rat model of intraventricular haemorrhage and post-haemorrhagic ventricular dilatation with long-term survival into adulthood

AIMS

post-haemorrhagic ventricular dilatation (PHVD) is a significant problem in neonatal care, with sequelae extending beyond childhood. Its management is important in determining outcome. Although rodent hydrocephalus models have been developed, PHVD, as a specific entity with a distinct pathophysiology, has not been studied in a small animal model surviving to adulthood. Our objective is to evaluate survival, to adulthood, in our immature (7-day-old, P7) neonatal rat model, and to analyse early motor reflexes and fine motor and cognitive function, and neuropathology, at 8-12 weeks.

METHODS

sixty-six rats underwent sequential bilateral stereotactic intraventricular haemorrhage (IVH); 36 more acted as controls. Staircase and radial maze evaluations were carried out at 7-11 weeks; animals were sacrificed at 12 weeks. Post mortem ventricular size and corpus callosum thickness were determined.

RESULTS

seventy-six per cent of IVH animals developed PHVD; median (interquartile range) composite ventricular area was 3.46 mm(2) (2.32-5.24). Sixteen (24%) animals demonstrated severe ventricular dilatation (area > 5 mm(2) ). IVH animals failed to improve on the negative geotaxis test at 2 weeks. The staircase test did not identify any significant difference. On the radial maze, animals with severe PHVD made more reference errors. Histopathology confirmed PHVD, ependymal disruption and periventricular white matter injury. Median anterior corpus callosum thickness was significantly lower in IVH animals (0.35 mm) than in those not undergoing IVH (0.43 mm).

CONCLUSION

our P7 neonatal rat IVH model is suitable for long-term survival and replicates many of the morphological and some of the behavioural features seen in human PHVD.

Decorin and colchicine as potential treatments for post-haemorrhagic ventricular dilatation in a neonatal rat model

BACKGROUND

Post-haemorrhagic ventricular dilatation (PHVD) after intraventricular haemorrhage (IVH) remains a significant problem in preterm infants. Due to serious disadvantages of ventriculoperitoneal shunt dependence, there is an urgent need for non-surgical interventions. Considerable experimental and clinical evidence implicates transforming growth factor β (TGFβ) in the pathogenesis of PHVD. Colchicine and decorin are both compounds with anti-TGFβ properties. The former downregulates TGFβ production and is in clinical use for another fibrotic disease, and the latter inactivates TGFβ.

OBJECTIVES

We hypothesized that administration of decorin or colchicine, which both have anti-TGFβ properties, would reduce ventricular dilatation in a model of PHVD.

METHODS

142 rat pups underwent intraventricular blood injection on postnatal days (PN) 7 and 8. Sixty-nine pups were randomized to colchicine 20 and 50 μg/kg/day or water by gavage for 13 days. Seventy were randomized to decorin 4 mg/kg or saline by intraventricular injection on PN8 and PN13. At PN21, the ventricular area was measured on coronal brain sections. Negative geotaxis was tested at PN14 in controls and in the decorin study group.

RESULTS

Ventricular size was not different between animals receiving either drug or water/saline. Intraventricular blood impaired neuromotor performance, but decorin had no effect.

CONCLUSION

Two drugs that block TGFβ by different mechanisms do not reduce ventricular dilatation in this model. Together with our previous work on losartan and pirfenidone, we conclude that blocking TGFβ alone does not prevent the development of PHVD.

Changes in neural dendrites and synapses in rat somatosensory cortex following neonatal post-hemorrhagic hydrocephalus

Neonatal post-hemorrhagic hydrocephalus is associated with cognitive decline and a serious deterioration in the patient's quality of life. The underlying impairments to neurons are not well understood. Here, we used the method described by Cherian et al. to construct a model of hydrocephalus after intra-ventricular hemorrhage and then observed the subsequent pathological changes in the morphology of neurons labeled by enhanced green fluorescent proteins (EGFP) using the in utero electroporation technique. Injection of venous blood into the lateral ventricles of 7-day-old rats in the operation group caused marked enlargement of the ventricles in 60% (9/15) of the rats after 2 weeks and in 53.3% (8/15) of the rats after 3 weeks. Compared with the control group, the length of the neural dendrites in the somatosensory cortex was shortened and the number of both neuron dendrite branches and synapses was significantly decreased. There was no evidence of cerebral cortical neuron death as shown by positive EGFP cell counting which suggest that neurological dysfunction after intra-ventricular hemorrhage-induced hydrocephalus may be related to the shortening of neural dendrites and the decreased number of synapses in somatosensory cortex and thus provides a possible neurological cause for hydrocephalus-induced cognitive decline and motor dysfunction.

Mechanisms of injury to white matter adjacent to a large intraventricular hemorrhage in the preterm brain

The purpose of this article is to investigate the hyperechoic lesion seen adjacent to a lateral ventricle that contains blood but is not distended. The literature on ependymal barrier dysfunction was reviewed in search of mechanisms of injury to the white matter adjacent to an intraventricular hemorrhage. The clinical literature on the clinical diagnosis of periventricular hemorrhagic infarction was also reviewed to find out how frequently this diagnosis was made. Support was found for the possibility that the ventricular wall does not always function as an efficient barrier, allowing ventricular contents to gain access to the white matter where they cause damage. Hemorrhagic infarction may not be the only or the most frequent mechanism of white matter damage adjacent to a large intraventricular hemorrhage.

Cerebrospinal fluid drainage in posthaemorrhagic ventricular dilatation leads to improvement in amplitude-integrated electroencephalographic activity

AIM

Progressive posthaemorrhagic ventricular dilatation (PHVD) may induce abnormal amplitude-integrated electroencephalographic (aEEG) activity prior to clinical deterioration or significant cerebral ultrasound changes. These abnormalities might be ameliorated with cerebrospinal fluid (CSF) drainage. The aims of this study were to investigate the occurrence of aEEG-abnormalities with progressive PHVD in relation to clinical and cerebral ultrasound changes and to evaluate whether CSF drainage results in aEEG improvement.

METHODS

aEEG and cerebral ultrasound scans were performed in 12 infants with PHVD, before and after CSF drainage, until normalization of aEEG occurred.

RESULTS

aEEG was abnormal with progressive PHVD in all patients. Concurrently, 60% of the patients were clinically stable without deterioration in ultrasonographic cerebral abnormalities. Post drainage, continuous pattern was restored in all but one patient, whereas the frequency of discontinuous pattern decreased in nine patients and burst-suppression pattern decreased in all but one patient. Low-voltage pattern was only observed in one patient who suffered severe grade IV IVH and died one week after EVD placement. Sleep-wake cycling matured in 75%.

CONCLUSION

These findings demonstrate the impact of CSF drainage on compromised aEEG-activity associated with PHVD. aEEG changes indicative of impaired cerebral function were apparent before clinical deterioration or major ultrasound changes. These changes were reversible with CSF drainage. aEEG should therefore be used in addition to clinical observation and ultrasound when monitoring PHVD.

A neonatal piglet model of intraventricular hemorrhage and posthemorrhagic ventricular dilation

OBJECT

The combination of intraventricular hemorrhage (IVH) and posthemorrhagic ventricular dilation (PHVD) remains an important cause of disability in children surviving prematurity. Currently, there is no clear agreement on the management of neonatal IVH, apart from the eventual insertion of a shunt to control PHVD. Cerebrospinal fluid (CSF) shunts are associated with a relatively high complication rate in this population. The development of new treatment options requires greater understanding of the pathophysiological mechanisms of IVH and PHVD, as well as an opportunity to monitor closely their effects on the immature brain. The authors have developed a neonatal large animal model of IVH with long-term survival, allowing the full development of PHVD.

METHODS

Fourteen piglets that were 3 to 24 hours old were randomized to receive slow injections of autologous blood, autologous blood with elevated hematocrit, or artificial CSF after induction of general anesthesia. A fourth group served as controls. All animals underwent surgery to form an artificial fontanelle at the bregma. Physiological parameters, including intracranial pressure and electroencephalography, were monitored during injection.

RESULTS

Serial cranial ultrasonography studies performed during the 23- to 44-day survival period demonstrated progressive ventricular dilation in the animals injected with blood. Ventricular volumes, measured with image analysis software, confirmed the highest dilation after injection of blood with an elevated hematocrit. Histological evaluation showed fibrosis in the basal subarachnoid space of hydrocephalic piglets.

CONCLUSIONS

This piglet model closely replicates human neonatal IVH and PHVD. It allows detailed physiological and ultrasonographic monitoring over a prolonged survival period. It is suitable for evaluation of noninvasive as well as surgical options in the management of IVH and PHVD.

Development of amplitude-integrated electroencephalography and interburst interval in the rat

Continuous monitoring of electrocortical brain activity with amplitude-integrated electroencephalography (aEEG) is important in neonatology. aEEG is affected by, for example, maturity, encephalopathy, and drugs. Neonatal research uses rat pups of different ages. Postnatal day (P) 7 rats are suggested to be equivalent neurodevelopmentally to near-term infants. We hypothesized that electroencephalography (EEG) and aEEG in P1-P21 rats follow the same developmental pattern with respect to background activity and the longest interburst interval (IBI) as that seen in infants from 23-wk gestational age (GA) to post-term. We examined aEEG and EEG on 49, unsedated rat pups with two clinical monitors. aEEG traces were analyzed for lower and upper margin amplitude, bandwidth and the five longest IBI in each trace were measured from the raw EEG. The median longest IBI decreased linearly with age by 5.24 s/d on average. The lower border of the aEEG trace was <5 microV until P7 and rose exponentially reaching 10 microV by P12. This correlated strongly with the decrease in IBI; both reflect increased continuity of brain activity with postnatal age. Based on aEEG trace analysis, the rat aEEG pattern at P1 corresponds to human aEEG at 23-wk gestation; P7 corresponds to 30-32 wk and P10 to 40-42 wk.

Do drugs that block transforming growth factor beta reduce posthaemorrhagic ventricular dilatation in a neonatal rat model?

AIM

Posthaemorrhagic ventricular dilatation (PHVD) after intraventricular haemorrhage (IVH) remains a significant problem in preterm infants. No treatment has reduced the need for cerebrospinal fluid (CSF) diversion. Considerable evidence implicates transforming growth factor-beta (TGF-beta) in the pathogenesis of PHVD. Pirfenidone and losartan reduce TGF-beta expression and decrease postinflammatory fibrosis in the lungs, kidneys, heart and liver. They have excellent CSF and brain penetration. We hypothesized that administration of pirfenidone or losartan would reduce ventricular dilatation.

METHODS

Ninety-two rat pups underwent intraventricular blood injection on postnatal days (PN) 7 and 8, and were randomised to pirfenidone, losartan or water by gavage for 14 days. Neuromotor testing was carried out twice weekly. After sacrifice at PN21, ventricular area was measured on coronal sections using image-analysis software.

RESULTS

Ninety-five percent of animals undergoing IVH developed PHVD. Ventricular size was not significantly different between animals receiving either drug or water. Neuromotor testing at PN14 was significantly worse in IVH animals than in controls; neither drug improved performance in IVH animals.

CONCLUSION

Drugs that block TGF-beta do not reduce ventricular dilatation in this model. Further study is required to identify other cytokine targets and to determine how PHVD differs from postinflammatory fibrosis in other organs.

Protein and synthetic polymer injection for induction of obstructive hydrocephalus in rats

Background

The objective of this study was to develop a simple and inexpensive animal model of induced obstructive hydrocephalus with minimal tissue inflammation, as an alternative to kaolin injection.

Materials

Two-hundred and two male Sprague-Dawley rats aged 3 weeks received intracisternal injections of kaolin (25% suspension), Matrigel, type 1 collagen from rat tail, fibrin glue (Tisseel), n-butyl-cyanoacrylate (NBCA), or ethylene vinyl alcohol copolymer (Onyx-18 and Onyx-34). Magnetic resonance imaging was used to assess ventricle size. Animals were euthanized at 2, 5, 10 and 14 days post-injection for histological analysis.

Results

Kaolin was associated with 10% mortality and successful induction of hydrocephalus in 97% of survivors (ventricle area proportion 0.168 ± 0.018). Rapidly hardening agents (fibrin glue, NBCA, vinyl polymer) had high mortality rates and low success rates in survivors. Only Matrigel had relatively low mortality (17%) and moderate success rate (20%). An inflammatory response with macrophages and some lymphocytes was associated with kaolin. There was negligible inflammation associated with Matrigel. A severe inflammatory response with giant cell formation was associated with ethylene vinyl alcohol copolymer.

Conclusion

Kaolin predictably produces moderate to severe hydrocephalus with a mild chronic inflammatory reaction and fibrosis of the leptomeninges. Other synthetic polymers and biopolymers tested are unreliable and cause different types of inflammation.

Animal models of germinal matrix hemorrhage

Germinal matrix hemorrhage refers to bleeding that arises from the subependymal (or periventricular) germinal region of the immature brain. Clinical studies have shown that infants who experience germinal matrix hemorrhage can develop hydrocephalus or suffer from long-term neurologic dysfunction, including cerebral palsy, seizures, and learning disabilities. Understanding the causative factors and the pathogenesis of subsequent brain damage is important if germinal matrix hemorrhage is to be prevented or treated. Appropriate animal models are necessary to achieve this understanding. A number of animal species, including mice, rats, rabbits, sheep, pigs, dogs, cats, and primates, have been used to model germinal matrix hemorrhage. This literature review critically evaluates the animal models of germinal matrix hemorrhage. Each model has its own advantages and disadvantages; no single model is suitable for the study of all aspects of brain damage.

Brain damage in neonatal rats following kaolin induction of hydrocephalus

Neonatal and congenital hydrocephalus are common problems in humans. Hydrocephalus was induced in 1-day-old rats by injection of kaolin into the cisterna magna. At 7 and 21 days, magnetic resonance (MR) imaging was used to assess ventricle size, then brains were subjected to histopathological and biochemical analyses. Hydrocephalic pups did not exhibit delays in righting or negative geotaxis reflexes during the first week. At 7 days, there was variable ventricular enlargement with periventricular white matter edema, axon damage, reactive astrogliosis, and accumulation of macrophages in severe but not mild hydrocephalus. Cellular proliferation in the subependymal zone was significantly reduced. The cortical subplate neuron layer was disrupted. In rats allowed to survive to 21 days, weight was significantly lower in severely hydrocephalic rats. They also exhibited impaired memory in the Morris water maze test. Despite abnormal posture, there was minimal quantitative impairment of walking ability on a rotating cylinder. At 21 days, histological studies showed reduced corpus callosum thickness, fewer mature oligodendrocytes, damaged axons, and astroglial/microglial reaction. Reduced myelin basic protein, increased glial fibrillary acidic protein, and stable synaptophysin content were demonstrated by immunochemical methods. In conclusion, impairment in cognition and motor skills corresponds to ventricular enlargement and white matter destruction. Quantitative measures of weight, memory, ventricle size, and myelin, and glial proteins in this neonatal model of hydrocephalus will be useful tools for assessment of experimental therapeutic interventions.

Persistent motor deficit following infusion of autologous blood into the periventricular region of neonatal rats

Periventricular hemorrhage (PVH) in the brain of premature infants is often associated with developmental delay and persistent motor deficits. Our goal is to develop a rodent model that mimics the behavioral phenotype. We hypothesized that autologous blood infusion into the periventricular germinal matrix region of neonatal rats would lead to immediate and long-term behavioral changes. Tail blood or saline was infused into the periventricular region of 1-day-old rats. Magnetic resonance (MR) imaging was used to demonstrate the hematoma. Rats with blood infusion, as well as saline and intact controls, underwent behavior tests until 10 weeks age. Blood-infused rats displayed significant delay in motor development (ambulation, righting response, and negative geotaxis) to 22 days of age. As young adults, they exhibited impaired ability to stay on a rotating rod and to reach for food pellets. MR imaging at 10 weeks demonstrated subsets of rats with normal appearing brains, focal cortical infarcts, or mild hydrocephalus. There was a good correlation between MR imaging and histological findings. Some rats exhibited periventricular heterotopia and/or subtle striatal abnormalities not apparent on MR images. We conclude that autologous blood infusion into the brain of neonatal rats successfully models some aspects of periventricular hemorrhage that occurs after premature birth in humans.

Transforming growth factor-betas in a rat model of neonatal posthaemorrhagic hydrocephalus

Posthaemorrhagic ventricular dilatation (PHVD) is a common complication of intraventricular haemorrhage in premature infants. The aim of this study was to investigate the role of transforming growth factor-betas (TGF-betas), a family of polypeptides with potent desmoplastic properties, in the aetiology of PHVD in a newly developed neonatal rat model of this disorder. Pups were injected with citrated rat blood or artificial cerebrospinal fluid (ACSF) into alternate lateral ventricles on postnatal days 7 and 8. The brains were perfusion-fixed 14 days later and immunohistochemistry was performed for TGF-beta1, -beta2 and -beta3, p44/42 mitogen-activated protein (MAP) kinases, and the extracellular matrix proteins laminin, vitronectin and fibronectin. Ventricular dilatation occurred in 58.3% of animals injected with blood and 36.7% of those injected with ACSF. Periventricular immunoreactivity for TGF-beta1 and -beta2 increased in injected animals irrespective of the presence or absence of ventricular dilatation, although the levels of both isoforms tended to be higher in animals with hydrocephalus. TGF-beta3 immunoreactivity was elevated in hydrocephalic rats only. The immunolabelling for phosphorylated p44/42 MAP kinases rose in a pattern similar to that for TGF-beta1 and -beta2. Expression of TGF-betas was accompanied by deposition of the extracellular matrix proteins fibronectin, laminin and vitronectin. The changes caused by injection of ACSF were the same as those caused by injection of blood. Our results raise the possibility that expression of TGF-betas, together with extracellular matrix protein deposition, may be involved in the development and/or maintenance of hydrocephalus after ventricular distension due to haemorrhage in the neonate.

The pathogenesis of neonatal post-hemorrhagic hydrocephalus

Hydrocephalus after intraventricular hemorrhage (IVH) has emerged as a major complication of preterm birth and is especially problematic to treat. The hydrocephalus is usually ascribed to fibrosing arachnoiditis, meningeal fibrosis and subependymal gliosis, which impair flow and resorption of cerebrospinal fluid (CSF). Recent experimental studies have suggested that acute parenchymal compression and ischemic damage, and increased parenchymal and perivascular deposition of extracellular matrix proteins--probably due at least partly to upregulation of transforming growth factor-beta (TGF-beta)--are further important contributors to the development of the hydrocephalus. IVH is associated with damage to periventricular white matter and the damage is exacerbated by the development of hydrocephalus; combinations of pressure, distortion, ischaemia, inflammation, and free radical-mediated injury are probably responsible. The damage to white matter accounts for the high frequency of cerebral palsy in this group of infants. The identification of mechanisms and mediators of hydrocephalus and white matter damage is leading to the development of new treatments to prevent permanent hydrocephalus and its neurological complications, and to avoid shunt dependence.